I've used a similar (simpler) test fixture which consisted of a small "grain-of-wheat" bulb, probably a 5V @ 30 mA, (??) wired directly across the non-active antenna feed. A rule-of-thumb is if you see a glow, you're asking for trouble. Watching the bulb connected to a 600' Beveridge, which is about 50 feet from both a 20-10M Log Periodic and a 40/60/80/160M dipole, the bulb would glow at varying intensities when transmitting up to 100 W on all bands that the antennas are designed for. Some bands would show hardly any glow at 100W but others would light the lamp to full brightness at < 50 W with no rhyme or reason to which bands.
It was enough to convince me to either NOT to leave the Beveridge connected or make sure I had some sort of protection. I use a commercial Collins "Receiver Protector" in line with the wire which seems to be adequate even running an amp. 73, Charlie k3ICH -----Original Message---- From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Ian White Sent: Wednesday, January 20, 2016 3:10 AM To: elecraft@mailman.qth.net Subject: Re: [Elecraft] Nearby Ham Interference In a multi-transmitter setup, use a simple throwaway RF detector to test for potentially damaging levels of RF *before* connecting the second radio. The simplest RF indicator consists of a 50-ohm resistor, one diode, one capacitor and an LED, haywired together on the rear of an SO-239. Sensitivity depends on the type of detector diode and LED, but typically the LED will begin to glow at RF levels above a few tens of milliwatts into 50 ohms. So if the LED shows anything more than a very dim glow, it would be risky to connect a radio. And if the detector burns out, well, that was the whole point of using a "throwaway" device - to take the bullet instead of your K3! Replace the damaged parts and carry on testing. (Obviously there's much more to say about this, but the details are currently buried in unsearchable Yahoo archives.) 73 from Ian GM3SEK ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
