[aprssig] 9600 APRS

ml41782 ml41782 at yahoo.com
Sun Feb 27 09:30:38 EST 2011

Original MSG 
From: "Wes Johnston, AI4PX" <wes at ai4px.com>
Subject: Re: [aprssig] 9600 APRS net experiment in Central NJ

1200  185ms  loud packet burst 
9600 158ms  small short burst of white noise. 

This is a savings of 27ms. based on his numbers. I have seen numbers shorter and 
longer than 150ms for keyup. This doesn't sound like alot of savings but every 
little bit helps.

9600 on VHF ?  I have never really seen this work on even on packet
I have seen 2400 & 4800 on VHF but a true 9600 no because of bandwidth 

9600 on UHF  yes it does work. 

injection points and output points
9600 input requires more drive than 1200 and is injected past the audio amp 
befor the exciter because of bandwith limits by filtering. 

9600 output is at the dicriminator before the filtering of the amplifier of the 

1200 input is at the microphone
1200 output is at the speaker. 

For the amount of data that is pushed we should drop back to 300bps, 150bps or 
slower. That is all that is used.
If you have a D700 you know of the blanking that takes place when the APRS 
transmits. and if you are in a conversation on the other side of the radio it 
gets that blanked out space while APRS is transmitting. 

Move that up to 440 and run APRS at 9600.  no blanked out conversation on EITHER 

or UHF.  Is that an improvement ? Yes. 
I don't know how the D710 or the other radios deal with this but the ideal here 
is to improve on systems and move forward out of the dark ages. I only see 
patches here and not fixes. There is only so much that we can get out of one 
frequency.  If you want to beat a dying horse then stay at 1200 and use multiple 
frequencies. One for travellers 144.390 giving local repeater info and digi's. 
145.390 for local service and they are both tied to Igates and both pulling data 
that they feel is needed but not everything. 

The points are different to get the needed speed. The manufacturers are putting 
them into the newer radios and you can adapt them to older rigs. 

I have been experimenting in Virginia for years with 110, 300, 1200, 9600 and up 
to 128k. The higher speeds are the direction we should have gone in years ago. I 
have 9600 APRS up in my area of virginia. unfortunately no one else in the are 
has used it but myself. I will be expanding it this spring and see if there is 
more interest. 

Should they mix information directly between bands ? Some of it yes the resto of 
it no. Keep them separate and let the data flow in and out of the IGATE. let the 
individual system put the data from the APRS IS servers. 

These messages are long enough without 20 messages behind them for a simple 

Mike K4MQF

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