Re: [amsat-bb] Orbit 250 apogee

[Mike73@xxxxxxx]

In a message dated 5/16/2001 12:35:07 PM Eastern Daylight Time, 
W10191@motorola.com writes:

> I asked this question a week ago and didn't get an answer:  Will the "final"
>  S-band downlink use more power and/or a higher-gain antenna?

Hi Wayne,

I can't speak to power, but there are 2 different S antenna/transmitters on 
AO-40. S1 uses the dish and S2 uses the helix. The antennas and transmitters 
are dedicated i.e. you can't put the helix into S1 xmtr and vice versa. The 
dish has 8dBi more gain (as I recall) But, here's the rub, with more gain 
comes a tighter pattern. So, while the S1 xmtr/dish combination will be great 
near perigee, you must remember there is more path loss. As AO-40 heads 
towards/away from perigee, the S2 helix should be better because of a wider 
pattern. The dish will remain very good near perigee, but the optimal 
footprint will be smaller due to the tighter pattern.

That's my understanding of the antennas after studying them. I could be way 
off base........ Work on your receive system. <grin>

73,
Mike, N1JEZ
AMSAT #29649
Local Area Coordinator
"A closed mouth gathers no feet."
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