[FRC] CB-QRM

Tue, 08 May 2001 19:01:11 -0400

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Hi Guys.
This is a copy of a message that was sent by PVRC...
Just thought I'd pass it along...
Ted

At the Visalia DX Convention I happened to remark to a fellow that on
occasion I get QRM from passing CB mobiles which not only bother me on
10
meters but wipe out 15 meters as well.  This happens until they get a
few
blocks away and then the interference gradually drops away.

My interlocutor was familiar with the CB scene and said that there are
even
groups out there who hold regional "Key Down" competitions to see who
can
generate the greatest field strength.

This guy said that there used to be some great photos of CB amps on Web
sites but now that FCC enforcement has stepped up many of these sites
have
been taken down.  He provided the following excerpts from one such site,
no
longer in business:

"Take for instance... 2X4CX15,000 being
driven by 3X8877 Ep was close to 14 kV on the
15,000s.... Power output was capable of over 80,000 watts Bird.
Tuning it up, with a 1 kW slug in the Bird meter for reverse
measurements (i.e. reflected power), we couldn't get it to wiggle up to
40
kW forward
output. At the 44 kW mark (or thereabouts), we blew the top of the
antenna off, a nice blue corona came, and the antenna spit flames!
Nice, to say the least. The tubes are run Class C, and tetrodes are the
tube of choice. What with screen volts, you get better efficiency. Just
have to keep those grids biased WAY negative, and you can live with
the higher plate voltage...After that, we went to a "fighting
stick" (Quarter wave, usually made from 3/4 inch copper pipe,
chrome plated) and we where able to tune the amp to 75 kW. It still
had more to go, but that was where we left it for a competition. This
was the inaugural run of the amp. You might wonder where the power
comes from for one of these beasts (and this is smallish. The last one
that I saw perform (over 4th of July) was capable of nearly 125 kW
Avg. output)). Usually it is a big block motor, using alternators
made by the Electrodyne company. They are designed as Locomotive
Braking motors, but run with a small voltage on the field, they will
act as an alternator. They are dual stator, single rotor,
producing 60 volts at 600 amps each stator, run full field. Run 5
to 7 of these. Engine: Large stroke, large bore with Nitrous is
the name of the game. Typically see 500+ horsepower. So, you
see, the CB community has really started going nuts. I
don't agree with the power levels run, but that is what the market
"demands"... I had one blow the high voltage power supply from my video
camera... I was about 100 yards away... This was from near field
radiation picked up by the power lines."

My correspondent has since provided me with references to a few web
sites
and after looking at most of them I have chosen these three as
representative of what can still be found on the Web even after most
sites
were taken down:

http://www.bigradios.com/nicodemus/events.htm

http://www.bigradios.com/shadow/longv.htm

http://www.davemade.com/photos.htm

Question:  Do you suppose the term "pills" = "KW"?

73, Fred

---
Submissions pvrc@qth.net

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<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
<html>
Hi Guys.
 This is a copy of a message that was sent by
PVRC...
 Just thought I'd pass it along...
 Ted
At the Visalia DX Convention I happened to remark to a fellow that on
 occasion I get QRM from passing CB mobiles which not only bother me
on 10
 meters but wipe out 15 meters as well.&nbsp; This happens until they
get a few
 blocks away and then the interference gradually drops away.
My interlocutor was familiar with the CB scene and said that there are
even
 groups out there who hold regional "Key Down" competitions to see who
can
 generate the greatest field strength.
This guy said that there used to be some great photos of CB amps on
Web
 sites but now that FCC enforcement has stepped up many of these sites
have
 been taken down.&nbsp; He provided the following excerpts from one
such site, no
 longer in business:
"Take for instance... 2X4CX15,000 being
 driven by 3X8877 Ep was close to 14 kV on the
 15,000s.... Power output was capable of over 80,000 watts Bird.
 Tuning it up, with a 1 kW slug in the Bird meter for reverse
 measurements (i.e. reflected power), we couldn't get it to wiggle up
to 40
 kW forward
 output. At the 44 kW mark (or thereabouts), we blew the top of the
 antenna off, a nice blue corona came, and the antenna spit flames!
 Nice, to say the least. The tubes are run Class C, and tetrodes are
the
 tube of choice. What with screen volts, you get better efficiency.
Just
 have to keep those grids biased WAY negative, and you can live with
 the higher plate voltage...After that, we went to a "fighting
 stick" (Quarter wave, usually made from 3/4 inch copper pipe,
 chrome plated) and we where able to tune the amp to 75 kW. It still
 had more to go, but that was where we left it for a competition. This
 was the inaugural run of the amp. You might wonder where the power
 comes from for one of these beasts (and this is smallish. The last
one
 that I saw perform (over 4th of July) was capable of nearly 125 kW
 Avg. output)). Usually it is a big block motor, using alternators
 made by the Electrodyne company. They are designed as Locomotive
 Braking motors, but run with a small voltage on the field, they will
 act as an alternator. They are dual stator, single rotor,
 producing 60 volts at 600 amps each stator, run full field. Run 5
 to 7 of these. Engine: Large stroke, large bore with Nitrous is
 the name of the game. Typically see 500+ horsepower. So, you
 see, the CB community has really started going nuts. I
 don't agree with the power levels run, but that is what the market
 "demands"... I had one blow the high voltage power supply from my video
 camera... I was about 100 yards away... This was from near field
 radiation picked up by the power lines."
My correspondent has since provided me with references to a few web
sites
 and after looking at most of them I have chosen these three as
 representative of what can still be found on the Web even after most
sites
 were taken down:
<A HREF="http://www.bigradios.com/nicodemus/events.htm">http://www.bigradios.com/nicodemus/events.htm</A>
<A HREF="http://www.bigradios.com/shadow/longv.htm">http://www.bigradios.com/shadow/longv.htm</A>
<A HREF="http://www.davemade.com/photos.htm">http://www.davemade.com/photos.htm</A>
Question:&nbsp; Do you suppose the term "pills" = "KW"?
73, Fred
 &nbsp;
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 Submissions pvrc@qth.net</html>

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