RadioBanter - Dow-key DKC-TR

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Looking for information on Dow-Key DKC-TR tube type TR switch. I have
one without documentation. I found the box it came in, no
instructions.
regards, cullen K5HAL

On Tue, 19 Jan 2010, cullen wrote:

Looking for information on Dow-Key DKC-TR tube type TR switch. I have
one without documentation. I found the box it came in, no
instructions.
regards, cullen K5HAL

What do you want to know? Any old Handbook is likely to have a circuit
that can't be too different from a commercial product (they all have to
be about the same) and describe how to hook them up.

If you're looking for historical information about the specific device,
then I don't know. What's so puzzling about the unit that you need to
know?

Michael VE2BVW

cullen K5HAL wrote:
Looking for information on Dow-Key DKC-TR tube type TR switch. I have
one without documentation. I found the box it came in, no
instructions.

Hi

I also have a DKC-TR, with no instructions.
It should be usable on 160 thru 10 meters.

The two SO-239 connectors that have continuity thru the center pins
are for antenna and TX connections (doesn't matter which is which).
The other SO-239 (at narrow end) goes to the RX.

The cable has a black lead to 6.3V, a red lead to approx 125 to 150 VDC,
and a shield to ground.

The tube used is a 6AH6 pentode.

You should include a low pass TVI filter between the TR switch
and your antenna.

The BAMA mirror site has instructions for the DowKey model TRM
TR switch, which includes general TR switch usage guidance,
but is a different design, using a dual triode tube type 12AZ7.
Keep the cable length between the TX and the TR switch as short
as possible, to avoid "suck out" effects on RX sensitivity.

Also, the TR switch should be used with a class C final, or one
which has cutoff bias applied to the finals during key-up, to avoid
increased white noise in the rcvr.

73,
Ed Knobloch

On Jan 19, 4:04�pm, Edward Knobloch wrote:
cullen K5HAL wrote:
Looking for information on Dow-Key DKC-TR tube type TR switch. I have
one without documentation. I found the box it came in, no
instructions.

Thanks everyone. I had found most of the references. The one piece of
information I did not have in hand was the wire color code. I used
this for years with an HQ-150, CE-20A plus the LA-1. The sheet on the
DKC-TRM did not satisfy my curiosity and my old handbooks are now in
storage.
Now that I have your attention, why is the tube type TR switch no
longer made or used? The idea seems great.
Regards, cullen

On Mon, 25 Jan 2010, cullen wrote:

On Jan 19, 4:04�pm, Edward Knobloch wrote:
cullen K5HAL wrote:
Looking for information on Dow-Key DKC-TR tube type TR switch. I have
one without documentation. I found the box it came in, no
instructions.

Thanks everyone. I had found most of the references. The one piece of
information I did not have in hand was the wire color code. I used
this for years with an HQ-150, CE-20A plus the LA-1. The sheet on the
DKC-TRM did not satisfy my curiosity and my old handbooks are now in
storage.
Now that I have your attention, why is the tube type TR switch no
longer made or used? The idea seems great.
Regards, cullen

Very few people use separate receivers and transmitters.

Few are interested in the sort of break-in that you could get
from a TR switch, they can live with relay changeover.

Transceivers sometimes use the same thing, but it's done with
semiconductors not tubes.

Michael VE2BVW

Michael Black wrote:
Very few people use separate receivers and transmitters.

Few are interested in the sort of break-in that you could get
from a TR switch, they can live with relay changeover.

Transceivers sometimes use the same thing, but it's done with=20
semiconductors not tubes.

And you can make a pretty good one for not much money using PIN diodes.
The Handbook even used to have a design.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Electronic T.R. Switch caution

Some transmitters produce a strong signal into the antenna
in spot mode when an electronic TR switch is used.
I measured about 275mW out from my Ranger II on 40m in "tune" mode,
and 125mW out in "standby" "VFO Zero" position.

You might consider switching in a dummy load before VFO-swishing
the band.

73,
Ed Knobloch

On Tue, 26 Jan 2010, Edmund H. Ramm wrote:

In cullen writes:

[...]
why is the tube type TR switch no longer made or used?

How did you arrive at the latter conclusion? I for one use an
E.F. Johnson T/R switch.

Have you been to your local ham store and looked over their selection
of T/R switches lately?

Michael VE2BVW

Michael Black wrote:
On Tue, 26 Jan 2010, Edmund H. Ramm wrote:

In cullen writes:

[...]
why is the tube type TR switch no longer made or used?

How did you arrive at the latter conclusion? I for one use an
E.F. Johnson T/R switch.

Have you been to your local ham store and looked over their selection
of T/R switches lately?

My local ham store doesn't have a good selection of anything other than
sealed appliance transceivers.

There are tube type TR switches made for military applications, but for
the most part they are too slow for modern signalling methods which is
why the PIN diode units are such a big deal.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On Wed, 27 Jan 2010, Edmund H. Ramm wrote:

In e.net Michael Black writes:

On Tue, 26 Jan 2010, Edmund H. Ramm wrote:

In cullen writes:

[...]
why is the tube type TR switch no longer made or used?

How did you arrive at the latter conclusion? I for one use an
E.F. Johnson T/R switch.

Have you been to your local ham store and looked over their selection
of T/R switches lately?

Have you overlooked "latter", which refers to "used"?

The fact that you aren't likely to find a T/R switch at your local
ham store (if you happened to still have such a local store) is
an indicator that they aren't used, because if there was demand
surely there'd be a commercial product. One would also see the lack of
separate receivers and transmitters, as I already mentioned, so one
could gather there is less reason for such a device nowadays, and even
fewer are using non-matched separates, so that S-line or the SB-line
or whatever handles the switchover.

The fact that some still use them doesn't negate his statement. Surely
it's only a relative handful, and they aren't visible enough. Enough
time has passed since they were common that many hams likely don't even
know what they are.

In the old days there were multiple reasons for using them, and they
were often simpler than the alternatives. Nowadays, other things take
care of the task, whether it's a current equivalent of the TR switch
hidden away inside that transceiver or something else, so the only
people using them are those who want to run an old type station, or
have some specific use for it.

If he'd asked somewhere else, chances are good nobody would question
his point about "nobody using them" since there is less likely to be
users except by boatanchor types, and chances are good that if posted
elsewhere someone would say "what's that?".

Michael VE2BVW