[OZAPRS] Decoding HF APRS

[Robert Thirkettle]

Hi All
	Another problem is that with AX-25 there is no forward error
correction just a check sum. If 1 bit is corrupted then whole packet is
discarded. AX 25 is not really suited to HF with its atmospheric
variations that can cause phase distortion and other problems to the data.
These types of problems are not obvious to the ear but the TNC sure sees
them.

Regards Rob Thirkettle  ZL3RX         
Dept  Physics & Astronomy
University of Canterbury     
Private Bag 4800,         
Christchurch 8020,
New Zealand
Tel: +64 3 364 2510
Fax: +64 3 364 2469
mailto:rob.thirkettle at canterbury.ac.nz


-----Original Message-----
From: ozaprs-bounces at aprs.net.au [mailto:ozaprs-bounces at aprs.net.au] On
Behalf Of G T & C A Beagley
Sent: Friday, 7 July 2006 2:47 p.m.
To: VK / ZL APRS Users
Subject: Re: [OZAPRS] Decoding HF APRS

I have similar problems. I regularly decode VK3MY and a couple of other 
VKs plus a W1 on my AEA DSP-2232 and although I can hear a lot more 
stations in there they rarely seem to decode even when signals are 
respectable. I have found tuning on HF to be extremely critical. About 
20hz either way can make a big difference.

Graham

ZL1GTB

Rob wrote:

>Not sure if anyone can help me
>I'm Trying to decode APRS on HF
>I have a Dual Port Kantronics KAM XL
>I find it excellent on VHF but when i tune it on HF i can decode VK3MY 
>every time ok but all the other stations i seem to be having trouble
>I'm using a Codan 7727 B tune to 10.147.10 USB
>I can audible here other traffic ok anyone got any Ideas
>
>Cheers
>de VK4HAB
>
>_______________________________________________
>Ozaprs mailing list
>Ozaprs at aprs.net.au
>http://aprs.net.au/mailman/listinfo/ozaprs
>
>  
>




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