[HBR] pondering an HBR

[Walt Hutchens]

Tom said:

> They worked for me

>>>> underside (left) http://w0ep.us/radio_stuff/unkown_rx/GEDC0205.JPG
>>>> underside (right) http://w0ep.us/radio_stuff/unkown_rx/GEDC0206.JPG
>>>> topside            http://w0ep.us/radio_stuff/unkown_rx/GEDC0213.JPG
>>>> front            http://w0ep.us/radio_stuff/unkown_rx/GEDC0218.JPG

And for me too on a computer with a different browser.   I will explore this
problem further as I have opened many, many .jpg files in the past without
difficulty.

Having spend some time studying the photos, I'd say get the receiver
working,  first.   It's an uncommon design, perhaps an original and
certainly innovative, the metalwork is quite decent, and the problems and
relatively klutzy wiring can be fixed or replaced.   Worst case you 'rekit'
the thing and rebuild it with new small parts, cleaned up metalwork, and
either a retouched or repainted front panel.   MUCH easier than starting
from scratch and you'll have a very unusual (but decently functioning)
piece.

(So many home brew receivers simply aren't good enough work to be worth
restoring.  When the metalwork is sloppy, holes were enlarged with a
screwdriver, and the parts salvaged from a 1940 BC receiver using a 250 watt
iron, and the wiring a mixture of bell wire and scraps, it's a parts set, at
best.)

This appears to be double conversion, first to an IF that might be 1415 or
2830 kcs (both are command set IFT frequencies) but might use a command set
IF that has been modified to some other frequency.   The clue will be that
pair of crystals visible underneath on the left side of the chassis between
the first pair of IFTs: They are most likely 85 kcs apart, centered on the
center frequency of the 1st IF which has just that one IFT.   The 'sideband'
switch selects one or the other so the 85 kcs signal is either passed as it
is or is flipped.   That allows use of a fixed frequency 85kcs BFO --
certainly an advantage.

The crystal at the rear of the chassis inside may be a calibrator crystal or
it may be something else -- the '455' is suspicious.   But it is most likely
a calibrator.  The missing 6AU6 would be a reasonable choice for that
function and if not there, the radio would still work.  I haven't seen that
particular crystal mount before -- looks like a shortened version of the one
that the Navy used in some HF transmitters of WW II vintage, having three
1/8" pins.   I do have some of the more common taller ones, as well as
(pretty sure) the socket for them.

Most of the knobs are from the BC 342 receiver, a design used in Army ground
applications in WW II.   It's basically a late 30's set.

That appears to be a home made rotating drum slide rule dial.   Those are
NOT common!   String drive from the bandswitch shaft to rotate the drum to
the proper band but it looks like that string may be missing.  Also a string
drive for the tuning cap.  Look at the gearing at the front of the set: I
don't know what it does but very few hams remount command set gearing like
that, as it takes careful work to get the spacing accurate enough for it to
work at all with gears of that (relatively fine) pitch.

The oscillator and antenna coils appear to be separately tuned.  I see only
two caps: perhaps another one is hidden in front of one of the two visible
ones or the mixer stage may be fixed-tuned.

I get the impression that this set may be unfinished.  The air trimmer caps
that would logically be for the oscillator don't seem to be hooked up.

There's really not much here that would be a strong foundation for another
set -- HBR or otherwise.   The 85 kcs IFTs are as close as it gets and
usually those can be found rather easily.   Except for those trimmers, the
air variables aren't great by any means.

I would either get it working in this form (with or without some degree of
rebuilding) or keep it as-is, as a museum piece.   It's plenty unusual.

If working I'd expect it to be usable but a bit short of stability and with
some backlash in the tuning due to the use of tuning caps that aren't suited
to a precision job.

Walt
KJ4KV