At 11:47 AM 6/16/00 -0500, you wrote:
>Now for a little antenna theory...
>
>Your AM/FM antenna is no where near resonance at 27 MHz. To make it
>"appear" to resonate at that frequency, the "secret CB antenna" idea
>places capacitance, resistance and inductance in-line so that your CB
>radio sees a 50 ohm load with low VSWR. You can adjust the "load" using a
>potentiometer -- thus "tuning" your non-resonant AM/FM antenna for good
>VSWR on 27 MHz.
>
>This "secret CB antenna" works more-or-less like a 50 ohm dummy load (a
>big 50 ohm resistor). It presents a good 50 ohm load with low VSWR to
>your radio. By no means does it make your AM/FM antenna an efficient RF
>radiator.
>
>If you want to be heard, you need an efficient RF radiator. Get a *real*
>antenna that's suited for your intended purpose. A 1/4 wave whip works
>best. Let's see, the middle of the CB band is 27.185 MHz (ch 19). 1/4
>wave on 27.185 MHz is 8.6 ft. (234 / 27.185 = 8.6).
>
>Good luck,
>-Mitch
>ARS: W5MEC
oooohhhh, brings back some headaches. Had a guy that worked with my dad
that was into high power CB. To make a long story short, we ran a 12V
battery at 18 Volts, battery had to sit in a plastic bucket to collect the
acid it spewed. Had two alternators, both 140 amps. Two "black boxes" and
a custom antennae that we designed that would make NASA jealous. On max
output, when he keyed the mic the truck would die from the RF interference
from the output. Not blowing smoke, or making this up, but he's talked to
people from as far away as Australia. Just had to point the truck in the
general direction. At 2000 RPMs with two 140 amp alternators and an
external modified GM regulator set at 18 volts, it would drop to 10-12
volts during transmission.
Needless to say, I got a fair dose of RF radiation to last a
lifetime. Just thought I'd share that :)
Mike Schwall
mschwall@flash.net
============================
Robotics Technician
Eddy Current Inspection
Veridian Engineering --Tinker AFB, OK
============================
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