[Elecraft] RF Feedback

[Trevor Day]

Hi All,
well I have now completed installing my new DEMI 6m transverter into the 
EC2 case and it works fine.  I particularly appreciate the enabling 
software for transverter use with the K2, it makes band changing and 
operation so easy :))

Now my problem;  I am getting tremendous RF feedback when I key up my 
single 4CX-250B PA on 6m.  It produces a conservative 200 watts output, 
but at that level the PA Anode current just lifts to max and stays 
there!  By unplugging cables and manually operating the PTT line etc etc 
I have determined that the problem is on SSB only and appears to be 
entering the rig via the mic (an EH2).  This is the same setup used with 
my previous transverter plus TS430S which seemed quite happy.

I should mention that the DEMI is the low power PCB only option driving 
a single stage amp to 2 watts prior to the 4CX-250B.  Output at the 2 
watt level is very clean.

I have tried changing cable lengths, re routing cables etc.  I have also 
reduced SSBA and SSBC settings to minimum which improved things very 
slightly in that the feedback now waits until I speak rather than just 
operate the PTT:)  My next step will be to de-couple the mic lines but I 
am conscious of not wishing to degrade the fine audio from the Heil mic.

Has anyone else had this problem and if so what was the cure?

Thanks,
73 Trev K2 #2637
-- 
Trevor Day