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Re: re: QRM 2m, question for sat builders



If you have a yagi at 70 cm, you can take advantage of the decreased sky
noise so the gain can be 7 dB less.

73,

John
KD6OZH

----- Original Message -----
From: "Robert McGwier" <rwmcgwier@comcast.net>
To: <amsat-bb@amsat.org>
Sent: Tuesday, February 15, 2005 12:52 UTC
Subject: RE: [amsat-bb] re: QRM 2m, question for sat builders


> The two of your are agreeing and then agreeing to disagree.
>
> FOR A YAGI, which is what Drew clearly has in mind,  the increased
> path loss has to be made up with a much larger yagi on 70cm since
> the increased path loss is 10 dB at (say) 1500 km slant range.  If
> you used a dish on 2 meters (I don't recommend it ;-), the same
> size dish will have the gain to overcome the increased path loss
> at 70 cm.  The same capture area in a yagi at 70cm makes it much
> larger.  Here is a path loss calculator.
>
> http://gbppr.dyndns.org/PROJ/mil/ew/path_loss.main.cgi
>
>
> Bob
> N4HY
>
>
> -----Original Message-----
> From: owner-AMSAT-BB@amsat.org [mailto:owner-AMSAT-BB@amsat.org]On
> Behalf Of Andrew Glasbrenner
> Sent: Tuesday, February 15, 2005 11:06 AM
> To: John B. Stephensen; amsat-bb@amsat.org
> Subject: Re: [amsat-bb] re: QRM 2m, question for sat builders
>
>
> >The path loss goes up with frequency but antenna gain goes up at the same
> >rate for a constant size antenna. The pointing accuracy must be greater
at
> >higher frequencies but for the size antennas that amateurs use, this
isn't
> a
> >limiting factor below 2 GHz.
>
> To bring this back to the original point, the required use of directional,
> gain antenna systems for receive is one of the factors that makes Mode J
> more difficult to the beginner. Theoretical this and that aside, my
> experience on the LEOs has shown that you can receive a 2m satellite
> downlink from LEO on just about anythng better than a wet noodle, and the
> same just can not be said for mode J.
>
> 73, Drew KO4MA
> ----
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> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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----
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