[600MRG] double reporting of strong wspr signals

[Brian Pease]

I tend to believe that my occasional sideband reports are on the 
receiving end.  I have looked for my +/-60Hz sidebands at my amp output 
with a spectrum analyzer, and cannot see them even though (with 
averaging) the noise level is 50dB below the carrier.  The noise appears 
to be phase noise from the DDS, as it is also -50dB at the sine wave 
output of the DDS, and is well above the analyzer noise.  The reported 
sidebands show up as only 20-25dB below the carrier.
The output power of my U3 (into 50 Ohms) on 137kHz increased from 110mW 
to 460mW when I increased C5, the coupling cap between amp and output 
filter from .01uf to 0.1uf.  I have three BS170s running on 5VDC.
On 3/4/2014 11:36 PM, Dave wrote:
> Tests over the last few years show Its usually due to non linearities in the
> soundcard. You will see the 120(and 100Hz) sideband reports fairly often on
> the wsprnet.org reports on all the hf bands. It has been seen on decodes as
> low as 0dB
>
> Even ground isolation transformers doesn't stop it
>
> Experiment has shown that even running the transmitter off DC (eg lead acid
> cell) you will still the "sideband" effects in the receiver, even when using
> a better spec soundcard (eg d44 or the edirol). The worst experience was
> with a $7 chinese USB soundcard where the main signal and the 2 "sidebands"
> were equal amplitude, which gave the wspr decoding software a headache
>
> Dave
>
> Ww2r
>
>   
>
> -----Original Message-----
> From: 600MRG [mailto:600mrg-bounces at w7ekb.com] On Behalf Of Hans Summers
> Sent: Tuesday, March 04, 2014 10:12 PM
> To: 600mrg at w7ekb.com
> Subject: Re: [600MRG] double reporting of strong wspr signals
>
> In my setup here I can often get 100Hz sidebands (50Hz mains power here, not
> 60Hz) produced in the receiver with very strong signals too. I'm not sure of
> the mechanism.
>
>
> 73 Hans G0UPL, creator of the U3 :-)
> Http://www.hanssummers.com
>
>
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