[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

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



There is not an improvement using omnidirectional antennas below 2 meters as
the noise level increases with decreasing frequency at 6 dB per octave.
Galactic noise levels intecept the earth-bound thermal noise level at about
200 MHz. Thus the 70 cm band is at a disadvantage if the antenna pattern
includes the horizon.

If the antenna points away from earth the antenna size is constant with
frequency as the gain increases at the same rate as path loss. The only
issue is then pointing accuracy.

73,

John
KD6OZH

----- Original Message -----
From: "Trevor M5AKA" <m5aka@hotmail.com>
To: <amsat-bb@AMSAT.Org>
Sent: Monday, November 07, 2005 22:00 UTC
Subject: RE: [amsat-bb] Satellite modes (Was - Hamsat or VO-52 Modes)


> 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
> >----
> >Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
> >Not an AMSAT member? Join now to support the amateur satellite program!
> >To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
> Not an AMSAT member? Join now to support the amateur satellite program!
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
----
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home