[Boatanchors] Close Call With a SX-100

[Garey Barrell]

Bill -

Not all that uncommon a problem.   The other way this can happen is if 
someone "tightens up" the coax fittings on either side of the relay 
output.  They CAN be screwed in far enough that the "arm" contacts are 
sandwiched between the two output contacts.  Dow-Key style relays worked 
very well for a LONG time, but as my dad used to say, "some people can 
break and anvil".  (Not referring to me of course!!  :-)  )

Drake put a #12 bulb (essentially a #47 bulb in a strange package) in 
series with the antenna input of the TR-4.  Not much good for lightning, 
but (probably) would have saved the antenna coil.   USUALLY you can get 
by with a couple of silicon diodes in series in parallel with another 
"reversed" pair across the antenna of a receiver.  That gives you about 
+/- 1.4V p-p limiting, which is ok unless you live close to a BC station 
or in a similar High RF area.   They should be power diodes (1N4004 or so).

73, Garey - K4OAH
Atlanta


Bill Stewart wrote:

>I recently built a wooden rack to house a SX-100 and several transmitters. I rigged up the control wiring so I could use a common Dow type (actually an Advance relay) T/R relay. First tests of the SX-100 and a Viking 2 combo thru the switching worked fine. I went back to dress up the wires and to add an elbow coax connector to the common connector on the end of the T/R relay and then sat down to enjoy my great switching circuit. Upon keying the Viking 2 I noticed the loading was way off and no output on the swr meter....also noticed the SX-100 was now dead as a hammer on 7 Mc (where I was loaded up)...other ranges were ok. On scratching my head and undoing some of my coax wiring I found that when I had screwed on the elbow, I had twisted the center contact lever on the T/R relay causing it to short across the transmit and receive connectors thus putting about 120 watts of RF into the SX-100. I found the ant. coil for the 7 MC range to be open and saw on some wires close by the coil the tell-tale black mark of a flash-over. I was lucky in that the burn-out occurred about 1/4 inch from the connection and was able to solder the burnt wires back together. The rcvr is back to normal now...whew!!.
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