Homebrew T/R relay for BA TX/RX

[w9bea]

Good Evening all:

I am re-assembling my BA stations after a hiatus.  I am interested in building 3-4 T/R relays similar to the Dow-Key product.

I have a few Dow-Key's.... One is NIB, the other well used and might have seen some zorch in it's youth.

I am thinking: A small bud-box with 3-SO-239's sprouting out of it. A DPDT relay with a NC to Common cantact that will route to the RX.  The TX energizes the relay swing the armature to the NO contact to pass RF to the antenna.  The other contact is used to short the STBY contacts on the RX.

Anyone got a schematic/pix of a homebrew TR switch I can look at for ideas?  I suppose that I could root around at a fester for 3-4 relays, but does Mouser or Newark have something cheap that I can send for?

If all goes well, I hope to be on the air this fall with my V3 and a few Johnsons.

Thanks for your help guys!

73--Wally W9BEA

w9bea@sbcglobal.net

[ve6pg]

...wally...i use simple ac relays,as you have suggested....energized by the 110v from the tx,mutes receiver,and throws the antenna to the transmitter,back to receiver,and un-mutes the receiver...these relays are cheap,and use a small metal box...i use 2 so239,and one phono jack,instead of 3 so239's...the phono jack goes to the receiver's antenna jack...cheaper,and the phono jack line carries no rf....check out a local web page here in ontario,  "VA3NTH'S SHORT SKIP"...it is used by local am guys,and i posted some info as what you are searching for...pix of a relay in box,and skizmatic....see ya...tim....sk...

[Ed-VA3ES]

....check out a local web page here in ontario,  "VA3NTH'S SHORT SKIP"...it is used by local am guys,and i posted some info as what you are searching for...pix of a relay in box,and skizmatic....see ya...tim....sk...

That URL is:
<A href="http://va3nth.no-ip.info:8080/forum/viewthread.php?forum_id=3&thread_id=27"><b>VA3NTH'S SHORT SKIP</b></a>

[WA1GFZ]

P&B 25 AMP DPDT work well. I use 120 VAC coils on 28 VDC.
5 KW tested with two sets of contacts in parallel.

[Bacon, WA3WDR]

I have used common relays and even SPDT AC wall switches on HF, and I have some 400-470 MHz amplifiers that not only use general purpose relays for antenna switching, but they put them on daughterboards to replace some other relay that I guess they couldn't get any more.  They work fine, although I would like it better if the PC board was laid out to use these relays directly.

[K6JEK]

By all means consider Don, K4kyv's simple and effective relay sequencing.   You can find threads about it in this forum and an article about it in Electric Radio.   I use it with DIP relays which directly handle the low current tasks and fire other relays for the big stuff, antenna switching.  The version Don describes is 24V.  The version I built is 12V, fits in a small plastic box with SO-239's for transmitter and antenna, BNC for receiver, color coded RCA's for PTT in and mute and a stereo mini jack for two stage transmitter keying.  If I needed it, I could add another jack for amp keying.

An alternative is to buy Bob Heil's foot switch.  It does sequencing all by itself.  

You'll sleep better, grow old more slowly and enjoy life more if you sequence.

Jon

[David, K3TUE]

By all means consider Don, K4kyv's simple and effective relay sequencing.   You can find threads about it in this forum and an article about it in Electric Radio.

This is the thread http://amfone.net/Amforum/index.php?topic=6211.0 to which he is referring.

You'll sleep better, grow old more slowly and enjoy life more if you sequence.

Glad I was set on the right path at this early age. 

[ve6pg]

...HEY ED...TNX FER POSTING THE LINK TO CHRIS' WEB PAGE....SK..

[Bacon, WA3WDR]

The current in an AC relay is substantially lower than E/R would suggest, because of the inductance of the winding.  I can believe that 28VDC would work OK Fine on a 120VAC relay.

[Jim, W5JO]

Several years ago I got tired of 115 volts all over my Globe King 500 A working the relays.  I found a small 28 volt transfomer, too the output and bridge rectified it, then use it to power all the relays.  Works just fine.

[w9bea]

Good Morning All:

I appreciate the good ideas that are being put out here.

I am still a month or two from getting the shack set up.....  Still building shelves, moving items, etc.  I will print up all of the aforementioned for use in a few weeks.

Thank you everybody!

73--Wally W9BEA

[WA1GFZ]

Mark it is an ac relay coil working at DC.  It works fine. Relays are usually over powered to handle vibration. The inductance of the coil also limits ac current.

[WBear2GCR]

One way or the other, I forget which, using the DC w/AC or the AC relay w/DC causes the coil to hum and buzz a bit more than one might like. Iirc there is some minor difference in the way the pole pieces are made and the material used (?) between the DC & AC relay. Afterall, they are just "solenoid" coils, wire wound around an iron core, and the copper sure as heck doesn't know AC from DC... the coils are usually spec'd by impedance/resistance - the voltage thing is just to make them easy to apply. Also the pull in voltage is usually well short of the "operating" voltage.

I thought that the main point of the "DowKey" style relay was that the coil & armature are outside the RF sealed case. This means that in the event of a zorch, no RF will find its way from the contacts to the coil and back out to the world, or through ur powersupply...

There is also the option of the tube based "TR" switch... the transmitter is always connected to the ant and the tube acts like a preamp when the xmiter is not transmitting and as a blocker/limiter when xmitting, up to a killowatt or so... Schematics are in some of the Bill Orr books and elsewhere. DowKey sold one for a while, still have one here. Works. No moving parts. Slick. Takes fils and one B+ line & gnd iirc. Used to plug it into the acc socket on the back of the rig...

        _-_-WBear2GCR