[TowerTalk] Re: [Amps] Relays for RF switching

[Pete Smith]

At 01:11 AM 4/15/04, Vic wrote:

>I needed a remote (indoor) antenna switching unit, and since I had 
>everything I needed in my junkbox, I decided to build it instead of paying 
>$140+ to Ameritron.  I used some relays that I had purchased from All 
>Electronics for $1.50 each; they are "power relays" with contacts rated 
>15a at 120 VAC.  After all, 1500 watts into a 50 ohm line is only about 
>280 volts and 5.3 amps.
>
>Hey, if it worked I'd be in the miser's hall of fame.  However, what 
>happened is that the relays got quite hot after about 15 seconds at the 
>1500 watt level.  They are enclosed in little plastic boxes, but it's 
>possible to touch the bottom of the armature and it is hot enough that I 
>am afraid of what would happen in a contest or long rag chew.
>
>I'm wondering if anyone has ever done anything like this, and if so, what 
>kind of relays they used.  Or, if someone has an Ameritron unit handy, if 
>you would be so kind as to look inside and see what kind of relay they use.
>
>I'm also curious as to why the relays heat up.
>

Puzzles me, too -- both the TopTen remote relay box and the WX0B Stackmatch 
use much smaller 12v SPDT PCBoard relays and are proven reliable at full 
power.  The part number is NAiS JW1FSN-DC12V, and they are available from 
Mouser for `$2 each.


73, Pete N4ZR
The World HF Contest Station Database
is back, at www.pvrc.org/WCSD/WCSDsearch.htm