[600MRG] XXM and XSV note

[John Langridge]

>What this indicates to me is folks probably need to clean-up their power supplies to minimize the residual AC-ripple in their power supplies.

Its actually much more complicated than that, Dick.  While its often easy to point fingers at a power supply, its also common when running some DSP systems, noise blankers or noise reduction.  For that matter, weird mixing with errant signals in the passband can also cause this problem.  I've observed very weak fundamental  wspr signals here whose sidebands would probably have been 50 or 60db+ down on a bad day, far below the wspr detection limit yet they sometimes result in decoded sidebands  when there is a lot of "noises"  floating around.  I suspect this involves mixing in the receiver, which in my case works fine but its not the fine quality rx at MF that it is as HF, for example.  Its kinda like the phantom decodes we get when there is trash in the passband.


Finally, I run a pair of very well filtered lab grade linear supplies here for my amps and periodically see dupes show up in the log.  I attribute it to RF getting into audio lines but there is also a seasonal component (seems to happen most around the transition from summer to fall and sping to summer)  that I don't fully understand here.  As its never persistent, I don't worry about it.  It almost always happens when I am +8 or +10 somewhere.  When I was running the remote RX a mile away from my main QTH, I never had harmonics reported by the SDR and I was plenty loud there.  That brings us back to the weird mixing thing in receivers when signals are stout.


73!

John XIQ





________________________________
 From: dick.bingham <dick.bingham at gmail.com>
To: KU4XR <ku4xrradio at gmail.com> 
Cc: "600MRG at w7ekb.com" <600MRG at w7ekb.com> 
Sent: Monday, October 27, 2014 8:49 PM
Subject: Re: [600MRG] XXM and XSV note
 

Greeting everyone

I, too, get the +\- n*60Hz decodes on some signals but only when the 'main' signal is in the plus dB range and the sideband levels are around SNR = -30 dB.

What this indicates to me is folks probably need to clean-up their power supplies to minimize the residual AC-ripple in their power supplies.

Dick/w7wkr and xsh-26 CN98pi

--------------------------------------------------------------------------------------------- 



> On Oct 27, 2014, at 5:54 PM, KU4XR <ku4xrradio at gmail.com> wrote:
> 
> Hi all:
> 
> Band is exceptionally quiet tonite, and signal are already quite strong..
> Ken - XXM started out in positive numbers.. 2 stations I have yet to decode,
> is XPQ, and XSV in Neils new QTH.. I have a problem that really nothing
> can be done about.. I get the 60 Hz Up and Down decodes on XXM all the
> time.. This starts in the early evening, and lasts until the wee hours of
> the morning, and then disappears.. I have also seen multiple decodes
> on XIQ several times, and even at 120 Hz from his mean frequency..
> XJM has also shown the extra 60 Hz decode on occassions..
> The thing that makes XXM's decodes " my problem " is that 60 Hz UP
> from his mean frequency of 475.706, puts the extra decode at 475.766 KHz
> which is right on top of where Neils signal is.. There is nothing that can
> be done about the " WSPR Anomaly " which has happened to probably
> about every receiver at some point.. Just wait it out, because it_Does_
> go away..
> An added observation here.. My cleaning of the ground connections
> recently, has also quieted 630 meters noticably.. The biggest problem
> as far as noise is concerned that I will now have to contend with, will
> be the noisy powerlines as the WX starts getting colder.. Buzz, Buzz, Buzz
> 
> 73 all:
> 
> Andy - KU4XR
> 
> _______________________________________________
> 600MRG mailing list
> 600MRG at w7ekb.com
> http://w7ekb.com/mailman/listinfo/600mrg_w7ekb.com


_______________________________________________
600MRG mailing list
600MRG at w7ekb.com
http://w7ekb.com/mailman/listinfo/600mrg_w7ekb.com