[ICOM] 756Pro and Compression

[Roger (K8RI)]

I purchased my 756 Pro new not long after they came out and never had 
any complaints on SSB or CW other than a pin 1 problem. I did change the 
mike grounding as it was picking up the 60 fields in the room.  I did 
have to give up some of the mike functions, but it cured that problem.  
HOWEVER something has changed recently.

I always ran a fair amount of compression with my voice characteristics 
and received good reports.  About 9 months ago I added a new Emtron 
DX-2sp to replace my old Alpha 76A.  Again, with the same settings for 
the mike gain, compression, and RF drive I was receiving good reports. 
One DX station even commented several times about the good quality of 
the signal.

I have had some RF getting into "things" on 75 with the LEDs on the 
6-pack control lighting up when I get above 1 KW, but not into the rig.  
By 1500 watts those LEDs are at full brilliance.
The station set-up is the 756Pro, through the DX-2sp, to a Palstar 
AT-5K.  I have a pair of coax switches that allow me to switch in the 
antenna analyzer, adjust the AT-5K for R=50-52 ohms and X = 0. Then I 
switch over to the amp and run it to the DL-5K for an off the air 
tune-up and adjust the drive to give just under 1500 PEP on voice peaks 
after peaking the amp tuning. It's pretty much set the controls to 
settings on a chart and it's ready to go.  Then I switch the tuner to 
the coax running to the tower where it goes to a 6-pack for SO2R 
operation. On 40 meters the coax goes from the 6-pack to a remote 
antenna switch.

My Yaesu 897D developed a problem and I have several amps to check out 
for others, so I sent it in for repair and replaced it with an Icom 
7000.  This involved some additional coax and grounds. After the change 
I received some reports of what sounded like RF getting into the 756Pro. 
So, assuming I had created a problem I undid all the changes, but no 
change.  THEN I started where I should have, with the audio gain, 
compression, and RF drive.  I could get rid of the problem by turning 
the compression off, so I took the amp out of line and found the problem 
was the same barefoot.  IOW, following the book procedure of set up, 
Mike Gain for ALC, then compression, and finally RF Drive, but instead 
of running a far amount of compression, I now have to leave the 
compressor off entirely. Before I could create the same problem but it 
required turning the compression wayyy up.   Yes, I'm using the same 
mike as I have all along, which is the one that came with the rig. 
Settings on 40 for the tuner and amp have not changed.

I'm far more concerned about the sudden need to leave the compressor off 
than the RF getting into the antenna switch.
One additional thought, I am running Ham Radio Deluxe on a Quad core 
Athlon but have not gone to running the audio to or from the computer 
yet.  Oh! The station is in my shop which is a 28 X 40' building with a 
bonded barn metal interior over walls and ceiling.  Not a good place for 
HTs or Cell Phones. <:-))  I have to hold the cell phone in the window 
and the tower is less than 2 miles from us.

Any thoughts?

73

Roger (K8RI)