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Author Topic: Dow Key Relay Issues  (Read 658 times)
N4PSE
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Posts: 69




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« on: October 06, 2005, 12:32:17 AM »

I think the dow key relay I am using with my BA stattion may have blown the 110v coil. What sort of resistence should I read between the 110 v terminals if it is good? And what about if it is bad? I was thinking that  a bad one goes to infinity resistence and this could be the cause of my TX (which suppllies the 110v) blowing fuses? Appreciate your advice and comments. Jim
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WA9FZB
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Posts: 171




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« Reply #1 on: October 06, 2005, 05:29:51 AM »

The coil of a relay could go bad in two ways.  The usual is the "open" circuit, which as you noted would show infinite resistance.  If this happens, nothing will happen to your transmitter due to the AC supplied to the relay.  The transmitter might, however, blow fuses because when the relay coil goes open, the transmitter will have no antenna when transmitting.  The resultant out-of-resonance condition of the final amp may draw enough current from the AC line to blow the fuse.  Try transmitting directly into the antenna, bypassing the relay to verify this.

On the other hand, once in a great while a relay coil will short out, and then would show near-zero resistance.  If this happens, it may immediately blow the AC line fuse.

Lots of things could cause the transmitter to blow its fuse.  You really need to isolate the cause if possible, then trouble-shoot.

Good luck, es 73

Steve  WA9FZB
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WB2WIK
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Posts: 20574




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« Reply #2 on: October 06, 2005, 07:56:15 AM »

Every bad one I've seen had either one of two problems: Blown open coil (infinite or near infinite resistance), or magnetic pole piece dislodged so the relay will no longer function on AC (usually still will work on DC, though).

Even for a BA station, I'd recommend, if you need to replace the relay coil anyway, go with low voltage DC and convert whatever's driving it so that will work.  Way safer, and the coils are easier to find.

WB2WIK/6
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K3HVG
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Posts: 149




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« Reply #3 on: October 07, 2005, 05:41:06 AM »

I measured two of them and both were 500 ohms.
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N4PSE
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Posts: 69




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« Reply #4 on: October 07, 2005, 08:23:51 AM »


Thanks for the feed back- will post what I find when I have time to trouble shoot it this weekend. Jim
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WA2DTW
Member

Posts: 91




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« Reply #5 on: December 28, 2009, 07:12:21 AM »

Does anyone know how much RF power one can switch with a Dow Key relay?
Thanks and 73
Steve WA2DTW
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W5RKL
Member

Posts: 891




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« Reply #6 on: December 28, 2009, 08:29:28 AM »

I believe the Dow Key relays were designed to handle 1KW.

You can build you own antenna change over relay using a metal box, 3 SO-239 connectors, some wire, and a heavy duty DPDT relays found on the various parts outlets such as All Electronics, Mouser Electronics, Allied Electronics, RF Parts, etc. I built 2 of them. Use them with my Apache TX-1 and Marauder HX-10 and they work perfectly.

73s
Mike W5RKL
Happy Holidays
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