Batboard

I've noticed that, in most professional settings where MDC1200 is used, next to no one has the receivers set up for muting. Is there a reason that not many radios are configured for it? (Do HT750/1250s support it?)

Everything current does. I attribute it to the intial programmer not understanding how to set up the options or not taking the time to do it.

It seems odd that it's simple incompetence, though. It's happening on the radios on my college campus, which are serviced by one of the big communication firms. Similarly, until the police back home switched to ASTRO, they never had it enabled either. I'd always assumed the radios either weren't capable of it, or that there was a reason for deliberately not enabling it.

All of the radios that I've been affiliated with that had DOS on them had it enabled. I love it because I HATE the MDC squawk. Just a single little "bleep" is all I hear.

On the other hand, I've heard other agencies that utilize MDC or for that matter people that are monitoring a system employing MDC that have their radios NOT set to DOS and that god-awful squawk blasts through their speaker. I don't even bother telling them anymore because for some reason, people either 1) like it (the squawk) or 2) think it's cool.

I've even had people tell me that I didn't know what I was talking about and the DOS did not not mute the MDC squawk...

EDIT - DOS does not inhibit the decoding of the MDC packet, so you still see the IDs and what-not if you have a display radio and the propper flash.

RESCUE161 wrote:people either 1) like it (the squawk) or 2) think it's cool.

I wonder if that's what it comes down to. The local news agency just replayed a radio transmission from an officer calling for backup earlier in the day and didn't bother to chop the MDC1200 burst off, either, even though I'm certain they have access to good audio editing equipment.

People do talk about using it on ham repeaters and whatnot and getting comments that it sounds like they're using a 'professional' radio or the like, which would also lend credence to that theory.

I thought I'd read something somewhere (but now can't find it) about some people not liking DOS because it was prone to chopping off parts of transmissions, although, having been running it for a few months on my own radios, I've never heard it happen.

I have it set on all of my Spectra's; however, the Spectra's seem to let more of it through than a CDM/HT1000/Jedi would for some reason.

The small "bleep" that DOS muting creates sounds much more pleasing to the ear than does the full burst, but either way it doesn't make a difference to me, so long the radios are working.

For the most part, recorders are tied directly into the audio lines at the CEB, and the DOS muting has no effect on the audio coming off of it. Your getting the real deal audio as it was heard by the system.

News agencies don't care about trival things like this, and in fact, gives it more "cop sound".

Besides, when you work with it everyday, you tend not to notice it. Kind of like living next to an airport or rail line. Just becomes part of the daily grind.

On the aside note, DOS muting tends to work really well with the post-ptt MDC than pre.

Apparently Kenwoods can't mute the Fleetsync at all. I asked about DOS muting during a Kenwood technical training course I attended about 6 months ago, and both the instructors looked at me like I had 2 heads. They claimed nobody ever mentioned it before, and couldn't understand why anyone wouldn't want to hear the nice data squawk. I told them if they wanted people to seriously consider switching from their near-silent Motorola MDC systems, then they'd better consider implementing it. Bizarre.

Todd

Or at least allow you to use a different PL for Fleetsync.

(My old state's ambulance service's MDTs operating over a conventional UHF system do that.)

Before I got a radio capable of displaying PTT IDs, I'd use it as a kind of poor man's ANI to tell who was talking; like, one guy whould have his all his radios set up to squawk on post, another guy would only run MDC600, another guy would run MODAT, and so on. Like PJ said, it became a part of the background noise over time, but as soon as I heard the squawk I'd know immediately who was talking.

On a side note, Houston FD used to use MDC1200 for all of their status-messaging before they got MDTs in the trucks. It drove the scannerheads nuts.

I don't have DOS setup on any of our HT1250's or CDM's, as after trying it, we have found out here that it SIGNIFIGANTLY slows down the scan rate and the time it takes to unmute a channel. I havent heard any complaints from my guys, and we have over 100 HT1250's in service like this....

While I cannot prove what I'm about the say, I believe that amongst older radio types there is sort of a negative bias against either time-based ID muting or code-based ID muting because in the early days, neither system worked all that well and both ran the risk of masking the ID. In some respects this was a function of product maturation and some respects it was a result of poor implementation of a new feature. But such prejudices linger.

For those who have experienced what Jayres reports, take a look at subscriber unit programming, and, in particular, "coast time." For the Motorola code-based DOS, "coast time" is the time delay between the end of data and the end of mute. The recommended value is on the order of 250 msec.

Coast time depends on what the system is set to. If you missmatch that, you'll definitely miss traffic. Never seen a scan rate issue because all of our radios were set right.

Can someone explain what this muting does?

We got rid of the pre mdc id because it was taking too long to get your message out on the tactical channel. We still use it on the repeater channel as it slows them down and the start of their message doesn't get chopped.

Thanks

DOS mutes the MDC sound on the receiving radios speaker so they won't hear the MDC burst. All they'll hear is a short bleep, that's all.

Every /\/\ot. radio I own has DOS enabled for every channel, just incase someone keys up with MDC. I HATE the MDC squak.

I believe us labbers are the only ones that understand DOS.....

Another option, at the system level, is Audio Hold-Off. This is enabled in the repeater. When the repeater detects an MDC data packet, it mutes the passing audio for a preset period of time. This eliminates it for all receivers, including those that do not have DOS such as scanners.

We have utilized this on the Micor, MSF5000, MTR2000, PDR3500, and Quantar.

Seems like this would be a good option to enable on any repeaters used in amateur service

SlimBob wrote:Seems like this would be a good option to enable on any repeaters used in amateur service

Yeah, if you never plan on using MDC Call, Page, or PTT ID.

What SFD_Radio described makes sense for a public safety agency who only use of MDC is PTT IDing at the console. Most, if not all amateur use of MDC would entail sending MDC to units in the field, which audio holdoff would effectively kill.

But, if you were using MDC as a "key" so to speak to open the repeater for use, then the bursts would be kept semi-secret.

Not exactly MDC, but up in Toronto the TTC (Toronto Transit Commission) uses an MPT1327 trunking system for their subway system. At the end of each call, there's a data burst that sounds like an MPT control channel. DOS does a pretty nice job at squelching this.

What does DOS stand for? (Besides the other billion explainations of the acronym).

Data Operated Squelch.

how you set that up on a ht1250? Cant stand the noise anymore and if there is a to avoid it i would like to.