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[aprssig] 9600 Packet was RE: EB-432/PCSAT2/APRS Question

John Ronan jronan at tssg.org
Mon Jun 5 08:57:05 UTC 2006


On 30 May 2006, at 10:34, Dave Baxter wrote:

> Hi...
>
Morning Dave,
> You may find that though the audio transformers will appear to  
> screw up
> stuff like 9k6 packet, it's not the frequency response as such that's
> the problem, but the phase shift or group delay vs frequency that they
> and associated passives cause.  After all, the apparent bandwidth even
> of a good transformer isolation system should be well in excess of
> what's needed even for 9k6 packet.
>
> However, from what I've seen so far, unless the radio has a dedicated
> 9k6 RX audio outlet, you need to tap off direct from the discriminator
> (or whatever FM/PM detector it uses) to go to the 9k6 modem etc.
>
Radio is an FT-847, and 'claims' to have 9k6 capability.  Yesterday I  
switched to the hardware modem and it appears to have better 'ears'  
than the soundmodem/soundmodem interface combination.

(the times in this log are local (output from listen -t -a) . The  
packets should already be in the system )
2m: fm PC2TLM to APRS via SGATE WIDE ctl UI pid=F0(Text) len 124  
08:48:25
0000  {TPoNscPlIcNssoLic1Jqc/HvlIFslRDzFZB55fACBmNQF2AYCK6wrxCgGC5QGB8
0040  jGCcyZ/20GAD0CAGkB7f0l7qUl710l8FEl8MEl8bEh3wE13wU138E14Dkx4.
2m: fm PC2TLM to APRS via SGATE WIDE ctl UI pid=F0(Text) len 124  
08:48:30
0000  {TPpQIjjEczjjU3jyPYkBGokQAFkrHGArGUKrGqN7GlR6+Gc6xgeK0zd6lQe6nZe
0040  qpFeqYFfaZQfaZwfabdfKJyf6Kwf6LffqMPfp7KgJ7JgJqRgprBgpaTg48Q.
2m: fm PC2TLM to APRS via SGATE WIDE ctl UI pid=F0(Text) len 124  
08:48:30
0000  {TPxuklimMQi2HSi1zri1BPjEUJjTn4ji4FjyKgkBbpkAuEkQANkQMAAgBBiWAO6
0040  AoAproEpdQXpZIjpVMtpS80pTE1pRw8pLtIpJdSpGBXpFpco/lmoJ1+oFV/.
2m: fm PC2TLM to APRS via SGATE WIDE ctl UI pid=F0(Text) len 124  
08:48:32
0000  {TPOSgpqVFSqVZXqVJcqWpeqW1po4+DowmEohiFoO2Gn2yHne+InyCInUaJm1eKm
0040  UaLlyKMl7+Lkp2NihGQdrqTZbGWVamXQzGZMbuaISqbEDqcAAudwy6D14NE.
2m: fm PC2TLM to APRS via SGATE WIDE ctl UI pid=F0(Text) len 124  
08:48:33
0000  {TPhfUq29mDRDPcg0SL3oNE4+CDRJjLg0TwzYNEe9CDRNPSg0Qr1YNEIwAPAIIK0
0040  wo7CwAHAAAA+Al1ChcLAAAAFADSCPIJLAsAHgAbAF5KpVoxCwAJAAYA/Qro.
2m: fm PC2TLM to APRS via SGATE WIDE ctl UI pid=F0(Text) len 124  
08:48:35
0000  {TPbaQtCD4JHQsAFAAGAIBJpVodCwAQAAAAQgovCTALAAAAAQDvSKVaGgsAAAAAA
0040  BSACgsMCwEAABUAE4ATgPwKAAcAAAATgBIIGAsAAAAAAF0J0gkdCwAHAAAA.
2m: fm PC2TLM to APRS via SGATE WIDE ctl UI pid=F0(Text) len 124  
08:48:35
0000  {TP4WAwEAATgCMI6goAAAAAAFQJnwkLCwAQAAAAawkOCe0KAAAAGgDcCBsJ+woAA
0040  AAKADhJpVr0CgAOABgAtgnyCP4KAAEAAwC/SKVaAQsAAgACAE2A8Qr2CgEB.
2m: fm PC2TLM to APRS via SGATE WIDE ctl UI pid=F0(Text) len 124  
08:48:35
0000  {TPpqIxAA0AE4ATgN0KAB8AHQATgCkI6goAAAATAMwL4goACwAAAAIAOA1iC+EKA
0040  AAAFAB3Dn8M7woAIAAIAJpLpVrnCgAOABkAhQpwDPMKAB8BhQHBTKVa/AoA.
2m: fm PC2TLM to APRS via SGATE WIDE ctl UI pid=F0(Text) len 124  
08:48:38
0000  {TP+Yo0CwASABsArwulDCkLAOYALgAFTaVaCQsAVQC4APWEAQv4CgEMAAQA0oLRg
0040  uoKABQAHwAWhDANFgsAAAAPAHALPgssCwAAAAAAcgqICwoLAA0AAABUCeYK.
2m: fm PC2TLM to APRS via SGATE WIDE ctl UI pid=F0(Text) len 104  
08:48:38
0000  {TPRHM1HwsADwADAEZLpVolCwAEAAAAWwvYCkYLAAEABgDNSqVaFgsABAAEACaAC
0040  wsECwEAAB0AE4AWgPoKAAAAAAAggO8JKgsAFt75.
2m: fm PC2TLM to BEACON via SGATE WIDE ctl UI pid=F0(Text) len 42  
08:48:42
0000  T#122,082,082,001,000,071,11111010,0001,1.

The soundmodem was working quite well (colinear/pre-amp) until I put  
up the EB-432/Pre-Amp, with enough signal levels it seems to work  
fine.  I'm beginning to suspect that I may have an iffy coax lead  
somewhere.   I could also remove the 'groundplane' kit of the antenna  
to see if that makes a difference.

[bigsnip]
>
> Cheers.  Hope you can work without isolation, or it's yet more
> hassle.....
>
For the moment, I'll leave the current set-up in place.  Its at least  
gathering some data, anyway, I've bigger problems.  I've to head  
outside and dismantle my central heating boiler and replace just  
about all the fittings/pipework.  It's worse than a sieve at the moment.

Thanks to everyone for their comments and input, when I get this  
boiler back together, I'll have a look at the best use I can put the  
soundmodem interface to for the duration.

Regards
de John
EI7IG

--
John Ronan <jronan at tssg.org>, +353-51-302938
Telecommunications Software &  Systems Group,  http://www.tssg.org







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