Long Squelch Tail on MT1000

[smiller]

I am noticing an odd condition on my UHF MT1000... there is an annoyingly long squelch tail whenever the received signal has a valid PL tone present. This condition occurs whether the selector switch on the radio is set to either PL _or_ carrier squelch... as long as there is a PL tone on the received signal I get the long squelch tail. If I remove the PL tone from the signal the squelch action becomes normal. Add the PL back to the received signal the long squelch tail returns (even when leaving the radio in carrier squelch - the condition appears to be completely dependant on whether or not a PL tone is present on the received signal). Setting the squelch (carrier or PL) tighter in the RSS software has no effect on the problem. It's not really that big a deal, just mildly annoying, but wondering why the squelch hysteresis changes just because a PL tone is present on the received signal? Is this normal for the MT1000? (I don't have another to compare right now).

Thanks in advance...

[alex]

Hrm. I'd need to know some more info about what your are recieving. For the most part, most if not all Motorola radios will drop the carrier before dropping the PL tone. That way the radio is still transmitting the PL tone when it drops its carrier. End result? no cur-chunk. (Sp? ). That Might be what your experienceing. I've found a couple other radios that do this, but not many. If other users of a system have other 3rd party radios, they might also cause this problem through a repeater.

I help run a Ham repeater and it has two maxtrac 100 radios in it (2channel 5 pin versions) and it has a very nice smooth de-key. However, people who use Yaesu radios, etc, will cur-chunk on dekey.

-Alex

[smiller]

It doesn't really matter what I'm receiving. I usually use an IFR service monitor for testing but the same thing occurs when using a repeater (if it doesn't have some kind of squelch tail elimination feature). If you drop the PL tone well before the carrier then there is no squelch tail, of course. The problem occurs when the carrier and PL tone drop at the same time, as with simplex communication or when using a repeater without a squelch tail elimination function.

Thanks,

- Seth

[alex]

I stand corrected on one thing. It would drop the PL, then the carrier, thus, the radio wouldn't "hear" the dekey. As opposed to the reverse of it keeping up the pl until the carrier droped - which looking at now didn't make much sense.

I don't have a service monitor, or any extream technical means to test this, but I believe it's a radio-radio thing interms of how it processes recieved signals. Play around with a couple of different brands of radios talking to eachother using PL decode, and see the different effects.

Going back to your origional question... I know that the Jedi series tends to do that while scanning. I haven't used an MT1000 long enough to notice an issue. The HT600 I had for a while worked just fine with encode/decode, so i don't know if that tells you anything.

-Alex

<font size=-1>[ This Message was edited by: alex on 2002-01-15 16:40 ]</font>

[Nand]

[Nand]

[powerlineman]

On 2002-01-15 18:49, Nand wrote:
Correction, should read:

The repeater must send a reverse burst before it drops the carrier. All Motorola radios do this unless purposely disabled. Its purpose is to close the audio path before the carrier drops. It does this by reversing the phase of the PL signal.
Nand.

[powerlineman]

I completely understand what you are talking about. I have 2 MT1000's that do the same thing while on PL. I have always wondered if it has to do with the squelch setting. If I remember correctly, there are independent settings for carrier, PL, and scan in RSS?

[Nand]

[smiller]

Thanks for all the responses.

To powerlineman: Thanks for your comment, now at least I know I'm not crazy. Yes, there are separate squelch settings in RSS but tightening the squelch set points does not seem to affect the problem at all.

To Nand: Thanks for the info, and I realize that when in PL mode the squelch uses PL as the primary input... but, what I was trying to point out is that it doesn't matter at all what configuration the radio's squelch is in (carrier or PL), rather it is the presence of a PL tone on the received signal that determines whether the problem is there or not. Even when in carrier squelch mode on the radio, if a PL tone is present on the received signal I get a long squelch tail, remove the PL on the received signal and the squelch operates normally - without touching the radio. Why would this happen even if the radio is set for carrier squelch..? As I said, when comminicating with a repeater with reverse burst, etc., there is no long squelch tail (as you would expect), but the problem is annoying when communicating via simplex or via a repeater that that not use reverse burst.

Thanks again to all...

[Nand]

[smiller]

Yes, the 'long squelch tail' effect only occurs when the received signal has the correct PL. Any other tone and the squelch operates normally.

From all I can tell this is just a built-in peculiarity of the radio. It appears that if a channel is programmed with a receive PL then the squelch operates in PL priority mode, regardless of the setting of the CSQ switch. I believe you hit the nail on the head when you said 'Motorola could have done a better job here'... because while it is true that this behavior won't really matter when the radio is used on a Motorola system or when communicating with other Motorola radios, it _is_ possible that the radio might actually be used to communicate with a radio of different manufacture (in this case a GE Mastr II repeater station). I suppose you could make the case that this isn't Motorola's problem, but a better solution would have been to make the CSQ switch _really_ put the radio into carrier squelch.

But as you point out the solution is simple, if not very elegant... just program up another channel with the same frequency but without a receive PL.

Once again, thanks for the response.

- Seth