[Boatanchors] DOW KEY info

[Ed Tanton]

///snip At 09:44 PM 2003-02-10, Dave Roscoe wrote:
>Can someone fill me in on info  re:  a Dow Key TRM-1 changeover relay. It 
>uses a 6EH5 tube.  I think they use the same scheme as the EF 
>Johnson  model  but not sure.
>
>1. What are the power supply requirements for the tube ?
>2.  Which are the RX and TX terminals?   Since there is no "hard" 
>contact  (as from a relay) , I am not sure how to pin down which is 
>which.  A schematic would help too.
>
>Thanks in advance from:
>    Dave W1DWZ
>///snip

Hi Dave... MY DKC-TRM-1 uses a 6CB6 Sharp Cutoff Pentode. I'd BET the power 
connections/etc. are the same. There were several variations... and the way 
you connect a T/R SW with only two connectors is: use a coaxial T connector 
right at the transmitter (attach a double-male connector to the TX, then to 
one side of the T connector.) Connect the ANT to one side of the T... and 
you have connected the other side to the transmitter. The 3rd (bottom of 
the T-so to speak) connector goes to the INPUT of the T/R SW. Your receiver 
then connects to the output. If this isn't clear... let me know, and I'll 
draw it. You can also take a look at the connection instructions I have 
written on one of my web pages: <http://www.qsl.net/n4xy/accessories-2.html> .

There should be a 3 conductor cable for power: RED is B+; Black is GND; and 
the other (white? I forget) is the filament. Double check this by measuring 
it out with your ohmmeter: The filament wire will look like a short... but 
have SOME resistance to GND. Obviously, GND ought to be zero ohms. The 
other wire is your B+.

If you need to identify which RF connector is the receiver output, find the 
coil, and note where the capacitor goes that taps from it. The other 
connector goes to the T-connector connection you have at the transmitter.

Now, if it's a THREE connector T/R SW, the ANT and TX connector center 
connectors are simply wired through the unit-as shown in the drawing. Zero 
ohms from one to the other, but infinite to ground. The 3rd connector is 
the receiver output.

I love using a T/R SW... the breakin is terrific! I use the B&W 380-B which 
is a 2-terminal unit. One thing to be CERTAIN of: ALWAYS use a Low Pass 
Filter AFTER a T/R SW, BETWEEN it and the ANTENNA.

By the way... T/R SW are CW ONLY.



73 Ed Tanton N4XY <n4xy@earthlink.net>

Ed Tanton N4XY
189 Pioneer Trail
Marietta, GA 30068-3466

website: http://www.n4xy.com

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