"Volker Tonn" wrote in message
...


Frank Bals schrieb:
How well do the Radio Shack and Diamond discones (with the low band
verticle
element) work in the 30-50 Mhz range and CB band? I know they are rated
for
25-1000 Mhz coverage.


I have a Diamond discone with two extended legs adjustablefor CB or
10mtr TX use. It does not work as good as a designated CB-antenna but is
DOES work with low SWR. For TX use you must be aware this antenna will
spread out a bunch of harmonics as well...
If you are in need of a specified frequency coverage below 140Mhz just
replace one or two cone elements with some 1/4 wave resonant elements
(shortened with coils) of that frequency.
If you want continous coverage down to 26Mhz you'll have to extend all
cone elements to full length of 10ft.

If the transmitter is within spec, the antenna will not "spread out
harmonics".

The popular discones stop functioning as a discone around 130 MHz. The
vertical section supplied with some operates as a 1/4 wave radiator and the
cone rods as a limited counterpoise- very narrow bandwidth
If you want to extend the range of the discone below 130 MHz, you need to
appropriatly lenghten not only the cone section, but also increase the size
of the disc- w/o doing this, you no longer have a discone antenna, and the
feedline will now become part of the antenna.

Dale W4OP