dummy loads

I'm wiring up my panel in my garage at home. It includes an SL-30, ICOM A210, and Garmin GTX320A. I'm about ready to fire that baby up. Before I do, I wondering about dummy antenna loads to keep from overloading amplifiers.

I expect it is possible that the transponder could get a ping and try to reply.

Since my antennas are mounted in the airplane at the airport and I do not want to remove them, I suppose I can just use rubber duckies for the comm radios, which would allow me to test comm radio functionality. I expect that I can use a 50 ohm bnc style terminating resistor on the xponder.

Anybody see a problem with this plan?

you can fire up whatever you want so long as you don't transmit. NAV radios can't transmit, of course, and it doesn't sound like you have any DME transponders in there, so no problems there. Leave your transponder on standby, don't turn it on, but realistically, without an antenna it shouldn't get any interrogations, so it won't try to reply.

I wouldn't worry much about a duckie antenna on a comm, but you won't really get much signal out. However, I would be concerned about using a BNC terminator as a dummy load for a transponder... transponders, when they are replying to interrogations, are 200W or so, and that's likely to FRY a BNC terminator.

I learned my lesson on that the hard way once upon a time.... I wanted to test a 100W HF ham radio, and I figured 'hey, a dummy load is just a 50 ohm resistor, right?' I took two 100ohm resistors, paralleled them, held them between my thumb and finger in place in the antenna jack, and keyed up the mic. I had perfect charred resistor-shaped indentations in my thumb and finger for a few weeks.

tmbg said:

I learned my lesson on that the hard way once upon a time.... I wanted to test a 100W HF ham radio, and I figured 'hey, a dummy load is just a 50 ohm resistor, right?' I took two 100ohm resistors, paralleled them, held them between my thumb and finger in place in the antenna jack, and keyed up the mic. I had perfect charred resistor-shaped indentations in my thumb and finger for a few weeks.

Click to expand...

What was the wattage of the resistors? They were dissipating 100W. I would expect them to get quite hot!

1/2W each, so 1W total


Yeah, I know. I was 17. Gotta learn stuff the hard way sometimes