Improve RFI

At the risk of asking a possibly really stupid question: Have you absolutely ruled out that you might have a defective universal remote? Have you tried using it in your other system?

There is an RFI indicator on the relay part of the remote.  It is on constantly.  The same relay unit is in the upstairs unit and the RFI indicator is never one.

  I have switched remotes as I indicated in posts above between the 2 systems.  No change.

   The tools that I have seen for measuring RFI, in YT videos, don’t isolate the RFI to a single source.  They basically say “There is RFI in the room” and the user then has to try turning of appliances, lights, etc.  I know that I have RFI because the indicator on the unit is on, and I’ve tried all the solutions, to no avail.  So buying another tool that will inform me that I have RFI isn’t in the cards.

@mahler123 ,

Not sure if this is any help.

From the owner manual:

Page 4
5. Observe the Status LED of the MRF-260. If it is glowing or flickering you must relocate the MRF-260 to a location where the LED doesn’t flicker.

If your installation location simply doesn’t offer you any choice
and you are detecting interference everywhere you place the
MRF-260, you have two last resort options:

a. Remove the MRF-260’s antenna. This will reduce the
range enormously, but may still be enough for this client.

b. Admit defeat and install the two piece MRF-350 base
station, which can have the RF Antenna module remotely located (even in another part of the house).

 

7. Once you have found a location that is absolutely free of RFI
with everything on, test to see if the range is adequate and that macro reliability is perfect. Start with the antenna angle set to 45 degrees and positioned so that the long side of the antenna is facing the customer’s favorite seating position.

When testing, set both the remote and the MRF-260 to the same
valid RF ID#. Keep in mind that zero (0) is not a valid RF ID#.
Watch the Status LED on MRF-260 - it should light every time
you press a button on the remote. This confirms that the signal
was received and understood perfectly. If you repeat any button
press multiple times and the Status LED lights correctly every
time, you have no interference and a very reliable installation. If
some of the presses do not light the Status LED, you still have
some RFI. Your best strategy is return to step 3 and try to find a
better location for the MRF-260.

8. Now that the location is fixed, connect each of the emitters to
the appropriate IR output and run the cable to the appropriate
component. Do not attach the emitters to the front panel yet!

https://www.urc-automation.com/product/mrf-260/

The only other thing I can think of if the RFI is coming from something within the house is to turn off every circuit breaker in the electrical panel except the one that feeds the wall wart for the MRF-260. Then check for RFI. 

IF RFI is gone turn on one breaker at a time and then check for RFI. Repeat process until you find the culprit causing the RFI. 

.

As @jea48 mentioned, the RFI could be coming from somewhere else in the house.  What is upstairs, directly above the MFR-260?  And by any chance are you using a cellular 5G internet access point in the house?

Just a thought...