[Heathkit] Low mic gain in HW/SB transceivers.

[Kenneth G. Gordon]

I know that some people complain of difficulty in getting enough 
modulation with the above rigs, having to set the MIC/CW LEVEL 
control at max in order to get anything like normal modulation 
levels.

Of course there are several possible reasons for this, among them, 
and probably the most common, a bad V-1 6EA8, and the incorrect 
microphone impedance or output level.

I know that there was at least one Heathkit service bulletin 
addressing this which stated that some 6EA8s were either mis-
manufactured or mis-labled and had incorrect filament voltage 
requirements.

However, today I tried something a bit different, and while I do 
NOT know what ALL the possible "side effects" of this are, I 
thought I would post this to the list to see if anyone cares to try this,
as I have, and report any problems.

Substitute a 6GH8A for the 6EA8 in V-1. The 6GH8A has much 
higher gain than the 6EA8, has identical filament requirements, 
identical base connections, and identical height to the 6EA8, and is 
VERY
cheap on places like Ebay, etc.

With the 6EA8 in my recently restored HW-101, using a Turner Plus 3 
mic, I have to set the  CW/MIC LEVEL control to  3/4 to 7/8s of max to 
modulate at the proper level.

With the 6GH8A, I can set the LEVEL control in the bottom 1/4 of 
its range to achieve the same modulation level.

Those using marginal mics may find this particularly useful.

If this tube provides too MUCH gain, a 6CQ8 will provide intermediate 
gain.

If anyone cares to try this, please post your results to the list.

Ken Gordon W7EKB