That's a real mystery John. Don should know if others have experienced it. It sure sounds like something in that environment. It's an even greater mystery since it's happened more than once, and now with a good solid d-c path to ground on that antenna.
I used to handle the annual SOLAS inspections for a lot of vessels around the San Francisco bay, demonstrating all the ship's gear to the FCC engineer. Often the SGC 230 ATU at the base of a 22 foot whip for the 2182 kHz SSB rig would be dead. Opening it up would reveal signs of arcing. If the Radio Officer was handy, he'd often say, "Yeah, it's been intermittent ever since we took a lightening hit a few months ago but it usually works..." Hi! So I have no trouble believing that something can be 'killed' - sort of - and work -sort of - afterwards - especially something hooked to an antenna on a ship. Y'know, the 1-mH choke to ground will keep draining the accumulating static, but how about a pulse from a sudden discharge somewhere (lightning or something else)? That may be a very fast-rise-time (high-frequency) pulse that the inductance of the choke may actually prevent shunting to ground, just as the inductance isolates the RF from ground. Is the transmit RF voltage low enough to allow you to add something like an NE-51 neon bulb that would ignite quickly if the voltage spike exceeds about 40 or 50 volts? I think I'd go for the larger caps too, if you can squeeze them in! Ron AC7AC P.S. Gentlemen, after the MFJ thing, I don't want to start an SGC-bashing thread ;-! Anything that survives out in the weather bolted to a ship's funnel has got to be good. -----Original Message----- Ron, your experience is similar to mine. Your snaps are identical to the ones i heard before I did what I describe next. There is a lot of history to the ESD problems on Arcadian ?and yes, in some conditions, you could hear the zaps all over the boat. The precautions are much more recent. I wound a 240 torroid to produce 1 milliHenry inductance and shunted the antenna lead-in to "ground/salt water" where it came into the cabin . No apparent ESD problems since then. No more fried 1N5711's. I feel, though, that the failing capacitors may be residual from some of the more exciting failures associated with no output power control due to SWR sniffing circuits having been fried by a Zap. I ususally feel that if a component doesn't fail when it is abused, it won't fail later either, but???? Radio is working fb right now. I'm thinking about doing what Bill recommends and I discussed with Don, upping the caps to 100 volt size. But if problem continues, even this might not be enough. It may also be good to see if I'm getting ESD into the radio via some other route than the obvious. This would be a real aggravation if I didn't enjoy working on the K2 so much. NO, I don't either have masochistic tendencies. 73 john ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
