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

[Matt NQ6N]

Thanks much for the tips, Jim.  Do you know if the wall warts can cause
mixing when they are not plugged into the wall or if the circuit breaker is
turned off?

In my testing the other day I did not see any difference in the 14.786 MHz
mixing product when turning off all of the breakers in the breaker box.
Does that test eliminate any warts on those circuits as culprits for the
specific mixing that remains present at 14.786?

My next test will be to power down the entire house and transmit with the
KX2 on battery, connected directly to the antenna, and confirm that the
mixing product is still there (eliminating anything in the shack itself).

73,
Matt NQ6N

On Mon, Feb 24, 2020 at 2:48 PM Jim Brown <jim at audiosystemsgroup.com> wrote:

> 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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