[Milsurplus] Harvey Wells AR-5A Military Aircraft

[David Stinson]

Jim Isbell wrote:

> I recently got a Harvey Wells AR-5A military aircraft radio.  It has two 
> bands, 200 to 400 Kcps and 550 to 1650 Kcps both AM detection.
Nice find.

> There is a switch on the front with a position for Tower and one for 
> Range and others...
This changed the audio characteristics for either talking to
the tower or direction finding.  One way notches to DFing tones,
the other enhances them.

 > I know that the Range was in the VLF frequency band,
> but did the tower in the late 40s and early 50s use VLF??
Many towers did, indeed talk on LF (sorry, Mac).
There was a "standard" freq (278 KC, IIRC) on which most
civil aviation airports had the tower, weather broadcasts
and directional beacon.  This freq, plus power and antennas
designed to limit transmit range, were intended to allow
operation from airport-to-airport without interference.
The aircraft would call the Tower on an HF freq- typically
3105 KC at night and 6210 KC in the day.  The Tower
would switch from a weather loop (if they used one) to
tower audio and talk back on LF.  While freqs varied
in places of high population density, some form of
this system was universal over North America throughout
the 1930s and 1940s.  HF-to-HF was common only between
aircraft in flight and in the military.
Contrary to the "early VHF" myth,
the dates for CONUS-wide acceptance and change-over to
aircraft VHF have been pushed back far beyond WWII.
I have new data received just this last week
that shows VHF was not in general use by the Navy
until after at least July of 1945.

> 
> This set is extremely clean and is complete with an attached AC power 
> supply.  I have not yet tried it out but am thinking of using it for the 
> final IF of an AM converter (yet to be built) for 80-40-20-10 where the 
> output of the converter will be 200 Kcps chunks of the various ham bands.

Two problems when doing this with an aircraft LF receiver-
First, IF bandwidth:
The IFs of these sets are pretty sharp.  Audio quality will suffer.
Second, Images:
300 KC is pretty low for 40 meters.  You'll have problems with images.
Using one on 75 meters is tolerable, but I wouldn't recommend using
it higher unless you double-convert, and that's a lot of trouble.
I've put aircraft LF receivers on 75 meters with simple converters,
but had to (reversably) "Q-damp" the IFs to make them sound good.

> I have also heard that there is conversion information for this receiver 
> that details the conversion of the receiver to the ham bands without 
> using a converter.

Please don't.  You'll have an unsatisfactory ham band
receiver that will end up in someone's junk pile going
for $1 at a hamfest.  Enjoy your Yea-Com-Wood for listening
to the ham bands.  Enjoy your Harvey Wells for it's history,
or even sans-conversions as a 75-meter IF set.

73 DE Dave AB5S