[RFI] advice wanted: finding the source of mixing products

Jim Brown jim at audiosystemsgroup.com
Mon Feb 24 15:47:58 EST 2020


On 2/24/2020 11:25 AM, Matt NQ6N wrote:
> I'd also welcome ideas for things to test/try that might shed some light on
> what is going on.

Hi Matt,

Several suggestions. Ideally, this is a quest that requires help from 
another ham. One of you transmits while the other pokes around with that 
portable RX. Without that help, a good first move is to listen for the 
mix product(s) on a second radio while a directional antenna is rotated 
while transmitting, noting the direction(s) where the IM product(s) 
peak. With that information, transmit keydown and poke around with your 
portable RX.

As to the harmonics -- they are generated by the rectification. Even the 
most heroic stubs or bandpass filters in you station have zero affect on 
the IM process.

A great first move is to first search out and destroy (replace) ALL 
outboard SMPS that you can find, and put serious ferrite chokes on the 
AC cord of any built into equipment (appliances, home entertainment 
systems, anything plugs into the wall and has any form of electronic 
control). Search out and replace anything with variable-speed control of 
a motor (HVAC systems, etc.)

73, Jim K9YC


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