Removing the tone works with ALL decoders, but it does take more time for some to realize that the tone is gone, so if the system can keep the transmitter on without modulation for 1/4 to 1/2 second, that'll do nicely.
But technically, no-burst is not the same as reverse-burst. Bob M. ====== --- skipp025 <[EMAIL PROTECTED]> wrote: > Another cute trick tried by some mfgrs is to simply > remove ctcss x-time before the rf goes away/drops. > > The decoder stops and the audio gate(s) close before > > the crash noise. The other famous anti crash noise > through repeaters is the audio delay module > clean-up, > which doesn't care what kind of signaling you use... > > including carrier squelch. > > s. > > > "Bob M." <[EMAIL PROTECTED]> wrote: > > > > The two "standards" for reverse-burst are > switchable > > in some of the newer radios, such as those that > use > > CPS for programming. Prior to about 10 years ago, > > Motorola was under the mind-set that you either > bought > > all your radios from them or none of your radios > from > > them, so system inter-operability didn't concern > them. > > If you bought a "Brand X" radio and used it in > your > > Motorola system, they hoped the audible squelch > burst > > would be annoying enough to get you to go with > their > > brand exclusively. Unfortunately this backfired > and a > > lot of customers went totally with "Brand X" > instead > > of "Brand M". Hence, we now have two slightly > > incompatible standard methods. > > > > Then we have some of the Japanese amateur radios > that > > don't recognize any reverse burst, and always give > you > > a squelch burst on a PL system. > > > > The old PL reed encode/decode units used until the > mid > > 1980s, tended to be a lot more forgiving about the > > phase difference. In fact, the very old encoders > from > > the 1960s used a center-tapped transformer on the > PL > > board, and switched from one phase to the other > with > > the undelayed section of a T/R relay, so the phase > was > > probably 180 degrees back then. It's only the > newer > > radios with microprocessor-based tone decoders > that > > can recognize and enforce the 120 degree shift. > > > > DCS (DPL in the Motorola world) got rid of this > dual > > standard by using a 134 Hz turn-off code for about > 200 > > mSec. ALL equipment now plays together a lot > better. > > The only incompatability is with normal vs > inverted > > codes, and this is more a function of the exciter > and > > modulator circuitry that is, by nature, different > > between various manufacturers. > > > > "So endeth the lesson for today, gentlemen." > (spoken > > by Mrs. Whistler, the little old lady in South > Africa > > in the opening scene of Ian Fleming's James Bond > 007 > > in "Diamonds Are Forever") > > > > Bob M. > > ====== > > --- Nate Duehr <[EMAIL PROTECTED]> wrote: > > > > > > > > On Nov 28, 2007, at 9:37 PM, Glenn Little WB4UIV > > > wrote: > > > > > > > The 1A is an EIA designation. > > > > > > > > See > > > > > > <http://www.personainternet.com/~northscan/dcss.html> > > > > > > > > Google is your friend. Searched for CTCSS > > > Frequency EIA. > > > > > > > > 73 > > > > Glenn > > > > WB4UIV > > > > > > There's also an EIA/TIA specification for the > > > reverse burst > > > standards. I don't have access to EIA/TIA > standards > > > (since you > > > typically have to pay for them) and judging by > the > > > various websites > > > that allude to it (marketing material), there's > > > other things in this > > > spec, it would appear. > > > > > > Here's a blurb from a modern Motorola radio's > > > marketing materials I > > > found a while back: > > > > > > "The industry standard EIA/TIA-603 lists two > formats > > > for CTCSS Reverse > > > Burst: The format used by Motorola is 120 degree > > > phase shift for 180 > > > milliseconds, while the format used by all other > > > manufacturers as well > > > as by aftermarket tone equipment makers is 180 > > > degree phase shift for > > > 150 milliseconds." > > > > > > They go on to explain that in RSS you can switch > to > > > "non-standard" > > > Reverse Burst on this particular radio. > > > > > > Would love to see the full EIA/TIA-603 spec. > But > > > these days when > > > standards are purchased instead of public > > > knowledge... oh well. I'm > > > also surprised the Moto marketing people forgot > to > > > put the "(TM)" > > > after the words "Reverse Burst". (GRIN) Maybe > it > > > was hiding in the > > > fine print of the document and I missed it. > > > > > > I was more interested in having found a > reference to > > > a real EIA/TIA > > > specification for the phase shifts and time > periods. > > > Then more > > > Googling found LOTS of manufacturer's marketing > > > materials referencing > > > it, but no copies of the spec sneaking around on > > > someone's website. > > > Oh well. > > > > > > -- > > > Nate Duehr, WY0X > > > [EMAIL PROTECTED] ____________________________________________________________________________________ Never miss a thing. Make Yahoo your home page. http://www.yahoo.com/r/hs
