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Re: [RFI] tips for finding the source of broadband mixing products

To: Matt NQ6N <matt@nq6n.com>, "rfi@contesting.com" <rfi@contesting.com>
Subject: Re: [RFI] tips for finding the source of broadband mixing products
From: Lee STRAHAN <k7tjr@msn.com>
Date: Mon, 30 Sep 2019 05:24:11 +0000
List-post: <mailto:rfi@contesting.com>
  Hi Matt,
   It looks and sounds to me like you are simply overloading the SDR receiver 
and generating the spurs and noise inside it. What level of the fundamental 
signal is actually being applied to the SDR? I am guessing the largest pip 
shown is the third harmonic you refer to. 
   One way to find out is to lower the transmitter power by 10 dBm of the 
transmitted signal. If the spurs go down by more than 10 dBm they are most 
likely being generated inside the SDR receiver by simply too much signal 
overload. You may be chasing a ghost. If the screen shot is really the third 
harmonic at 14 MHz why are you transmitting on 14/3 or 4.67 MHz?
    Any way lower the signal into the SDR and find out if the problem spurs go 
away. I think you are simply overloading the SDR with way too much signal.
  Lee   K7TJR   OR 

-----Original Message-----
From: RFI <rfi-bounces@contesting.com> On Behalf Of Matt NQ6N
Sent: Sunday, September 29, 2019 7:00 PM
To: rfi@contesting.com
Subject: [RFI] tips for finding the source of broadband mixing products

Hello,

I'm noticing that the second harmonic of my transmitted signal is accompanied 
by all sorts of broadband noise.

I am in the process of ruling out the equipment inside the shack as a cause of 
this noise.

But I want to be prepared to begin the search outside the shack for things 
(wall warts, etc.) that might be generating the broadband noise when exposed to 
RF.

What are some techniques for localizing the causes of this kind of broadband 
noise?

A screen shot of the pan adapter and a recording of the audio of the third 
harmonic + noise is attached via the below link:

https://www.dropbox.com/sh/2639h09dhr8qxkf/AADr4-Nl4GS7e-Cl3TKSuq5aa?dl=0

Any advice would be much appreciated.

73,
Matt NQ6N
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