[GreenKeys] Various XMission forms

[Ralph Mowery]

Depending on the shift and deviation using FM on the low bands could be 15
khz wide or wider. That would eat up a lot of the band.

 

At one time there was some activity on 2 meter FM using rtty.  When I got
involved (around 1980 or so) there was a repeater on the 220 mhz band with
about 20 users.  That was back when the Clegg transceivers could be bought
for about $ 150.  By then ham rtty had gone to 170 hz shift.  

 

I bought a model 19 from a ham and he gave me a TU that was set for the 850
hz shift.  It was the one out of the handbook that used tubes and horizontal
output coils from a TV. I retuned it for the narrow shift.  I had an old
Hamurland receiver that drifted like all get out.  I  had a VFO that was
somewhat stable,so I used the receiver in the AM mode and the VFO to inject
a signal  to get the tones to the speaker.  

 

A friend had a 15 in a room with hard wood floors .  Boy was that loud.  I
was lucky I lived in a house that had a single car carport that had
beenconverted into a room.  The floor was cement and had a layer of
indoor/outdoor carpet.  Not too much noise.  It is  now in y basement with
about the same type of floor.  

 

From: greenkeys-bounces at mailman.qth.net
[mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Dale
Sent: Sunday, February 18, 2018 11:46 AM
To: Ralph Irish; Greenkeys
Subject: Re: [GreenKeys] Various XMission forms

 

Ralph,

 

Very interesting.  I imagine AFSK using NBFM would have been legal above 29
MHz, but disastrous on the lower bands.

 

I've often thought of trying to use the reactance modulator in my AF-67 as a
direct FSK driver: just inject +/- FSK voltage directly to pin 1 of the
reactance modulator tube and see what it does.

 

BTW - In the early 1980's I was in college and poor as a church mouse, yet
still wanted to get on RTTY.  A friend gave me a Model 15 Teletype (but no
cover - man was that loud for the roommates in my apartment!).  I designed
and built a solid state terminal unit that detected only the space tone.  I
think I set it up for around 1000 Hz.  I used an Elmac PMR-8 receiver.  I
had to constantly readjust the frequency using the BFO knob to keep up with
the drift.  Interesting that overloading the receiver with too much RF/IF
gain never really affected copy.  For transmit I used a shift pot keying
circuit tied to the cathode of the VFO tube on my AF-67.  It worked well.

 

When I graduated from college I moved up to an ST-5 T/U and threw the
homebrew away.  Dumb.  But I also moved up to a Drake 2B receiver which was
and is still a fantastic RTTY receiver.

 

73,

Dale

W9DKB

 

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