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

Jim Brown jim at audiosystemsgroup.com
Sun Sep 29 22:48:23 EDT 2019

On 9/29/2019 7:00 PM, Matt NQ6N wrote:
> 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?

Hi Matt,

As with any source, try to use antenna directivity. Transmit on a 
directional antenna that excites it and listen on another RX to see 
where it peaks. Use the minimum antenna on the RX that hears the 
product. Likewise, use a portable RX, again with minimal antenna, to DF 
the source. My app note and slide set on the topic of chasing RX noise 
lists several useful candidates.

W3LPL has observed that mixing products often occur within antenna 

73, Jim K9YC

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