Tony Estep wrote: >Nobody commented on my question last night, but I'd still like to hear from >your collective wisdom, so here's a repeat: I set up my sub-rx to listen on >transmit antenna B while the main is listening and transmitting on A, and to >listen on A while main is listening and transmitting on B. This allows for >diversity reception. > >"...here's my question: My two antennas are located so each is in the >other's null, but they are not far apart, maybe 50 feet at most. When I >transmit, I don't hear any carrier-operated relays or see any adverse >reactions, but I'm still not sure that it's okay. The manual sez "well >isolated," but what I'm looking for is some objective way to test or >measure. Can anyone tell me how I can establish for sure that I can, or >cannot, transmit on A when the sub is connected to B, and vice versa? " > >Any info (especially first-hand knowledge) would be much appreciated.
Connect a simple diode milliwattmeter to the feed from the RX antenna. All it needs is a 47 ohm resistor, a 1N914/4148 diode, a .01uF ceramic cap and your DVM. (This is truly a "Construction 101" project - can anyone supply a suitable web reference, please?) Gently ramp up the power to the TX antenna, and see how much power is coming back on the RX input. Repeat with every combination of bands and antennas. Also read "Managing Interstation Interference" by George Cutsogeorge W2VJN: <http://www.inrad.net/product.php?productid=248&cat=148&page=1> The first chapter is available as a free download and contains key information about power levels for receiver front-end damage. The K3 can protect itself... but as you say, you should make sure it doesn't have to. For diversity I am using an active antenna based on a small horizontal dipole, which works very well in combination with the low-band verticals. Checking with the milliwattmeter and gradually ramping up to full TX power, both the active antenna and the K3 are well enough protected by the cross-polarization. But the 20-10m beam is horizontal and also much closer, so additional protection is needed on those bands. -- 73 from Ian GM3SEK http://www.ifwtech.co.uk/g3sek ______________________________________________________________ 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
