..With the amp at even 250 watts, I broadcast through anything with a speaker. Lou assures me its a ground issue as does Dale at Par who's antenna I use.
No, an RF ground won't help. The problem is that the speaker leads are close to resonance
act as an antenna, picking up RF and turning it into audio.
Where is the RF radiating? If it is from the antenna (as it should be), then an RF ground won't
help at all, since in the best case all the RF would STILL be radiated from the antenna.
If not, then the RF is either being radiated from the coax or the power cable. An RF ground
can change the currents on the coax if there isn't a balun at the feedpoint, but it is just
as likely to make things WORSE as to make them BETTER. If the problem is RF on the power
cables, a ferrite choke and some bypass capacitors is a better choice, as the RF ground may
not make any difference to that, either.
Using 468/f, the longest ground wire I can have is around 9' and I am not sure if that includes the 4' bar copper bar that everything is grounded to. The MFJ-931 Artificial RF Ground is not an option for two reason. First is only works to 30 MHz and second it's only rated to 300 watts. So my big question is, Now What???
468 isn't the proper number to use here: a half wave ground wire will actually provide a
reasonable RF ground, but the center of it will act like an antenna in the process. A quarter
wave wire (which should be 246/f, since the 468 includes a correction for end effect where
the insulators are attached) will invert the impedance, so putting a good ground at the far
end gives a poor ground at the rig and vice versa. While a quarter wave open wire will act
like a ground radial and provide a low impedance at the rig, it will still radiate like an antenna
if there is sufficient current flowing on it. So really you want something shorter than, say,
1/10 wavelength, made of flat copper sheet rather than wire. That is rarely practical.
The MFJ "Artificial Ground" only works reliably on wires less than perhaps 3/8 wavelength
or so if they are open at the far end, and all it can do is make them look like 1/4 wave
wires - they will still radiate like an antenna. If the ground wire presents a high impedance
at the shack end, no amount of reactance cancellation will help. You could build your own
6m version of the circuit, but it won't work any better than a 54" wire connected to the
ground lug on the back of the radio.
Now what? Make sure you have a balun on the coax, and that there isn't any common mode
current. Wrap the power cord several times though a couple of snap-on cores. If that
doesn't fix the problem, either add RF bypassing or chokes to the offending speakers or
replace the devices with ones that have proper filtering.