My Vertex RSS offers a choice of 120 or 180 degrees under the reverse burst CTCSS option, but I don't understand exactly what it means, though I understand what the burst is used for. Can someone please enlighten me?
Not Motorola, but a current thread has been discussing reverse burst, among other things.
Tom, W2NJS
...in D.C.
CTCSS Reverse Burst Question...
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Tom in D.C.
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Its another attempt to have a "commercial standard" for the reverse burst "quenching" of the PL reed (or electronic equivalent). I will have to check, but I think that Mot uses the 120 degree phase shift, and everyone else uses 180 degree. Either that or its the other way around. Again, I would have to check. Its another of those annoying things where if you bot GE or RCA the the "burst" is wrong for your old MICORS, or if you have MASTR II repeaters, and wanted to buy MICORS then the burst was wrong. I think it was a misguided attempt to keep "market share" or force brand "loyalty".
It was either that or hear that squelch "crash" after every transmission...
It was either that or hear that squelch "crash" after every transmission...
I understand the concept and use too, but never worried much about exactly HOW it works, so thanks Tom for asking a question I never thought about.
As for brand loyalty, that may have been an issue once upon a time, but . . .
I use a Syntor X and the ham repeater I call "home" is a GE Mastr. I leave no squelch tail. Causes confusion among those hams not used to it, but then again, that's half the fun!
Good luck,
As for brand loyalty, that may have been an issue once upon a time, but . . .
I use a Syntor X and the ham repeater I call "home" is a GE Mastr. I leave no squelch tail. Causes confusion among those hams not used to it, but then again, that's half the fun!
Good luck,
Chris,
Hamming 31 years
http://www.wa2zdy.com
Wesley Chapel, Pasco County, Florida
Snow? What's that?!
The human race is proof that Darwin was wrong.
Hamming 31 years
http://www.wa2zdy.com
Wesley Chapel, Pasco County, Florida
Snow? What's that?!
The human race is proof that Darwin was wrong.
In the early days of radio and tone squlech (ctcss).
motorola and other radios used mechanical reeds for encode and decode.
the decode reeds would continue to vibrate after the transmission
ended leaving a squelch tail.
to stop this the xmtr would send a 120 or 180 out of phase ctcss
tone being the same freq as the tone in use.
this out of phase tone would dampen the reeds vibration and elimanate the squelch tail.
just useing this post as an excuse to drudge up some old tech trivia
Bill
motorola and other radios used mechanical reeds for encode and decode.
the decode reeds would continue to vibrate after the transmission
ended leaving a squelch tail.
to stop this the xmtr would send a 120 or 180 out of phase ctcss
tone being the same freq as the tone in use.
this out of phase tone would dampen the reeds vibration and elimanate the squelch tail.
just useing this post as an excuse to drudge up some old tech trivia
Bill
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MRFLASHPORT
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Vertex Radios
The standard for Vertex is the 180 selection. I have a VX4000 and a couple of buddies who have VX900's. They were all set to the 180 selection when I read the radios.
I have also heard from other people who have Vertex radios, that the 180 sounds the best on the squelch tail.
I have also heard from other people who have Vertex radios, that the 180 sounds the best on the squelch tail.
Do an archive search on this subject and you will find a previous thresd. Here is a post from wb6fly:
"I have made numerous postings to various lists on this topic, and the responses ranged from "I've never HEARD of such a thing!" to "Yeah, I've known about that problem for YEARS!" Both Motorola and Kenwood have consistently denied the existence of a reverse burst compatibility problem, stating that they followed the standard specified in EIA/TIA-603. However, it just happens that there are TWO standards for CTCSS reverse burst in EIA/TIA-603, and they are NOT COMPATIBLE.
The compatibility issue surfaced when I added a Kenwood TK-762 radio to a fleet of Motorola radios. Immediately, I discovered that the Kenwood radio caused squelch crashes on all the Motorola radios, and the Motorola radios caused squelch crashes on the Kenwood. I brought in another Kenwood radio to test, and it reacted in exactly the same manner as the first. A bench check proved that the reverse bursts were exactly on spec, and both Kenwood radios muted silently between each other.
I dug into this topic with the help of engineers and technicians at both Motorola and Kenwood, and gradually realized that Motorola used a 120 degree phase shift for 180 milliseconds, while Kenwood used a 180 degree phase shift for 150 milliseconds. This difference is almost immaterial for mechanical reeds or simple tone decoders, but is easily discriminated by the digital signal processors used in the latest radio models.
Motorola has finally acknowledged this compatibility issue in the latest version of Professional CPS, HVN9025K R06.02.03. There is now a check box on the Personality Configuration - Advanced page that has a box labeled "Non-Standard Reverse Burst." When this box is checked, the radio will encode and decode the CTCSS reverse burst in the format used by Kenwood and other major radio makers. When unchecked, its default condition, the radio will encode and decode the CTCSS reverse burst in the Motorola format. I tried using this new feature on a brand-new HT-750, and I can say that it works perfectly. Since the feature is programmed for each personality, I can now use just one radio in either a Motorola or a Kenwood system, and it will mute silently in either.
I expect that Motorola will begin including this capability in all future RSS releases for all radios. It remains to be seen if Kenwood will offer a similar upgrade in their software. At this time, you must send a Kenwood radio back to a service center to get it flashed so that it will be compatible with the Motorola reverse burst. That's too much trouble for me!
73, Eric Lemmon WB6FLY"
"I have made numerous postings to various lists on this topic, and the responses ranged from "I've never HEARD of such a thing!" to "Yeah, I've known about that problem for YEARS!" Both Motorola and Kenwood have consistently denied the existence of a reverse burst compatibility problem, stating that they followed the standard specified in EIA/TIA-603. However, it just happens that there are TWO standards for CTCSS reverse burst in EIA/TIA-603, and they are NOT COMPATIBLE.
The compatibility issue surfaced when I added a Kenwood TK-762 radio to a fleet of Motorola radios. Immediately, I discovered that the Kenwood radio caused squelch crashes on all the Motorola radios, and the Motorola radios caused squelch crashes on the Kenwood. I brought in another Kenwood radio to test, and it reacted in exactly the same manner as the first. A bench check proved that the reverse bursts were exactly on spec, and both Kenwood radios muted silently between each other.
I dug into this topic with the help of engineers and technicians at both Motorola and Kenwood, and gradually realized that Motorola used a 120 degree phase shift for 180 milliseconds, while Kenwood used a 180 degree phase shift for 150 milliseconds. This difference is almost immaterial for mechanical reeds or simple tone decoders, but is easily discriminated by the digital signal processors used in the latest radio models.
Motorola has finally acknowledged this compatibility issue in the latest version of Professional CPS, HVN9025K R06.02.03. There is now a check box on the Personality Configuration - Advanced page that has a box labeled "Non-Standard Reverse Burst." When this box is checked, the radio will encode and decode the CTCSS reverse burst in the format used by Kenwood and other major radio makers. When unchecked, its default condition, the radio will encode and decode the CTCSS reverse burst in the Motorola format. I tried using this new feature on a brand-new HT-750, and I can say that it works perfectly. Since the feature is programmed for each personality, I can now use just one radio in either a Motorola or a Kenwood system, and it will mute silently in either.
I expect that Motorola will begin including this capability in all future RSS releases for all radios. It remains to be seen if Kenwood will offer a similar upgrade in their software. At this time, you must send a Kenwood radio back to a service center to get it flashed so that it will be compatible with the Motorola reverse burst. That's too much trouble for me!
73, Eric Lemmon WB6FLY"
Another solution that is sometimes available for this situation is where the 3d party mobile or portable equipment allows a programming option of causing the carrier to be sustained for a period of time (usually about 150 mils) after tone drops. If the repeater's receiver is programmed for OR muting, it will not hear the squelch noise. Most of the RELM radios had (have?) this option.
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firephoto39
- Posts: 16
- Joined: Sun Aug 11, 2002 12:10 pm
The other day one of the sheriff's repeaters here (what we get dispatched to fires on) would get stuck with an open squelch after dispatch would unkey. Everything was fine when a mobile unit unkeyed. This thread has provided me a probable answer to this now. 
Now a question.
Is the reverst burst only necessary for equipment with mechanical reeds? I always thought that once the PL tone was gone, the radio (without mechanical reeds) would mute.
Tom
Now a question.
Is the reverst burst only necessary for equipment with mechanical reeds? I always thought that once the PL tone was gone, the radio (without mechanical reeds) would mute.
Tom
Even assuming the radio (for present purposes, let us assume a repeater's receiver) mutes on loss of PL, if PL and carrier are lost at the same time, the process of filling up the squelch circuit will allow FM no-signal noise to pass for a short burst. Squelch tail elmination is provided by having the sending radio causing the receiving radio to squelch audio WITHOUT the sending radio dropping carrier until the receiving radio has had a chance to do so. Reverse burst is one way of doing this, and while it was first designed to deal with resonant momentum of mechancal PL filters, it is still used today to force receiver squelch. Another way of doing it is, as I noted, by holding carrier on the sending radio long enough for the loss of PL by itself to cause the receiver to squelch, but this requires holding carrier for a longer period of time (usually on the order of 150 msec.). Moreover, the situation gets complicated if the receiver is programmed for "and" muting, which requires loss of both carrier and PL to squelch, or if the receiver is programmed for PL "hold off," which will continue unsquelched for a limited period of time, notwithstanding loss of PL, in order to compensate for PL roll-off. Regardless of these features, the receiver will squelch audio if it receives a turn-off code (either reverse-burst with analog PL or the defined bit sequence for DPL).