At 6/20/2005 12:28 PM, you wrote:
>At 07:34 AM 6/20/05, you wrote:
>
> >Other than the fiberglass sticks, what options are available to me in
> >multiband antennas?
> >At the outset, we will be putting up 2M and 440, and we are
> >contemplating a 902 system.
> >Of course I'd rather have one site on the tower, and one feedline if
> >practical, but I'm leery of excessive losses.
>
>All multiband antennas are a compromise - even using an
>18" whip on a vehicle as a 2m and as a 3/4 wave 440mhz
>(the compromise there is the pattern).
I disagree with the above statement that ALL multiband antennas are a
compromise. By strict definition of the word "compromise" you're correct,
but in many cases that "compromise" is insignificant. The multiband
antennas I use in repeater service (GP9) offer no significant compromise in
performance over single-band antennas (I've compared the on-horizon gain of
a GP9 against a known KLM yagi & found it to be within 1 dB of the
manufacturer's spec at 440), & in fact work better than two separate
antennas would since one of the two antennas would have to be located in a
much less optimum location. The below-horizon nulls are worse than
commercial single-band antennas, but in my specific case they're all within
10 miles of the site & do not cause coverage problems.
The example you cite is one of a poorly designed mobile antenna, where the
440 pattern peaks 45° above the horizon. I once had one; solution was to
cut it down to a 1/4 wave @ 440 & forget 2 meters. A properly-designed
antenna won't have this problem.
Bob NO6B
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