[aprssig] Corrupted Data Pushed into APRS-IS

[Steve Dimse]

This may have nothing to do with the IGate that sends the data. The  
most common cause is digis and IGates with PASSALL ON. This TNC  
parameter turns off CRC checking on received packets and forwards  
whatever it hears, even if it is garbage. AFAIK the D700 has no such  
parameter, but if a nearby digi has it on, the corrupt data may appear  
to be coming from an innocent station.

Occasionally people report problems where rebooting the IGate and/or  
digis is curative.

There has been a problem like this in the South Florida area for many  
months, looking at a findU near page shows the problem clearly

http://www.findu.com/cgi-bin/near.cgi?call=K4HG-8

If you dig out an ASCII table you will see many of the variations on  
the callsign are single or double bit errors which is diagnostic of  
this problem.

Steve K4HG

On Aug 10, 2009, at 6:42 PM, Brian McCarthy wrote:

> Hello All,
>
> I have been lurking here for almost a month and have been learning
> quite a lot. Thank you!
>
> I am seeing a problem in my nearby area. APRS packets with corrupted
> callsigns are being forwarded into APRS-IS by a station near mine. I
> had previously contacted the owner and asked he look at the situation.
> He had not found a solution, and eventually turned off the igate he
> was running. It took more a month for all the bad data to finally
> decay out of the aprs.fi pages, but now the station is on and
> forwarding bad data again.
>
> Example bad callsigns include: B4KDKZ-5, R00O-9, DE3X9O, TW4DKZ-5,  
> HX9O, 5X9O-9.
>
> If these callsigns were real, I would be having one whale of a good
> time swapping HF DX'ing stories since many of them appear to be at my
> location. Some of the calls are rare DX that I would enjoy working for
> real. Anyhow, the bad data makes it hard to see what else is going on
> in the near field.
>
> In exchanging email with the owner of the station posting the bad
> data, I gather that the radio and TNC are a TM-D700 connected to a PC
> with UI-View. I have never owned a D700 and cannot begin to suggest
> where to look to find the problem.
>
> Does the list at large have any suggestions?
>
> Thank you,
> Brian
> NX9O
>
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