>"From experience, I'd say nearby lightning strikes would be the culprit."
Highly unlikely. Clear skies for days. No lightning activity here in a long time here. Two years ago, I had a similar problem with static-damaged Schottky diodes in an Alpha 9500. Those diodes are used to sample RF for the amp's EBS circuit. >"I strongly urge everyone to use protection devices on all coax and balanced lines at the point where the feed lines and rotor lines enter the house. I prefer Polyphaser devices." Already installed and we never disconnect at the remote site. The site conforms to Motorola R56. No lightning-induced damage in almost 3 years of operation in a very lightning-intense location near the Okefenokee Swamp. High power Alpha-Delta arc-plug devices are located at the master ground bus where all coaxial and control lines enter the station. Low power (200W) Alpha-Delta devices are installed between the K3 and amplifiers. The Alpha-Delta devices use field-replaceable arc-plugs. Like Polyphaser, these devices are intended to mitigate lightning-induced charge, not necessarily antenna static charge. Still, it's possible that one or more of the Alpha-Delta arc plugs has failed, leaving the K3 vulnerable to static damage. In looking at the K3 SWR bridge circuit, both sides of the Schottky diodes have a reasonably low impedance to chassis ground. One side is slightly less than 22K-ohm. However, it may not be low enough. To supplement protection, I may add a pi-section 1 mH choke between T3 and the chassis. It's the same choke used as a static drain in the Alpha 89 and 87A amplifiers to prevent static-induced PIN diode damage, and the type used at the output of many vacuum tube amps to function as a safety device in the event a plate blocking capacitor fails in a shorted condition that would otherwise allow high-voltage on the output network, transmission line, and antenna. Although fun to discuss and contemplate fixes, it's conjecture until validated and the root-cause may not be related to any of this. Paul, W9AC ly failed. ______________________________________________________________ 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 Message delivered to [email protected]
