Improve RFI

@mahler123 said:

 I placed the transmitter -relay device on the floor next to the rack.  Previously it had been on the top half of the rack, and then placed on top of a surround that is wall mounted at near the same height.  The RFI light is off now and the Universal Remote works again.

Me thinks you found the source of the RFI. If you want to verify, I would suggest you place the transmitter -relay device back on the rack. Unplug all the associated A/V equipment from the 120Vac AC mains outlets. Then check for the presence of  RFI.

If you are using a surge protector plug strip, or a power conditioner with surge protection, unplug it as well from the AC mains wall outlet.

.

@mahler123 said;

 I also have a surround sound system on the main floor; same AVR, same universal remote, and no RFI.  

Did you try using the main floor level remote in place of the one in the basement?

What is the "firebox" in the basement?

.

@mahler123,

Are you sure it is RFI and not EMI interference? You will measure a lot of EMI in front of the breakers in the electrical panel. (metal panel door open). Especially large running loads like the outdoors central air conditioner unit, and refrigerator, and other such motor loads when running. It is normal. There is a large EM, Electromagnetic field present around the loaded breakers. 

.

@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. 

.