Digital QRM on 144.930

[Brian Lawler]

Hey all;

We have been hearing something that sounds kind of like fraction of a second digital bursts at random intervals on 144.930 Mhz.  They occur from every .5 to 3 seconds, and have been going on for at least a few days.  This is the freq where the W7ECG-10 RMS node lives at SAR.  I just stopped there and confirmed that it is NOT that station, but it is pretty loud there (+10 db S meter).  The signal is quite weak at my QTH.  Let's see if we can figure out where this is coming from.

-Brian/KN0N

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Brian Lawler (KNØN)  PGP key.

[Keith Williamson]

Hi Brian,

The bursts are full scale on my ID-5100 S-meter here at Mission and Hemmi.

-Keith

KF7DRV

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[Andy Sayler]

Time to dig out the Yagi... Isn't Tom/KE7JOE good with that sort of thing?

[KNØN]

Well, the mystery of the noise on 144.9300 has been solved.  Thanks Tom, Matt and others who worked to track it down.  Unfortunately it appears that the operators of the Canadian station that is broadcasting the noise are not concerned and don't intend to fix their equipment.  We will need to look for a new home for the W7ECG-10 RMS node.  I did inform Lee that this is a NEW phenomenon, only beginning about six weeks ago.

-Brian

Email from:

Lee Woldanski

So, I had a listen to 144.930.

This is almost certainly the full-duplex bit-regenerating 1200 baud repeater, VE7HNY-8, operating on 144.930+ (144.530 input).

The burps of packet you hear are "artifacts" of the TAPR/Pac-comm DCD firmware. It is looking for a preamble string, and periodically (even on random noise), it thinks it sees it, and asserts DCD. This causes the repeater to repeat what it hears, even if it is a false alarm. Note that the Bell 202 modem system that was used here previously did the same thing, maybe just not as often.

The current implementation uses a Pac-Comm TNC-2 with some logic on the modem disconnect header to receive and re-transmit any packet heard. It also drops a user port at the site for the on-site node to connect through (ie VE7HNY-8 for FPAC or VE7HNY-10 for WinLink).

These full duplex repeaters have been operating since c. 1995, when TPARC was formed. 145.090+ at VE7TEL is a similar design, as is the BCFMCA's VE7LAN on 145.070+. You will likely hear similar bursts on those frequencies as well.

VE7HNY-8 should be beaconing periodically with its callsign and connect info. If it isn't let me know, and I will look at it further.

WinLink is available with the -10 SSID at all sites. See http://www.tparc.org for more details, including network map.

Regards,

Lee

On Tuesday, August 15, 2017 at 3:35:36 PM UTC-7, KNØN wrote: