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RE: Satellite modes (Was - Hamsat or VO-52 Modes)



Except that starting at 2m the atomspheric noise
begins to rise the further down you go.  The 9 dB
link advantage at 2m is reduced by at least 3 dB 
of increased noise.  The much higher noise at 10m
just about cancels the link advantage.  But I agree
with you that mode B is best downlink for systems
intended to be received by an omni...  de WB4APR

>>> "Trevor M5AKA" <m5aka@hotmail.com> 11/07/05 5:00 PM >>>
and of course you get a corresponding increase if you have a downlink on 29 
MHz and less power is required for a 145 MHz uplink.

For stations using simple omni-directional antennas the lower the frequency 
the better.

73 Trevor M5AKA

>From: Anthony Monteiro <aa2tx@comcast.net>
>Hi Kenneth,
>
>Pat is referring to the lower free-space path loss on 2m.
>
>
>Let's say someone launches a new LEO satellite with 1 watt
>of output power and a 0 dB gain transmit antenna. On the
>ground you listem for it with a quarter-wave vertical.
>
>If the satellite uses 2m on the downlink, the received
>signal level will be nearly 10 dB higher than if it used
>70cm for the downlink.
>
>So, mode B satellites like VO-52 tend to be much easier to
>hear than similar mode J satellites when you are using
>omni antennas to receive them.
>
>On your uplink side, you need 10dB more EIRP but this tends to
>be no problem as even QRP rigs have more than enough power
>for the uplink.
>
>73,
>Tony AA2TX
>----
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