I had an interesting occurrence my last hunt using the Tritronics collar with beeper and the Garmin GPS tracker on the same dog. (That's a lot of "bling" on the dog!) I noticed the Tritronics beeper collar turning itself on and off as we hunted! Being the inquisitive type, I assumed it was a run down battery on the beeper and changed that in the field, but the problem recurred. Then, since it was a hot day in WI and the birds weren't cooperating and I had plenty of time to walk along on ponder the situation, I started thinking about interference between the Tritronics collar and the Garmin.
As best I know, the Garmin receives the signal from the GPS and then the collar sends the info from the transmitter on the bottom of the collar to the handheld. Depending on the settings you choose, it could be every 5 seconds (the setting I chose). So we know the Garmin is transmitting at least every 5 seconds. The Tritronics, on the other had, controls the remote beeper through the collar. When you send the signal to turn the beeper on or off, the handheld unit sends a signal to the collar and it sends a signal to the beeper. (Very short range signal from the collar to the beeper.)
What I noticed was my beeper was turning itself on and off every 5 seconds, when I was running a dog with both units on and functioning. I checked the location of the collars on the dog and noticed the Garmin unit was riding up the dogs neck and was within 90 degrees of the Tritronics beeper, which was close to the top of the dogs neck. Which unit was moving on my dog is irrelevant, it's the relative location and distance between the units that is important. I adjusted the Garmin to stay underneath the neck and the problem went away.
My conclusion, based on my totally scientific experiment near Clam Lake in the Wisconsin woods (Laughing!), was there there may be some frequency interference between the two units from different manufacturers.
How to address this problem is beyond me. I will send this to each company and let them chew on it- and it may not be fixable or even a real problem (see "scientific experiment" in previous line). If it happens to you, you'll see how I fixed the problem.