[600MRG] Dual decodes

[John Langridge]

Hi Claude - 

No filter, NB or DSP in use here.. straight RX with AGC off...

While I am inclined to believe in the idea of the products being generated in the RX,  this appears to be something other than that.  In fact just last week both WG2XPJ and WG2XKA encountered an oscillation resulting in dual decodes that required additional filtering on PS due to sagging.  After adding caps, the problem went away.  

I had a recent problem with dual decodes.  I knew there was an issue because the RF current wave form on my scope match was not smooth.  There was a product embedded on the waveform and tweeking the vario while watching the scope match resolved the problem completely.

As I told Ken, these dual decodes create zero problem for me at all.  If they are real, the only way to know for sure  would be to look at the passband with  a spectrum analyzer.  As the band becomes busier, this  might become a problem, but right now, its not.  As far as I am concerned, he has nothing to worry about running it as is.

73,

John XIQ




________________________________
 From: Claude Baker <ac0zl at yahoo.com>
To: "600mrg at w7ekb.com" <600mrg at w7ekb.com> 
Sent: Thursday, December 12, 2013 5:45 PM
Subject: [600MRG] Dual decodes
 

Ken,

My personal experience is that dual decodes are GENERATED at the receiver. 


Today, I was tuned for WSPR reception but using Argo to look at Mike's signal, XSH/12. His signal is about the right strength for me to use my tooth fillings for demodulation. In Argo's full band view, I noticed 120 Hz harmonics of Mike's signal.  I turned off my noise blanker and the harmonics went away. I've noticed the same behavior with very strong WSPR signals - back off noise blanker action and multiple decodes go away.

John Langridge - if you're seeing dual decodes, turn off your noise blanker and see if they go away. You'll save Ken a lot of work and worry over his new baby.

I don't know about the rest of you but any time I put something new into operation and see unexpected results, itmust be my fault - no other explanation seems possible. Looked at objectively, we all know that is wrong.

Cheers,

Claude Baker, AC0ZL
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