[Heathkit] Using a speech clipper for AM punch

[David Thompson]

Veteran AM ers back in the 1950's used the speech clipper to increase punch 
in the then crowded
AM bands.  The best was one in the Editors and Engineers Radio Handbook 15th 
Edition edited by Bill Orr, W6SAI.  Its a 15 watt clipper-amp designed to 
drive a modulator with sat 811A's (or bigger).

To make a clipper work effectively the clipping level must be adjustable 
between 0 to 15 DB.  In conjunction with a low pass filter of say 3000 or 
3500 cycles.  The ideal circuit is found on page 657 of the 15th Edition. 
This was incorporated into a single 4-400A amplifier modulated by a pair of 
811A's.  This made an effective transmitter for both rag chewing and 
breaking DX piles ups even on 20.  This rig was pictured on the cover of 
Electric Radio April 1994.

I remember the outstanding AM signals from W6SAI, W6YMD, W8BKP and all used 
this type of clipping effectively.  Mine must have been decent as I have 263 
countries on AM from 1958 to 1962.
Still its hard to compete with 400 to 500 watts compared to the big KW rigs. 
Lets say I worked my fair share.

I assume Heath tried to add just the 6AL5 clipper to the Apache and this 
probably caused the scratchy modulation.  I had a DX-100 for awhile and it 
did have great audio.  I was called upon to MC a net set up on 40 AM to 
monitor a speed boat race down the Mississippi River from St. Louis
to New Orleans.  Using a dipole at 50 feet I was able to stay in touch with 
other control stations on my shifts (day or night).   My only interaction 
with an Apache was one I picked up at a hamfest in about 1995 or 1996.  Back 
when my eyesight let me work on a rig I get it working but found the audio 
scratchy.  Heath may have tried to stay current with more modern modulator 
tubes than the old 1625's (in the DX-100).  I did not have the space for the 
Apache so I did some trading and it wound up with Greg, KX4R.  I do recall 
the nice audio from K4TEA and WA2CLQ (now K1ZM).

These days there is not as much need for QRM busting AM but back when AM was 
king clipping was needed (required) to maintain your spot on a crowded 20 
meter band.

That is my 2 cents worth
73 Dave K4JRB   Then K5MDX