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

To: rfi@contesting.com
Subject: Re: [RFI] tips for finding the source of broadband mixing products
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Sun, 29 Sep 2019 19:48:23 -0700
List-post: <mailto:rfi@contesting.com>
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 rotators.

73, Jim K9YC
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