[Hallicrafters] HT-37 CW

[W5HTW at att.net]

 I need an explanation of the Function and Operation switch settings on my
HT-37 for CW operation.  I do have the operating manual and a schematic and
have studied them.  I'm using a Dow antenna relay to a shared antenna.  The
manual states for CW operation to set the Function switch to CW (that seems
entirely reasonable) and implies the receiver will be active only on Standby
and CAL positions of the Operation switch - which the receiver is.
   The problem is there is no key-closed output in these settings.  In fact
the schematic shows that when the Operation switch is in Standby and CAL
positions the key is out of the circuit (switch OS 1R).  Keyed output will
only occur in the MOX position of the Operation switch.
   Do I need to manually switch to Standby (or CAL) every time after sending
CW to make the receiver active?  It seems to me the Control Output and Dow
relay ought to allow automatic transmit then receive.  Am I missing something?
 Thanks.
Skip Magnuson  KD7VRM
P.S. One of these days I will get on the air.


It sounds like you are asking if, using the word "automatic", the combination
can be switched to transmit or receive by simply pressing or releasing the
key.  In other words, 'break-in operation.'  My guess (and it is only  a
guess!) is the answer is "no."  Or:  "Yes, you do have to switch manually to
Standby to make the receiver active."  

Many of the older transmitters, Collins, Drake, etc., did semi-break-in, by
using the VOX circuitry of the rig.  Since the CW oscillator actually keyed an
audio circuit, unbalancing the modulator to inject carrier, pressing the key
switched the rig from receive to transmit, and releasing the key switched it
back to receive.   That would also operate the external DOW relay, though most
such rigs had internal antenna changeover relays.  

Using MOX, you have to manually switch the rig from transmit mode to receive
mode by switching the MOX back to Standby.  If you were using separate
antennas, and not the Dow relay, you could indeed leave the transmitter in
MOX, and still receive, but then you would be feeding full output to the
unmuted receiver.  A lot of us did that with lower power, like 15-25 watts
output, but at higher levels, even with tube receivers, the receiver doesn't
recover from that 'shock' to its AGC very quickly, and remains desensitized
for a couple of seconds.  Of course, that method also allowed direct
monitoring of the transmitted CW signal, but at greatly reduced RF gain.  

If your HT37 can be keyed 'automatically' using VOX, then, yes, it can be done
the way you think.  When you press the key, the audio tone will trip the VOX
and send the rig into transmit mode.  That will operate your Dow relay and
mute the receiver (or desense it, whatever you are doing.)  When you release
the key, at a time determined by the VOX DELAY, the combination will return to
receive mode.  

What I am discussing is general theory, not specifics, for I have not owned
nor used the HT37.  I don't know if it has VOX and if so, if it used an audio
tone to tigger it on CW.  (Most did, but not all.  Many rigs of that era
required a VOX accessory be purchased and plugged in.)   If it does not have
VOX, the answer is pretty much no, you can't do that.  It would have to be
manually switched. 

Nothing wrong with that.  Often on my Drakes I used manual switching (via a
footswitch) on CW, rather than using the semi-breakin.  This is especially
true if I drop to slow-speed CW where pauses between characters, or even
within characters, may cause T-R switching.  At higher speeds, 8 wpm or so and
above, the VOX delay is set long enough it does not drop out between
characters, so I can return to vox-controlled T-R.  

Put it on the air and we'll have a go at it!  Will be glad to work you on CW.
Probably 80 or 40 meters. 

73
Ed


.  
--
Ed Brooks, W5HTW
http://w5htw.home.att.net/index.html
Active since June 1956 Extra since
Jan 1970