[aprssig] E Coast 9600 baud backbone 15W radios.
Stephen H. Smith
wa8lmf2 at aol.com
Sat May 28 20:10:55 CDT 2016
On 5/28/2016 3:57 PM, Andrew Rich via aprssig wrote:
> I don't know why we don't use vhf upper side band and psk31
1) Radio complexity - SSB circuity is far more complex than basic FM radios.
You just don't find sub-$100 (US) SSB transceivers for VHF.
2) Frequency stability - APRS operation is random transmitting in the blind;
you don't have a chance to tune in the other station first. You must maintain
absolute frequency accuracy within +/- 15 Hz end-to-end for PSK31 to work.
Unlike FM, on SSB, RF frequency errors translate hz for hz to AUDIO frequency
errors at the receive end. It's very difficult and expensive to achieve RF
frequency stablility of +/- 10 Hz or so on VHF/UHF, especially in
reasonably-priced ham gear. (It works out to around .01 PPM at VHF.)
Stephen H. Smith wa8lmf (at) aol.com
EchoLink: Node # 14400 [Think bottom of the 2-meter band]
Home Page: http://wa8lmf.net
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