[AMRadio] Relay Rating (JAMES HANLON)

Jack Griffin jtg4300 at yahoo.com
Thu Dec 17 05:48:46 EST 2009

Jim Hanlon, W8KGI
Do you have the relay specs for a Western Electric 303J?
It is an octal and may have the coil on pins 7 and 8; I measure about 100 ohms across them. It is sealed with a High Pressure warning on the metal case which is about 2 inches high.
Thank you, Jack, WA1BRI

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Subject: AMRadio Digest, Vol 71, Issue 23
To: amradio at mailman.qth.net
Date: Wednesday, December 16, 2009, 12:00 PM

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Today's Topics:

   1. Re: Relay Rating (JAMES HANLON)


Message: 1
Date: Tue, 15 Dec 2009 10:54:29 -0700
From: "JAMES HANLON" <knjhanlon at msn.com>
Subject: Re: [AMRadio] Relay Rating
To: "John King" <k5pgw at yahoo.com>
Cc: AMradio <amradio at mailman.qth.net>
Message-ID: <SNT106-DS60CC16FAACA64484D9923A0880 at phx.gbl>
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I can't beat Bernie's reply from experience, but I will add that 300 watts of carrier would produce 2.45 amps of current into a 50 ohm load and 2.04 amps into a 72 ohm load, so you won't be anywhere near "overloading" the 10 amp rated contacts.  

Personally I use a mercury-wetted relay to switch my tuned-to-50-ohm antenna load between my transmitter and receiver.  The transmitter can deliver as much as 600 watts CW from my SB-200, which corresponds to 3.46 amps into 50 ohms.  My relay is a Western Electric 276 rated for 5 amps "DC."  I do not hot switch it, at least intentionally, since I have a timed QSK system.  It holds up just fine in this service.  

Jim Hanlon, W8KGI


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