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 >-----Original Message----- >From: Elecraft [mailto:[email protected]] On Behalf Of >Dave Olean >Sent: 20 January 2016 06:36 >To: [email protected] >Subject: Re: [Elecraft] Nearby Ham Interference > > >Hello Brendan, >I have two ten meter 5 el yagi antenna arrays that are just under 300 ft >apart. One is on a 70 ft tower and consists of three yagis. The other is a >single yagi at 30 ft. If the two yagis are boresighted on each other, I see >only 17 dB of attenuation between them. I checked the isolation with a >signal generator and a crystal detector with an HP 415E meter. This can >blow >out a front end even running 100 watts. Each yagi has almost 9 dBd gain in >free space. I guess it depends on what ur antenna is, but yagis on the >higher bands can cause problems when aimed at each other. I did fry one K3 >using an amp with this setup. I took out a diode. >Be careful, and make a few checks to avoid surprises. >Dave K1WHS >----- Original Message ----- >From: "Jim Brown" <[email protected]> >To: <[email protected]> >Sent: Wednesday, January 20, 2016 12:30 AM >Subject: Re: [Elecraft] Nearby Ham Interference > > >> On Tue,1/19/2016 3:05 PM, Ian wrote: >>> Consider one of these:http://www.dxengineering.com/parts/dxe- >rg5000hd >> >> The K3 is pretty well protected -- if, for example, you hit it with too >> much signal, the attenuator will kick in and the preamp will turn off. And >> if that doesn't reduce the signal enough, you'll get a HIGH SIGNAL warning >> on your display. In addition to that, there's a diode on the front end. >> >> I'd verify that an RX is getting overloaded before spending dollars on >> this product. With antennas 300 ft apart, it's unlikely that you're going >> blow anything up unless the other station is running an amp. >> >> 73, Jim K9YC >> ______________________________________________________________ >> 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] > >______________________________________________________________ >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] ______________________________________________________________ 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]
