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

FW: Mode B vs. Mode S



Fred wrote:
I personally think the net sum of all of the tradeoffs is 
that 1269 MHz is a good choice for an uplink (it would have been super for a 
downlink, but we can't do that), and 70cm is a good choice for a downlink.  

Wayne replies:
>From a purely TECHNICAL perspective, 70 cm downlink and 23 cm uplink is very good.  But from a PRACTICAL perspective, it would be very limiting to the user population to have the lowest-frequency uplink on 23 cm. The 23cm transmitting equipment is very expensive, and for most people it has no secondary non-satellite uses.  Even if somebody wants to do 23cm terrestrial stuff, the satellite uplink band is so far away from the terrestrial band that a lot of 23 cm equipment can't be used for both purposes.

The real beauty of Mode B is that the equipment has lots of non-satellite uses.  That's VERY important to most hams who want to "try" satellites.  They don't know if they will like satellites, so they are reluctant to spend money on stuff that has no non-satellite application.

>From a practical perspective, 70cm is an excellent uplink band because:
1. It's the highest band where power is cheap and widely available.
2. It's the highest band where feedline loss is manageable.
3. It's the lowest band where gain antennas are reasonably small (see my 7x7 Arrow antenna).
4. 70cm equipment has widespread non-satellite use.

I'm not saying it's bad to have a 23cm uplink.  I just think it's bad to have 23cm as the LOWEST frequency uplink.

Wayne Estes W9AE
Mundelein, IL, USA

----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home