Can you connect the amplified speaker directly to the AF output of rhe SG 8 without going through the transmitter? Directly to the output connector, without using the old SG 8 cables? use clip leads or just hold the connector of the amplified speaker against the output connector of the SG 8.
Set SG 8 to “internal” to turn on the audio generator.
RF appears to be working well enough to drown out 60 Hz interference buzz from power supplies, lamp dimmers, chargers LED house lights and other switch mode power supply pests.
Do you have a manual for the SG 8?
http://tubularelectronics.com/Heath_.../SG-8/SG-8.pdf
jr