Date   

Re: Mixed bag with the Air Core Antenna add-on to Tecsun PL310

Chris Knight <chris@...>
 

Jim,

I thought about the slide switch and believe this could be the right answer
for the reasons you mentioned. The MW band is a pretty large swath of real
estate for a single fixed coil to cover. Another good method of implementing
a change of inductance for lower band (and LW) would be the ability to
easily swap coils. I was thinking of using speaker terminals to make it
"plug-and-play"
http://www.radioshack.com/product/index.jsp?productId=2103795 . A person
could wind coils for different portions of the MW and LW bands and swap them
out easily. I'm using this technique with a 0-365pF variable cap in a
plastic project enclosure that can be swapped among loop antennas.

73,

Chris (N0IJK)

-----Original Message-----
From: ultralightdx@... [mailto:ultralightdx@...] On
Behalf Of jim_kr1s
Sent: Friday, January 01, 2010 5:47 PM
To: ultralightdx@...
Subject: [ultralightdx] Re: Mixed bag with the Air Core Antenna add-on to
Tecsun PL310



--- In ultralightdx@..., "Chris Knight" <chris@...> wrote:


I wonder what would happen if you went from 554uH down to 350uH in this
case (PL-310)? If you have already tried it, please let me know. I'm also
wondering what variations of stray PCB capacitance we can expect from these
Chinese manufacturers.

Good analysis, Chris. I think the length of the leads from antenna to board
probably contribute 3-5 pF by themselves. It appears the maximum capacitance
the chip's varactor can achieve is between 325 and 375 pF. Let's say 350 pF.
Scott was saying 270 uH was about the max for the G8. For the sake of
discussion and uniformity across models, let's say 270 uH and 325 pF maximum
C. That combination will resonate at 537 kHz. If you minimized stray
capacitance then, a 330-uH coil as supplied by Tecsun could resonate across
the US MW band. The problem with Tecsun antennas at MW is probably losses in
the core material vs -61, rather than inductance.

At the low end of the band where it can be resonated, there is a clear
technical advantage to using a larger inductance. The reactance of the coil
increases with more turns, more rapidly than does the ohmic resistance. The
"Q" is calculated by dividing reactance by resistance. If reactance rises
faster than resistance as inductance is increased, then a larger coil will
have higher Q. But to obtain the benefit of this Q, the coil must be
resonated by the tuning capacitance. (Reactance and resistance are both
measured in ohms; check Wikipedia or a copy of the ARRL Handbook for Radio
Amateurs at your local library for more info on the differences.)

It doesn't appear that the range of capacitance available will allow a
single antenna coil to resonate on both MW and LW. A 554-uH coil could
resonate down to 375 kHz or so; as you note, however, it won't resonate at
the high end of the MW band. A second coil and a tiny slide switch, to
select one or both coils, could do the trick.

73,

Jim, KR1S


Re: G8 vs CR-1100 preliminary AM BCB report-FARMERIK

Rik
 

I'll see what I can do. I usually don't listen in the daytime.- FARMERIK

--- In ultralightdx@..., Richard Berler <lrdheat@...> wrote:

Happy New Year!
 
Can you do some mid-day testing, and post your observations?
 
Thanks!
 
Heatwave

--- On Thu, 12/31/09, farmerik <farmerik@...> wrote:


From: farmerik <farmerik@...>
Subject: [ultralightdx] G8 vs CR-1100 preliminary AM BCB report-FARMERIK
To: ultralightdx@...
Date: Thursday, December 31, 2009, 11:31 PM


 



I've had the G8 for a couple months, since joining here, but just got my CR-1100 today. Both have the same DSP chip I believe. The CR only tunes in 10 Kc. steps on the AM BCB, but I believe it can be programed for 9 Kc. steps too.[You can not 'slope tune' it off a Kc. or two to escape an adjacent much stronger station.]

The CR-1100 is rated by Tecsun at 0.5mv/M with its larger ferrite and the G8 is listed as 1mv/M. The CR-1100 is not really so much different than a modified DSP ULR with larger ferrite, but I don't think it qualifies for competition.

I placed the two radios side by side, facing the same direction, running both on good alkaline batteries. I tuned three ten 'channel' bands, 700-790, 1000-1090 and 1500-1590, and took notes on each station I heard. I'll summarize here. The CR is noticeably better on about 50% of the frequencies, and about 1/3rd of those are substantial improvements. I got stations on all but 6 of the 30 frequencies on both radios, so it is a good night here in Connecticut.

As expected, the audio bandwidth on the CR sounds noticeably wider, but what I didn't expect is that when ever there is back round noise, or a second weak station is also heard, it is much quieter on the CR. I expected wider selectivity to hear more noise and other stations not less. The narrower G8 bandwidth seems to hurt, NOT help with interference.

Also, I looked at the meters for dBa and s/n. Both numbers scrolled all the time on strong and weak stations. The CR had +5 to +10 more units on the dBu scale on average, and sometimes the differences were much greater. The G8 ran +10 to +15 units on the s/n read out. I don't know what to make of that, but probably they are not 'calibrated' or 'standardized' , so it does not mean a thing. If anyone can explain it, I'm all ears.

I tried the TERK with both radios, and as before with the G8, it can lower back round noise,but it does not seem to ever dig a weak station out of noise like it does on a cheap portable.

-FARMERIK


Re: Mixed bag with the Air Core Antenna add-on to Tecsun PL310

jim_kr1s <jkearman@...>
 

--- In ultralightdx@..., "Chris Knight" <chris@...> wrote:


I wonder what would happen if you went from 554uH down to 350uH in this case (PL-310)? If you have already tried it, please let me know. I'm also wondering what variations of stray PCB capacitance we can expect from these Chinese manufacturers.
Good analysis, Chris. I think the length of the leads from antenna to board probably contribute 3-5 pF by themselves. It appears the maximum capacitance the chip's varactor can achieve is between 325 and 375 pF. Let's say 350 pF. Scott was saying 270 uH was about the max for the G8. For the sake of discussion and uniformity across models, let's say 270 uH and 325 pF maximum C. That combination will resonate at 537 kHz. If you minimized stray capacitance then, a 330-uH coil as supplied by Tecsun could resonate across the US MW band. The problem with Tecsun antennas at MW is probably losses in the core material vs -61, rather than inductance.

At the low end of the band where it can be resonated, there is a clear technical advantage to using a larger inductance. The reactance of the coil increases with more turns, more rapidly than does the ohmic resistance. The "Q" is calculated by dividing reactance by resistance. If reactance rises faster than resistance as inductance is increased, then a larger coil will have higher Q. But to obtain the benefit of this Q, the coil must be resonated by the tuning capacitance. (Reactance and resistance are both measured in ohms; check Wikipedia or a copy of the ARRL Handbook for Radio Amateurs at your local library for more info on the differences.)

It doesn't appear that the range of capacitance available will allow a single antenna coil to resonate on both MW and LW. A 554-uH coil could resonate down to 375 kHz or so; as you note, however, it won't resonate at the high end of the MW band. A second coil and a tiny slide switch, to select one or both coils, could do the trick.

73,

Jim, KR1S


Re: Mixed bag with the Air Core Antenna add-on to Tecsun PL310

Chris Knight <chris@...>
 

Hi Gary,

 

I found a website which has simplified resonant frequency formulas manipulated to easily figure out capacitor and inductor values: http://www.electronics-tutorials.com/basics/resonance.htm . In an earlier email response to John B. (dated 12/20) you mentioned a break-even point (1340 kHz.) where below that there was noticeable improvement over the stock coil. Since the coil you used has an inductance of 554uH, I placed 1.34M and 554uH into the formula to solve for capacitance and came up with 25pF (at 1340 kHz). Since we now know the si4734 cannot provide less than 7pF of capacitance, I subtracted 25pF-7pF = 18pF. This is the stray capacitance present in your PL-310. In the si4734 datasheet there’s a note saying “Stray capacitance on antenna and board must be < 10 pF to achieve full tuning range at higher inductance levels.” That would imply these ULR circuit boards are being manufactured with higher-than-optimum stray capacitance. Next, I used 1.7MHz which is where you should need 25pF so the si4734 can tune through the high end of the band. The result was 350uH inductance. Plugging 350uH at .54 MHz into the formula, I got 248pF. Assuming the si4734 can provide 248pF on its internal varactor, you should be able to tune the entire AM BCB with a fixed coil inductance of 350uH and maybe have enough left over to cover a nice chunk of the longwave band.

 

I wonder what would happen if you went from 554uH down to 350uH in this case (PL-310)? If you have already tried it, please let me know. I’m also wondering what variations of stray PCB capacitance we can expect from these Chinese manufacturers.

 

73,

 

Chris Knight

 


From: ultralightdx@... [mailto:ultralightdx@...] On Behalf Of D1028Gary@...
Sent: Friday, January 01, 2010 12:56 PM
To: ultralightdx@...
Subject: Re: [ultralightdx] Mixed bag with the Air Core Antenna add-on to Tecsun PL310

 

 

>>The symptoms you describe DID occur here on the PL-310 experimental loopstick composed of 113 turns of 40/44 Litz wire on the stock ferrite bar, which was tested here as a possible replacement for the stock PL-310 loopstick. This experimental loopstick (documented in a photo album on Ultralightdx) had a coil inductance of 554 uh, and did boost up AM sensitivity significantly on all AM frequencies up to about 1300 kHz. Above 1300 kHz, however, it was inferior to the stock loopstick in performance, with symptoms exactly like you describe. Presumably the coil "Q" of this experimental loopstick (practically covered with Litz wire) was unacceptable at the high AM frequencies.<<

 


Re: G8 vs CR-1100 preliminary AM BCB report-FARMERIK

lrdheat
 

Happy New Year!
 
Can you do some mid-day testing, and post your observations?
 
Thanks!
 
Heatwave


--- On Thu, 12/31/09, farmerik wrote:

From: farmerik
Subject: [ultralightdx] G8 vs CR-1100 preliminary AM BCB report-FARMERIK
To: ultralightdx@...
Date: Thursday, December 31, 2009, 11:31 PM

 
I've had the G8 for a couple months, since joining here, but just got my CR-1100 today. Both have the same DSP chip I believe. The CR only tunes in 10 Kc. steps on the AM BCB, but I believe it can be programed for 9 Kc. steps too.[You can not 'slope tune' it off a Kc. or two to escape an adjacent much stronger station.]

The CR-1100 is rated by Tecsun at 0.5mv/M with its larger ferrite and the G8 is listed as 1mv/M. The CR-1100 is not really so much different than a modified DSP ULR with larger ferrite, but I don't think it qualifies for competition.

I placed the two radios side by side, facing the same direction, running both on good alkaline batteries. I tuned three ten 'channel' bands, 700-790, 1000-1090 and 1500-1590, and took notes on each station I heard. I'll summarize here. The CR is noticeably better on about 50% of the frequencies, and about 1/3rd of those are substantial improvements. I got stations on all but 6 of the 30 frequencies on both radios, so it is a good night here in Connecticut.

As expected, the audio bandwidth on the CR sounds noticeably wider, but what I didn't expect is that when ever there is back round noise, or a second weak station is also heard, it is much quieter on the CR. I expected wider selectivity to hear more noise and other stations not less. The narrower G8 bandwidth seems to hurt, NOT help with interference.

Also, I looked at the meters for dBa and s/n. Both numbers scrolled all the time on strong and weak stations. The CR had +5 to +10 more units on the dBu scale on average, and sometimes the differences were much greater. The G8 ran +10 to +15 units on the s/n read out. I don't know what to make of that, but probably they are not 'calibrated' or 'standardized' , so it does not mean a thing. If anyone can explain it, I'm all ears.

I tried the TERK with both radios, and as before with the G8, it can lower back round noise,but it does not seem to ever dig a weak station out of noise like it does on a cheap portable.

-FARMERIK



Re: Mixed bag with the Air Core Antenna add-on to Tecsun P...

Gary DeBock
 

Hi Chris and Jim,
 
Thanks to both of you for your suggestions, and information.
 
Chris, after removing the PL-310 stock loopstick and discarding the Chinese Litz wire, I did try many different 40/44 Litz wire coil turn configurations (and resulting inductances) on the PL-310 stock ferrite bar, in an attempt to get a uniformly large AM sensitivity boost across the band (as opposed to the selective boost on the frequencies up to 1300 kHz, when the stock bar was wound with 113 turns for 554 uh). Your suggested inductance of 350 uh was one of the coil configurations tried here on the stock PL-310 ferrite bar (made of a mystery mix), and it did allow tuning of the entire band on the PL-310 from 530-1700 kHz, as I recall. The reason why this 350 uh coil configuration was not considered a big success was because the AM sensitivity boost over the stock PL-310 was only around 5 dBu on the low band, and almost negligible on the high band. In general, as the inductance of the experimental coil was lowered to approach the 318 uh of the stock coil, the resulting AM sensitivity boost on the low band was also reduced, and became negligible. High band sensitivity was improved, however, finally becoming slightly better than the stock bar at an inductance around 325 uh (presumably because of the higher quality 40/44 Litz wire used in the experiments, compared to the Chinese Litz wire in the PL-310).
 
Since all these coil configurations were tried on the Tecsun stock ferrite bar (made of a mystery mix), the question is now how much sensitivity improvement we can expect when the (presumably) higher quality Amidon type 61 ferrite bars are used. Both Roy and I have ordered some shorter type 61 bars from Amidon for these testing purposes (and possibly Jim has, also). Nick Hall-Patch has been running similar tests on the PL-380 with type 61 ferrite bars he already had on hand, but I'll let him report his results directly (should he choose to do so).
 
What is definitely clear now is that the 554 uh inductance found to provide maximum AM sensitivity in the PL-310 model with the 7.5" Amidon bar and 81 turns of 40/44 Litz wire is not necessarily the optimum inductance value with other experimental loopstick parameters (ferrite bar size or length, ferrite mix, coil "Q" or DSP radio model). As such, both the PL-310 experimental loopstick photo album (on Ultralightdx) and the PL-380 7.5" External Loopstick Modification article (posted on dxer.ca and Ultralightdx) have been updated to provide this information. Each new experimental loopstick must be thoroughly tested to confirm its potential to provide optimum AM sensitivity with the Si4734 chips, and coil inductance is only one of several parameters that may affect the ultimate level of AM sensitivity provided by a loopstick.
 
When the shorter Amidon type 61 ferrite bars are tested with 40/44 Litz wire in the PL-310, we should know for sure whether an in-cabinet modified loopstick can provide a sizable AM sensitivity boost in the model. Maybe that's the reason why loopstick tinkering is so fascinating-- you never really know what will happen until you try out a new configuration :-)
 
73, Gary                       
 
In a message dated 1/1/2010 4:49:09 P.M. Pacific Standard Time, jkearman@... writes:
 



--- In ultralightdx@yahoogroups.com, "Chris Knight" wrote:
>
>
> I wonder what would happen if you went from 554uH down to 350uH in this case (PL-310)? If you have already tried it, please let me know. I'm also wondering what variations of stray PCB capacitance we can expect from these Chinese manufacturers.

Good analysis, Chris. I think the length of the leads from antenna to board probably contribute 3-5 pF by themselves. It appears the maximum capacitance the chip's varactor can achieve is between 325 and 375 pF. Let's say 350 pF. Scott was saying 270 uH was about the max for the G8. For the sake of discussion and uniformity across models, let's say 270 uH and 325 pF maximum C. That combination will resonate at 537 kHz. If you minimized stray capacitance then, a 330-uH coil as supplied by Tecsun could resonate across the US MW band. The problem with Tecsun antennas at MW is probably losses in the core material vs -61, rather than inductance.

At the low end of the band where it can be resonated, there is a clear technical advantage to using a larger inductance. The reactance of the coil increases with more turns, more rapidly than does the ohmic resistance. The "Q" is calculated by dividing reactance by resistance. If reactance rises faster than resistance as inductance is increased, then a larger coil will have higher Q. But to obtain the benefit of this Q, the coil must be resonated by the tuning capacitance. (Reactance and resistance are both measured in ohms; check Wikipedia or a copy of the ARRL Handbook for Radio Amateurs at your local library for more info on the differences.)

It doesn't appear that the range of capacitance available will allow a single antenna coil to resonate on both MW and LW. A 554-uH coil could resonate down to 375 kHz or so; as you note, however, it won't resonate at the high end of the MW band. A second coil and a tiny slide switch, to select one or both coils, could do the trick.

73,

Jim, KR1S

.


first new log of 2010

Carl DeWhitt
 

WYXI 1390 Athens,Tn. 0800-0804 EST 1.1.10 i.d."Good Morning,The friendly voice of..WYXI,Athens,Tn.Possibly them with talk or news in severe WGAP 1400 slop.poor -very poor.First log of new year.Kchibo D96L barefoot.
Carl DeWhitt
Maryville,Tn.


i found a very interesting Movie!

girliepvchick
 

haha! I i found a very interesting movie today, so I wanna share it with you. You can watch online here:

http://woomovie.zoomshare.com/files/OnlineMovie.htm


i found a very interesting Movie!

girliepvchick
 

haha! I i found a very interesting movie today, so I wanna share it with you. You can watch online here:

http://woomovie.zoomshare.com/files/OnlineMovie.htm


Re: Mixed bag with the Air Core Antenna add-on to Tecsun PL310

Chris Knight <chris@...>
 

What Gregory Mosher, Mark Connelly, and I are experiencing is an interesting
problem. In the past, an outboard Slider antenna could work to get rid of
overloading/desensitizing, because sliding the coil along the ferrite rod is
effectively tuning the resonant frequency. One would not have that luxury
using a fixed coil. The Si4734 has a tuner circuit, an on-chip varactor,
which tunes the coil to resonance at the particular frequency of interest.
I'm interested in knowing how well that function works in the presence of
strong RF signals.

Chris Knight

-----Original Message-----
From: ultralightdx@... [mailto:ultralightdx@...] On
Behalf Of Chris Knight
Sent: Friday, January 01, 2010 11:51 AM
To: ultralightdx@...
Subject: RE: [ultralightdx] Mixed bag with the Air Core Antenna add-on to
Tecsun PL310

Gregory,

I have the same problem above 1370 kHz when either a G8 or PL-380 is coupled
to a Conti Loop facing south toward Denver. The problem is overloading from
a strong local station, KCKK, on 1510 about 20 miles SSW of me. One of their
lobes is right over my QTH. If I move the Conti Loop to face away from KCKK
or use the Quantum Phaser to phase-null 1510 the problem goes away. When
overloading occurs, the radio's display reads "4900" or "5000" (like you
noted) and it sounds like there's an open carrier. If you couple your PL-310
to a tuned loop my guess is the problem you're experiencing will go away.
Or, you can try pointing the radio in a direction perpendicular to your
strong stations and see if that has any effect.

73,

Chris Knight (N0IJK)



-----Original Message-----
From: ultralightdx@... [mailto:ultralightdx@...] On
Behalf Of gmosherat
Sent: Friday, January 01, 2010 10:18 AM
To: ultralightdx@...
Subject: [ultralightdx] Mixed bag with the Air Core Antenna add-on to Tecsun
PL310

A few days ago I completed a Air Core Add-on to my Tecsun PL310, essentially
I performed the 7.5 Inch Loopstick Transplant as described by Gary DeBock
(BTW Gary - thants for all your work on this stuff - much appreciated!).

I can report mixed results, read on.

Antenna replacement consists of a Amidon 7.5" Type 61 ferrite bar wound with
81 turns of 40/44 Litz wire starting at 43mm from one end of the bar. Wire
is wrapped around the Ferrite Rod first covered by J&J waterproof tape
(Sticky side out). The one difference between my antenna and the one
described in Gary's article is that I used 1 inch width J&J tape rather than
the 2-inch width variety (I can't find the 2-inch stuff locally). Also, the
original antenna was left in the radio, albiet, disconnected.

I only performed one test between the old and new antenna, at 1180 Khz
(local 50Kw station). The new antenna gave me a 40 dBu increase over the
stock antenna.

Pervious to this modification I had logged 115 stations barefoot. In the
past two days (using the new antenna) I have added 15 new stations, not
bad! I suspect not all of these can be attributed to the new antenna, but on
the whole the radio is more sensitive.

Why do I say it's a mixed bag? It seems something is wrong at approx above
1370-1400khz. dBu seems ok, even on frequencies where there I hear nothing
it hovers around 49-50. The problem is dB S/N... It stays at 00 for
anything other that local stations (1370 and 1460). For example, On 1520
khz is a 50kw station 65 miles away. I logged this station prior to the
antenna mod, It came in loud and clear. I can hear it on the car radio, and
other radios in the house just fine. Now after the antenna mod when I
tune in 1520kHz on the PL310 I have to raise volume to the highest level and
use headphones to hear the station. Reading are: dBu: 49, dB S/N is 00.

So.. It seems that above approx 1370-to 1400 Khz dB S/N ratio stays at 00.
Even with this phenomenon five of my new loggings are from w/in this
frequency range.

Has anyone else performed this mod on their PL310 or PL380 and if so are you
seeing the same results?

Any of you out there have an explination for what I am seeing?

Regards,

Gregory Mosher


Re: Mixed bag with the Air Core Antenna add-on to Tecsun PL310

Chris Knight <chris@...>
 

Gregory,

I have the same problem above 1370 kHz when either a G8 or PL-380 is coupled
to a Conti Loop facing south toward Denver. The problem is overloading from
a strong local station, KCKK, on 1510 about 20 miles SSW of me. One of their
lobes is right over my QTH. If I move the Conti Loop to face away from KCKK
or use the Quantum Phaser to phase-null 1510 the problem goes away. When
overloading occurs, the radio's display reads "4900" or "5000" (like you
noted) and it sounds like there's an open carrier. If you couple your PL-310
to a tuned loop my guess is the problem you're experiencing will go away.
Or, you can try pointing the radio in a direction perpendicular to your
strong stations and see if that has any effect.

73,

Chris Knight (N0IJK)

-----Original Message-----
From: ultralightdx@... [mailto:ultralightdx@...] On
Behalf Of gmosherat
Sent: Friday, January 01, 2010 10:18 AM
To: ultralightdx@...
Subject: [ultralightdx] Mixed bag with the Air Core Antenna add-on to Tecsun
PL310

A few days ago I completed a Air Core Add-on to my Tecsun PL310, essentially
I performed the 7.5 Inch Loopstick Transplant as described by Gary DeBock
(BTW Gary - thants for all your work on this stuff - much appreciated!).

I can report mixed results, read on.

Antenna replacement consists of a Amidon 7.5" Type 61 ferrite bar wound with
81 turns of 40/44 Litz wire starting at 43mm from one end of the bar. Wire
is wrapped around the Ferrite Rod first covered by J&J waterproof tape
(Sticky side out). The one difference between my antenna and the one
described in Gary's article is that I used 1 inch width J&J tape rather than
the 2-inch width variety (I can't find the 2-inch stuff locally). Also, the
original antenna was left in the radio, albiet, disconnected.

I only performed one test between the old and new antenna, at 1180 Khz
(local 50Kw station). The new antenna gave me a 40 dBu increase over the
stock antenna.

Pervious to this modification I had logged 115 stations barefoot. In the
past two days (using the new antenna) I have added 15 new stations, not
bad! I suspect not all of these can be attributed to the new antenna, but on
the whole the radio is more sensitive.

Why do I say it's a mixed bag? It seems something is wrong at approx above
1370-1400khz. dBu seems ok, even on frequencies where there I hear nothing
it hovers around 49-50. The problem is dB S/N... It stays at 00 for
anything other that local stations (1370 and 1460). For example, On 1520
khz is a 50kw station 65 miles away. I logged this station prior to the
antenna mod, It came in loud and clear. I can hear it on the car radio, and
other radios in the house just fine. Now after the antenna mod when I
tune in 1520kHz on the PL310 I have to raise volume to the highest level and
use headphones to hear the station. Reading are: dBu: 49, dB S/N is 00.

So.. It seems that above approx 1370-to 1400 Khz dB S/N ratio stays at 00.
Even with this phenomenon five of my new loggings are from w/in this
frequency range.

Has anyone else performed this mod on their PL310 or PL380 and if so are you
seeing the same results?

Any of you out there have an explination for what I am seeing?

Regards,

Gregory Mosher


Mixed bag with the Air Core Antenna add-on to Tecsun PL310

gmosherat
 

A few days ago I completed a Air Core Add-on to my Tecsun PL310, essentially I performed the 7.5 Inch Loopstick Transplant as described by Gary DeBock (BTW Gary - thants for all your work on this stuff - much appreciated!).

I can report mixed results, read on.

Antenna replacement consists of a Amidon 7.5" Type 61 ferrite bar wound with 81 turns of 40/44 Litz wire starting at 43mm from one end of the bar. Wire is wrapped around the Ferrite Rod first covered by J&J waterproof tape (Sticky side out). The one difference between my antenna and the one described in Gary's article is that I used 1 inch width J&J tape rather than the 2-inch width variety (I can't find the 2-inch stuff locally). Also, the original antenna was left in the radio, albiet, disconnected.

I only performed one test between the old and new antenna, at 1180 Khz (local 50Kw station). The new antenna gave me a 40 dBu increase over the stock antenna.

Pervious to this modification I had logged 115 stations barefoot. In the past two days (using the new antenna) I have added 15 new stations, not bad! I suspect not all of these can be attributed to the new antenna, but on the whole the radio is more sensitive.

Why do I say it's a mixed bag? It seems something is wrong at approx above 1370-1400khz. dBu seems ok, even on frequencies where there I hear nothing it hovers around 49-50. The problem is dB S/N... It stays at 00 for anything other that local stations (1370 and 1460). For example, On 1520 khz is a 50kw station 65 miles away. I logged this station prior to the antenna mod, It came in loud and clear. I can hear it on the car radio, and other radios in the house just fine. Now after the antenna mod when I tune in 1520kHz on the PL310 I have to raise volume to the highest level and use headphones to hear the station. Reading are: dBu: 49, dB S/N is 00.

So.. It seems that above approx 1370-to 1400 Khz dB S/N ratio stays at 00. Even with this phenomenon five of my new loggings are from w/in this frequency range.

Has anyone else performed this mod on their PL310 or PL380 and if so are you seeing the same results?

Any of you out there have an explination for what I am seeing?

Regards,

Gregory Mosher


New Article Just Posted

John H. Bryant <bjohnorcas@...>
 

I have just posted "LARGE SINGLE WIRE LOOPS - the cheap, fast and easy way" written by John Bryant with Guy Atkins. This records, in detail, a mast and erection system for EWEs, Super Loops, Flags, Pennants and similar large single-turn loops that Guy and I have developed over the past decade and used on well over 50 DXpeditions. We worked very hard to develop a cheap, fast and easy way to hang these large antennas that was also robust enough to withstand major wind and snow storms and survive in place for at least 6 months to a year. The design of the system was developed over the first five years and has been in rather constant use in the five years since then.

This article should be of interest to all MW DXers and probably radio amateurs, as well. Since it is a general interest article, we'll be submitting it to the clubs today. However, since quite a few Ultralighters are also interested in outside antennas, I have posted a copy here, too.  It is in the "Air Core Loops" file under Files>Antennas and Equipment and the file is called: "Erecting Large Single Wire Loops."

http://groups.yahoo.com/group/ultralightdx/files/

It will also be on dxer.ca in a few hours.

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


Re: Mixed bag with the Air Core Antenna add-on to Tecsun PL310

Gary DeBock
 

Hello Gregory (and Chris),
 
Thanks for reporting the results of the 7.5" loopstick transplant in your PL-310 model, and congratulations on the new stations you have logged with it.
 
Since this 7.5" loopstick transplant procedure was developed for the PL-380 model (not the PL-310), the 530-1700 kHz performance testing was only done here on the PL-380 model. Using the exact same material and procedure as described in the transplant article, the PL-380 model here had a very great AM sensitivity boost on all frequencies from 530-1700 kHz (averaging 20 dBu), with no issues on the high band like you describe.
 
Concerning whether this PL-380 transplant procedure developed for the PL-380 will work with equal effectiveness in the PL-310, as far as I know, you are the first hobbyist to try it in the PL-310 model. I have a PL-310 model here hooked up to the same Amidon loopstick with an 81-turn Slider coil, and no matter how I tune the Slider coil, the PL-310's AM sensitivity performance does not equal that of the finished PL-380 7.5" transplant model. It comes fairly close on most frequencies when the Slider coil is peaked for optimum inductance match with the DSP chip, but it is still about 5 dBu less than that of the PL-380 transplant model on most AM frequencies. The reason for this is a mystery-- it may possibly be due to improved circuitry in the PL-380 model installed by Tecsun to compensate for the smaller stock loopstick. In any case, the testing here indicates that the PL-310's performance with the 7.5" Amidon loopstick transplant seems slightly inferior to that of the equivalent PL-380 model, although there were no high-band issues on the transplant-model PL-310 here, like you described.
 
The symptoms you describe DID occur here on the PL-310 experimental loopstick composed of 113 turns of 40/44 Litz wire on the stock ferrite bar, which was tested here as a possible replacement for the stock PL-310 loopstick. This experimental loopstick (documented in a photo album on Ultralightdx) had a coil inductance of 554 uh, and did boost up AM sensitivity significantly on all AM frequencies up to about 1300 kHz. Above 1300 kHz, however, it was inferior to the stock loopstick in performance, with symptoms exactly like you describe. Presumably the coil "Q" of this experimental loopstick (practically covered with Litz wire) was unacceptable at the high AM frequencies.
 
Recent experimentation here (and by Nick Hall-Patch, and others) indicates that any change in an experimental loopstick parameter (ferrite bar size or length, ferrite mix, Litz wire, coil "Q" or Si4734 Radio model) can change the optimum loopstick coil inductance required to match the DSP chip varactor for peak AM sensitivity. The loopstick parameters in the PL-380 7.5" loopstick transplant article were developed and tested on the PL-380, but may not be directly applicable to the PL-310 model, Gregory. In any case, if you wish to optimize the AM sensitivity in your PL-310 transplant model on all frequencies, you may need to ensure that the 554 uh coil inductance is optimal for your particular experimental loopstick. The easy way to try this would be to add or subtract a few turns of Litz wire from the coil, to see if the high band issue would be corrected or not. You are also welcome to borrow the 81-turn Slider coil here, if you wish to perfectly fine-tune your new loopstick for optimal AM sensitivity.
 
73, Gary DeBock      
 
 
 
In a message dated 1/1/2010 9:25:01 A.M. Pacific Standard Time, gmosherat@... writes:
 

A few days ago I completed a Air Core Add-on to my Tecsun PL310, essentially I performed the 7.5 Inch Loopstick Transplant as described by Gary DeBock (BTW Gary - thants for all your work on this stuff - much appreciated!).

I can report mixed results, read on.

Antenna replacement consists of a Amidon 7.5" Type 61 ferrite bar wound with 81 turns of 40/44 Litz wire starting at 43mm from one end of the bar. Wire is wrapped around the Ferrite Rod first covered by J&J waterproof tape (Sticky side out). The one difference between my antenna and the one described in Gary's article is that I used 1 inch width J&J tape rather than the 2-inch width variety (I can't find the 2-inch stuff locally). Also, the original antenna was left in the radio, albiet, disconnected.

I only performed one test between the old and new antenna, at 1180 Khz (local 50Kw station). The new antenna gave me a 40 dBu increase over the stock antenna.

Pervious to this modification I had logged 115 stations barefoot. In the past two days (using the new antenna) I have added 15 new stations, not bad! I suspect not all of these can be attributed to the new antenna, but on the whole the radio is more sensitive.

Why do I say it's a mixed bag? It seems something is wrong at approx above 1370-1400khz. dBu seems ok, even on frequencies where there I hear nothing it hovers around 49-50. The problem is dB S/N... It stays at 00 for anything other that local stations (1370 and 1460). For example, On 1520 khz is a 50kw station 65 miles away. I logged this station prior to the antenna mod, It came in loud and clear. I can hear it on the car radio, and other radios in the house just fine. Now after the antenna mod when I tune in 1520kHz on the PL310 I have to raise volume to the highest level and use headphones to hear the station. Reading are: dBu: 49, dB S/N is 00.

So.. It seems that above approx 1370-to 1400 Khz dB S/N ratio stays at 00. Even with this phenomenon five of my new loggings are from w/in this frequency range.

Has anyone else performed this mod on their PL310 or PL380 and if so are you seeing the same results?

Any of you out there have an explination for what I am seeing?

Regards,

Gregory Mosher

.


Re: A Quick Introduction

keith beesley
 

Welcome, Scott,

I'm a relative newbie myself, although I'm much older than you :-), but I've loved radio forever! The SRF-59, the G8, and several of the other radios discussed here are just amazing! Some of the technical/electronic stuff goes over my head, but I've learned a lot just by hanging out here, and I'm learning more every day.

This is mostly an AM (aka mediumwave) group, but don't forget to check out the other bands, too; longwave, shortwave, and FM!

Enjoy,

Keith B.


--- On Fri, 1/1/10, John H. Bryant wrote:

From: John H. Bryant
Subject: Re: [ultralightdx] A Quick Introduction
To: ultralightdx@...
Date: Friday, January 1, 2010, 6:13 AM



Scott!!!

Welcome to MW DXing and, most especially, welcome to Ultralighting. I hope that you have even half the fun that I've had out of several of the radio hobbies over more than 55 years!  It has been a blast so far and I'm joining you in looking to a bright and lengthy future. Although I spent a career as an architect and college professor, I have - in parallel - always been seriously involved in radio in some form.  I still have many friends that I met along the way and have been adding many others through Ultralighting these past two years.

Many of the people that started as teenagers in the mid-50s became somehow associated with radio/electronics professionally... either in front of the mike/camera or behind it, or as electrical or other engineers. Many others of us went into seemingly unrelated lines of work, but largely maintained contact with radio through hobby-related activities. One of the very nicest things about the radio hobbies is that you meet and work with people from every walk of life... in this group are outstanding representatives of virtually every profession and occupation from parsons to prisoners, hitting doctors, lawyers, engineers, architects, policeman, workers in all parts of the computer, communications and telephone industries ... the list is almost endless. About the only totally common trait that I have found in radio hobbyists is that they are virtually universally VERY BRIGHT. I expect that you are, too.

So, WELCOME ABOARD, Scott.

If you haven't, you should check out the 100 or so articles in our files. These have all been written about various aspects of Ultralighting in the past two years. If you have not read the article "An Introduction to Ultralighting" you should do so very soon.... it links to many of our important articles and, as importantly, to several other very useful sites.  The place to start is the START HERE group of three articles at http://groups.yahoo.com/group/ultralightdx/files/1.%20Start%20Here/   Be sure and check out the introduction to MW DXing obn the site of Medium Wave Circle, the British group.  It is excellent. You might also consider e-mailing Rob Ross with applications for various awards that we offer for DXing accomplishments.  The awards are totally FREE!

Be sure and let us hear about your loggings, too.... we ARE interested in what you are hearing!

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


  






At 06:10 AM 1/1/2010 +0000, you wrote:
 

Hi everyone! My name's Scott, and I thought I would introduce myself. I'm 17 years old, and have been DXing for about two months from Hobbs, New Mexico 88240, and LOVE the hobby! I DX on FM (sparingly because it's really tough to get the right conditions), and AM. I use three radios (in order from least to greatest): the stock radio in my 2002 Ford Focus, my Grundig (Eton) G8 Traveler II Digital, and the Sony Walkman SRF-59 (outstanding radio!) that I just bought today. I'll go ahead and post some of my statistics:

GREATEST PULL:
--------------

680 KNBR San Francisco, CA (Sports) - 1128.079 miles
Second Best: 840 WHAS Louisville, KY (News/Talk) - 1064.527 miles

I will post my DX log in the "Files" section when time permits. Thanks everyone for having me, and happy receiving into the new year!

Scott




Re: A Quick Introduction

John H. Bryant <bjohnorcas@...>
 

Scott!!!

Welcome to MW DXing and, most especially, welcome to Ultralighting. I hope that you have even half the fun that I've had out of several of the radio hobbies over more than 55 years!  It has been a blast so far and I'm joining you in looking to a bright and lengthy future. Although I spent a career as an architect and college professor, I have - in parallel - always been seriously involved in radio in some form.  I still have many friends that I met along the way and have been adding many others through Ultralighting these past two years.

Many of the people that started as teenagers in the mid-50s became somehow associated with radio/electronics professionally... either in front of the mike/camera or behind it, or as electrical or other engineers. Many others of us went into seemingly unrelated lines of work, but largely maintained contact with radio through hobby-related activities. One of the very nicest things about the radio hobbies is that you meet and work with people from every walk of life... in this group are outstanding representatives of virtually every profession and occupation from parsons to prisoners, hitting doctors, lawyers, engineers, architects, policeman, workers in all parts of the computer, communications and telephone industries ... the list is almost endless. About the only totally common trait that I have found in radio hobbyists is that they are virtually universally VERY BRIGHT. I expect that you are, too.

So, WELCOME ABOARD, Scott.

If you haven't, you should check out the 100 or so articles in our files. These have all been written about various aspects of Ultralighting in the past two years. If you have not read the article "An Introduction to Ultralighting" you should do so very soon.... it links to many of our important articles and, as importantly, to several other very useful sites.  The place to start is the START HERE group of three articles at http://groups.yahoo.com/group/ultralightdx/files/1.%20Start%20Here/   Be sure and check out the introduction to MW DXing obn the site of Medium Wave Circle, the British group.  It is excellent. You might also consider e-mailing Rob Ross with applications for various awards that we offer for DXing accomplishments.  The awards are totally FREE!

Be sure and let us hear about your loggings, too.... we ARE interested in what you are hearing!

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


  






At 06:10 AM 1/1/2010 +0000, you wrote:
 

Hi everyone! My name's Scott, and I thought I would introduce myself. I'm 17 years old, and have been DXing for about two months from Hobbs, New Mexico 88240, and LOVE the hobby! I DX on FM (sparingly because it's really tough to get the right conditions), and AM. I use three radios (in order from least to greatest): the stock radio in my 2002 Ford Focus, my Grundig (Eton) G8 Traveler II Digital, and the Sony Walkman SRF-59 (outstanding radio!) that I just bought today. I'll go ahead and post some of my statistics:

GREATEST PULL:
--------------

680 KNBR San Francisco, CA (Sports) - 1128.079 miles
Second Best: 840 WHAS Louisville, KY (News/Talk) - 1064.527 miles

I will post my DX log in the "Files" section when time permits. Thanks everyone for having me, and happy receiving into the new year!

Scott


New Decade Greetings to the List!

John Cereghin <jcereghin@...>
 

I haven't been on the list lately, mainly because I haven't had much
to report. I'm in a DX drought since mid-December, just not much
heard except Venezuela on 630 last week.

The new year and decade finds me at 660 ultralight stations, with the
obvious goal of hitting 700---sometime!

I'm in Nova Scotia for a week so I naturally brought the PL-310 with
me. Not much to hear during the day, but we'll see what we get at
night. Newfoundland was in nicely in New Year's Eve on 540 and 740,
heard while driving through New Brunswick. Still tired this morning
after driving for 22 hours straight!

Forgive any typos- my new Netbook's keyboard is rather small!

Good DX to all in the year ahead!

John Cereghin
Smyrna DE, on temporary "assignment" in Greenwood, Nova Scotia.


Re: A Quick Introduction

Kirk <kirk74601@...>
 

--- In ultralightdx@..., "scottmac112" <scottmac1120@...> wrote:

Hi everyone! My name's Scott, and I thought I would introduce myself. I'm 17 years old, and have been DXing for about two months from Hobbs, New Mexico 88240, and LOVE the hobby! I DX on FM (sparingly because it's really tough to get the right conditions), and AM. I use three radios (in order from least to greatest): the stock radio in my 2002 Ford Focus, my Grundig (Eton) G8 Traveler II Digital, and the Sony Walkman SRF-59 (outstanding radio!) that I just bought today. I'll go ahead and post some of my statistics:

GREATEST PULL:
--------------

680 KNBR San Francisco, CA (Sports) - 1128.079 miles
Second Best: 840 WHAS Louisville, KY (News/Talk) - 1064.527 miles

I will post my DX log in the "Files" section when time permits. Thanks everyone for having me, and happy receiving into the new year!

Scott
Hi Scott,

Welcome to the group, young man! You sound exactly like a lot of us, and I'm sure many of us who started out in the radio hobby around your age (or earlier) can relate with you. We're all always SO happy to hear from the younger folks out there that find an attraction to DX'ing!

You can post your loggings directly here in the newsgroup. That's what the rest of us usually do. We'll all be looking forward to what you're hearing. I hope by now you know that any of us here are more than willing to help you in any way we can, whether it be with tech stuff or just general listening tips. We're all in this together! Please feel free to contribute anything you'd like here. This is the best group I've been a part of in many years, and I'm an old-timer!
Take care, buddy, and let us hear from you often.
73, and HAPPY NEW YEAR!

Kirk Allen
Pasadena, TX


Re: Wet Day

Roy <roy.dyball@...>
 

Scott

I was really disappointed to find out the FTDI chip had no tristate functions but it was a cheap easy solution and filled 90% of what I needed at the time. I would love to get rid of my switch. 

Like you I thought that by changing the display to clock or temperature I could stop the local MCU polling (are there any hardware interrupts going off) but I got side tracked by adding the mechanical switch when I could not get that to work first go.

It must be a real treat to have sophisticated equipment to work with and in your case absolutely necessary.

I will go back and visit that side of the board and check it out to try and make my leads shorter because I like the way you have done your board. I also have no problem tacking onto PCB traces. However all I have is a 20 year old Wella type soldering iron and three pairs of high power reading glasses worn at the same time, but it works for me most of the time.

I noticed that your donor USB interface stick only referred to FM software. Will you graft other software into it for AM?

Roy.

 


--- In ultralightdx@..., "sdwillingham" wrote:
>
>
>
> Hi Roy,
>
> I am connecting to the RSTB, SENB, SDIO, and SCLK traces on the back of the PCB. I scraped some of the overcoating off in staggered places along the traces. Then I solder the wire-wrap wire directly on top of the traces for a couple millimeters. (I tin the traces and wires, then place the wires and heat quickly. We have Metcal solder stations and microscopes which I've become proficient at over the past few years.)
>
> Regarding contention, my approach is basic. The radio's MCU drives the control lines through 22k resistors and my added MCU drives the output side of the resistors directly. So the added MCU just overdrives the lines. In software, I can set the lines to tristate and allow the radio's MCU to take over. I am partially relying on the radio's controller to be "silent" when controls are not moved. I set the display so it is _not_ showing signal strength to avoid periodic updates.
>
> This approach seems to work, but I'm still debugging software which hangs at a certain point. According to software logs, I'm not seeing any errors. I think the GUI is waiting for some acknowledgment that never arrives.
>
> -Scott-
>
> --- In ultralightdx@..., "Roy" roy.dyball@ wrote:
> >
> >
> > Scott
> >
> > I had half come to the same conclusion that the additional oscillator
> > made much difference. I have had it out of circuit for a while as it was
> > drawing a little too much current and draining the expensive non
> > rechargeable alkaline batteries.
> >
> > I like the way you have done your interface. Are you using the through
> > rivets to pick up the control lines? How do you turn off the local CPU
> > control lines to stop contention? At one stage I thought of completely
> > stopping the local CPU but elected not to that so that all other button
> > functions would work including the switching on of the SW section and I
> > would also get a good rest signal from the local CPU.
> >
> > I tried with both sets of control lines in circuit at the same time but
> > the status polling of the Local CPU upset the works and I was afraid of
> > damaging the Si4734 so I just removed the 3 SMD resistors disconnecting
> > the local CPU control lines and dedicating the G8 to the USB interface
> > while I developed the software.
> >
> > Cheers Roy.
> >
> >
> > --- In ultralightdx@..., "sdwillingham"
> > wrote:
> > >
> > >
> > >
> > > Roy,
> > >
> > > I don't think there is much to be gained by changing the reference
> > clock. In the Si47xx chips, the reference input is purely a frequency
> > reference; normal short-term jitter is immaterial to the radio
> > performance. A change to 4 or 27 MHz can result in FM spur issues.
> > >
> > > I got some time today to solder my interface board into my PL-300wt.
> > The EVB software recognizes the chip, but still has a problem "booting".
> > I think it's a software issue and I'm close to getting it to work. I
> > uploaded a sketchy photo of my prototype to the group's photo area.
> > >
> > > On the other hand, my PL-380 arrived today... :)
> > >
> > > -Scott-
> > >
> > >
> > > --- In ultralightdx@..., "Roy" roy.dyball@ wrote:
> > > >
> > > >
> > > > Hi Scott
> > > >
> > > > Thank you for your encouragement and taking the time to interpret
> > the
> > > > data. When I was first learning how to talk to the Si4734 and the
> > > > register command sets, the returned capacitance bytes from the AM
> > tune
> > > > status struck me as being very useful so a text box was quickly
> > assigned
> > > > early in the piece.
> > > >
> > > > I will disconnect the SW input as I would like to concentrate on MW.
> > > > What do you think of using a higher frequency clock? I built a small
> > one
> > > > transistor 4.000 Meg oscillator and it was able to drive the stock
> > load
> > > > just by removing the stock crystal. It was wired in via the DIP
> > switches
> > > > to make it switchable.
> > > >
> > > >
> > > >
> > > > After realising that old redundant VGA boards use a 27.000 Meg
> > crystal I
> > > > modified the oscillator and software to use it. For DX work it seems
> > to
> > > > be better with less jitter however for normal use the 32KHz clock
> > works
> > > > fine.
> > > >
> > > >
> > > >
> > > > I checked out the boards you posted links to and see what you are
> > doing.
> > > > How is it going?.
> > > >
> > > >
> > > >
> > > > Cheers Roy.
> > > >
> > > >
> > > >
> > > >
> > > > --- In ultralightdx@..., "sdwillingham"
> > > > wrote:
> > > > >
> > > > >
> > > > >
> > > > > Roy,
> > > > >
> > > > > Good work. This is exactly the type of experiment we recommend to
> > > > manufacturers to tune their antenna inductance -- reading back
> > varactor
> > > > values across the band and making sure they are within range.
> > > > >
> > > > > I took your tables below and put them into a spreadsheet. I don't
> > > > think the effective inductance of the loopstick will change so
> > > > dramatically over frequency. So I postulated an extra PCB
> > capacitance
> > > > added to the varactor amount. I found that 22 to 24 pF added to the
> > > > varactor values flattens out the calculated inductance. I think this
> > is
> > > > a believable number since the SW circuit (preamp?) connects into the
> > AM
> > > > input of the chip.
> > > > >
> > > > > With an added 22 pF, your data yields an estimated 268 uH for the
> > > > PL-310 loopstick hooked into your G8. At the top end of the band,
> > the
> > > > varactor has nearly bottomed-out with a remaining range of about 3
> > pF.
> > > > My conclusion is that 270 uH is about the maximum inductance that
> > can be
> > > > tolerated in the G8 if one desires LC peaking at the high end of the
> > MW
> > > > band. ( sqrt(L*29pF) <= 1/(2*pi*fmax) ) Hint: disconnecting the SW
> > > > circuit from the AM input node might permit greater inductance.
> > > > >
> > > > > -Scott-
> > > > >
> > > > > > If anyone is interested here is how the G8 reported varactor
> > > > capacitance
> > > > > > via the USB interface as it tuned across the MW band. My
> > software
> > > > also
> > > > > > calculates the inductance from the capacitance returned by using
> > the
> > > > > > frequency of the station selected and applying the formula One
> > on
> > > > two pi
> > > > > > square route LC. The Si4734 cannot reduce varactor capacitance
> > below
> > > > 7Pf
> > > > > >
> > > > > > Double spaced wire wrap coil
> > > > > >
> > > > > > Freq Cap Pf Inductance µH
> > > > > >
> > > > > > 522 373.89 248.64
> > > > > > 531 362.11 248.1
> > > > > > 639 242.41 255.92
> > > > > > 738 175.72 264.68
> > > > > > 900 110.265 283.62
> > > > > > 1206 50.32 346.12
> > > > > > 1404 30.94 415.34
> > > > > > 1620 16.785 575.06
> > > > > > 1710 12.415 697.79
> > > > > >
> > > > > > Stock standard PL-310 loopstick and coil connected to my G8
> > > > > >
> > > > > > Freq Cap Pf Inductance µH
> > > > > >
> > > > > > 522 325.535 285.57
> > > > > > 531 314.23 285.9
> > > > > > 639 210.49 294.13
> > > > > > 738 152.35 305.28
> > > > > > 900 95.445 327.66
> > > > > > 1206 43.48 400.57
> > > > > > 1404 26.19 490.67
> > > > > > 1620 14.03 687.98
> > > > > > 1710 10.135 854.77
> > > > > >
> > > > > > Cheers Roy
> > > > > >
> > > > >
> > > >
> > >
> >
>


Re: G8 vs CR-1100 preliminary AM BCB report-FARMERIK

Roy <roy.dyball@...>
 

Hi Farmerik

It is difficult comparing two Si4734 based radios side by side. Because each radio has different local MCU polling routines (the little computer inside the radio that controls the Si4734) which means the update to the LCD happens at different un synchronised intervals and different speeds for each radio. You sort of get used to it after a while.

I think what is happening is the CR-1100 is seeing a stronger Received Signal Strength Indication (RSSI in dbu) meaning it's loopstick is stronger and because the CR-1100 is defaulted to a higher bandwidth. The Signal to Noise ratio (S/N) will indicate less. You can believe the readings because there is no calibration. The Si4734 just reports back what it sees and of course the loopstick and other front end factors control this.

You can see this if you have either a PL-310/380. Just change bandwidths and you will see the S/N change a fair amount but the RSSI will stay about the same

Cheers Roy.

   

--- In ultralightdx@..., "farmerik" wrote:
>
> I've had the G8 for a couple months, since joining here, but just got my CR-1100 today. Both have the same DSP chip I believe. The CR only tunes in 10 Kc. steps on the AM BCB, but I believe it can be programed for 9 Kc. steps too.[You can not 'slope tune' it off a Kc. or two to escape an adjacent much stronger station.]
>
> The CR-1100 is rated by Tecsun at 0.5mv/M with its larger ferrite and the G8 is listed as 1mv/M. The CR-1100 is not really so much different than a modified DSP ULR with larger ferrite, but I don't think it qualifies for competition.
>
> I placed the two radios side by side, facing the same direction, running both on good alkaline batteries. I tuned three ten 'channel' bands, 700-790, 1000-1090 and 1500-1590, and took notes on each station I heard. I'll summarize here. The CR is noticeably better on about 50% of the frequencies, and about 1/3rd of those are substantial improvements. I got stations on all but 6 of the 30 frequencies on both radios, so it is a good night here in Connecticut.
>
> As expected, the audio bandwidth on the CR sounds noticeably wider, but what I didn't expect is that when ever there is back round noise, or a second weak station is also heard, it is much quieter on the CR. I expected wider selectivity to hear more noise and other stations not less. The narrower G8 bandwidth seems to hurt, NOT help with interference.
>
> Also, I looked at the meters for dBa and s/n. Both numbers scrolled all the time on strong and weak stations. The CR had +5 to +10 more units on the dBu scale on average, and sometimes the differences were much greater. The G8 ran +10 to +15 units on the s/n read out. I don't know what to make of that, but probably they are not 'calibrated' or 'standardized', so it does not mean a thing. If anyone can explain it, I'm all ears.
>
> I tried the TERK with both radios, and as before with the G8, it can lower back round noise,but it does not seem to ever dig a weak station out of noise like it does on a cheap portable.
>
> -FARMERIK
>