Looks like the problem was the Stridsberg active multicoupler. My Austin Ferret antenna is only about 20 feet away from my HF dipole antenna. Been spending lots of time on 75 meter AM, running a Flex 5000 into an Alpha 86 running at full legal limit. Looks like I cooked either the FET or the pair of back to back Schottky diodes, that SHOULD provide protection from strong RF fields.
I called Stridsberg Engineering, explained the situation, they said send it in & we will fix it, no charge. They also said that they would do some upgrades, too, as mine was purchased from them around 2002.
Nice to see a company that stands behind their products, even though it was my fault the product failed.
I ordered the parts to cobble together a 40 Mhz hi-pass filter that should eliminate the problem. All this got me thinking about the antenna & feedline that I put up in the mid 90's. I ordered a DPD productions OMNI X antenna and some Bury Flex low loss coax from Davis RF. The Ferret antenna may or may not be good, but the air core coax cable is surely no good. It wouldn't surprise me if it's filled with water after 20+ years. I'm also moving the antenna to a chimney mount, where it will be about 35 feet away from the dipole.
Hopefully, this will get everything back up & running.
Happy New Year & 73 to all,
Bob
N2OAM