Date   

Re: Resonance

sdwillingham
 

--- In ultralightdx@..., "jim_kr1s" quotes me:
> "First, the AM front-end of the Si4734 is a tuned-tank circuit with a
> fairly conventional LNA and quadrature mixer as shown in the block
> diagram....
> "As Roy has pointed out, the loopstick (or air-loop) inductance is
> resonated with an on-chip varactor, which tunes in small discrete steps.
> This tuning is done each time the frequency is changed."


Gentlemen,

Radio reception and antennas involve complex, multidimensional tradeoffs, 
so I'm not taking sides (yet, anyway) in this debate.  I do agree with
Jim that a necessary first step to resolving the disagreement is to 
carefully understand loopstick resonance and how the Silabs' tuning 
method differs from that implemented in all other radios.

For the techies in the group who are interested, I think this can
answer most of your questions: US Patent 7561865 .

Cheers,
Scott


Sliders - the word from Silicon Labs

jim_kr1s <jkearman@...>
 

Before mailing sliders off to the antipodes, I thought some experimenters might want to re-read Scott Willingham's (of Silicon Labs) comments on how the Tecsun DSP radios work. I've highlighted the main point.

"As Roy has pointed out, the loopstick (or air-loop) inductance is resonated with
an on-chip varactor, which tunes in small discrete steps. This tuning is done
each time the frequency is changed. 
Roy is absolutely correct that it is vital
to repeatedly re-tune the radio as one evaluates different antenna changes.
The
chip's tuning method actively adapts to the inductance, bringing the tank to
resonance regardless of the change. 
In other words, the varactor value is not
set simply by a lookup table corresponding to frequency. The chip measures and
peaks the resonance upon each tuning event."


Here's a link to the full post, from December 26, 2009: http://groups.yahoo.com/group/ultralightdx/message/6928

I would take a SiLabs engineer seriously. Some of our comrades must have missed that post, because this one just appeared:

"When Tecsun and Kchibo switched to loopstick coils without movable forms (as in the D96L, PL-310 and PL-380 models), it was no longer possible to use this sliding-coil method to find the optimal coil position providing maximum AM sensitivity. Rather than accept all these DSP models as already having the maximum level of AM sensitivity thoughtfully provided by the Chinese factories (a ludicrous thought, for someone who has performed as many AM alignments as me), I decided to set up an actual dynamic testing method that would perform the exact same function as the sliding-coil tests in the PL-300WT/ G8 models, allowing the use of a sliding a coil to peak a weak AM audio signal under actual reception conditions.

"I turned to one of our ULR group innovations, the Slider coil, which provides a variable inductance by means of a special 40/44 Litz wire coil that can be easily shifted across a 7.5" Amidon ferrite bar. When transplanted into these newer DSP models in place of the stock loopstick, this Slider coil provides the exact same AM-sensitivity testing function as the stock sliding coils in the PL-300WT/ G8 models (that Steve and I aligned).

"When this 81-turn Slider coil is shifted along the ferrite bar after being transplanted into a PL-310 or PL-380 model, it can always quickly determine the actual coil inductance providing the maximum AM sensitivity in the model, by showing a sharp audio peak whenever the coil is close to the optimal position during reception of a weak AM station. This diagnostic test immediately corrects for any circuitry changes (from previous models) in the Si4734 radio, or in the DSP chip itself, since it is being performed under actual DXing conditions, with the best weak-signal AM reception being the bottom line. As such, it essentially creates a test where the radio tells you exactly which loopstick coil inductance it wants, to provide the best possible AM weak-signal reception. "

http://groups.yahoo.com/group/ultralightdx/message/7504
 

No matter where you put the coil on the ferrite, as soon as you retune the radio, the radio readjusts the varactor to peak it. If you keep moving the coil you're chasing your tail. If this is not clear, re-read the highlighted portion of  Scott's post. The tests cited just above were performed before the experimenters understood how the chip worked. It was an honest mistake. They happen. But now that we know, direct from SiLabs, could we please stop repeating it? And BTW, Roy Dyball has verified what I just said on his digital test bench connected to a G8, with a sliding inductor on a 7.5" -61 rod. Are Roy, the chip and the SiLabs engineer all wrong?

73,

Jim, KR1S
http://qrp.kearman.com/ 


Re: 2 New Ones

john445 <john445@...>
 

Hi Michael, I have a Eton E-100 and Tecsun PL-380. I will try to do some comparisons soon.

John


On Fri, Jan 22, 2010 at 5:39 PM, Michael <cglynn321@...> wrote:
 

Hi John
Interested to know how what other UL's you have and how the 310 compares to them.I have been siting on the fence trying to decide between the 380 and the 310.
Thanks
Michael Glynn
Niagara Falls, Canada


--- In ultralightdx@..., "john445" wrote:
>
> Hello all:
>
> Received the Tecsun PL-310 yesterday putting me at three ultralights. Interesting the English manual cover says PL-310, but the insides is all about the PL-380.
>
> 540 WAUK Jackson WI 1/22/10 2145U Ads, mention of Milwaukee, Milwaukee Bucks and ESPN Wisconsin several times. (Tecsun PL-310 BF)
>
> 680 WMFS Memphis TN 1/22/10 2250U ESPN Radio, matched web broadcast, talking about player Rudy Gay of Memphis Grizzlies. (Eton E100 BF)
>
> John Mosman
> WPE9GIZ
> Madison, WI
>




--
John Mosman
847-350-9566


1540 KGBC (Was Latest DX - Thursday Afternoon - 21 Jan 2010)

Stephen Ponder <n5wbi@...>
 

Well, it looks like I jinxed myself! I tuned to 1540
last nite and KGBC was back on, but at reduced power.

At least I can pick out stations on 1530 and 1550!

The AM band has been pretty active and unpredictable
lately. You never know what station will pop up on
frequency!

73,

Steve N5WBI
Clear Lake City TX


Re: Resonance

John H. Bryant <bjohnorcas@...>
 

Friends,

I think that Gary has hit on a wonderful idea.....

Gary, as I understand it, Roy's set up is almost an exact match for the 380, as well, with the 310 being a bit of a strange duck, having longer leads and some other differences that the 300 and the 380 don't exhibit.  ANYWAY, sending Roy a 554 Slider plus a Amidon bar would let him watch it operate with his software as well as try it in his 380.  He should have a bare Amidon bar, already, so he can emulate your Slider if he wants and monkey around with the new one, leaving your original un-monkeyed with as the "control."  If he doesn't have a spare Amidon bar, could you please send him two... and I insist on paying for the second one.

Other than that, I'm making out a whole lot of Awards and getting ready to announce a new award category and graphic.... the graphic has been dubbed "Our Lady of the Globes" by Rob Ross and me.... she is barely dressed, but we are dismayed to report that the model was likely born about 1905 and the graphic first published as the cover of Citizen's Radio Callbook in their Spring 1928 issue.

Gary, I really do want to pay for that second rod! (And all this assumes that Roy will play Ball.... erh Dyball.... )

John Bryant
Stillwater, OK
WinRadio G313e + Ultralights
Wellbrook Phased Array



The Slider coils can be somewhat intimidating to construct without experience (the process is described at  http://www.mediafire.com/?nqggfm2jymc ), but they are routinely made here, and I would be happy to send one to you (complete with an Amidon type 61 ferrite bar) free of charge, if you wish to try out this method in PL-380.

Thanks for listening, and of course I respect any differences of opinion. Thanks also for your detailed descriptions of the Si4734 chip functions, which are greatly appreciated.

73 and Good DX,

Gary DeBock (in Puyallup, WA USA)

 

 

        

 

When I first started experimenting with the original G8 loopstick moths ago I found it did not make much difference where I put the stock coil on the rod because as soon as I retuned the station the signal strength readings came back to about where they were before I moved it. I could not just simply slide the coil and look for a peak. Not then knowing how this little radio worked it made me want to find out what was happening. After obtaining a programming manual and seeing the range of commands available I was hooked and then spent hundreds of hours leaning how to talk to the Si4734 chip by building a USB interface and writing software to use it.
 
In a message dated 1/23/2010 2:06:52 P.M. Pacific Standard Time, roy.dyball@... writes:
 

Hi Jim

Thank you for the links to the Rider article, I have just had a skim through but can see it is well written and I will enjoy digesting it.

I first learnt about resonance 45 years ago during a 6 year traineeship in electronic telecommunications which I started straight out of school. Resonance fascinated me as much then as it does today (funny how the formulas haven't changed).

I have experienced very similar results with loopstick coils with my Tecsun radios as you have noted. Yesterday I wound a large inductance sliding coil to check the upper limit of the loopstick coil in the G8 radio by using the Si4734 AM_TUNE_STATUS function to return the value of varactor capacitance being used to tune the loopstick coil at different inductances.

The lowest value of capacitance the Si4734 can tune to (just like turning a mechanical variable capacitor to one end) is when the varactor is set to (decimal) 1 this represents a value of 0.095Pf, however SiLabs says we must add 7Pf to this value giving us 7.095Pf.

The upper limit of the varactor in decimal is 6143 and that equals 590.5Pf.

The chip in my G8 reported it was at 7.095Pf (rock bottom) with a value of 430µH adjusted on the loopstick. At around 350µH the varactor was reading around 12Pf which is where I found my best results.

When I first started experimenting with the original G8 loopstick moths ago I found it did not make much difference where I put the stock coil on the rod because as soon as I retuned the station the signal strength readings came back to about where they were before I moved it. I could not just simply slide the coil and look for a peak. Not then knowing how this little radio worked it made me want to find out what was happening. After obtaining a programming manual and seeing the range of commands available I was hooked and then spent hundreds of hours leaning how to talk to the Si4734 chip by building a USB interface and writing software to use it.

Now that we are all in love with our PL-380 PL-310 I recommend you put your old G8 to good use and convert it to a USB interface. You can do this in an afternoon just by removing three SMD resistors and attaching three wires plus earth. The USB interface PCB already assembled and only cost a little over twenty dollars. When it is finished you can use it as a tool for winding loopsticks and see for yourself what the radio is telling you (no guessing). The G8 380 310 have similar front ends in that the loopstick goes straight to SI4734 AM input via a coupling capacitor. The results you get on your G8 will be valid for the 310 and the 380. The project is on this site and it is free

Chreers Roy.
--- In ultralightdx@..., "jim_kr1s" wrote:
>
> Roy Dyball's notes on winding an antenna coil mentioned the need to
> re-tune the radio after each change in the number of turns on the
> antenna. As Roy mentioned, confirmed by my experiments, the Tecsuns (I
> have a G8 and a PL-380) don't like inductances higher than about 350 uH.
> What's that all about?
>
> The antenna forms half of a tuned circuit, the other half being on the
> integrated circuit. Is resonance important? You betcha! It's been shown
> that inductances greater than 350 uH give improved signal strengths at
> frequencies below the broadcast band. The integrated circuit has limited
> tuning range, so what you gain at the bottom you necessarily give up at
> the top. The problem with removing turns until you just see an increase
> at the top is two-fold. First, you may stop before you actually achieve
> resonance. It isn't either-or. The integrated circuit has lots of
> amplification, and you may see stronger signals, but they could be even
> stronger if you keep going!
>
> The other problem comes when you don't have local stations at the high
> end of the band, or they are far enough away to vary in signal strength.
> That's why I built a shielded enclosure, into which I can inject signals
> of repeatable strength. Starting at about 500 uH and removing turns, I
> do see X-band signal strengths starting to improve at around 430 uH, but
> they improve further at lower inductances. Signal strengths at LW are
> reduced with lower inductance, so you have to decide what's more
> important. Tecsun made their PL-380 coils about 330 uH, which does a
> good job from 530-1710 kHz. Again: You can't have good LW and good
> high-band MW performance with one coil.
>
> Looking around for a lay-person's explanation of resonance and its
> effects, I found an old Rider publication from the early days of radio.
> It's in DJU format; you can get the free reader here:
> http://djvu.org/resources/
>
> The file is here: http://www.tuberadio.it/download/rrider.djvu
>
> Like Roy, I'm not seeing evidence that using a spacer under the coil
> improves reception; test-bench measurements by Ben Tongue, a well-known
> engineer (co-founder of Blonder-Tongue) and crystal-set experimenter
> make me think it's not worth doing. See Table 2 here:
> http://www.bentongue.com/xtalset/29MxQFL/29MxQFL.html His best results
> across the band were with 1/16-inch polyethylene sheet, but not greatly
> different than with no spacer. Steve Ratzlaff, who has an expensive
> Hewlett Packard "Q" meter has also found no advantage to using a spacer.
> My own Q-measurement setup (from http://w7zoi.net/coilq.pdf -- Wes
> Hayward, W7ZOI was co-author of "Solid State Design" and "Experimental
> Methods in RF Design," and author of "Introduction to Radio Frequency
> Design," as well as many articles on related subjects) is not as
> accurate as Steve's meter, but nothing I've seen contradicts Tongue's
> and Steve's results. If you can get some 1/16-inch polyethylene, it will
> smooth out the Q (see the Rider book) across the band, and perk it up as
> much as 10-percent at the high end.
>
> What is critical is using an inductance the integrated circuit can
> resonate at the frequencies of interest. The tuning varactor has a
> design minimum capacitance, and there is stray capacitance in the
> circuit between the board and antenna (the connection between the rf
> board and the display board is a separate circuit). If the inductance is
> too large the varactor will be adjusted to its minimum capacitance, like
> a mechanical variable capacitor turned fully clockwise. You might still
> hear signals, just as you can still hear signals when a tunable loop
> antenna is mistuned. I can still hear Radio Enciclopedia on 530 kHz when
> my Terk is tuned to 1600 kHz, but the ladies are much stronger when the
> Terk is tuned to 530 kHz. Here's an article about varactors:
> http://en.wikipedia.org/wiki/Varactor
>
> While I cite others' work in this post, I speak only for myself. My
> results, which I feel are corroborated by others, are at variance with
> some other results reported here. You are free to make up your own mind.
> It is suggested that, if you have enough Litz wire and time, it might be
> worth experimenting with the coil size on your antenna modifications.
> When you can remove one or two turns without seeing any difference in
> high-band signal strength, you've hit the mark. This is hard to do
> accurately with off-air signals. Anyone who has a stable, accurate
> signal generator with an output meter, a big cardboard box, and some
> aluminum screen material can duplicate my tests. If you'd like to
> discuss the tests, email me at jkearman at att dot net. Thanks to Roy,
> Steve and other correspondents for sharing data!
>
> 73,
>
> Jim, KR1S
> http://qrp.kearman.com/
>


Re: Resonance

Gary DeBock
 

Hi Scott,
 
Thanks for the link to the US Patent reference, and I'll certainly read it over.
 
If I was a businessman I'd certainly be very thankful for this "debate"--  demand for the 7.5" loopstick PL-380's seems to be going through the roof :-)
 
73, Gary
 

In a message dated 1/23/2010 11:01:34 P.M. Pacific Standard Time, sdwillingham@... writes:
 

--- In ultralightdx@yahoogroups.com, "jim_kr1s" quotes me:
> "First, the AM front-end of the Si4734 is a tuned-tank circuit with a
> fairly conventional LNA and quadrature mixer as shown in the block
> diagram....
> "As Roy has pointed out, the loopstick (or air-loop) inductance is
> resonated with an on-chip varactor, which tunes in small discrete steps.
> This tuning is done each time the frequency is changed."


Gentlemen,

Radio reception and antennas involve complex, multidimensional tradeoffs, 
so I'm not taking sides (yet, anyway) in this debate.  I do agree with
Jim that a necessary first step to resolving the disagreement is to 
carefully understand loopstick resonance and how the Silabs' tuning 
method differs fro m that implemented in all other radios.

For the techies in the group who are interested, I think this can
answer most of your questions: US Patent 7561865 .

Cheers,
Scott


Re: Directional ferrite? - FARMERIK

Rik
 

You know I was wondering about that. I would think a highly directional antenna in an entertainment radio would be undesirable. You could miss even a local station if the radio was turned in the wrong direction. I am not much on radio theory, but I was wondering why some radios are much more directional than others. The PL-600 and the 911 triplets are all pretty small compared to the Heathkit. - FARMERIK

--- In ultralightdx@..., "jim_kr1s" <jkearman@...> wrote:



--- In ultralightdx@..., "farmerik" <farmerik@> wrote:

It just got me wondering if I could block signals from more of the
sides, and make any portable much more directional on the internal
ferrite rod. Thanks - FARMERIK

Probably not, I'm afraid. In your collection you have that fine Heathkit
portable, with a 7-inch ferrite rod. I'll bet it's more directional than
the ULRs with only internal antennas. When it comes to antennas, size
matters.

73,

Jim, KR1S
http://qrp.kearman.com/ <http://qrp.kearman.com/>


Re: Directional ferrite? - FARMERIK

jim_kr1s <jkearman@...>
 



--- In ultralightdx@..., "farmerik"
> It just got me wondering if I could block signals from more of the sides, and make any portable much more directional on the internal ferrite rod. Thanks - FARMERIK

Probably not, I'm afraid. In your collection you have that fine Heathkit portable, with a 7-inch ferrite rod. I'll bet it's more directional than the ULRs with only internal antennas. When it comes to antennas, size matters.

73,

Jim, KR1S
http://qrp.kearman.com/ 


Re: Resonance

jim_kr1s <jkearman@...>
 


--- In ultralightdx@..., "Roy" wrote:
>
>
> Hi Jim
>
> Thank you for the links to the Rider article, I have just had a skim
> through but can see it is well written and I will enjoy digesting it.

Thanks, Roy! After the up-front theory, the old-time circuits are interesting, too. Radio hasn't changed all that much, though the devices we use sure have. I started out messing with radios similar to the circuits in that book, before I got my ham license. And I have the scars to prove it!

> I first learnt about resonance 45 years ago during a 6 year traineeship
> in electronic telecommunications which I started straight out of school.
> Resonance fascinated me as much then as it does today (funny how the
> formulas haven't changed).

Got my ham license in 1962, FCC commercial license in 1964, and graduated from Hutchinson Technical HS, an engineering-college prep school in Buffalo, NY in 1965. Joined the USAF, where I was a ground-radio tech, but I bypassed tech school by taking a "bypass specialist's" test in Basic training. The ham training really paid off, especially for the AF, which didn't have to pay to train me! I worked on some interesting gear in some interesting places, and came to appreciate mil-spec quality.

After the service I went for a liberal arts education, but always worked in tech environments, including 5 years for ARRL, the U.S. ham-radio  organization, as a technical editor and author. I like writing, and I like the precision of science. I find it impossible to write about things I don't understand, but the basics always come through for me.

I'm contemplating hacking the G8. Lately it's serving to look for parallel SW transmissions, but the soft mute's driving me nuts. The ULRs were a diversion from my home-made radios. Now that we've put the antenna business to rest, I plan to get back to them.

73,

Jim, KR1S
http://qrp.kearman.com/ 


Re: Resonance and Training

Chris Knight <chris@...>
 

Just to throw in my hat, I too appreciate the contributions of everyone
concerned, whether they are experimental or discussions of proven radio
theory. Each has their own merit. Everything that has been said here in
discussion, or posted as an article, has increased my knowledge of these
little radios.

This forum is a great place for these types of discussions and I hope it
continues. Myself and others are making purchasing decisions based on what
is said here. So the more discussion (even contention at times) is well
worth it to me.

Lookin forward to the work you are doing along with all the input from Jim
Gary and in fact all the others - When you dont have a raft of test gear its
good to rely on others test results

Thanks to all

Neil<<

73,

Chris

Chris Knight (N0IJK)
Fort Lupton, Colorado
http://sites.google.com/site/ftluptonulrlogs/


Re: Directional ferrite? - FARMERIK

Rik
 

I had a wave trap many years ago, and it was great at blocking adjacent frequencies. What I wanted to do is block stations on the same frequency, but in slightly different directions. In other words make a radio sitting in between the shields much MORE directional.

I recently got a PL-600, and it easily more than one station on some frequencies, without using a loop antenna to help.In the reviews here, the $20 Tecsuns do that too. It just got me wondering if I could block signals from more of the sides, and make any portable much more directional on the internal ferrite rod. Thanks - FARMERIK

--- In ultralightdx@..., "jim_kr1s" <jkearman@...> wrote:



--- In ultralightdx@..., kevin asato <kc6pob@> wrote:

That would be your null.

If there are particular stations/frequencies you want to remove from
your reception, maybe a wave trap will be what is needed. Do a search on
crystal or xtal radios. Those guys have done a lot of work on reception
techniques to increase selectivity and reduce (not necessarily
eliminate) unwanted stations from their bare bones radios to enhance
their DX capabilities. (Of course we would all like to live in a dream
location like Mike Tuggle (Hawaii) where almost every station you hear
is DX!).


Even without the DX, Hawaii would be okay! A wave trap (a resonant
circuit that blocks signals) would work swell with an external antenna.
Here, instead of a top-mounted ferrite-rod antenna, I think I'd favor
John Bryant's mod, that adds a coupling loop to the internal antenna,
connected to a mini jack. It's in the Files section. The internal
antenna would be essentially replaced by a system comprised of a tuned
external antenna and wave trap. It would be hard to get a wave trap
working with an antenna tuned by the radio.

But -- if you installed John's mod and built a good-sized tunable air
loop, 2-feet or more on a side, it might null those pests well enough by
itself, and you wouldn't need a wave trap. If you're interested in wave
traps, I recommend http://theradioboard.com/rb/index.php
<http://theradioboard.com/rb/index.php> It has a search engine.
Searching the "Crystal Radios" forum for "wavetrap OR wave AND trap" I
found 34 threads! Friendly group, just watch out they don't lure you
into building crystal sets. Nan may bake you into a pumpkin bread. :)

73,

Jim, KR1S
http://qrp.kearman.com/ <http://qrp.kearman.com/>


Re: Resonance and Training

neil.findlay52
 

Roy

Spot on 20th January 1969 in Hobart - started with 47 others 4 groups of 12

Very few of us still work for Telstra -- I am now with Optus after 30 years exchange install and then design doing Trafdata for axe exchanges.

That training has carried me and others through all walks of life. Woodwork, Metal work, Draughting and oh the AC theory drummed into us.

I remember the CRO project and the way we were taught to terminate PROPERLY and solder correctly and the instructor making us do it again when it was not right. And contrary to the views of many in society those skills were not lost to the community or a waste of money to Government as we have taken them to our subsequent employment in a variety of fields. Even our work on our little radio projects will ultimately benefit others.

Lookin forward to the work you are doing along with all the input from Jim Gary and in fact all the others - When you dont have a raft of test gear its good to rely on others test results

Thanks to all

Neil




From: Roy
To: ultralightdx@...
Sent: Sun, 24 January, 2010 10:02:55 AM
Subject: [ultralightdx] Re: Resonance and Training

 

Neil

Spot on. I was a T.I.T. with the PMG. Did my first year at Strathfield (NSW) in 1966. That first year we were hammered with AC theory. I really enjoyed the practical especially building the cathode ray oscilloscope in sections and  VTVM and all the associated meter  and instrument theory. 

I think my favourite was building an electric motor from a block of steel. We were only allowed to use a file. It took three months during the practical periods. Some of the students took them home and had them machined but they were found out.

I really enjoyed the valve theory and the new fangled transistor theory (LOL). The next 5 years for me consisted of many unit courses centring on crossbar switching, multiplexing and broadband transmission, rural exchanges, alternate power supplies and diesel nonstop supplies and all of this and we were paid a decent wage. I don't think the kids of today have that good.

Cheers Roy.

 

 


--- In ultralightdx@ yahoogroups. com, Neil Findlay wrote:
>
> Hi Roy
>
> Yep that will be the next project -- except that I will have to purchase another PL300 as my mother has my old one
> as she lives in a deep fringe area. Thanks for showing us how to implement the programming to best effect
>
> On a seperate note you did you start ot as a T.I.T. - sound like you had similar or maybe the same training as i had - straight out of year 10 and back into another set of classroom for most of the first year. I started as a T.I.T. ( technician in training ) with the PMG 41 years ago. Almost a quarter of that first year was AC theory - trigonometry and so forth - it amazing how many times we go back and use that stuff.
> In telecommunications today so many technicians do not understand the basics so when a problem arises they dont know what to do next. Only the military could have provided better training.
>
> Thanks to for Jim's article and references - again reminding me of my early training - would to have jusy half the gear in some of those workshops. Wiith everyones input we can make the best use of our little portable radios.
>
> Neil
>
>
>
>
> ____________ _________ _________ __
> From: Roy roy.dyball@. ..
> To: ultralightdx@ yahoogroups. com
> Sent: Sun, 24 January, 2010 8:06:14 AM
> Subject: [ultralightdx] Re: Resonance
>
>  
> Hi Jim
> Thank you for the links to the Rider article, I have just had a skim through but can see it is well written and I will enjoy digesting it.
> I first learnt about resonance 45 years ago during a 6 year traineeship in electronic telecommunications which I started straight out of school. Resonance fascinated me as much then as it does today (funny how the formulas haven't changed).
> I have experienced very similar results with loopstick coils with my Tecsun radios as you have noted. Yesterday I wound a large inductance sliding coil to check the upper limit of the loopstick coil in the G8 radio by using the Si4734 AM_TUNE_STATUS function to return the value of varactor capacitance being used to tune the loopstick coil at different inductances.
> The lowest value of capacitance the Si4734 can tune to (just like turning a mechanical variable capacitor to one end) is when the varactor is set to (decimal) 1 this represents a value of 0.095Pf, however SiLabs says we must add 7Pf to this value giving us 7.095Pf.
> The upper limit of the varactor in decimal is 6143 and that equals 590.5Pf.
> The chip in my G8 reported it was at 7.095Pf (rock bottom) with a value of 430µH adjusted on the loopstick. At around 350µH the varactor was reading around 12Pf which is where I found my best results.
> When I first started experimenting with the original G8 loopstick moths ago I found it did not make much difference where I put the stock coil on the rod because as soon as I retuned the station the signal strength readings came back to about where they were before I moved it. I could not just simply slide the coil and look for a peak. Not then knowing how this little radio worked it made me want to find out what was happening. After obtaining a programming manual and seeing the range of commands available I was hooked and then spent hundreds of hours leaning how to talk to the Si4734 chip by building a USB interface and writing software to use it.
> Now that we are all in love with our PL-380 PL-310 I recommend you put your old G8 to good use and convert it to a USB interface. You can do this in an afternoon just by removing three SMD resistors and attaching three wires plus earth. The USB interface PCB already assembled and only cost a little over twenty dollars. When it is finished you can use it as a tool for winding loopsticks and see for yourself what the radio is telling you (no guessing). The G8 380 310 have similar front ends in that the loopstick goes straight to SI4734 AM input via a coupling capacitor. The results you get on your G8 will be valid for the 310 and the 380. The project is on this site and it is free
> Chreers Roy.
> --- In ultralightdx@ yahoogroups. com, "jim_kr1s" jkearman@ wrote:
> >
> > Roy Dyball's notes on winding an antenna coil mentioned the need to
> > re-tune the radio after each change in the number of turns on the
> > antenna. As Roy mentioned, confirmed by my experiments, the Tecsuns (I
> > have a G8 and a PL-380) don't like inductances higher than about 350 uH.
> > What's that all about?
> >
> > The antenna forms half of a tuned circuit, the other half being on the
> > integrated circuit. Is resonance important? You betcha! It's been shown
> > that inductances greater than 350 uH give improved signal strengths at
> > frequencies below the broadcast band. The integrated circuit has limited
> > tuning range, so what you gain at the bottom you necessarily give up at
> > the top. The problem with removing turns until you just see an increase
> > at the top is two-fold. First, you may stop before you actually achieve
> > resonance. It isn't either-or. The integrated circuit has lots of
> > amplification, and you may see stronger signals, but they could be even
> > stronger if you keep going!
> >
> > The other problem comes when you don't have local stations at the high
> > end of the band, or they are far enough away to vary in signal strength.
> > That's why I built a shielded enclosure, into which I can inject signals
> > of repeatable strength. Starting at about 500 uH and removing turns, I
> > do see X-band signal strengths starting to improve at around 430 uH, but
> > they improve further at lower inductances. Signal strengths at LW are
> > reduced with lower inductance, so you have to decide what's more
> > important. Tecsun made their PL-380 coils about 330 uH, which does a
> > good job from 530-1710 kHz. Again: You can't have good LW and good
> > high-band MW performance with one coil.
> >
> > Looking around for a lay-person's explanation of resonance and its
> > effects, I found an old Rider publication from the early days of radio.
> > It's in DJU format; you can get the free reader here:
> > http://djvu. org/resources/
> >
> > The file is here: http://www.tuberadi o.it/download/ rrider.djvu
> >
> > Like Roy, I'm not seeing evidence that using a spacer under the coil
> > improves reception; test-bench measurements by Ben Tongue, a well-known
> > engineer (co-founder of Blonder-Tongue) and crystal-set experimenter
> > make me think it's not worth doing. See Table 2 here:
> > http://www.bentongu e.com/xtalset/ 29MxQFL/29MxQFL. html His best results
> > across the band were with 1/16-inch polyethylene sheet, but not greatly
> > different than with no spacer. Steve Ratzlaff, who has an expensive
> > Hewlett Packard "Q" meter has also found no advantage to using a spacer.
> > My own Q-measurement setup (from http://w7zoi. net/coilq. pdf -- Wes
> > Hayward, W7ZOI was co-author of "Solid State Design" and "Experimental
> > Methods in RF Design," and author of "Introduction to Radio Frequency
> > Design," as well as many articles on related subjects) is not as
> > accurate as Steve's meter, but nothing I've seen contradicts Tongue's
> > and Steve's results. If you can get some 1/16-inch polyethylene, it will
> > smooth out the Q (see the Rider book) across the band, and perk it up as
> > much as 10-percent at the high end.
> >
> > What is critical is using an inductance the integrated circuit can
> > resonate at the frequencies of interest. The tuning varactor has a
> > design minimum capacitance, and there is stray capacitance in the
> > circuit between the board and antenna (the connection between the rf
> > board and the display board is a separate circuit). If the inductance is
> > too large the varactor will be adjusted to its minimum capacitance, like
> > a mechanical variable capacitor turned fully clockwise. You might still
> > hear signals, just as you can still hear signals when a tunable loop
> > antenna is mistuned. I can still hear Radio Enciclopedia on 530 kHz when
> > my Terk is tuned to 1600 kHz, but the ladies are much stronger when the
> > Terk is tuned to 530 kHz. Here's an article about varactors:
> > http://en.wikipedia .org/wiki/ Varactor
> >
> > While I cite others' work in this post, I speak only for myself. My
> > results, which I feel are corroborated by others, are at variance with
> > some other results reported here. You are free to make up your own mind.
> > It is suggested that, if you have enough Litz wire and time, it might be
> > worth experimenting with the coil size on your antenna modifications.
> > When you can remove one or two turns without seeing any difference in
> > high-band signal strength, you've hit the mark. This is hard to do
> > accurately with off-air signals. Anyone who has a stable, accurate
> > signal generator with an output meter, a big cardboard box, and some
> > aluminum screen material can duplicate my tests. If you'd like to
> > discuss the tests, email me at jkearman at att dot net. Thanks to Roy,
> > Steve and other correspondents for sharing data!
> >
> > 73,
> >
> > Jim, KR1S
> > http://qrp.kearman. com/
> >
>
>
>
>
> ____________ _________ _________ _________ _________ _________ _________ _________ _______
> See what's on at the movies in your area. Find out now: http://au.movies. yahoo.com/ session-times/
>



See what's on at the movies in your area. Find out now.


Re: Directional ferrite? - FARMERIK

jim_kr1s <jkearman@...>
 



--- In ultralightdx@..., kevin asato wrote:
>
> That would be your null.
>
> If there are particular stations/frequencies you want to remove from your reception, maybe a wave trap will be what is needed. Do a search on crystal or xtal radios. Those guys have done a lot of work on reception techniques to increase selectivity and reduce (not necessarily eliminate) unwanted stations from their bare bones radios to enhance their DX capabilities. (Of course we would all like to live in a dream location like Mike Tuggle (Hawaii) where almost every station you hear is DX!).


Even without the DX, Hawaii would be okay! A wave trap (a resonant circuit that blocks signals) would work swell with an external antenna. Here, instead of a top-mounted ferrite-rod antenna, I think I'd favor John Bryant's mod, that adds a coupling loop to the internal antenna, connected to a mini jack. It's in the Files section. The internal antenna would be essentially replaced by a system comprised of a tuned external antenna and wave trap. It would be hard to get a wave trap working with an antenna tuned by the radio.

But -- if you installed John's mod and built a good-sized tunable air loop, 2-feet or more on a side, it might null those pests well enough by itself, and you wouldn't need a wave trap. If you're interested in wave traps, I recommend http://theradioboard.com/rb/index.php   It has a search engine. Searching the "Crystal Radios" forum for "wavetrap OR wave AND trap" I found 34 threads! Friendly group, just watch out they don't lure you into building crystal sets. Nan may bake you into a pumpkin bread. :)

73,

Jim, KR1S
http://qrp.kearman.com/ 


Re: Resonance

jim_kr1s <jkearman@...>
 


--- In ultralightdx@..., D1028Gary@... wrote:
>
> Hello Jim,
>
> Thanks for your amusing comments. Since you have already apologized once
> for doubting the 554 uh inductance value in the PL-380 7.5" external
> loopstick project (as pasted below), I find it amusing that you are now rehashing
> the same arguments for which you apologized :-)
>
> Since you are obviously contradicting yourself, I'll let everyone decide
> whether to take you seriously, or not. I have already made my decision, by
> the way :-)
>
> 73, Gary

Gary,

I'm sorry you're making this about you. I hope that others besides you have the right to talk about ULR experiments, even when their findings differ from yours. I have gone out of my way to explain my equipment and methods, even providing online references where possible. I won't respond to your condescending sarcasm, but will continue to stick to provable theory and experimental results. For those who just tuned in, Gary's ire stems from my repeated attempts to convince him that the antenna circuit is tuned, which is critical to understand if you're winding antenna coils. I don't know if Gary accepts that, so let's get it out of the way right now. We heard it from Scott Willingham, an engineer at Silicon Labs, the chip manufacturer:

"First, the AM front-end of the Si4734 is a tuned-tank circuit with a fairly conventional LNA and quadrature mixer as shown in the block diagram....

"As Roy has pointed out, the loopstick (or air-loop) inductance is resonated with an on-chip varactor, which tunes in small discrete steps. This tuning is done each time the frequency is changed."

http://groups.yahoo.com/group/ultralightdx/message/6928 

Now, on to tonight's episode: After Scott Willingham of Silicon Labs made his initial comment about the chip possibly tuning a 550 uH at 1700 kHz, which prompted my apology, he backed away from it. (I guess I should have then backed away from my apology, but I was trying to maintain the peace.) I quote (emphasis mine):

"I will slightly amend what I said about the stock inductance range topping out
at about 550 uH. My assumption there is that parasitic capacitance stays
constant. It occurs to me now that as the inductance is increased, the
loopstick's self-capacitance will increase as well, limiting the ultimate
achievable inductance. On the other hand, at 10% too high inductance, you will
only give up at the top 5% of the band. And if the Q at the top of the band is
only 20..."

http://groups.yahoo.com/group/ultralightdx/message/7345

The "top 5% of the band" is 1624-1710 kHz. I count 51 active stations in the U.S. and Canada from 1630-1700 kHz. I'm not willing to give them up. YMMV.

In a private email to me, Steve Ratzlaff reported these Q values for a 562-uH coil wound on the center of a 7.5" -61 rod with foam-core spacer:

1300 kHz, Q 400
900 kHz Q 442
700 kHz Q 460
530 kHz Q 449
530 kHz Q 442
400 kHz Q 420
300 kHz Q 361
200 kHz Q 303

Steve was unable to measure above 1300 kHz, but you can discern the trend. Q is starting to decline at 900 kHz. Q declined about 10-percent from 900-1300 kHz. Extending the curve, we might expect Q=357 at 1700 kHz. I think Steve may have measured the Q of a Tecsun antenna and posted the results to this forum, but I don't feel like looking for them. Even if the rewound Tecsun ferrite's Q is half of Amidon's, and even if the varactor is low Q (the similar, discrete MVAM108 varactor has a specified minimum Q of 150. Data sheet:  http://kearman.com/images/MVAM108.pdf), circuit Q probably exceeds 20 at 1710 kHz, especially when better-quality Litz wire replaces the original stuff.

Therefore, my statement,

"The problem with removing turns until you just see an increase at the top is two-fold. First, you may stop before you actually achieve resonance. It isn't either-or. The integrated circuit has lots of amplification, and you may see stronger signals, but they could be even stronger if you keep going!"

is valid. If you find it amusing, perhaps you don't understand resonant circuits and Q. That Rider booklet may help. http://www.tuberadio.it/download/rrider.djvu Or dust off that ARRL Handbook I know you have on the shelf.

NB, though, I never once mentioned "554 uH" in this thread. Since you brought it up, however, let me quote now from an email from Roy Dyball, from three days ago (January 20): "I wound that 81 [-turn] coil on the 7.5" rod and it needed 18 turns off it* before the varactor came off the bottom." * Removing 18 turns works out to about 338 uH. In other words, the chip was unable to resonate the 81-turn coil at the high end of the MW BC band. Roy's isn't an empirical, subjective observation; he's seeing varactor (tuning) capacitance reported by the chip.

I, too, could not get an 81-turn coil on a 7.5-inch -61 rod to resonate. (Hint: There's too much stray capacitance (Scott Willingham calls it "parasitic capacitance," but we are referring to the same thing) in the radio, the wires going up to the rod, and in the coil winding.)

You have previously stated that you have no nearby X-band stations to use for references, so given your experimental methods the error is understandable. At the time you didn't understand how the chip tuned the antenna, either, though I tried more than once to explain it. You may not take me seriously, but I took you seriously enough to try to help you understand something. According to John Bryant, that's the great thing about this forum. Until somebody disagrees with a founder. That I disagree with your methods and results is no reflection on you as a person, though I'm afraid that's how you perceive it.

Last weekend you told me to repeat your experiments, and I did. Then I reported what I found. To ensure my observations were not skewed by fading signals I made a Faraday box, and used a stable signal source in lieu of off-air signals. Based on my results, some of which have been independently verified by Roy Dyball, I suggested people try removing more turns from the internal re-wound loopstick, and the consequences of boosting LW reception: a reduction in high-band sensitivity.  Where's the harm in that suggestion? (BTW, your observation of increased LW sensitivity provided a clue, which you overlooked. The chip cannot tune the same inductance from 1710 kHz far down into the LW band. If it's perking up on LW, it has to be sucking wind higher up. As I mentioned at the beginning of this thread, just because you're hearing stations doesn't mean the antenna is resonated.)

It is hard to discuss technical subjects without using formal language, lest we fall into the tar pits of ambiguity and imprecision. My regrets to those who find my writing too instructive or professorial. This isn't rocket science, but it is science, and I take it seriously. If you want to discuss radios, let's do it. If you want to attack me, let's take it off-line.

73,

Jim Kearman, KR1S
http://qrp.kearman.com/ 


Re: Resonance and Training

Roy <roy.dyball@...>
 

Neil

Spot on. I was a T.I.T. with the PMG. Did my first year at Strathfield (NSW) in 1966. That first year we were hammered with AC theory. I really enjoyed the practical especially building the cathode ray oscilloscope in sections and  VTVM and all the associated meter  and instrument theory. 

I think my favourite was building an electric motor from a block of steel. We were only allowed to use a file. It took three months during the practical periods. Some of the students took them home and had them machined but they were found out.

I really enjoyed the valve theory and the new fangled transistor theory (LOL). The next 5 years for me consisted of many unit courses centring on crossbar switching, multiplexing and broadband transmission, rural exchanges, alternate power supplies and diesel nonstop supplies and all of this and we were paid a decent wage. I don't think the kids of today have that good.

Cheers Roy.

 

 


--- In ultralightdx@..., Neil Findlay wrote:
>
> Hi Roy
>
> Yep that will be the next project -- except that I will have to purchase another PL300 as my mother has my old one
> as she lives in a deep fringe area. Thanks for showing us how to implement the programming to best effect
>
> On a seperate note you did you start ot as a T.I.T. - sound like you had similar or maybe the same training as i had - straight out of year 10 and back into another set of classroom for most of the first year. I started as a T.I.T. ( technician in training ) with the PMG 41 years ago. Almost a quarter of that first year was AC theory - trigonometry and so forth - it amazing how many times we go back and use that stuff.
> In telecommunications today so many technicians do not understand the basics so when a problem arises they dont know what to do next. Only the military could have provided better training.
>
> Thanks to for Jim's article and references - again reminding me of my early training - would to have jusy half the gear in some of those workshops. Wiith everyones input we can make the best use of our little portable radios.
>
> Neil
>
>
>
>
> ________________________________
> From: Roy roy.dyball@...
> To: ultralightdx@...
> Sent: Sun, 24 January, 2010 8:06:14 AM
> Subject: [ultralightdx] Re: Resonance
>
>  
> Hi Jim
> Thank you for the links to the Rider article, I have just had a skim through but can see it is well written and I will enjoy digesting it.
> I first learnt about resonance 45 years ago during a 6 year traineeship in electronic telecommunications which I started straight out of school. Resonance fascinated me as much then as it does today (funny how the formulas haven't changed).
> I have experienced very similar results with loopstick coils with my Tecsun radios as you have noted. Yesterday I wound a large inductance sliding coil to check the upper limit of the loopstick coil in the G8 radio by using the Si4734 AM_TUNE_STATUS function to return the value of varactor capacitance being used to tune the loopstick coil at different inductances.
> The lowest value of capacitance the Si4734 can tune to (just like turning a mechanical variable capacitor to one end) is when the varactor is set to (decimal) 1 this represents a value of 0.095Pf, however SiLabs says we must add 7Pf to this value giving us 7.095Pf.
> The upper limit of the varactor in decimal is 6143 and that equals 590.5Pf.
> The chip in my G8 reported it was at 7.095Pf (rock bottom) with a value of 430µH adjusted on the loopstick. At around 350µH the varactor was reading around 12Pf which is where I found my best results.
> When I first started experimenting with the original G8 loopstick moths ago I found it did not make much difference where I put the stock coil on the rod because as soon as I retuned the station the signal strength readings came back to about where they were before I moved it. I could not just simply slide the coil and look for a peak. Not then knowing how this little radio worked it made me want to find out what was happening. After obtaining a programming manual and seeing the range of commands available I was hooked and then spent hundreds of hours leaning how to talk to the Si4734 chip by building a USB interface and writing software to use it.
> Now that we are all in love with our PL-380 PL-310 I recommend you put your old G8 to good use and convert it to a USB interface. You can do this in an afternoon just by removing three SMD resistors and attaching three wires plus earth. The USB interface PCB already assembled and only cost a little over twenty dollars. When it is finished you can use it as a tool for winding loopsticks and see for yourself what the radio is telling you (no guessing). The G8 380 310 have similar front ends in that the loopstick goes straight to SI4734 AM input via a coupling capacitor. The results you get on your G8 will be valid for the 310 and the 380. The project is on this site and it is free
> Chreers Roy.
> --- In ultralightdx@ yahoogroups. com, "jim_kr1s" jkearman@ wrote:
> >
> > Roy Dyball's notes on winding an antenna coil mentioned the need to
> > re-tune the radio after each change in the number of turns on the
> > antenna. As Roy mentioned, confirmed by my experiments, the Tecsuns (I
> > have a G8 and a PL-380) don't like inductances higher than about 350 uH.
> > What's that all about?
> >
> > The antenna forms half of a tuned circuit, the other half being on the
> > integrated circuit. Is resonance important? You betcha! It's been shown
> > that inductances greater than 350 uH give improved signal strengths at
> > frequencies below the broadcast band. The integrated circuit has limited
> > tuning range, so what you gain at the bottom you necessarily give up at
> > the top. The problem with removing turns until you just see an increase
> > at the top is two-fold. First, you may stop before you actually achieve
> > resonance. It isn't either-or. The integrated circuit has lots of
> > amplification, and you may see stronger signals, but they could be even
> > stronger if you keep going!
> >
> > The other problem comes when you don't have local stations at the high
> > end of the band, or they are far enough away to vary in signal strength.
> > That's why I built a shielded enclosure, into which I can inject signals
> > of repeatable strength. Starting at about 500 uH and removing turns, I
> > do see X-band signal strengths starting to improve at around 430 uH, but
> > they improve further at lower inductances. Signal strengths at LW are
> > reduced with lower inductance, so you have to decide what's more
> > important. Tecsun made their PL-380 coils about 330 uH, which does a
> > good job from 530-1710 kHz. Again: You can't have good LW and good
> > high-band MW performance with one coil.
> >
> > Looking around for a lay-person's explanation of resonance and its
> > effects, I found an old Rider publication from the early days of radio.
> > It's in DJU format; you can get the free reader here:
> > http://djvu. org/resources/
> >
> > The file is here: http://www.tuberadi o.it/download/ rrider.djvu
> >
> > Like Roy, I'm not seeing evidence that using a spacer under the coil
> > improves reception; test-bench measurements by Ben Tongue, a well-known
> > engineer (co-founder of Blonder-Tongue) and crystal-set experimenter
> > make me think it's not worth doing. See Table 2 here:
> > http://www.bentongu e.com/xtalset/ 29MxQFL/29MxQFL. html His best results
> > across the band were with 1/16-inch polyethylene sheet, but not greatly
> > different than with no spacer. Steve Ratzlaff, who has an expensive
> > Hewlett Packard "Q" meter has also found no advantage to using a spacer.
> > My own Q-measurement setup (from http://w7zoi. net/coilq. pdf -- Wes
> > Hayward, W7ZOI was co-author of "Solid State Design" and "Experimental
> > Methods in RF Design," and author of "Introduction to Radio Frequency
> > Design," as well as many articles on related subjects) is not as
> > accurate as Steve's meter, but nothing I've seen contradicts Tongue's
> > and Steve's results. If you can get some 1/16-inch polyethylene, it will
> > smooth out the Q (see the Rider book) across the band, and perk it up as
> > much as 10-percent at the high end.
> >
> > What is critical is using an inductance the integrated circuit can
> > resonate at the frequencies of interest. The tuning varactor has a
> > design minimum capacitance, and there is stray capacitance in the
> > circuit between the board and antenna (the connection between the rf
> > board and the display board is a separate circuit). If the inductance is
> > too large the varactor will be adjusted to its minimum capacitance, like
> > a mechanical variable capacitor turned fully clockwise. You might still
> > hear signals, just as you can still hear signals when a tunable loop
> > antenna is mistuned. I can still hear Radio Enciclopedia on 530 kHz when
> > my Terk is tuned to 1600 kHz, but the ladies are much stronger when the
> > Terk is tuned to 530 kHz. Here's an article about varactors:
> > http://en.wikipedia .org/wiki/ Varactor
> >
> > While I cite others' work in this post, I speak only for myself. My
> > results, which I feel are corroborated by others, are at variance with
> > some other results reported here. You are free to make up your own mind.
> > It is suggested that, if you have enough Litz wire and time, it might be
> > worth experimenting with the coil size on your antenna modifications.
> > When you can remove one or two turns without seeing any difference in
> > high-band signal strength, you've hit the mark. This is hard to do
> > accurately with off-air signals. Anyone who has a stable, accurate
> > signal generator with an output meter, a big cardboard box, and some
> > aluminum screen material can duplicate my tests. If you'd like to
> > discuss the tests, email me at jkearman at att dot net. Thanks to Roy,
> > Steve and other correspondents for sharing data!
> >
> > 73,
> >
> > Jim, KR1S
> > http://qrp.kearman. com/
> >
>
>
>
>
> __________________________________________________________________________________
> See what's on at the movies in your area. Find out now: http://au.movies.yahoo.com/session-times/
>


Re: Resonance and Training

neil.findlay52
 

Hi Roy
 
Yep that will be the next project -- except that I will have to purchase another PL300 as my mother has my old one
as she lives in a deep fringe area. Thanks for showing us how to implement the programming to best effect
 
On a seperate note you did you start ot as a T.I.T. - sound like you had similar or maybe the same training as i had - straight out of year 10 and back into another set of classroom for most of the first year. I started as a T.I.T. ( technician in training ) with the PMG 41 years ago. Almost a quarter of that first year was AC theory - trigonometry and so forth - it amazing how many times we go back and use that stuff.
In telecommunications today so many technicians do not understand the basics so when a problem arises they dont know what to do next. Only the military could have provided better training.
 
Thanks to for Jim's article and references - again reminding me of my early training - would to have jusy half the gear in some of those workshops. Wiith everyones input we can make the best use of our little portable radios.
 
Neil


From: Roy
To: ultralightdx@...
Sent: Sun, 24 January, 2010 8:06:14 AM
Subject: [ultralightdx] Re: Resonance

 

Hi Jim

Thank you for the links to the Rider article, I have just had a skim through but can see it is well written and I will enjoy digesting it.

I first learnt about resonance 45 years ago during a 6 year traineeship in electronic telecommunications which I started straight out of school. Resonance fascinated me as much then as it does today (funny how the formulas haven't changed).

I have experienced very similar results with loopstick coils with my Tecsun radios as you have noted. Yesterday I wound a large inductance sliding coil to check the upper limit of the loopstick coil in the G8 radio by using the Si4734 AM_TUNE_STATUS function to return the value of varactor capacitance being used to tune the loopstick coil at different inductances.

The lowest value of capacitance the Si4734 can tune to (just like turning a mechanical variable capacitor to one end) is when the varactor is set to (decimal) 1 this represents a value of 0.095Pf, however SiLabs says we must add 7Pf to this value giving us 7.095Pf.

The upper limit of the varactor in decimal is 6143 and that equals 590.5Pf.

The chip in my G8 reported it was at 7.095Pf (rock bottom) with a value of 430µH adjusted on the loopstick. At around 350µH the varactor was reading around 12Pf which is where I found my best results.

When I first started experimenting with the original G8 loopstick moths ago I found it did not make much difference where I put the stock coil on the rod because as soon as I retuned the station the signal strength readings came back to about where they were before I moved it. I could not just simply slide the coil and look for a peak. Not then knowing how this little radio worked it made me want to find out what was happening. After obtaining a programming manual and seeing the range of commands available I was hooked and then spent hundreds of hours leaning how to talk to the Si4734 chip by building a USB interface and writing software to use it.

Now that we are all in love with our PL-380 PL-310 I recommend you put your old G8 to good use and convert it to a USB interface. You can do this in an afternoon just by removing three SMD resistors and attaching three wires plus earth. The USB interface PCB already assembled and only cost a little over twenty dollars. When it is finished you can use it as a tool for winding loopsticks and see for yourself what the radio is telling you (no guessing). The G8 380 310 have similar front ends in that the loopstick goes straight to SI4734 AM input via a coupling capacitor. The results you get on your G8 will be valid for the 310 and the 380. The project is on this site and it is free

Chreers Roy.
--- In ultralightdx@ yahoogroups. com, "jim_kr1s" wrote:
>
> Roy Dyball's notes on winding an antenna coil mentioned the need to
> re-tune the radio after each change in the number of turns on the
> antenna. As Roy mentioned, confirmed by my experiments, the Tecsuns (I
> have a G8 and a PL-380) don't like inductances higher than about 350 uH.
> What's that all about?
>
> The antenna forms half of a tuned circuit, the other half being on the
> integrated circuit. Is resonance important? You betcha! It's been shown
> that inductances greater than 350 uH give improved signal strengths at
> frequencies below the broadcast band. The integrated circuit has limited
> tuning range, so what you gain at the bottom you necessarily give up at
> the top. The problem with removing turns until you just see an increase
> at the top is two-fold. First, you may stop before you actually achieve
> resonance. It isn't either-or. The integrated circuit has lots of
> amplification, and you may see stronger signals, but they could be even
> stronger if you keep going!
>
> The other problem comes when you don't have local stations at the high
> end of the band, or they are far enough away to vary in signal strength.
> That's why I built a shielded enclosure, into which I can inject signals
> of repeatable strength. Starting at about 500 uH and removing turns, I
> do see X-band signal strengths starting to improve at around 430 uH, but
> they improve further at lower inductances. Signal strengths at LW are
> reduced with lower inductance, so you have to decide what's more
> important. Tecsun made their PL-380 coils about 330 uH, which does a
> good job from 530-1710 kHz. Again: You can't have good LW and good
> high-band MW performance with one coil.
>
> Looking around for a lay-person's explanation of resonance and its
> effects, I found an old Rider publication from the early days of radio.
> It's in DJU format; you can get the free reader here:
> http://djvu. org/resources/
>
> The file is here: http://www.tuberadi o.it/download/ rrider.djvu
>
> Like Roy, I'm not seeing evidence that using a spacer under the coil
> improves reception; test-bench measurements by Ben Tongue, a well-known
> engineer (co-founder of Blonder-Tongue) and crystal-set experimenter
> make me think it's not worth doing. See Table 2 here:
> http://www.bentongu e.com/xtalset/ 29MxQFL/29MxQFL. html His best results
> across the band were with 1/16-inch polyethylene sheet, but not greatly
> different than with no spacer. Steve Ratzlaff, who has an expensive
> Hewlett Packard "Q" meter has also found no advantage to using a spacer.
> My own Q-measurement setup (from http://w7zoi. net/coilq. pdf -- Wes
> Hayward, W7ZOI was co-author of "Solid State Design" and "Experimental
> Methods in RF Design," and author of "Introduction to Radio Frequency
> Design," as well as many articles on related subjects) is not as
> accurate as Steve's meter, but nothing I've seen contradicts Tongue's
> and Steve's results. If you can get some 1/16-inch polyethylene, it will
> smooth out the Q (see the Rider book) across the band, and perk it up as
> much as 10-percent at the high end.
>
> What is critical is using an inductance the integrated circuit can
> resonate at the frequencies of interest. The tuning varactor has a
> design minimum capacitance, and there is stray capacitance in the
> circuit between the board and antenna (the connection between the rf
> board and the display board is a separate circuit). If the inductance is
> too large the varactor will be adjusted to its minimum capacitance, like
> a mechanical variable capacitor turned fully clockwise. You might still
> hear signals, just as you can still hear signals when a tunable loop
> antenna is mistuned. I can still hear Radio Enciclopedia on 530 kHz when
> my Terk is tuned to 1600 kHz, but the ladies are much stronger when the
> Terk is tuned to 530 kHz. Here's an article about varactors:
> http://en.wikipedia .org/wiki/ Varactor
>
> While I cite others' work in this post, I speak only for myself. My
> results, which I feel are corroborated by others, are at variance with
> some other results reported here. You are free to make up your own mind.
> It is suggested that, if you have enough Litz wire and time, it might be
> worth experimenting with the coil size on your antenna modifications.
> When you can remove one or two turns without seeing any difference in
> high-band signal strength, you've hit the mark. This is hard to do
> accurately with off-air signals. Anyone who has a stable, accurate
> signal generator with an output meter, a big cardboard box, and some
> aluminum screen material can duplicate my tests. If you'd like to
> discuss the tests, email me at jkearman at att dot net. Thanks to Roy,
> Steve and other correspondents for sharing data!
>
> 73,
>
> Jim, KR1S
> http://qrp.kearman. com/
>



See what's on at the movies in your area. Find out now.


Re: Directional ferrite? - FARMERIK

kevin asato <kc6pob@...>
 

That would be your null.

If there are particular stations/frequencies you want to remove from your reception, maybe a wave trap will be what is needed. Do a search on crystal or xtal radios. Those guys have done a lot of work on reception techniques to increase selectivity and reduce (not necessarily eliminate) unwanted stations from their bare bones radios to enhance their DX capabilities. (Of course we would all like to live in a dream location like Mike Tuggle (Hawaii) where almost every station you hear is DX!).

73,
kevin
kc6pob


--- On Sat, 1/23/10, farmerik wrote:

From: farmerik
Subject: [ultralightdx] Re: Directional ferrite? - FARMERIK
To: ultralightdx@...
Date: Saturday, January 23, 2010, 1:31 PM

 

What I am trying to design in my head would be to block AM radio stations from the sides, I guess that is what you mean by Null. But if it could narrow the direction signals are received from, it might really help DXing. Especially if it could block one direction from the figure 8 pattern too. Maybe a milk jug or filing crate could support the sides, and be easy to move around, like the crate wound loops. Just a thought. - FARMERIK

--- In ultralightdx@ yahoogroups. com, kevin asato wrote:
>
> There's a short discussion of that antenna in my 9th Edition ARRL Antenna Book in Chapter 14. It may also be in later editions, too, but this is the latest I own.
>
> 73,
> kevin
> kc6pob
>
> --- On Sat, 1/23/10, jim_kr1s wrote:
>
> From: jim_kr1s
> Subject: [ultralightdx] Re: Directional ferrite? - FARMERIK
> To: ultralightdx@ yahoogroups. com
> Date: Saturday, January 23, 2010, 9:33 AM
>
>
>
>
>
>
>
>  
>
>
>
>
>
>
>
>
>
> Back in the 1980s, the late Doug DeMaw of ARRL Headquarters, just down the road from you in Newington, got interested in the 160-Meter (1800-2000 kHz) ham band. His house was on a small suburban lot, so he invested a lot of time investigating small receiving and transmitting antennas.  One I recall was a tuned ferrite-loop receiving antenna set lengthwise in a pair of aluminum L brackets, forming a U-shaped channel. The purpose of the shield wasn't to improve directivity, though; it was to reduce electrostatic noise pickup.
>
>
> A long-popular receiving loop design uses a piece of coaxial cable formed
> into a large hoop. The center conductor is the antenna, and the ends
> are connected to the tuning capacitor, both terminals of which are
> above ground. The shield is grounded at either end, but split at the
> top center, so as not to form a shorted turn. The shield reduces pickup
> of locally generated noise. DeMaw applied the same principle to his
> ferrite-core loop.
>
> The only article I could find on ARRL's on-line archives (only open to members) that shows this antenna has a terrible photograph: "Beat the Noise with a 'Scoop Loop,'" QST for July 1977, pp 30-34. There's quite a bit of discussion of this antenna, winding methods for maximizing ferrite-core antenna Q, as well as tuned air loops and preamplifiers. Though oriented toward 160-M use, all of the information is applicable to our interests.
>
> Theoretically, a large shield (needed because of the relatively long wavelengths, about 200-600 meters!) would block signals, but as you know, a loop antenna does not so much provide directivity as nulls. Larger loops, either air or ferrite-core, usually give deeper, narrower nulls.
>
> Depending on what metallic objects are in the walls of your house, sometimes one room favors certain directions, while another favors other directions. In my wiring-and-ducting- infested condo that's certainly the case. It's worth roaming around the house, twisting and turning your portable radio as you go, to see where a particular station comes in best!
>
> 73,
>
> Jim, KR1S
> http://qrp.kearman. com/ 
>



Re: Resonance

Roy <roy.dyball@...>
 

Hi Jim

Thank you for the links to the Rider article, I have just had a skim through but can see it is well written and I will enjoy digesting it.

I first learnt about resonance 45 years ago during a 6 year traineeship in electronic telecommunications which I started straight out of school. Resonance fascinated me as much then as it does today (funny how the formulas haven't changed).

I have experienced very similar results with loopstick coils with my Tecsun radios as you have noted. Yesterday I wound a large inductance sliding coil to check the upper limit of the loopstick coil in the G8 radio by using the Si4734 AM_TUNE_STATUS function to return the value of varactor capacitance being used to tune the loopstick coil at different inductances.

The lowest value of capacitance the Si4734 can tune to (just like turning a mechanical variable capacitor to one end) is when the varactor is set to (decimal) 1 this represents a value of 0.095Pf, however SiLabs says we must add 7Pf to this value giving us 7.095Pf.

The upper limit of the varactor in decimal is 6143 and that equals 590.5Pf.

The chip in my G8 reported it was at 7.095Pf (rock bottom) with a value of 430µH adjusted on the loopstick. At around 350µH the varactor was reading around 12Pf which is where I found my best results.

When I first started experimenting with the original G8 loopstick moths ago I found it did not make much difference where I put the stock coil on the rod because as soon as I retuned the station the signal strength readings came back to about where they were before I moved it. I could not just simply slide the coil and look for a peak. Not then knowing how this little radio worked it made me want to find out what was happening. After obtaining a programming manual and seeing the range of commands available I was hooked and then spent hundreds of hours leaning how to talk to the Si4734 chip by building a USB interface and writing software to use it.

Now that we are all in love with our PL-380 PL-310 I recommend you put your old G8 to good use and convert it to a USB interface. You can do this in an afternoon just by removing three SMD resistors and attaching three wires plus earth. The USB interface PCB already assembled and only cost a little over twenty dollars. When it is finished you can use it as a tool for winding loopsticks and see for yourself what the radio is telling you (no guessing). The G8 380 310 have similar front ends in that the loopstick goes straight to SI4734 AM input via a coupling capacitor. The results you get on your G8 will be valid for the 310 and the 380. The project is on this site and it is free

Chreers Roy.
--- In ultralightdx@..., "jim_kr1s" >
> Roy Dyball's notes on winding an antenna coil mentioned the need to
> re-tune the radio after each change in the number of turns on the
> antenna. As Roy mentioned, confirmed by my experiments, the Tecsuns (I
> have a G8 and a PL-380) don't like inductances higher than about 350 uH.
> What's that all about?
>
> The antenna forms half of a tuned circuit, the other half being on the
> integrated circuit. Is resonance important? You betcha! It's been shown
> that inductances greater than 350 uH give improved signal strengths at
> frequencies below the broadcast band. The integrated circuit has limited
> tuning range, so what you gain at the bottom you necessarily give up at
> the top. The problem with removing turns until you just see an increase
> at the top is two-fold. First, you may stop before you actually achieve
> resonance. It isn't either-or. The integrated circuit has lots of
> amplification, and you may see stronger signals, but they could be even
> stronger if you keep going!
>
> The other problem comes when you don't have local stations at the high
> end of the band, or they are far enough away to vary in signal strength.
> That's why I built a shielded enclosure, into which I can inject signals
> of repeatable strength. Starting at about 500 uH and removing turns, I
> do see X-band signal strengths starting to improve at around 430 uH, but
> they improve further at lower inductances. Signal strengths at LW are
> reduced with lower inductance, so you have to decide what's more
> important. Tecsun made their PL-380 coils about 330 uH, which does a
> good job from 530-1710 kHz. Again: You can't have good LW and good
> high-band MW performance with one coil.
>
> Looking around for a lay-person's explanation of resonance and its
> effects, I found an old Rider publication from the early days of radio.
> It's in DJU format; you can get the free reader here:
> http://djvu.org/resources/
>
> The file is here: http://www.tuberadio.it/download/rrider.djvu
>
> Like Roy, I'm not seeing evidence that using a spacer under the coil
> improves reception; test-bench measurements by Ben Tongue, a well-known
> engineer (co-founder of Blonder-Tongue) and crystal-set experimenter
> make me think it's not worth doing. See Table 2 here:
> http://www.bentongue.com/xtalset/29MxQFL/29MxQFL.html His best results
> across the band were with 1/16-inch polyethylene sheet, but not greatly
> different than with no spacer. Steve Ratzlaff, who has an expensive
> Hewlett Packard "Q" meter has also found no advantage to using a spacer.
> My own Q-measurement setup (from http://w7zoi.net/coilq.pdf -- Wes
> Hayward, W7ZOI was co-author of "Solid State Design" and "Experimental
> Methods in RF Design," and author of "Introduction to Radio Frequency
> Design," as well as many articles on related subjects) is not as
> accurate as Steve's meter, but nothing I've seen contradicts Tongue's
> and Steve's results. If you can get some 1/16-inch polyethylene, it will
> smooth out the Q (see the Rider book) across the band, and perk it up as
> much as 10-percent at the high end.
>
> What is critical is using an inductance the integrated circuit can
> resonate at the frequencies of interest. The tuning varactor has a
> design minimum capacitance, and there is stray capacitance in the
> circuit between the board and antenna (the connection between the rf
> board and the display board is a separate circuit). If the inductance is
> too large the varactor will be adjusted to its minimum capacitance, like
> a mechanical variable capacitor turned fully clockwise. You might still
> hear signals, just as you can still hear signals when a tunable loop
> antenna is mistuned. I can still hear Radio Enciclopedia on 530 kHz when
> my Terk is tuned to 1600 kHz, but the ladies are much stronger when the
> Terk is tuned to 530 kHz. Here's an article about varactors:
> http://en.wikipedia.org/wiki/Varactor
>
> While I cite others' work in this post, I speak only for myself. My
> results, which I feel are corroborated by others, are at variance with
> some other results reported here. You are free to make up your own mind.
> It is suggested that, if you have enough Litz wire and time, it might be
> worth experimenting with the coil size on your antenna modifications.
> When you can remove one or two turns without seeing any difference in
> high-band signal strength, you've hit the mark. This is hard to do
> accurately with off-air signals. Anyone who has a stable, accurate
> signal generator with an output meter, a big cardboard box, and some
> aluminum screen material can duplicate my tests. If you'd like to
> discuss the tests, email me at jkearman at att dot net. Thanks to Roy,
> Steve and other correspondents for sharing data!
>
> 73,
>
> Jim, KR1S
> http://qrp.kearman.com/
>


Re: Directional ferrite? - FARMERIK

Rik
 

What I am trying to design in my head would be to block AM radio stations from the sides, I guess that is what you mean by Null. But if it could narrow the direction signals are received from, it might really help DXing. Especially if it could block one direction from the figure 8 pattern too. Maybe a milk jug or filing crate could support the sides, and be easy to move around, like the crate wound loops. Just a thought. - FARMERIK

--- In ultralightdx@..., kevin asato <kc6pob@...> wrote:

There's a short discussion of that antenna in my 9th Edition ARRL Antenna Book in Chapter 14. It may also be in later editions, too, but this is the latest I own.

73,
kevin
kc6pob

--- On Sat, 1/23/10, jim_kr1s <jkearman@...> wrote:

From: jim_kr1s <jkearman@...>
Subject: [ultralightdx] Re: Directional ferrite? - FARMERIK
To: ultralightdx@...
Date: Saturday, January 23, 2010, 9:33 AM







 









Back in the 1980s, the late Doug DeMaw of ARRL Headquarters, just down the road from you in Newington, got interested in the 160-Meter (1800-2000 kHz) ham band. His house was on a small suburban lot, so he invested a lot of time investigating small receiving and transmitting antennas.  One I recall was a tuned ferrite-loop receiving antenna set lengthwise in a pair of aluminum L brackets, forming a U-shaped channel. The purpose of the shield wasn't to improve directivity, though; it was to reduce electrostatic noise pickup.


A long-popular receiving loop design uses a piece of coaxial cable formed
into a large hoop. The center conductor is the antenna, and the ends
are connected to the tuning capacitor, both terminals of which are
above ground. The shield is grounded at either end, but split at the
top center, so as not to form a shorted turn. The shield reduces pickup
of locally generated noise. DeMaw applied the same principle to his
ferrite-core loop.

The only article I could find on ARRL's on-line archives (only open to members) that shows this antenna has a terrible photograph: "Beat the Noise with a 'Scoop Loop,'" QST for July 1977, pp 30-34. There's quite a bit of discussion of this antenna, winding methods for maximizing ferrite-core antenna Q, as well as tuned air loops and preamplifiers. Though oriented toward 160-M use, all of the information is applicable to our interests.

Theoretically, a large shield (needed because of the relatively long wavelengths, about 200-600 meters!) would block signals, but as you know, a loop antenna does not so much provide directivity as nulls. Larger loops, either air or ferrite-core, usually give deeper, narrower nulls.

Depending on what metallic objects are in the walls of your house, sometimes one room favors certain directions, while another favors other directions. In my wiring-and-ducting- infested condo that's certainly the case. It's worth roaming around the house, twisting and turning your portable radio as you go, to see where a particular station comes in best!

73,

Jim, KR1S
http://qrp.kearman. com/ 


Re: Grundig G6 - ultralight or not?

Gary Kinsman
 

Hi Kevin,

The FM on my R9012 is terrible (it is the newer version). It picks up the same station at multiple spots on the dial, and it can't pick up several stations that my DT-400W gets with no problem. I don't live close to any FM stations, so overload should not be an issue. I've seen other comments on the Internet about problems with the FM on the R9012.

The MW (AM) is pretty good for the size, and that's what I bought it for. As has been pointed out in this group before, the MW sensitivity increases when the whip antenna is rotated away from the top of the radio. This radio has better nulls on MW than any of my digital ultralights.

Regards,
Gary

--- In ultralightdx@..., "dhsatyadhana" <satya@...> wrote:

Hi:

If you go the 9012 route, make sure you get one that was made after 2005, asking the seller for the serial number. Per Gary's message #3432 here on the Group, "Please be aware that a lemon variant issue exists with the Tecsun R9012, and that some "black lemons" from 2005 have been identified. If the serial number is 0892005xxxxxxx, it indicates that the model was manufactured in 2005 and is a probably a "lemon," regardless of color. Models with serial numbers of 0892008xxxxxxx and 0892009xxxxxxx have all proven to be "good" so far, regardless of color. The loopstick design on models manufactured in 2005 has inferior sensitivity, compared to the recently-manufactured models. The eBay seller "tquchina" has been sending out newly manufactured R9012's for free, to replace substandard 2005 models purchased from him."

Regards - Kevin S
Bainbridge Island, WA