wrote in message
oups.com...
I keep reading discones cover a very wide frequency. Are these truly
the best scanner antenna to have? Or would a ground plane tuned to the
freqency you are listening to be better?


If you have one specific frequency, or a narrow frequency band of less than
about 10%, then a properly designed and built ground plane antenna will have
significantly more gain. It would be easy to get 5 to 8 more dB of signal
from the ground plane over the discone. It is possible to get 10 to 12 dB
or more from the ground plane (over the discone only, I am not saying 10-12
dB gain over an isotropic), but this starts to narrow up the bandwidth below
the above mentioned 10%.

What is 5 to 12 dB more signal? Every 3 dB is double the signal strength.
A gain of 12 dB would be a signal about 17 times the signal of the discone.

What does 10% of bandwidth mean? If you design a ground plane for a center
frequency of about 150 MHz it will work across about a 10% bandwidth (this
is a rule of thumb, but not hard and fast). 10% means the antenna will have
a 15 MHz band width of optimum performance. Or about 142 to 157 MHz
(rounded off). The antenna will work outside this range, naturally, but the
gain will fall off rapidly.

For broad band applications it is very hard to beat the discone antenna.
This is why the discone is so popular with the military and countermeasures
community. The discone is not best at any one thing, but it takes the place
of a multitude of other antennas and does it reasonably well.

C