[BC] Isotron AM Antennas

[RichardBJohnson at comcast.net]

I didn't read what broke. It you still have a tower standing
over a ground-plane, short out the base insulator with some
automobile battery jumper cables, string a piece of #10 stranded bare copper
wire that electricians use for grounding, from about 1/3 the way up
your tower to your transmitter shack. Fasten it with a pair of vice-grips
that cut into the paint on a cross-member.

Borrow a vacuum-variable series resonating capacitor, max size about
400 pF, and resonate the slant-wire. It will be somewhere between
30 and 100 ohms. Guestimate how much to move the connection and
try again. once you get between 40 and 60 ohms, you are good to go.

Run the transmitter.

BTW I have slant-wire fed many transmitting antennas when tower work
was being done, installing FM bays, etc. The riggers don't mind the
RF on the tower, but need to have the base-insulator shorted out so
they can use their steel hoisting cables, etc., and climb without having
to start using a step-ladder.

If you have no tower standing, get a 20 ft section of 2-1/2 in plastic sewer pipe
(two 10-foot sections). Support it over your ground-plane with three guys
made of plastic rope. Run coax to its bottom, and connect the shield to your
ground-plane (dig a hole and locate one radial). Wind the plastic pole with
#10 insulated wire over its entire length before you erect it You will need
a 100 ft roll. This will be the "tower." Find its resonant frequency by connecting
the end near ground to ground and bringing a real portable radio (the kind with
a continuously- tuning dial) near it. A sharp peak in noise (or distant stations) will occur
at resonance. Cut off some wire to bring the resonant frequency up to your
station's frequency. Do the final tuning by spreading out turns. 

Connect this gigantic "rubber duckey" to the coax center and go on the air.
Depending upon ground-system losses, it will probably be near 40 ohms which should be
close enough for low power operation. If you make one, and have a FI meter, measure
its field at 1 km. You will probably be surprised that it works as well as it does.

One trade-off is it has a horrible Q. However, you can turn off IBUZ during
the emergency operation!

Cheers,
Richard B. Johnson
Website http://AbominableFirebug.com

----- Original Message -----
From: wmroradio at bellsouth.net

Sounds like this antenna is a piece of junk and no use for an emergency for an AM station. My engineer is putting up a temporary 1 wire, vertical unipole type antenna to get me back on the air today, until my unipole kit comes in.