Date   

Ultralight

Phil Bytheway <phil_tekno@...>
 

Gary,

There will be a "World of Ultralight" in this week's DXM eventually into print in 3 weeks.
Hope it's OK what I "borrowed".... and thanks.
 

Phil Bytheway
IRCA Editor-in-Chief
IRCA Bookstore
Seattle WA
Drake R-7 / KIWA Loop



KCBQ overloads PL-380 (Re: Tecsun PL-360 3" Loopstick Testing)

jim_kr1s <jkearman@...>
 

Scott,

Got it! Will do this tomorrow. I see how it effectively shorts
interwinding-C through the ground connections. Have been twisting the
wires coming off the transformers. It would be interesting to get hold
of the transformer used in some consumer AM/FM tuner, just to see how
they pulled it off. I'll bet there's one kicking around your lab
somewhere.

Thanks!

Jim


Re: Graham Maynard's Tecsun PL-380 Modification Article

jim_kr1s <jkearman@...>
 

Gary,

Thanks for posting those interesting results. The part I have reproduced below  told me all I needed to know.

Test Freq.  

300 uH    

400 uH    

500 uH    

554 uH  

750-KXL

39/ 13  

41/ 13  

43/ 13

43/ 15

1610 kHz

37/ 19

37/ 19

38/ 19

42/ 19

1706 kHz  

35/ 13

36/ 13

36/ 13

41/ 00

1640-KDZR

32/ 18 

34/ 18 

34/ 18

34/ 18


I note that there is substantially no high-band improvement from 300-500 uH. In view of the slight RSSI differences between 300, 400 and 500 uH, the 554-uH numbers in the second and third  lines look anomalous. For1640-KDZR, it is  consistent.

On 735 and 750, the numbers increase with inductance exactly as I would expect. Yet even though the the 750-kHz RSSI reading was 4 dB higher at 500 uH than 300 uH, the S/N number was the same. (To put this in perspective for non-techies, a 4-dB increase means the signal was about 2.55 times stronger. Because the second number, S/N, is unchanged, it's equivalent to turning up the volume control 1.275 clicks.)

Your results contain no surprises: A high inductance works well at the low end, not well at the high end. You should expect to see higher numbers at 1610 for example, than at 750. You can see this in your data: Compare RSSI numbers at 525 and 735, and at 620 and 750. For all coils, the higher frequencies in those two pairs have higher RSSI numbers. The RSSI numbers should keep climbing all the way to the top of the band, but yours level off somewhere below 1600 kHz.

Further, the RSSI numbers at 1610 and 1640, which we would expect to be higher than at 750, are in fact lower, for all coils. At 750, the 500-uH coil was 4 dB better than the 300-uH coil. At 1610 there's only a dB of difference between them, which could be simple round-off error, as the display resolution is 1 dB. (There's 2-dB difference at 1640, but that was an off-air test, and thus subject to fading error as well.)

The numbers you obtained for the stock and Stealth antennas vary all over the place. This may be because those antennas were inside the radio, but there is no way to properly analyze them, or make a meaningful comparison between them and the external antennas. Clearly, 7.5-inch external antennas outperform shorter internal ones, but we expect that.

None of this means they are "bad" antennas, and I can't prove your radio-antenna combinations won't resonate at the high end unless I test them myself. (I've provided a test procedure which you are equipped to reproduce.) I truly believe, however, that your results completely validate what Roy and I have been claiming about their high-band operation.

73,

Jim, KR1S
http://kr1s.kearman.com/ 
http://qrp.kearman.com/ 


KCBQ overloads PL-380 (Re: Tecsun PL-360 3" Loopstick Testing)

sdwillingham
 

Jim,

I just had an epiphany about the balun transformer today! I tried it out and quick tests are amazing for CM rejection. Please give it a try.

1) Keep your secondary windings the same.
2) Wind the primary (antenna side) with a bifilar pair. If your are using 2N primary windings, wind N times with the bi-pair. You can wind over the secondary as you described.
3) Now, if your pair of wires is red and green: at one end connect the green to one side of your loop feed and connect red to ground. At the other end, red to the other loop feed and green to ground.
4) Dress all your wires to keep loop areas minimized, i.e. twist the two wires from the primary to gnd and twist the two wires that go to your loop.

So this is now like you had before, but with a center tap to ground. The big win here is that if the total primary winding inductance was Lp for differential signals, now the common-mode signals see Lp/4 to ground before they even touch the stray winding capacitance. This slaughters the common mode signal. Without a center tap on the primary, the loop is free floating and couples all its potential through the parasitic cap. On a local station with 72 dB strength, I can short the loop terminals and the signal drops to zero!
My cheezy loop's symmetry and nulls seem quite a bit improved too.

Easy mod. I think you'll like it.

-Scott-

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


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


To test the balance of your balun, I suggest just doing a common-mode
measurement. Connect both sides of your primary (antenna side) to the
signal generator. The ground of the generator to a ground plane.
Connect one side of the secondary to ground and the other to your 'scope
or spectrum analyzer. You want the smallest signal possible relative to
the alternative of wiring the primary between generator and ground.

Scott,

Thanks for the suggestion. The light went on as soon as I read it. I
tried a few variations of winding the primary, but the one that did best
(about 15 dB better isolation than any other configuration) was with
the primary turns evenly spaced around the secondary. That doesn't agree
with your earlier suggestion, so I want to keep trying. A close-wound
coil offset as much as possible from either end of the secondary (which
would seem to give the least capacitive coupling) wasn't as good.

Was thinking of winding a new transformer as a bifilar 4:1. To match the
Hoop Loop the high-Z part has to be 256 uH. Not sure that will tune all
the way up, but will be worth it to get a benchmark.

With the loop disconnected and with the primary shorted or open, only
two local stations at 1450 and 1590 get through. Those are the ones that
make me want to shield the coil. Even with the secondary connection
shielded, the toroid still gets plenty of signal. This is an
improvement though, as before, a few other stations leaked in. One
notable absentee was a pest down the road on 760. If I could knock them
down and tilt-null WSB on 750, maybe I could hear KOA! I think the
high-band stations are still strong because the coil's reactance is
about twice as high up there.

It got into sunset time so I couldn't compare null depth measurements
made earlier, but my sense is they are deeper because a greater
percentage of signal is coming only from the antenna. Shorting the
antenna at its feed point after peaking the radio, I don't hear any
additional stations.


But here's what I found out: you need to adjust the altitude (vertical
tilt) of the loop to get better than a few dB nulls. Just a vertical
loop will not do all that well.

Chris Knight has been after me about that. I had an alt-az 4-footer in
Connecticut, which was good at nulling every Nutmegger's favorite
station, WTIC. Tilting the Hoop Loop last night I found a few stations
where it helped, and the null of the tilt is, as you say, very sharp.
Couldn't hold the antenna steady and the signals were fading, but on
some stations the nulls were better than 30 dB.

It'll be easy to elevate the hoop from the base and add a hinge, by
extending the screw that tightens the outer hoop, so V 2.0 is underway.

73,

Jim, KR1S
http://kr1s.kearman.com/ <http://kr1s.kearman.com/>
http://qrp.kearman.com/ <http://qrp.kearman.com/>


Re: Graham Maynard's Tecsun PL-380 Modification Article

Roy <roy.dyball@...>
 

Hi Gary,

Your figures are very interesting. And it seems that the S/N values only vary by one point between the 300 to 500uH range of coils and across all your measurements. Would not the 300uH coil moounted in the centre be the best choice as you are using less wire? Or are you more concerned about it working on long wave?

I hope you continue to experiment with thicker Litz wire because I am sure you will find out as I have with the 7.5" rod that it performs better than the above results. It is virtually impossible to wind too much inductance on the 7.5 inch rod as the thickness of 630 Litz wire won't allow it. Once you have listened to how well the radio performs with the thicker wire I think you will forget about the previous configurations.

Cheers Roy.

 

--- In ultralightdx@..., D1028Gary@... wrote:
>
> Hello All,
>
> Scott is referring to comprehensive measurements performed here on four
> different 7.5" loopstick PL-380 test models of varying inductances and coil
> configurations, using both signal generator and live signal inputs. These
> results have been shared already with those who have made significant
> contributions to the 7.5" loopstick experimentation (Roy, Scott, Guy, and Nick),
> as well as with the recipients of 7.5" loopstick PL-380 models prepared
> here.
>
> Scott's summary is essentially correct, although it was the 554 uh model
> that had an indication of varactor lock-up on the (out-of-band) frequency of
> 1706 kHz. The 500 uh model had unsurpassed RSSI and S/N performance
> throughout the MW frequency spectrum, and based upon this fact and its
> performance edge on the LW frequencies, it was chosen as the final configuration for
> the 7.5" loopstick PL-380 models shipped to others. The test readings are
> pasted below, contained in the pending revision to the PL-380 7.5" loopstick
> transplant article:
> ____________________________________________________________________________
> ____________
>
>
> High Sensitivity Coil Options At the suggestion of Scott Willingham (one
> of the Si4734 design team engineers), various 7.5� loopstick coil
> inductance models were constructed and tested by the author, to determine the
> relative coil performance at differing inductances and MW frequencies. In
> addition, two of the coils were wound in the center of the ferrite bar,
> to determine if this coil orientation would provide any advantage in the
> final RSSI and/or S/N readings on the PL-380’s digital display.
>
> Model Model A- 300 uh (center-wound): 54 turns of 40/44 Litz wire,
> starting 80 mm from either end of the bar
> Model Model B- 400 uh (center-wound): 64 turns of 40/44 Litz wire,
> starting 78 mm from either end of the bar
> Model Model C- 500 uh (offset coil): 75 turns of 40/44 Litz wire,
> starting 41 mm from closest end of the bar
> Model Model D- 554 uh (offset coil): 81 turns of 40/44 Litz wire,
> starting 42 mm from closest end of the bar
> These four test models were extensively compared using both signal
> generator and live AM signal inputs, in an outdoor environment free from other
> conducting materials. All the loopsticks had identical plastic mounting
> frames, with rubber shock mounts isolating the ferrite bars from the plastic. The
> TSG-17 signal generator test readings were repeated several times, to
> ensure stability and accurate results. The stock PL-380 model was also included
> in several tests as a reference, as well as a PL-380 with the stock
> ferrite bar rewound with 40/44 Litz wire at a 432 uh inductance (referred to as “
> Stealth�). The test data (RSSI and S/N) is recorded below:
>
>
> Sig. Gen.Test Freq. Stock Stealth 300 uh Model 400 uh Model
> 500 uh Model 554 uh Model
> 525 kHz 15/ 00 17/ 00 24/ 07
> 24/ 07 26/ 08 27/ 08
> 735 kHz 39/ 13
> 41/ 14 42/14 43/ 14
> 1610 kHz 37/ 19
> 37/ 19 38/ 19 42/ 19
> 1706 kHz (out of band) 35/ 13 36/
> 13 36/ 13 41/ 00
> Live Station Signals (averaged readings)
> 620-KPOJ 19/ 11 20/ 15 33/ 20 34/ 20
> 34/ 20 35/ 20
> 750-KXL 30/ 00 32/ 00 39/ 13 41/ 13
> 43/ 13 43/ 15
> 1110-KWDB 24/ 09 29/ 11 35/ 20 36/ 20
> 37/ 20 39/ 20
> 1600-KVRI 24/ 14 25/ 15 32/ 24 34/
> 24 34/ 24 36/ 24
> 1640-KDZR 22/ 02 25 03 32/ 18 34/ 18
> 34/ 18 34/ 18
> As can be seen in the test results, although the higher-inductance models
> have greater RSSI readings across
> the band, the S/N readings are remarkably similar for all four models (and
> are a more accurate indicator of
> actual signal strength). The lower-inductance models have a very slight
> drop off in S/N readings at the extreme
> low end of the band, while the 544 uh inductance model could not produce
> an S/N reading at the (out-of-band)
> ffrequency of 1706 kHz. Despite these minor differences, all four coil
> designs essentially have equal performance across the MW frequency spectrum,
> and all four would be very viable choices to greatly boost the DXing
> performance of the Tecsun PL-380 model. Detailed assembly instructions for
> all four coil types will be contained
> in the revised PL:-380 7.5" loopstick transplant article, and all four
> test models will be retained here for future
> reference.
> The above test models were constructed in a serious effort to inform
> everyone of the actual experimental
> performance of the different coil designs, an effort which required
> significant time and expense. I feel confident
> that the results are accurate and trustworthy, and that I have gone the
> "extra mile" to promote mutual
> understanding. If someone refuses to accept the results, it certainly
> won't ruin my day :-) I have respect
> for those with differing opinions, but do suggest that they perform some
> actual PL-380 7.5" loopstick
> experimentation for greater mutual understanding.
> 73, Gary DeBock (in Puyallup, WA, USA)
>
>
> . In a message dated 4/19/2010 7:19:38 A.M. Pacific Daylight Time,
> sdwillingham@... writes:
>
> Those of us who have measured the resonance have seen that it works
> correctly. Gary's later comprehensive measurements also confirm that 300uH,
> 400uH, and 500uH loopsticks all "track" (the 500 starts to fail a touch at the
> high end) and further, they all have nearly the same RSSI within a dB or
> two. Graham further states that his transplant loopstick has 10 dB more gain
> across the band, but provides no objective data for that.
>


Re: Ultralight

Gary DeBock
 

Hi Phil,
 
Thanks very much for doing this, and sorry that I haven't provided help (having been tied up with other projects). I would be very happy to assist you in drafting the "World of Ultralight" for future issues of DXM, if you can provide a time frame for completion.
 
As usual, our group has many fascinating new Ultralight radios to enjoy, including the latest Tecsun DSP model with plug-in loopsticks. We should have been so lucky 40 years ago, when we were all broke teenagers :-)
 
73, Gary 
 
In a message dated 4/19/2010 9:52:39 P.M. Pacific Daylight Time, phil_tekno@... writes:

 

Gary,

There will be a "World of Ultralight" in this week's DXM eventually into print in 3 weeks.
Hope it's OK what I "borrowed".... and thanks.
 

Phil Bytheway
IRCA Editor-in-Chief
IRCA Bookstore
Seattle WA
Drake R-7 / KIWA Loop



Re: Directional Antenna at WTIC Hartford CT? - Farmerik

Powell
 

WTIC is directional at night. Down here in South Carolina they just disappear at the time they go directional.


Powell


Re: Opinions of IDEAL inductance for MW and for LW PL-360?

jim_kr1s <jkearman@...>
 


--- In ultralightdx@..., "farmerik" wrote:
>
> Speaking of [copper] wire, what would you recommend? Solid or stranded? Any easy to work with gauge, or something in particular? - FARMERIK

In a loop that big there may not be much difference, but I'd use #28 magnet wire. It should be easy to pull snug around the corners, but not likely to break if you pull too hard.  You'll be hearing a lot of beacons, which will help you learn the Morse Code!

73,

Jim, KR1S
http://kr1s.kearman.com/ 
http://qrp.kearman.com/ 


Re: Opinions of IDEAL inductance for MW and for LW PL-360?

Rik
 

Speaking of [copper] wire, what would you recommend? Solid or stranded? Any easy to work with gauge, or something in particular? - FARMERIK

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


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


I ran the numbers for a 40 X 40 inch square loop, with 1/3 inch
spacing, and came up with 24 turns for 2208 uH. That should do. It looks
like my 4 foot loop is around 3500 uH. - FARMERIK

That's not bad, only a bit less than a half pound of #28 wire, at 320
feet, about $18.00. The Hoop Loop has 19 feet of wire, and the
transformer has less than 30 feet. The toroid cost $7.00 and the Hoop
Loop cost $10.00. So I guess you're getting a bargain. Let us know how
it works.

73,

Jim, KR1S
http://kr1s.kearman.com/ <http://kr1s.kearman.com/>
http://qrp.kearman.com/ <http://qrp.kearman.com/>


Re: Graham Maynard's Tecsun PL-380 Modification Article

Gary DeBock
 

Hi Roy,
 
Thanks for your comments, and suggestions throughout the experimentation (which have all been appreciated).
 
According to the test results, the choice of coil configuration among the four test models is not likely to make a significant AM-DXing difference over the vast majority of MW frequencies. Even on the extreme band edges, a difference of 1 dB in S/N ratio is unlikely to provide much of a DXing boost, since live signals typically vary in strength more than this every few seconds. As you point out, the 300 uh center-wound model would be the most economic option, and if my location was in Europe, Australia or NZ (with X-band frequencies as my primary DXing target), the 300 uh coil would be my own first choice. It's also very suitable for North American DXers who don't care about LW-DX.
 
The choice of the 500 uh coil option for myself (and the DXers who have ordered the modified model) was based on the unsurpassed performance throughout the MW frequency spectrum during the tests, plus the fact that it offered LW performance slightly greater than the lower-inductance models. There was extensive testing on the 1700 kHz frequency with these 500 uh models, to ensure that there was no trace of varactor lock-up. Their live-signal reception on 1700 kHz is indeed equivalent to that of the 300 uh and 400 uh models, and because of this, the extra LW performance was judged a bonus. The 554 uh model had varactor lock-up on the out-of-band frequency of 1706 kHz, and although this did not seem to make much of a difference in its X-band performance, I lowered the inductance to 500 uh on the "export models," to provide an extra safety margin. I would recommend that coil options other than the 554 uh model be used for those DXers whose top priority is X-band DXing, although such a configuration would probably be fine for TP-DXers who rarely tune those frequencies.
 
73, Gary
 
  
 
coil configuration would probably be the one I would choose as a DXer in Australia, NZ or Europe looking for maxim
 
In a message dated 4/19/2010 7:07:01 P.M. Pacific Daylight Time, roy.dyball@... writes:

 

Hi Gary,

Your figures are very interesting. And it seems that the S/N values only vary by one point between the 300 to 500uH range of coils and across all your measurements. Would not the 300uH coil moounted in the centre be the best choice as you are using less wire? Or are you more concerned about it working on long wave?

I hope you continue to experiment with thicker Litz wire because I am sure you will find out as I have with the 7.5" rod that it performs better than the above results. It is virtually impossible to wind too much inductance on the 7.5 inch rod as the thickness of 630 Litz wire won't allow it. Once you have listened to how well the radio performs with the thicker wire I think you will forget about the previous configurations.

Cheers Roy.


--- In ultralightdx@yahoogroups.com, D1028Gary@... wrote:
>
> Hello All,
>
> Scott is referring to comprehensive measurements performed here on four
> different 7.5" loopstick PL-380 test models of varying inductances and coil
> configurations, using both signal generator and live signal inputs. These
> results have been shared already with those who have made significant
> contributions to the 7.5" loopstick experimentation (Roy, Scott, Guy, and Nick),
> as well as with the recipients of 7.5" loopstick PL-380 models prepared
> here.
>
> Scott's summary is essentially correct, although it was the 554 uh model
> that had an indication of varactor lock-up on the (out-of-band) frequency of
> 1706 kHz. The 500 uh model had unsurpassed RSSI and S/N performance
> throughout the MW frequency spectrum, and based upon this fact and its
> performance edge on the LW frequencies, it was chosen as the final configuration for
> the 7.5" loopstick PL-380 models shipped to others. The test readings are
> pasted below, contained in the pending revision to the PL-380 7.5" loopstick
> transplant article:
> ____________________________________________________________________________
> ____________
>
>
> High Sensitivity Coil Options At the suggestion of Scott Willingham (one
> of the Si4734 design team engineers), various 7.5” loopstick coil
> inductance models were constructed and tested by the author, to determine the
> relative coil performance at differing inductances and MW frequencies. In
> addition, two of the coils were wound in the center of the ferrite bar,
> to determine if this coil orientation would provide any advantage in the
> final RSSI and/or S/N readings on the PL-380’s digital display.
>
> Model Model A- 300 uh (center-wound): 54 turns of 40/44 Litz wire,
> starting 80 mm from either end of the bar
> Model Model B- 400 uh (center-wound): 64 turns of 40/44 Litz wire,
> starting 78 mm from either end of the bar
> Model Model C- 500 uh (offset coil): 75 turns of 40/44 Litz wire,
> starting 41 mm from closest end of the bar
> Model Model D- 554 uh (offset coil): 81 turns of 40/44 Litz wire,
> starting 42 mm from closest end of the bar
> These four test models were extensively compared using both signal
> generator and live AM signal inputs, in an outdoor environment free from other
> conducting materials. All the loopsticks had identical plastic mounting
> frames, with rubber shock mounts isolating the ferrite bars from the plastic. The
> TSG-17 signal generator test readings were repeated several times, to
> ensure stability and accurate results. The stock PL-380 model was also included
> in several tests as a reference, as well as a PL-380 with the stock
> ferrite bar rewound with 40/44 Litz wire at a 432 uh inductance (referred to as “
> Stealth”). The test data (RSSI and S/N) is recorded below:
>
>
> Sig. Gen.Test Freq. Stock Stealth 300 uh Model 400 uh Model
> 500 uh Model 554 uh Model
> 525 kHz 15/ 00 17/ 00 24/ 07
> 24/ 07 26/ 08 27/ 08
> 735 kHz 39/ 13
> 41/ 14 42/14 43/ 14
> 1610 kHz 37/ 19
> 37/ 19 38/ 19 42/ 19
> 1706 kHz (out of band) 35/ 13 36/
> 13 36/ 13 41/ 00
> Live Station Signals (averaged readings)
> 620-KPOJ 19/ 11 20/ 15 33/ 20 34/ 20
> 34/ 20 35/ 20
> 750-KXL 30/ 00 32/ 00 39/ 13 41/ 13
> 43/ 13 43/ 15
> 1110-KWDB 24/ 09 29/ 11 35/ 20 36/ 20
> 37/ 20 39/ 20
> 1600-KVRI 24/ 14 25/ 15 32/ 24 34/
> 24 34/ 24 36/ 24
> 1640-KDZR 22/ 02 25 03 32/ 18 34/ 18
> 34/ 18 34/ 18
> As can be seen in the test results, although the higher-inductance models
> have greater RSSI readings across
> the band, the S/N readings are remarkably similar for all four models (and
> are a more accurate indicator of
> actual signal strength). The lower-inductance models have a very slight
> drop off in S/N readings at the extreme
> low end of the band, while the 544 uh inductance model could not produce
> an S/N reading at the (out-of-band)
> ffrequency of 1706 kHz. Despite these minor differences, all four coil
> designs essentially have equal performance across the MW frequency spectrum,
> and all four would be very viable choices to greatly boost the DXing
> performance of the Tecsun PL-380 model. Detailed assembly instructions for
> all four coil types will be contained
> in the revised PL:-380 7.5" loopstick transplant article, and all four
> test models will be retained here for future
> reference.
> The above test models were constructed in a serious effort to inform
> everyone of the actual experimental
> performance of the different coil designs, an effort which required
> significant time and expense. I feel confident
> that the results are accurate and trustworthy, and that I have gone the
> "extra mile" to promote mutual
> understanding. If someone refuses to accept the results, it certainly
> won't ruin my day :-) I have respect
> for those with differing opinions, but do suggest that they perform some
> actual PL-380 7.5" loopstick
> experimentation for greater mutual understanding.
> 73, Gary DeBock (in Puyallup, WA, USA)
>
>
> . In a message dated 4/19/2010 7:19:38 A.M. Pacific Daylight Time,
> sdwillingham@... writes:
>
> Those of us who have measured the resonance have seen that it works
> correctly. Gary's later comprehensive measurements also confirm that 300uH,
> 400uH, and 500uH loopsticks all "track" (the 500 starts to fail a touch at the
> high end) and further, they all have nearly the same RSSI within a dB or
> two. Graham further states that his transplant loopstick has 10 dB more gain
> across the band, but provides no objective data for that.
>


Re: Graham Maynard's Tecsun PL-380 Modification Article

Roy <roy.dyball@...>
 

Hi Jim,

Just read your description on how you test that the loopstick is resonating and performing correctly into the high end of the band. I agree that this would work well and should be applied as a final check, allowing confidence that the Si4734 is working to its maximum design criteria.

I like you have never had good results with high inductance coils (for me above 350uH) finding that by winding them any larger all you are doing is increasing the capacitance which is now working against you to stop the coil resonating at the top of the band. I find the bigger coils (above 400uH) give you a bloated RSSI figures with no improvement in S/N across the MW band. The listening experience is not as good and harsher on the ears. Yes use the bigger coil if you are interested in the low end of the MW band and want better LW performance.

The Pl-380 is a great little radio and is designed for capitol city sales (bigger market) where AM signals are at a reasonable level. The Tecsun engineers are not as silly as you think and they know what they are doing. The ferrite rod in the PL-380 is very thin and has in its standard winding configuration about 10pf more capacitance than other larger loopsticks, adding additional turns to this loopstick will increase the capacitance , a fully wound PL-380 ferrite rod would have a very high capacitance and that's why the Tecsun have chosen the values that we have. When you have a properly matched loopstick combination in these little radios the listening experience is obvious and a joy to the ears, but a bigger (inductance) coil is not always better.

I feel compelled to publish my results as I believe them to be correct and I know that not everybody will agree. Just as I expect and welcome criticism of my results because it matters not if I am wrong. Similarly I reserve the right to question other people's results not in any other way but with respect.

Cheers Roy.

--- In ultralightdx@..., "jim_kr1s" wrote:
>
>
> --- In ultralightdx@..., "sdwillingham" sdwillingham@
> wrote:
>
> > Summarizing, I agree that loopsticks pushing 500 uH will be fine in MW
> and give some extension to LW performance.
>
> Scott,
>
> I'll summarize my measurement method because I know you'll understand
> it. I'll be glad to email a detailed explanation to anyone who asks.
>
> Couple a stable signal generator and a measuring device -- which can be
> another ULR, an rf voltmeter (I used a selective rf voltmeter also
> loosely coupled). or a scope -- into the antenna
>
> Tune receiver under test and signal generator to, say, 1500 kHz. Observe
> voltage.
>
> Leaving signal generator tuned to 1500 kHz, tune receiver under test
> higher in frequency. The voltage should drop as the LC circuit is tuned
> out of resonance at 1500 kHz.
>
> If the voltage does not drop within a few kHz, it implies that the
> tuning capacitance has reached its minimum and the radio cannot tune
> that inductor to a higher frequency.
>
> My tests with a 550-uH coil showed it could not be resonated in the
> upper part of the MW band. RSSI readings across the band were higher
> than with the stock antenna. This is deceiving, and I attribute it to
> higher reactance. But the peaking effect of resonance was absent. I note
> that coupling the antenna to a large, separately tuned loop antenna will
> provide the higher frequency selectivity lost by using the larger
> antenna coil. Any 240-uH coil I've tried peaks well anywhere from
> 530-1710 kHz, and that's the value I've been using for MW.
>
> As you mentioned to Stephen, a larger coil delivering more signal to the
> receiver on the low end of the band, where it resonates, can create a
> new set of problems in areas where there are more strong local stations
> than are found in the Seattle area, such as in San Diego, and Stuart,
> Florida.
>
> 73,
>
> Jim, KR1S
> http://kr1s.kearman.com/ > http://qrp.kearman.com/
>


Re: Opinions of IDEAL inductance for MW and for LW PL-360?

jim_kr1s <jkearman@...>
 


--- In ultralightdx@..., "farmerik" wrote:
>
>
> I ran the numbers for a 40 X 40 inch square loop, with 1/3 inch spacing, and came up with 24 turns for 2208 uH. That should do. It looks like my 4 foot loop is around 3500 uH. - FARMERIK

That's not bad, only a bit less than a half pound of #28 wire, at 320 feet, about $18.00. The Hoop Loop has 19 feet of wire, and the transformer has less than 30 feet. The toroid cost $7.00 and the Hoop Loop cost $10.00. So I guess you're getting a bargain. Let us know how it works.

73,

Jim, KR1S
http://kr1s.kearman.com/ 
http://qrp.kearman.com/ 


Re: Opinions of IDEAL inductance for MW and for LW PL-360?

Rik
 

With 7 turns, that loop would be perfect for AM.- FARMERIK

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


I ran the numbers for a 40 X 40 inch square loop, with 1/3 inch spacing, and came up with 24 turns for 2208 uH. That should do. It looks like my 4 foot loop is around 3500 uH. - FARMERIK


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


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

If I wanted to wind an inductive loop antenna to be connected directly
to the PL-360, [no lead wire, no cap] what should the values be for MW
and for LW ? - FARMERIK

You never struck me as the agent provocateur type. :)

By now you've seen everyone's comments on MW antennas. For LW, you can
calculate based on the predicted maximum C of the radio's tuning cap.
The SiLabs data sheet says the chip will tune inductances as low as 180
uH on MW. Assuming it will tune a 180-uH inductance down to 530 kHz, its
maximum capacitance is 500 pF.

The inductance that resonates with 500 pF at 153 kHz is 2164 uH. Give
yourself a little leeway and figure 2200 uH. That inductance will more
than cover the full LW band and beyond. WHYN in Springfield will make
your radio glow in the dark.

For a -61 ferrite rod you'll need about 175 turns, about 23 feet of
wire. Using #24 or #28 wire, it will fit nicely on a 7.5-inch rod. Don't
even think about making an air-core loop that big, unless you own stock
in a copper mine. You won't be hanging that one from your ceiling,
either! If you want an air-core loop you'll have to use a transformer.
(The usual practice for tuned air-core LW loops is to use combinations
of very large fixed and variable capacitors that will resonate with a
smaller, practical loop inductance.)

The transformers I've used on LW varied from 2650 to 3500 uH. As we
know, higher reactance yields greater signal strengths. These
inductances work well on the LWBC band, which is 153-279 kHz, and that's
where my interest lies. There is far less adjacent-channel interference
on LWBC, and the Hoop Loop is small for that band, so I figured a bit
more gain wouldn't hurt, as it might on MW. A 3500-uH inductor just
covers the entire LW band, including beacons, and that's what I'm
currently using. RSSI indications on European and North African LWBC
stations run 20-45 dBu, but remember, I'm only 6-10 miles from the
ocean.

73,

Jim, KR1s
http://kr1s.kearman.com/ <http://kr1s.kearman.com/>
http://qrp.kearman.com/ <http://qrp.kearman.com/>


Re: Opinions of IDEAL inductance for MW and for LW PL-360?

Rik
 

I ran the numbers for a 40 X 40 inch square loop, with 1/3 inch spacing, and came up with 24 turns for 2208 uH. That should do. It looks like my 4 foot loop is around 3500 uH. - FARMERIK

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


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

If I wanted to wind an inductive loop antenna to be connected directly
to the PL-360, [no lead wire, no cap] what should the values be for MW
and for LW ? - FARMERIK

You never struck me as the agent provocateur type. :)

By now you've seen everyone's comments on MW antennas. For LW, you can
calculate based on the predicted maximum C of the radio's tuning cap.
The SiLabs data sheet says the chip will tune inductances as low as 180
uH on MW. Assuming it will tune a 180-uH inductance down to 530 kHz, its
maximum capacitance is 500 pF.

The inductance that resonates with 500 pF at 153 kHz is 2164 uH. Give
yourself a little leeway and figure 2200 uH. That inductance will more
than cover the full LW band and beyond. WHYN in Springfield will make
your radio glow in the dark.

For a -61 ferrite rod you'll need about 175 turns, about 23 feet of
wire. Using #24 or #28 wire, it will fit nicely on a 7.5-inch rod. Don't
even think about making an air-core loop that big, unless you own stock
in a copper mine. You won't be hanging that one from your ceiling,
either! If you want an air-core loop you'll have to use a transformer.
(The usual practice for tuned air-core LW loops is to use combinations
of very large fixed and variable capacitors that will resonate with a
smaller, practical loop inductance.)

The transformers I've used on LW varied from 2650 to 3500 uH. As we
know, higher reactance yields greater signal strengths. These
inductances work well on the LWBC band, which is 153-279 kHz, and that's
where my interest lies. There is far less adjacent-channel interference
on LWBC, and the Hoop Loop is small for that band, so I figured a bit
more gain wouldn't hurt, as it might on MW. A 3500-uH inductor just
covers the entire LW band, including beacons, and that's what I'm
currently using. RSSI indications on European and North African LWBC
stations run 20-45 dBu, but remember, I'm only 6-10 miles from the
ocean.

73,

Jim, KR1s
http://kr1s.kearman.com/ <http://kr1s.kearman.com/>
http://qrp.kearman.com/ <http://qrp.kearman.com/>


Re: Opinions of IDEAL inductance for MW and for LW PL-360?

jim_kr1s <jkearman@...>
 


--- In ultralightdx@..., "farmerik" wrote:
>
> If I wanted to wind an inductive loop antenna to be connected directly to the PL-360, [no lead wire, no cap] what should the values be for MW and for LW ? - FARMERIK

You never struck me as the agent provocateur type. :)

By now you've seen everyone's comments on MW antennas. For LW, you can calculate based on the predicted maximum C of the radio's tuning cap. The SiLabs data sheet says the chip will tune inductances as low as 180 uH on MW. Assuming it will tune a 180-uH inductance down to 530 kHz, its maximum capacitance is 500 pF.

The inductance that resonates with 500 pF at 153 kHz is 2164 uH. Give yourself a little leeway and figure 2200 uH. That inductance  will more than cover the full LW band and beyond. WHYN in  Springfield will make your radio glow in the dark.

For a -61 ferrite rod you'll need about 175 turns, about 23 feet of wire. Using #24 or #28 wire, it will fit nicely on a 7.5-inch rod. Don't even think about making an air-core loop that big, unless you own stock in a copper mine. You won't be hanging that one from your ceiling, either! If you want an air-core loop you'll have to use a transformer. (The usual practice for tuned air-core LW loops is to use combinations of very large fixed and variable capacitors that will resonate with a smaller, practical loop inductance.)

The transformers I've used on LW varied from 2650 to 3500 uH. As we know, higher reactance yields greater signal strengths. These inductances work well on the LWBC band, which is 153-279 kHz, and that's where my interest lies. There is far less adjacent-channel interference on LWBC, and the Hoop Loop is small for that band, so I figured a bit more gain wouldn't hurt, as it might on MW. A 3500-uH inductor just covers the entire LW band, including beacons, and that's what I'm currently using. RSSI indications on European and North African LWBC stations run 20-45 dBu,  but remember, I'm only 6-10 miles from the ocean.

73,

Jim, KR1s
http://kr1s.kearman.com/ 
http://qrp.kearman.com/ 


Re: Graham Maynard's Tecsun PL-380 Modification Article

Gary DeBock
 

Hello All,
 
Scott is referring to comprehensive measurements performed here on four different 7.5" loopstick PL-380 test models of varying inductances and coil configurations, using both signal generator and live signal inputs. These results have been shared already with those who have made significant contributions to the 7.5" loopstick experimentation (Roy, Scott, Guy, and Nick),  as well as with the recipients of 7.5" loopstick PL-380 models prepared here.
 
Scott's summary is essentially correct, although it was the 554 uh model that had an indication of varactor lock-up on the (out-of-band) frequency of 1706 kHz. The 500 uh model had unsurpassed RSSI and S/N performance throughout the MW frequency spectrum, and based upon this fact and its performance edge on the LW frequencies, it was chosen as the final configuration for the 7.5" loopstick PL-380 models shipped to others. The test readings are pasted below, contained in the pending revision to the PL-380 7.5" loopstick transplant article:
________________________________________________________________________________________
 
 

High Sensitivity Coil Options   At the suggestion of Scott Willingham (one of the Si4734 design team engineers), various 7.5” loopstick coil inductance models were constructed and tested by the author, to determine the relative coil performance at differing inductances and MW frequencies. In addition, two         of the coils were wound in the center of the ferrite bar, to determine if this coil orientation would provide   any advantage in the final RSSI and/or S/N readings on the PL-380’s digital display.

                                                                  

 

 

 

Model Model A- 300 uh (center-wound):  54 turns of 40/44 Litz wire, starting 80 mm from either end of the bar

Model Model B- 400 uh (center-wound):  64 turns of 40/44 Litz wire, starting 78 mm from either end of the bar

Model Model C- 500 uh (offset coil):        75 turns of 40/44 Litz wire, starting 41 mm from closest end of the bar

Model Model D- 554 uh (offset coil):        81 turns of 40/44 Litz wire, starting 42 mm from closest end of the bar

 

These four test models were extensively compared using both signal generator and live AM signal inputs, in an outdoor environment free from other conducting materials. All the loopsticks had identical plastic mounting frames, with rubber shock mounts isolating the ferrite bars from the plastic. The TSG-17 signal generator test readings were repeated several times, to ensure stability and accurate results. The stock PL-380 model was also included in several tests as a reference, as well as a PL-380 with the stock ferrite bar rewound with 40/44 Litz wire at a 432 uh inductance (referred to as “Stealth”). The test data (RSSI and S/N) is recorded below:
 

Sig. Gen.Test Freq.   Stock       Stealth   300 uh Model   400 uh Model   500 uh Model   554 uh Model 

 

  525 kHz                  15/ 00       17/ 00        24/ 07               24/ 07                26/ 08            27/ 08

  735 kHz                                                   39/ 13               41/ 14                42/14             43/ 14

  1610 kHz                                                 37/ 19               37/ 19                38/ 19            42/ 19

  1706 kHz (out of band)                             35/ 13               36/ 13                36/ 13            41/ 00

 

  Live Station Signals (averaged readings)

                                                                                                                                                              

  620-KPOJ                19/ 11      20/ 15        33/ 20              34/ 20                 34/ 20            35/ 20

  750-KXL                  30/ 00      32/ 00        39/ 13              41/ 13                 43/ 13            43/ 15

  1110-KWDB            24/ 09      29/ 11        35/ 20              36/ 20                 37/ 20            39/ 20

  1600-KVRI              24/ 14      25/ 15        32/ 24              34/ 24                 34/ 24            36/ 24

  1640-KDZR             22/ 02      25 03         32/ 18              34/ 18                 34/ 18            34/ 18

 

 As can be seen in the test results, although the higher-inductance models have greater RSSI readings across 

 the band, the S/N readings are remarkably similar for all four models (and are a more accurate indicator of

actual signal strength). The lower-inductance models have a very slight drop off in S/N readings at the extreme

low end of the band, while the 544 uh inductance model could not produce an S/N reading at the (out-of-band)

ffrequency of 1706 kHz. Despite these minor differences, all four coil designs essentially have equal performance across the MW frequency spectrum, and all four would be very viable choices to greatly boost the DXing

performance of the Tecsun PL-380 model. Detailed assembly instructions for all four coil types will be contained

in the revised PL:-380 7.5" loopstick transplant article, and all four test models will be retained here for future 

reference.

 

The above test models were constructed in a serious effort to inform everyone of the actual experimental 

performance of the different coil designs, an effort which required significant time and expense. I feel confident 

that the results are accurate and trustworthy, and that I have gone the "extra mile" to promote mutual 

understanding. If someone refuses to accept the results, it certainly won't ruin my day :-)  I have respect 

for those with differing opinions, but do suggest that they perform some actual PL-380 7.5" loopstick 

experimentation for greater mutual understanding.

 

   73, Gary DeBock (in Puyallup, WA, USA)      

 

 

 . In a message dated 4/19/2010 7:19:38 A.M. Pacific Daylight Time, sdwillingham@... writes:

Those of us who have measured the resonance have seen that it works correctly. Gary's later comprehensive measurements also confirm that 300uH, 400uH, and 500uH loopsticks all "track" (the 500 starts to fail a touch at the high end) and further, they all have nearly the same RSSI within a dB or two. Graham further states that his transplant loopstick has 10 dB more gain across the band, but provides no objective data for that.


KCBQ overloads PL-380 (Re: Tecsun PL-360 3" Loopstick Testing)

jim_kr1s <jkearman@...>
 


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


> Of course if your listening post is a corner of the Living room, you might hear complaints! But white nylon blends in pretty well on a white ceiling [SMILE] - FARMERIK

I live alone, so no one would complain, but I'm not going there. :)

73,

Jim, KR1S
http://kr1s.kearman.com/ 
http://qrp.kearman.com/ 


Re: Graham Maynard's Tecsun PL-380 Modification Article

jim_kr1s <jkearman@...>
 


--- In ultralightdx@..., "sdwillingham" wrote:

> It's all a bit of a tradeoff. The PL-380 tends to have a fairly high stray capacitance on the antenna, but much of that is in the loopstick itself. I think a well-designed 450 uH inductor will reach the top of the band and 500 uH will fall a bit short.

Scott,

The key term is "well-designed." Spacing the turns on an external rod, as I believe Roy did, should reduce self-capacitance and let you go a little higher. Raising the gain does little to improve DX performance here though, because adjacent and on-channel pests and external noise are raised an equal amount. The stronger the signals the more AGC reduces receiver gain. That renders weaker signals inaudible, exactly the opposite of what we want. In some parts of the country it might be okay, but not here.

IMO it's better to keep signal levels farther down, to gain more headroom. You can always turn up the volume, but you can't turn down the AGC (without hacking into the MCU). Improved selectivity improves S+N/N ratio and reduces off-channel interference. For DXing, I place those factors above increased gain. You folks designed the chip for use with tiny antennas, and it already has plenty of gain! What it wants is a sharp tuned circuit in front of it.


> Your measurement method sounds correct to me, as long as your voltmeter or scope coupling is weak enough to keep the loading below a couple picoFarads.

The HP 312B is extremely sensitive, and a short probe a foot away from the antenna is good enough. The 312B has an untuned front end, so there's no risk of mutual coupling. Someone was kind enough to give me a G8 with a defective volume control, and I'm tempted to hack in the USB port. My laptop is quite the crud generator, though, so I've been holding off.

73,

Jim, KR1S
http://kr1s.kearman.com/ 
http://qrp.kearman.com/ 


Opinions of IDEAL inductance for MW and for LW PL-360?

Rik
 

If I wanted to wind an inductive loop antenna to be connected directly to the PL-360, [no lead wire, no cap] what should the values be for MW and for LW ? - FARMERIK


KCBQ overloads PL-380 (Re: Tecsun PL-360 3" Loopstick Testing)

Rik
 

Just a reminder, hanging a loop from the ceiling, and having a series of attachment points allows you to tilt it without a complicated mechanism. One attachment point hangs the antenna vertical, and a few more behind it give different tilts. With a nylon swivel, made for key chains, it's easy to point, and when you are done, a hooking place on the bottom allows you to stow it horizontal near the ceiling. That is how I normally use my 4 foot loop. I only drop it down for directional work.
Of course if your listening post is a corner of the Living room, you might hear complaints! But white nylon blends in pretty well on a white ceiling [SMILE] - FARMERIK

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


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


To test the balance of your balun, I suggest just doing a common-mode
measurement. Connect both sides of your primary (antenna side) to the
signal generator. The ground of the generator to a ground plane.
Connect one side of the secondary to ground and the other to your 'scope
or spectrum analyzer. You want the smallest signal possible relative to
the alternative of wiring the primary between generator and ground.

Scott,

Thanks for the suggestion. The light went on as soon as I read it. I
tried a few variations of winding the primary, but the one that did best
(about 15 dB better isolation than any other configuration) was with
the primary turns evenly spaced around the secondary. That doesn't agree
with your earlier suggestion, so I want to keep trying. A close-wound
coil offset as much as possible from either end of the secondary (which
would seem to give the least capacitive coupling) wasn't as good.

Was thinking of winding a new transformer as a bifilar 4:1. To match the
Hoop Loop the high-Z part has to be 256 uH. Not sure that will tune all
the way up, but will be worth it to get a benchmark.

With the loop disconnected and with the primary shorted or open, only
two local stations at 1450 and 1590 get through. Those are the ones that
make me want to shield the coil. Even with the secondary connection
shielded, the toroid still gets plenty of signal. This is an
improvement though, as before, a few other stations leaked in. One
notable absentee was a pest down the road on 760. If I could knock them
down and tilt-null WSB on 750, maybe I could hear KOA! I think the
high-band stations are still strong because the coil's reactance is
about twice as high up there.

It got into sunset time so I couldn't compare null depth measurements
made earlier, but my sense is they are deeper because a greater
percentage of signal is coming only from the antenna. Shorting the
antenna at its feed point after peaking the radio, I don't hear any
additional stations.


But here's what I found out: you need to adjust the altitude (vertical
tilt) of the loop to get better than a few dB nulls. Just a vertical
loop will not do all that well.

Chris Knight has been after me about that. I had an alt-az 4-footer in
Connecticut, which was good at nulling every Nutmegger's favorite
station, WTIC. Tilting the Hoop Loop last night I found a few stations
where it helped, and the null of the tilt is, as you say, very sharp.
Couldn't hold the antenna steady and the signals were fading, but on
some stations the nulls were better than 30 dB.

It'll be easy to elevate the hoop from the base and add a hinge, by
extending the screw that tightens the outer hoop, so V 2.0 is underway.

73,

Jim, KR1S
http://kr1s.kearman.com/ <http://kr1s.kearman.com/>
http://qrp.kearman.com/ <http://qrp.kearman.com/>