Hello Don and All---- Answering Dons questions plus a little:
The presence of a 100 hz. PL component was suspected as that is the PL that we use and the signal reliablely opened us. Three DTMF zeros decoded properly but as they didn't mean anything to our controller, it announced an error-----this is what got us looking into the situation. The signal was then run through a "waterfall" audio analysis program ----it identified a 100 Hz PL component as well as the components of the DTMF "zeros" and maybe some data. 1. The answer would be no in that it was properly opening in response to the 100 Hz PL tone. The last thing I want to do is change our PL tone----we have over 150 registered users of our three emergency services repeaters all using 100 Hz. 2. The signal repeats at 23 min. + 30 seconds and 53 min. + 30 seconds. It is clearly controlled by a good clock. We have done some DF work and have more to do. So far, we are suspicious of a large municipal tower in our area-----we have just made contact with responsible people there but so far have only gotten -----"Its not us" responses. Definitely more to do there. At this point we don't think that we are a jammer's target---we haven't been bothered for a long long time and this signal is to unusually technical to be a jammer-----it looks like a three digit announcer or data reporter of some sort to me----I wouldn't normally worry about it as we have simply made the repeater immune to it with a kerchunk first opening delay timer but until I know just what is bothering us, I'm worried about it as it is strong enough to wipe us out if it ever gets stuck on or a lot more active. ----- Original Message ----- From: Don Kupferschmidt To: [email protected] Sent: Tuesday, December 12, 2006 3:07 PM Subject: Re: [Repeater-Builder] Mystery Signal Scott, Some questions and comments. I listened to the audio clip. It sounds like it's being generated by some type of automatic device. Your post (below) states that you detect 100 hz PL and three DTMF zeros. 1. Can you put the machine on another PL in full CTCSS receive? Does the machine go into repeat mode at that point when the offending signal is received? 2. The signal repeats exactly two times an hour. What time exactly? Is it constantly there, say at 10 and 40 minutes past the hour? Are you able to DF it? If you can program the machine to another PL frequency, and, when placed in full CTCSS receive the signal is still present, then I would have to believe that someone may be interfering. If it doesn't follow the new PL frequency, it's got to be something else. I had an interesting situation a number of years ago with my machine. My neighbor, who is probably one of the nicest people on earth, bought himself a "Christmas gift". It was a Bearcat scanner. Sure enough, the interference started just prior to Christmas day and ended just after the holidays. (He was a snow bird). It started back up in late spring, when he returned from the south. Couldn't figure it out until one day he came over asking me what were the local PD / sheriff frequencies. A light came on in my head. You know the rest of the story. Keep us informed. Don, KD9PT ----- Original Message ----- From: Scott Overstreet To: [email protected] Cc: Scott Overstreet ; Dave Platt Sent: Tuesday, December 12, 2006 1:10 PM Subject: [Repeater-Builder] Mystery Signal Hello All An interfering mystery signal has suddenly appeared on the input (144.670 mhz.) of our repeater. Using a five kc. wide FM detector---The signal is approximately one second in duration----opens with 100 hz. PL (which continues throughout) and then three DTMF "zeros" follow in rapid succession and then possibly a short period of some sort of data. The signal repeats exactly two times an hour and the source is off in between transmissions. This goes on continuously without interruption or apparent change. Our area is between urban and big city and the signal is strong enough to be heard over a wide area using only an HT. A wave file of the mystery signal is at: http://www.radagast.org/~dplatt/hamradio/Signal_3.wav using an FM detector with wide open squelch. We are obviously very interested in identifing this signal and its origin---- What is it ? Thanks-- Scott, N6NXI !DSPAM:1016,457f01de530501073714974!
