Interesting HB Transmitter

Wilson Lamb infomet at EMBARQMAIL.COM
Tue Mar 30 09:32:44 EDT 2010

I have recently come into a HB XMTR built by a friend of my dad, in the late 
50s or 60s.  It works on 80 and 40, but not yet higher.  I'd like to find 
documentation of the original design, to save my having to dope out the 

The tubes are 6AG7 (2), 6N7, 6146, 6AX5(2), 5R4.
There is a bandswitch, with five positions.
The rectifier is the old bridge circuit using cathode type rectifiers to 
avoid multiple filament windings.
The multiplier string is tuned by B&W type air core coils and other coils on 
brown plastic forms.  There are many compression trimmers, at least two for 
each band.  The interesting thing about the tuning hardware is that there 
are translucent plastic plates mounted over holes in the chassis with the 
brown coil forms below and the trimmers on top.  These coil/trimmer 
assemblies look like commercial components, but he may have fabricated them, 
who knows.

The rig is fairly complex and took considerable time to get together.  Most 
of the filament/B+ wiring is shielded, probably for TVI considerations.  The 
coil is a roller assmbly from an ARC-5.  It looks like the output was meant 
to be a pi network, but there is no loading capacitor.  The output is taken 
right to the back of the chassis from the far end of the coil, like he meant 
to feed some sort of external tuner or 50 Ohm antenna.  It loads nicely into 
a 50 Ohm dummy load, but I clipped a 500pF cap across the output for 80 

I know it's a long shot, but does any of this sound familiar to anyone, 
especially the tube lineup?  It's a little unusual to have a 6N7 mixed in 
with 6AG7s.  I have been through the QST archive and have even asked Zack 
Lau about the rig, but found nothing.  I don't think it was an ARRL design, 
but doubt it was original either.

Thanks for any ideas you can provide,

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