[RJMiranda]

interference can come by 2 ways: thru the AC line and by radio waves.
If you can´t find a suitable AC line filter, you may use a uninterrupted power supply made for computer use that has a set of AC outlets labeled "surge and noise protection" that means a line filter is inserted between the power line and these outlets.
If the monster, I mean, radio can be plugged there, you would be filtering line noise. Make sure the wiring of the building is according to the modern codes (that is, 3-pronged outlets, and the round pin of the AC plug of the UPS is being really connected to earth). APC brand UPS have a LED near where the AC cable enters the UPS. If this LED is lit, the ground is faulty and the UPS´ line filter will not protect you from interference.
For airborne RF interference, now that you have connected the scope to the radio, look at the waveforms on the receiver while you operate the remote control. (Use the AC coupling). On the 78´s plate must appear RF bursts while the remote dial is being turned. The same on the 6J7G´s plate but at a higher amplitude. Look for suspicious noise on these points with the remote control inactive. If any appears, try turning off fluorescent lights, computers and the like to isolate the source of noise.