[AMRadio] In Defence of Old Buzzard Transmissions


Donald Chester k4kyv at charter.net
Mon Oct 12 04:13:35 EDT 2015



From: AMRadio [mailto:amradio-bounces at mailman.qth.net] On Behalf Of Rob
Atkinson

> When I first started regularly operating AM, I don't think I realized what
has to happen to get from receive to transmit with separate transmitters and
receivers.  When I go from receive to transmit with the 3-400 rig, the
following events take place when I flip the toggle switch to transmit
(having expelled all foot switches from the
station):

> The T/R sequencer sends 24 v. to relays that key on the VFO, flip the big
T/R antenna relay to the transmitter and switch all receivers and rx antenna
preamps to ground.
about 2/10s of a second later the sequencer sends 24 v. to a pilot relay in
the rig that switches on 120 v. to a bigger relay coil and it closes and
energizes the final plate supply primary and driver to put the transmitter
on the air.

> Then I can start talking, although if the other fellow has a strapping
signal with good audio, I'd rather keep listening.

> On going to receive the reverse of everything happens.

> All of the above is probably standard procedure and common knowledge for
most operators.  It also explains why once I get into transmit I am willing
to stay there for a while.  Not interested in flipping through all that and
back again to make a 5 second transmission on a regular basis.

But if I read that correctly, you only flip one switch, and the sequencer
takes care of the rest, so you have about a 4/10 second delay.  That
shouldn't affect your ability to do the fast-break type of QSO if that's
what you wish.  My sequencing completes in only about a quarter of a second.
I hold my T/R switch in one hand while operating, or rest it in my lap on a
hook attached to the operating desk.  It is tied to the rig via a spiral
cord similar to that of a hand mic, actually a stereo headphones extension
cord on which I replaced the connector with the switch on one end.  It
extends out fully to about 12 feet, allowing me to hold the switch in one
hand and walk behind the transmitter where I can switch the transmitter on
and off to see what's happening if I need to observe or troubleshoot
something. 

I tried a foot switch one time shortly after getting my first station
together and it sucked, so I mounted the T/R switch on a small sub-panel on
the operating desk. Later on, I added a D-104 desk mic  with G-stand for
operating phone, before coming up with the idea of attaching the T/R switch
to the end of the spiral cord, something that wasn't totally my own idea.
It occurred to me after visiting another ham's station (don't remember who
or where).  He had a regular toggle switch attached to the end of a piece of
zip  cord with electrical tape wrapped over exposed screw terminals - a JS
arrangement but it worked. I improved on the idea by using the spiral cord,
and instead of a run-of-the-mill toggle switch with exposed terminals I have
a high quality Bakelite a.c. line cord switch.  Rob, you remember the
switch; we found a bunch at Dayton a couple of years ago, where I picked up
some for  spares. I hate a switch attached to a desk mic almost as much as I
hate a foot switch (I think a foot switch is just plain silly). My T/R
switch on the spiral cord works well with my boom-mounted microphone.

With this arrangement, I can do fast break or old buzzard round table as I
see fit.


> If the final comes on, then about 2/10 second later, h.v. comes on for the
rig's modulator.

Looks like your sequencer set-up has a total of three-steps.  Do you have
two separate sequencers in tandem, so that step 2 of the first sequencer
initiates step one of the second, or did you design the sequencer to operate
in three steps? Mine is two-step. When I first actuate the switch to
transmit, the antenna change-over relay, the monitor scope and the VFO all
come on instantly, as the receiver turns off, along with the antenna
shorting relay I use as an added precaution to protect the receiver's rf
input coil. In step two following about 2/10  second of delay, the
transmitter comes on. When I switch back to receive, the whole  process is
reversed.  One master relay controls power to all the plate transformers in
the transmitter, so the rf exciter, modulator and final all come on
simultaneously.  I use arc gaps across the primary of the modulation
transformer to protect it in case the load is lost as a result of a failure
associated with the RF final. Like you, I use a  pilot relay to activate the
big antenna change-over, since its heavy-duty coil is 115 volts a.c. while
all the rest of my relays run on about 30 volts d.c. The main purpose of my
sequencer is to avoid  hot-switching the antenna change-over relay, which
was burning up the contacts.


> One thing that is irritating is when a ham with a weak signal lets his
carrier drop with
> no indication that he deliberately ended this transmission.   If he is
> piss weak you might not even know.

That drives me up a  wall, when someone makes a lengthy transmission and
then abruptly drops the carrier for me to reply, unannounced.  It's not all
that difficult to say "go ahead" or "over" at the end of a transmission.  If
the QSO is fast-break, that's not so much a problem because everyone
anticipates that you will say only a few words before dropping the carrier.
In fact, in a fast-break QSO where everyone has a solid signal, it can be
annoying for everyone to say "over" at the end of each transmission. If
signals are marginal, it helps to give some kind of indication that the
transmission has ended, regardless. (anything except a CB style "roger
beep")

Speaking of annoying and chaotic, the very worst has to be to operate AM
using VOX, particularly making long transmissions with the carrier dropping
out and back in at every pause in speech.

Don k4kyv


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