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Author Topic: Three inputs on dow-key?  (Read 3626 times)
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« on: January 05, 2006, 07:51:43 AM »

Well, a DX-100 finally goes on the air at WN5T today.  Grin  It's not the one I'm refurbing...but I stumbled into another fully working model for not much more than the price of re-capping the hamfest special.  In any case, I'll have pleny of spare parts! 

My question is about my t/r relay.  I have a Magnecraft 110V relay...with three inputs.  I have ohm'ed them out to see which is NO and which is NC.  There is a third SO-239 that puzzles me.  With the relay open, it is connected to the NC.  With the relay closed, it is connected to the NO... In no case is it connected to what I'm considering the ANT.

NO  >------- |
  ?   >------- | -------< ANT
NC   >------  |

Am I considering the wrong SO-239 as ANT?  If not, what, pray tell is this thrid eye for?
I guess it could be considered....

NC >------|
ANT>-----|------< ?
NO >----- |

Thanks for your help.  Hope to see you on the bands. 

Now, which RX to use?.....  (No great choices...just choices...SX-110 or SB-310...hmmm....)


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Posts: 144

« Reply #1 on: January 05, 2006, 05:42:53 PM »

The antenna goes to the common port.The RX goes to the NC port and the TX goes to the NO port.When the relay activates it swings the antenna AWAY from the RX and connects it TO the TX.

Learn from others mistakes.You will never live long enough to make them all yourself.
« Reply #2 on: January 06, 2006, 12:35:10 AM »

My confusion related to the extra (?) so-239.  One fellow suggested that the configuration might be to allow instllation options...  I guess the question of "which one is the right ANT conx" is moot, 'cuz either way will work.  I just was wondering if there was additional functionality made possible by the "extra" conx. 

BTW, got the DX-100 up and running.  Sounds like a 3kc rig.  I still have some fiddling to do in order to accustom myself to this TX...including playing with different mics...before I contemplate the massive number of recommended mods.   One interesting thing about this rig is that it has BNC conx's added to the chassis.  I'm assuming that they are for o-scope monitoring...though I haven't any documentation proving that.   I wish the Heathkit manuals  gave more information on tuning.  I guess I'll just have to try the BNCs to see if they are for a scope.  That would sure make fine tuning a snap. 

Rob K2CU
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Posts: 346

« Reply #3 on: January 09, 2006, 07:12:00 AM »

Yoiu are assuming that the relay is an ANT?TX?RX changeover relay. It sounds like it was intended to be used to insert something in the tranmission line path, or a means of provding a termination to an otherwise open line. For example: Suppose you had a pair of cross mounter 2 meter yagis and wanted to do circular polarization. you would be inserting a 90 degree delay in one feedline. If you wanted to reverse the polarization, you would want to insert an additional 180 degrees in the other feedline. this relay would allow you to do this.  The terminal you call ANt and NC would be the normal path. you polkace the extra coax delay line between the NO and mystery terminals.  When energized, the added line is inserted.  For low band woirk, you could use this to steer a pair of phased verticals.

Another use is to provide a proper terminataion of a non selected transmission line. Suppose you are using the relay to select either of two antennas. By outting a 50 ohm termination on the mystery connector, you correctly terminat the line of the unsed antenna, reducing unwanted stray RF from getting into your shack from the unterminated and now high VSWR line.  Energy would go into the dummy load, not your shack.
« Reply #4 on: January 09, 2006, 12:27:04 PM »

I hadn't considered that, Rob...  Thanks.

A friend has a ham radio store and ordered this one for his Ranger...but it uses 110VAC (perfect for the DX-100) and the Ranger uses (or has been modded) for I picked it up for a song.  The locals with the most AM experience looked at it like it was a red-headed step-child, but deemed it functional aftering e-mailing pics of their 3-connector relay switches. 

Even it is FUBARS, 'fest season is a-comin'...

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