[HBR] That General Coverage HBR Project -- 3

[Walt Hutchens]

There are some pictures of the chassis with parts mounted at:

http://timbreblue.com/radio/hbr1006.html

Looking at the under chassis view, the upper left compartment is the 1st
mixer (no RF stage) and crystal calibrator.  The extra socket hole is in
case I wind up using two tubes for the calibrator -- I want 50 kcs from
a 100 kc crystal, so ... don't know.  The center compartment is the 2nd
mixer and 1454-1704 kcs local oscillator.  Upper right quarter is the
simpleminded synthesizer that supplies the mixing signal to the 1st mixer.

The signal leaves the 2nd mixer box through a 4096 kcs ladder filter
that will be mounted on top of the chassis.  You can just see the 1/4" 
holes for that below the coil form in the compartment and above the IFT
directly below, outside the compartment.  Two stages of IF run off to
the left from there.  The two tubes all the way to the left are the
BFO/AM  (plate) detector and a 6BN6 product detector.  Coming back to
the right are the 1st audio/phase splitter, and p-p 12AU7 2nd audio.

The variable cap at the lower left corner tunes a VXO BFO.   The two
tubes sitting by themselves at center left are 12X4 rectifiers for the
160V HV -- all four sections in parallel.  Bias needed for the AGC and 
standby circuits is rectified by a diode-connected triode section of the 
triode-pentode 1st IF stage.

The top rear view shows the two mixer subassemblies -- they can be
removed/replaced without major destruction.  The three dual crystal
sockets contain the band crystals for 250-kcs segments of the six 'real'
ham bands.  The two black dots toward the upper left are the holes for
the crystal filter assembly.  The speaker is stolen from a military
LS-166.   I checked the response with an audio oscillator -- it is 
indeed 'communications,' with almost no low end and little above 3500 cps.

The front view shows the usual suspects.  The crystal is the 'external'
crystal that can be used to add any desired additional 250 kcs band
within the range of coverage.  The dial's a Miller MD-4 with a two-speed
drive and replacement (LARGE) knob.  The dial and drive are actually
made by Jackson Brothers, though labeled 'Miller.'

The knob at the lower left corner and the top one just left of the dial
have 5:1 J-B drives; these are the front end and synthesizer tuning,
respectively.  The pointers are made from aluminum and will be painted
white to match the fixed pointers on the other knobs.

The empty hole at the lower left of the dial is for the bandswitch.

Walt
KJ4KV