[Elecraft] Elecraft : K2 SSB audio quality

[Martin.Evans at costain.com]

Hello, I've recently started to use my K2/KPA100 on SSB running 100W
with an MH2 mike mostly on 80m. I use 2:1 compression and mic preamp is
set to 2. The antenna is an 120ft doublet, 30ft of 300ohm ribbon feeder,
remote mounted z match tuner right under the centre of the doublet and
approx 70ft RG58 coax to the rig. I have no RF earth but neither do I
get much RFI in the house. One end of the antenna is about 10m above the
operating position and I'm on the ground floor. I've had varying reports
on the audio quality. Here are a few things I have done/found:
 
Every now and then I would get a high current message after which my RF
peaks (as shown on the K2 bargraph) would drop right down. My remote
mounted z match tuner uses old broadcast receiver variable caps and I
think one of them might have been flashing on speech peaks. I have
backed off the power to 90W and it seems a lot better. The funny thing
is that when I run at 100W on CW I don't have any probs (ie no high
current messages). Is there something about the RF peaks on SSB, do they
overshoot sometimes or is it something to do with rate of rise of the RF
voltage?
 
When I first start an over on SSB the bargraph follows the speech
waveform and is what I could call "lively" but sometimes it goes very
sluggish and doesn't seem to be following the audio, is this normal.
Sometimes the bargraph seems to disappear altogether.
 
The antenna and tuner are balanced and I've added a choke balun and
various ferrites (inc 3 turns on the mic lead and 4 turns on the power
supply lead) to keep any RF off the rig chassis. I hold the mic about 4
inches away since I thought I might be overdriving the audio.
 
I did have reports of sounding like I was speaking through a kazoo but I
think I may have fixed that by moving the power supply (linear one with
big toroidal tx) a bit further away from the rig. 
 
Some guys report that it sounds a bit scratchy. 
 
I have checked the KPA100 biasing and it is spot on with the manual and
also the carrier suppression.
 
Unfortunately I don't have another rig to monitor my signal. I do have a
30Meg scope.
 
I don't think the audio is bad but perhaps not the best I could get out
of the K2. Are there any tests/mods/tricks I could try??

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