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[aprssig] NWS ON rf

Steve Dimse steve at dimse.com
Fri May 8 21:57:15 UTC 2009


This packet appears to be an APRS Internet System packet. Although  
some programs have been written that can take an APRS IS packet and  
transmit it in the APRS IS form, AFAIK none has been deployed outside  
of testing. Furthermore, the use of the lowercase q in the path makes  
it a deviation from the AX-25 standard. Tests have shown most TNCs can  
handle it, but on general principles it should not be sent.

If this packet actually was sent on the air with a from-call of  
DVNWSO, tracing it from the text is impossible, the only choice is  
good old fashion DFing. It is made slightly easier by the fact that  
there is no valid digipeater in the path, so whoever sent it is in  
direct RF range of your friend. Still, I doubt this actually appeared  
on the air.

What an IGate typically will do is take this packet as seen on the  
APRS Internet System and repackage it as a third party packet, looking  
something like (if the IGate is K4HG)

K4HG>APRS,WIDE1-1:}DVNSWO>TCPIP,K4HG*:;DVN_OUTLK*0...

A receiving program is able to remove the transmitting header  
(everything up to and including }) , and feed the payload into its  
parser recursively (a feature Bob created for his zip-lan and I  
appropriated for the APRS IS):

DVNSWO>TCPIP,K4HG*:;DVN_OUTLK*0...

When you do this, the new path makes it clear that the packet  
originated on the Internet. This is missing from the packet you  
displayed. If it actually was transmitted in this form on RF it is not  
compliant with the APRS specification.

Steve K4HG

On May 8, 2009, at 5:30 PM, Danny Pease wrote:

> I have a question about WX information from the NWS in Davenport, IA  
> is
> being gated to RF on APRS. The following appears on RF north of me  
> near
> Muscatine, IA. I do not see this myself, but a friend up there,  
> NW0X, is
> seeing this on RF. NW0X is on RF only, no internet.
>
> DVNSWO>APRS,qAS,WXSVR:;DVN_OUTLK*090915z4124.00N\09101.20WyCheck For
> Activation {8IFAA
>
> My question is, how do you tell who is sending this to RF?
>
> Danny  NG9R
>
>
>
>
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