[amsat-bb] Re: Comet CX-902 as sat antenna?

[Glenn Little WB4UIV]

When we go back to antenna theory, we find that to get gain from a 
vertical antenna we reduce the height of the donut around the 
antenna, thereby increasing the diameter of the donut. The donut 
represents the coverage of the antenna in azimuth and elevation. The 
area of the donut represents the power of the transmitter or the 
sensitivity of the receiver. We change the dimensions of the donut 
with antenna gain, while the volume remains constant. The higher the 
vertical antenna gain, the thinner the donut and the larger the 
diameter. Since the satellite is above you, and the vertical antenna 
has gain, you will not receive the satellite unless the satellite is 
near the horizon.

To receive the satellite with a simple vertical, use a unity gain 
ground plane. This will work for all but the passes directly overhead.

73
Glenn
WB4UIV



At 10:37 PM 3/22/2008, Bill Dzurilla wrote:
>Hi,
>
>I'm trying to help one of the local Honduran hams get
>started on the sats.  He has a dual bander and a Comet
>CX-902 vertical antenna, 9 db gain, about 35' in the
>air.  We set up to work tonight's AO-51 pass but did
>not hear a thing.  About halfway through the pass,
>when it was obvious we were not hearing the bird, we
>switched the antenna from his rig to mine, just to
>verify that the rig was not at fault.  But we still
>heard nothing.  This suggests to me that the problem
>is the antenna or feedline.  Is there any reason why
>the Comet would not work at all on the sats?  He can
>raise the local repeater with this antenna.
>
>73, Bill NZ5N
>
>PS - Several of the Swan Island guys were intrigued by
>my sat operation and we hopefully we have a few more
>HRs active soon.
>
>
> 
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