[Heath] HW-101 LMO alignment and other matters...

[Kenneth G. Gordon]

On 2 Apr 2015 at 15:25, Jim's wrote:

> Thanks Ken, I aligned the VFO and its good now. 
> 
> 73
> Jim K8DHC

Excellent, Jim. 

I find my HW-101 to be an excellent rig. I have done many of the upgrades 
shown here:

http://www.w7ekb.com/glowbugs/ModsEtc/modifications.htm

Go down to this one:

http://www.w7ekb.com/glowbugs/ModsEtc/Optimizing%20the%20HW101.pdf

and this one may also give you some hints:

http://www.w7ekb.com/glowbugs/ModsEtc/HW-101tips.pdf

If you simply remove C-912, a 0.05 mfd capacitor which connects the 
cathode, pin 7 of the 6GW8 audio amplifier to a tap on the audio output 
transformer, and which is mounted UNDER the audio circuit board, audio 
output will be considerably increased.

C-912 adds some inverse feedback to the audio stage, enhanceing fidelity 
at the expense of output power. I routinely remove this from any HW/SB 
transceiver I have here. I have never noticed any real difference in the 
audio output quality either.

But each time I have done this, I no longer had to set the AF gain knob 
at 10 or higher to really "hear" it: usually, I end up setting the AF 
gain knob at about 5 or 6 instead.

Lastly, although Heathkit used the 6HS6 tubes as receiver RF amp and 
first mixer tubes in order to improve the sensitivity of the receiver 
(and this does work just fine) the 6HS6s in this circuit are operating 
"red-lined" so to speak. They don't last very long in this condition, and 
they are expensive.

The original RF amp and 1st mixer tubes were 6AU6s, and those will work 
fine, last much longer, and are certainly less expensive.

But, I have found that usiing 6AH6s works even better, are cheaper yet, 
are far more robust, and achieve sensitivity on par with the 6HS6 (0.01 
microvolt for MDS).

However, if you are going to swap tubes like this (their base connections 
are all identical) you must swap them both, RF and 1st mixer, since their 
filament currents differ, and if you swap only one, the filament string 
may become unbalanced.

YMMV.

Ken W7EKB