[462ron]

Hi Captain, your concern whether or not you should have used a cap in series with the RF cable is precisely why I added one inside when I changed over to BNC connectors. That way I don’t need to think about it and it’s less cumbersome than adding the cap to the cable. My SG-8 was my dad’s from the late 50s early 60s and the RF level control was burned out. I figured it must have been exposed to some hv at one time when dad used it, thus the reason I added the cap to the BNC. My conversion that I did works perfectly for me, no noise problems and the 400hz audio is fine, I don’t know what would have happened in your case. Oh, and I should have mentioned too that my frequency counter will go crazy if the internal modulation is turned on, only works properly on an unmodulated RF carrier.
   As for your ‘tuned harmonics’ , if you look at the signal coming from your SG-8 on an oscilloscope, you will see it’s not a pure sine wave at all. It has harmonics of the base frequency in it also. So for example, if you set your generator for 1Mhz, the second harmonic is 2 MHz, the third harmonic 3Mhz. If you have a sw radio tuned to 2 MHz, it will hear your generator that is set to 1 MHz. It is hearing the second harmonic. That is how they extend the range of frequencies on some generators. 

Ron