Ron, I hope my response got to the list.  I didn't see it, but Martin's post
had yesterday's date on it.
Who knows?


-----Original Message-----
From: For blind ham radio operators [mailto:[log in to unmask]]
On Behalf Of martin McCormick
Sent: Tuesday, August 11, 2015 11:50 AM
To: [log in to unmask]
Subject: Re: Ham gear accessibility

   message dated "Mon, 10 Aug 2015 13:30:46 -0500."
	Here's how I still tune up at least for now. I have a Halicrafter
HT37. My receiver is a modern Icom R75 receiver but I do enjoy using split
transmit and receive for a couple of reasons. On a practical level, if the
transmitter blows up, one still has a receiver.

	Technically, one is supposed to be able to monitor one's own
transmissions and this can be done best by actually listening to them if
possible.

	When you run separate TX and RX, you must use a TR or
Transmit/Receive switch or relay. Most transmitters either supply a voltage
to the TR relay or close a set of relay contacts that have the relay voltage
on one side of the contacts and the relay coil on the other side. TR relays
come in all kinds of designs with many of them using a 120-volt coil and
running on AC which means you always need to handle the relay coil voltage
with care but it gets even more interesting.

	I have, for example a Dow Key TR relay which is meant to run on 120
volts but that's not how I actually do it.

	A 120-volt AC coil has quite a bit of inductive reactance which
looks like series resistance when run on AC but if you run it on DC, you can
get the coil to pull that relay closed very nicely on 30 volts AC. The relay
doesn't buzz and it runs a lot cooler plus there is no 120 volt power out
there to accidently contact.

	The relay removes the receiver from the antenna during transmit and
instead puts the antenna across the output of the transmitter. There is also
a set of contacts on the relay that corresponds to a mute or standby input
on the receiver. Many communications receivers have standby inputs on them
for just this situation.

	The idea is that you don't want to hear your receiver's audio while
transmitting as it may cause feedback. Sometimes, you do want to hear it if
you want to monitor your own output.

	I added a couple of special features to my TR relay hookup.

	First, there is a toggle switch that breaks the mute circuit so that
you can still hear the receiver audio during transmit if the switch is open.

	Another feature is a second toggle switch that causes the relay to
always be energized even if the transmitter hasn't closed it's relay
contacts.

	Now, here's why these two switches were necessary.

	The HT37 has something called Calibrate Mode. When you are in that
position, the transmitter sends out a carrier that can be varied from no
output at all up to a few watts. Most people use that to zero their VFO to
their receiver's frequency.
When in that mode, the transmitter does not close the TR relay so my extra
switch closes it and puts the weak carrier on to the antenna.

	Next, I disable the mute and then I can hear the VFO output in the
receiver. I may have to de-tune the receiver for a beat note but one can
easily hear it even though the receiver's antenna is technically only a few
inches of coax between the receiver and the switching relay.

	At this point, one can adjust the grid drive and plate tank until
the tone is loudest.

	As I said, a test with someone actually watching the output signal
strength verified that this works.

	Another thing one can do is adjust the phasing. The HT37 is a
phasing sideband rig which means that the carrier must be nulled out. I turn
the microphone gain down to 0 and listen to the receiver's audio for
carrier. There's lots of stray noise so you have to get used to what you are
listening to.

	If the two phasing pots are way out of adjustment, you hear the
noise I was talking about plus the tone of the carrier.
As you adjust the two pots, the tone nulls out and you're just left with the
noise. When you transmit, you can hear your audio and get a pretty good idea
whether or not there is a problem.

	After that, I can flip both toggle switches to a normal mode where
the receiver mutes during transmit and the relay is controlled by the
transmitter.

	In the seventies, I was a student at Oklahoma State University and
belonged to W5YJ which is OSU's amateur radio club. Our HF rig was a Central
Electronics 100V which was quite a beast in it's day. It was also a phasing
rig but like today's rigs did not need to be tuned. You did, however, have
to sometimes null out the phasing circuit and I also did that by listening
to the transmitted audio.

	That's one way to do things and I am sure many more people have come
up with such things as listening to their power transformer's hum and, of
course, the audio tuning gimics which were quite useful.

	As for how to stay on frequency. One feature that used to be common
on older receivers was the crystal calibrator. This was a 100-KHZ crystal
oscillator that was deliberately designed to have a very dirty output full
of harmonics.

	If you cause the output to be a pulse wave form, one gets harmonics
well up in to VHF. So, you would hear a strong carrier at every 100
kilohertz throughout your receiver's tuning range. I remember a few rigs
that had 25-KHZ crystal calibrators also so you could use the 100-KHZ
calibrator to count from some known spot up to near where you needed to be
and then switch to 25-KHZ and count those birdies to as close as possible.

	I never went outside an amateur band that I know of but I sure got
mixed up, one day, and got out of the General part of 15 meters. I called CQ
and didn't get a contact and then realized what I had done but never got a
ticket. I think my signal was probably too lousy for the FCC to mess with.

Martin WB5agz

> Attention all hams here on our list who have been hams going back into 
> the 40's, 50's, and early 60's!!
> 
> 
> 
> Post back to me and share with me how you tuned your transmitters and 
> receivers back in those days. What kinds of creative methods did you 
> use for, say, tuning up your transmitters with the PI output networks, 
> dipping and loading, to make sure you were not only in resonance, but 
> resonance on the right band? What kinds of techniques did you use to 
> make sure you were within  the frequency boundaries permitted by your 
> license class and didn't get over into the Advanced or Extra Class 
> frequencies, or outside the American band allocations entirely? What 
> kinds of advancements or features were eventually added or available 
> over time that made these kinds of tasks easier?
> Be as detailed and descriptive as you can. I am incorporating this 
> information in a research project I am working on.