Motorola Acknowledges Reverse Burst Incompatibility

[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

[Alan]

I have found the same thing. there is also an incompatibility between Motorola products as well.
My memory is a bit foggy but I think it was the SP10 (or was it SP21) and some Radius products (P1225?) that had the same squelch crash beween them, as well as talking to the Kenwood product.
We found a fix it it though, we changed them all to DPL. It was the only way we were able to resolve the issue.

[Will]

Just a small note here, the SP21 and most Sprit radios do NOT have any reverse burst. Also some Motorola radios allow programming the Reverse Burst or turn off as disabled. I think this comes from days when some radios would falsely decode another PL code's reverse burst.

[radioinstl]

I expect that Motorola will begin including this capability in all future RSS releases for all radios. 73, Eric Lemmon WB6FLY

Coming up on 10 years later and you still do not have the choice in top teir radios. Neither the ASTRO25 line or the APX allows you to choose. I wonder if either the Quantar or GRT800 recognize both formats or still force you to only use the format Motorola has picked.

[MTS2000des]

I expect that Motorola will begin including this capability in all future RSS releases for all radios. 73, Eric Lemmon WB6FLY

Coming up on 10 years later and you still do not have the choice in top teir radios. Neither the ASTRO25 line or the APX allows you to choose. I wonder if either the Quantar or GRT800 recognize both formats or still force you to only use the format Motorola has picked.

hey even thought Ma M only wants you to buy THEIR repeaters and subscriber radios?
Nah...they'd never do a thing like that.

[RFguy]

Are they still designing analog radios?