[Lowfer] Wolf with SDR-IQ

Thu Apr 9 21:55:00 EDT 2009

Garry Paul et al  -  Thanks - 

My correction is also -  wanted 1000Hz cal 1020Hz for Argo (or very
close on the two dells) - my Thinkpads in Alaska were closer and prob a
function of the clock on chip divide down I guess. John W1TAG has a
great piece on his web site about cal - 

I liked the old Thinkpads as the screen res gave me the opportunity to
run 4 x Argo sessions. 

I'm a lazy old soul and use the "close enough feature" of setting the RX
to WWVH on 10MHz, when I can hear it,  switching the SDR to USB and
listening to the zero beat (if you can get it within 1 beat a sec given
Doppler this is close enough), adjust the clock speed as required on the
SDR to slow it down - I only do this when the SDR isn't sitting on the
window ledge getting blasted by cold winds or heat from the sun - , then
tune down to 59KHz USB listen to JJY or WWVH/BPY and then set WOLF for
1000Hz cal and look for the offset from the derived 1Khz tone. - same
for Argo looking for a 1000Hz tone.

 I find this rough and ready approach normally keeps me within 0.25Hz at
137kHz, although it would be better closer the SDR lack of, or as
designed non locked ref osc is probably the best you can get...or close
enough given I don't have any form of test gear here in China (nor any
receivers of course!)

I suppose with the stereo output and dual receiver (within span sic) the
SDR is I may be able to configure two instances of Argo or what ever,
but Ive not done that. One for left hand channel one for right....

I also use Virtual cable (VC) and so far the tests indicate I don't see
any reduction or clutter when at the  44Khz sampling rate. I.e. I cant
tell the difference good or bad on clocking, sensitivity, or whatever
between the sounds card loop or the VC, well not on this incantation,
but I'm very new to the VC world.

On the issue of IF gain - Ive found the response to be tidier on LF with
0dB IF and RF gains. This is probably due to my relatively high level of
injected signal from the probe. My base signal to noise hangs around
-90dBm  (per display) but Ive not cal'd this against the true field
strength.

I run a 7 ele LPF before the SDR - Designed for and starts attenuating
around 550kHz - and knocks off the -10dBm multiple bcsts on MW we get
here by some 40dBs or so . Makes a ton of difference on my set up and
the SDR doesn't have a lot of Bpass or other filtering. Without it I get
warnings to reduce gain etc...a load of RF around here of course.

I need to do some cal work on Loran here but the trees are blossoming
and taking the opportunity to get outside before we get roasted - up to
87F today I'm told...

Thanks

Laurence BY3A- KL1 X Tanngu China OM89UA

-----Original Message-----
From: lowfer-bounces at mailman.qth.net
[mailto:lowfer-bounces at mailman.qth.net] On Behalf Of PAUL DAULTON
Sent: Friday, April 10, 2009 9:17 AM
To: k3siw at sbcglobal.net; lowfer at mailman.qth.net
Subject: Re: [Lowfer] Wolf with SDR-IQ

Garry it is interesting to read you have to use 1020hz correcton for
ARGO
 for 100hz tone. I ran into the same correction(1020) on 
two Gateway Profile III's I use for ARGO. Earlier computers I used were
 dead on at 1000hz, even an IBM 166mhz Thinkpad.
My two TS50's are within 1hz. I was lucky that when I started the
 equiupment was close or I wouldn't have copied anything!
I've managed a copy of Warren's XGJ on my Elektor SDR but no luck so far
 with John's Wolf signal. I have copied XES wolf when he 
was running higher power using the TS50, but at lower power no luck with
 the TS50 either.
WEB is off due to power supply malfunction,  so I'll have to wait untill
 he is back on to check the part 15 performance of the Elektor.
I wonder if the jitter problem would show up on Psk-31. I dont have any
 other way to evaluate mine.
The software I use, By G8JCF, for the Elektor allows the filter bandwith
 to be adjusted by the scroll wheel on the mouse. For instance
I can find two cw signals, one at 800hz and one at 1300 hz, on 2khz
 bandwith and lower the upper filter limit to 1200 hz and eliminate the
1300hz signal. Filter skirts are 50hz in width.
Thanks for sharing your experience with the RFspace SDR.
Paul K5wms
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