[600MRG] double reporting of strong wspr signals

[Neil Klagge]

Very interesting, JM !  (There are so many "Johns" that I have started
using initials to keep them straight - Hi)

Today I improved the filtering on my resurrected power supply. I used to
use it to fast charge my car battery years ago. It was full of cobwebs and
dust. I only had a 1500 uF cap on it for filtering. Today I added an iron
inductor and another 2000 uF after it for a pi-section filter. I hope it
helps. Rudy might not get any more double decodes from me now (hopefully).

Thanks to Rudy for pointing out the 120 hz difference between the two
decodes. I only noticed the dB difference and never caught the fact that
the freqs were 120 hz apart.

Let's see what tonight brings...
73, Neil


*"I use the original form of social networking: Amateur Radio." *
 *(my ham radio sites are at 'w0yse.webs.com <http://w0yse.webs.com>'  and
'wg2xsv.webs.com <http://wg2xsv.webs.com>' )*




On Tue, Mar 4, 2014 at 12:01 PM, John Molnar <wa3etd at gmail.com> wrote:

> Rudy, many of us have experienced the same double decodes from various
> stations.
>
> In some cases the transmitting stations DID have marginal PS filtering.
>
> I set up a test here awhile back, monitoring myself with a completely
> independent line up.  Running WSPR on my main transmitter at about 250W
> out, no doubles were noted.  The PS for said transmitter is unregulated,
> consisting of a 40V (AC)
> 100A transformer, full waved into 150,000 uF, consisting of 8 banks of
> series/parallel caps.  I removed one bank at a time and doubling began with
> 30,000 uF remaining in the filter.
>
> The U3 board is very susceptable to producing doubles without good solid DC
> and common sense bypassing.  The creator of the U3 was not a believer in
> bypass caps.
>
> Just my observations here.
>
> John XKA
>
>
> On Tue, Mar 4, 2014 at 1:41 PM, Rudy Severns <n6lf at epud.net> wrote:
>
> > I have a bit of a mystery that someone might be able to shed light on.
> >  Some time back XSH/26 pointed out to me that he was getting two reports
> in
> > the same time slot for my wspr signals.   Last night Neil, XSV, was very
> > strong here and I generated double reports on him through the night.  He
> > asked me about this and I told him the following:
> >
> >      2014-03-04 13:42   WG2XSV   0.475625   -26   0   DN41ac   1
> WD2XSH/20
> >   CN83lu   958   292
> >       2014-03-04 13:42   WG2XSV   0.475745   -10   0   DN41ac   1
> > WD2XSH/20   CN83lu   958   292
> >
> >
> > Hi Neil,  here is an example of a double decode of your signal.  Notice
> > that there are two frequencies 120 Hz apart.  The strong signal is on
> your
> > normal frequency but the weaker one is 120 Hz lower.  Since your signal
> was
> > very strong last night one of those signals may be a sideband introduced
> by
> > 120 Hz ripple from your power supply.  There were many of these double
> > decodes and almost always the second signal is -16 dB and 120 Hz
> different.
> >  That's just a guess.
> >
> > Now to cast some cold water on that explanation,  I got a similar report
> > from XSH/26 who is relatively close to me so I have +dB snr's at his
> place.
> > I quickly slapped my HP spectrum analyzer on my signal and sure enough
> > there were AC ripple sidebands, but in my case they were -60 dB down from
> > the carrier which is pretty good considering I have a 55 dB gain
> amplifier.
> >  I keep a very close eye on my signal quality so this did not explain the
> > double reports?????
> >
> > The other explanation would be something going on at the receiver end but
> > what I have no clue???
> >
> > 73, Rudy
> >
> >
> >
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