What's all this business I hear people talking about blasting people's
car stereos or killing cars altogether with high-power RF? I run 2m,
10m, and 11m in my jeep and I'd like to sort out the fact from the
legend and find out what kind of power I can use without risking
damage to my jeep or cars around me. At what power level is front-end
overload to a nearby radio likely? At what power level is damage
likely, and to what componets?

I am currently using only 50 watts on a 5/8 wave (2m), 25w on a 1/4
wave (10m), legal 4w on a 1/4 wave (11m)

About 2 years ago I was in a rather frivolous mood, brought about by a drop
of absolute vodka. I wondered just how certain things reacted when put in a
750 Watt microwave oven.

I first tried a new way of burning a CD. Amid sparks and a pyrotechnic
display that appealed to my sense of ****edness, it sort of got crazy-paved.
After about 20 seconds I had to switch off the microwave because of the
stench.

Then I turned to more "electronic" things. A Fujian MP3 player bit the dust
instantly. Basically there was one huge "wooooofff!", then the PCB set fire
to the plastic case after about 30 seconds.

Then I tried an old hamradio rig. It was an old Trio (Kenwood in the USA)
2200GX, crystal-controlled rig, with a rubber-duck antenna, and a battery
compartment that had not held batteries for several years. I put it in as it
was, but without the mic. Battery door open, rubber-ducky antenna on.

It sat there for about 15 seconds before anything happened, then the front
panel sparked a bit and caught fire. The front panel looked similar to the
CD, but a bit more melted-down, and the knobs had changed to a totally new
shape. But apart from that, the radio itself still worked fine after a 30
second 750W cook. It just looked more of a mess then it did originally.

Out of interest I tested it. I was expecting RF to get in the antenna and
coarse its way through the PCB, but no! The RF sensitivity was 1.25uV PD for
20dB sinad. Perhaps that was 10dB down, but it was still quite useable The
TX was still delivering 1.5 Watts.

I took off the case and tried again, and THAT killed it for sure. After only
10 seconds the PCB "whooffed", with loads of sparks and spitting.

But the point is that you cannot couple more power into a rig than that,
even with the cover on. The antenna was connected, and 750 W did not kill it
instantly, as expected. These rigs are far more resilient than one would
imagine.

BR Hairy
NOSPAM_oeieio(at)hotmail.com