At 01:15 AM 03/23/10, you wrote: >Hello again. > >I have a UHF MSR2000 up and running now. Most of my radios have the >reverse burst in them. But just about all ham grade radios do >not. Is there a way to get rid of the squelch crash from the >repeater when a non commercial grade radio is used? > >Repeater is stock, and would like to try and keep it that >way. Hoping there is maybe a jumper setting or a trick that someone >might know. > >Single PL tone card in the repeater, card number trn073app on back, >trn5073 on front. > >thanks
Encoding reverse burst ifs a function of the transmitter, responding to it requires a receiver that has a tone decoder that is designed to respond to it. Many electronic decoders never "see" the reverse burst and continue to decode the phase-delayed tone until it goes away (when the transmitter PTT drops). An electronic decoder has to be specifically designed to respond to reverse burst (and almost all of the current crop are microprocessor based... detecting and responding to a phase shift is easy to do in software) Are you aware of the old GE and RCA technique that was given the derogatory name of "chicken burst" ?? It's how everybody avoided a patent infringement lawsuit from Moto Legal in the 60s and 70s. This article may be of interest... "A Historical and Technical Overview of Tone Squelch Systems - A primer on tone systems, with a little on digital systems." <http://www.repeater-builder.com/tech-info/ctcss/ctcss-overview.html> "Chicken Burst" is when you shut the tone off, then drop the PTT a quarter second or so later. The decode reed coasts to a stop instead of slamming to a stop with reverse burst. It works with any decoder, be it reed or electronic, except the Alinco DR-series design (which takes as much as two seconds to mute the audio after the tone goes away) and the Yaesu VX1 that is broken from the beginning (it functions like a tone burst decoder). Years ago I had a UHF Micor repeater that came out of IMTS service (i.e. it started out life as a carrier squelch station). I had added a stock PL decoder board to it but the transmitter had no factory PL encoder. We wired the exciter to a leftover TS32 that was being used as an encoder only. The PTT line from the controller was cabled to a 200ms time delay that was implemented with a 555 chip. When the controller PTT was activated the timer activated the TS32 and the transmitter PTT line immediately, when it was released the TS32 shut off and it delayed the PTT for about 200ms. This gave dead carrier for 200ms after the tone encoder went away. Everybody was happy. No squelch tails anywhere. Hope the above description helps. Your implementation may vary. You may chose to use a timer in the repeater controller, or you may decide to build a small timer like I did. The Scom 7K has a audio gate circuit that is specifically designed to mute the PL encoder... you could route your encoder audio out of the station, through the 7K and back into the station and to the transmitter and everything else is set up in the controller programming... from looking at the schematics and programming options you'd swear that the designer had chicken burst from the repeater transmitter in mind... I've not looked at the MSR schematics in several months, but you might be able to modify the encoder on the PL card to turn off the tone completely instead of going into reverse burst (on the TRN5075A you'd ground the base of Q8 to shut off the tone), then change the cap that holds the transmitter on to a larger value (probably on the station control card). Mike WA6ILQ PS - have your users pressure the Kenwood, Icom and Yaesu reps at every hamfest ... have each user tell the reps in their own words that the factory should start using the commercial tone encode/decode circuits and firmware code that they are using in their commercial radio product lines and have been for years. It would be nice to get reverse burst, tone, DPL, and split tones/codes in ham rigs.
