Twin / Dual MDC1200 PTT ID burst

Spatch713 · Post by **Spatch713** » Tue Feb 20, 2007 7:11 am

I recently noticed that one of our paramedics has two MDC1200 data bursts upon key up (pre PTT ID). It's definetly two distinct and seperate MDC bursts. I can tell you they are using CDM1250 VHF mobiles. I have not had a chance to park my XTS5K on a channel and see if I can decode the transmitted ID but will try tonight. They switch to whatever fire companies district they are responding to so I will have to program those in the XTS.

I can tell you that their dispatch center does not support any MDC functions but some other centers they talk to do.

I have never heard this before. I almost suspect that some of the medics are hitting the PTT twice? If not and it has a valid application what would it be?

Thanks for the help!

HLA · Post by **HLA** » Tue Feb 20, 2007 7:36 am

never seen that unless he's using some kind of aftermarket board installed in the radio?

jedi_saber · Post by **jedi_saber** » Tue Feb 20, 2007 8:14 am

perhaps the Preamble-MDC is enabled during the pre-time, so that's what you might be hearing.

jackhackett · Post by **jackhackett** » Tue Feb 20, 2007 8:17 am

I've seen a few CDMs where some rocket surgeon* installed an aftermarket ID board and then programmed the radio for MDC too.

*combination rocket scientist/brain surgeon, not to be confused with a brain scientist, which is a combination brain surgeon/rocket scientist.

Spatch713 · Post by **Spatch713** » Tue Feb 20, 2007 8:24 am

Yeah, that would be odd... its definetly not the preamble (chirping kinda sound prior to the MDC burst). I could care less about it but its weird - so now I am curious!

nmfire10 - you may hear this from the medics (not sure about Medic 6 - but possibly 2). Do you have any clue?

DPL · Post by **DPL** » Tue Feb 20, 2007 8:37 am

If you have both MDC repeater access *and* MDC pre ID turned on you will hear something like this. That's what my Visar does, anyway; I don't have any experience with the CDM mobiles.

There is a police department near me that has one of their radios set for MDC repeater access, MDC pre ID, *and* MDC post ID. Talk about annoying.

Spatch713 · Post by **Spatch713** » Tue Feb 20, 2007 11:55 am

Yeah, that would get old fast. Hopefully they use DOS! In my case this is really odd since all the repeaters are DPL/PL accessed just like the norm (at least in my area of CT). Well, it seems as though this is more of a 'error' in programming - with no actual purpose.

HLA · Post by **HLA** » Tue Feb 20, 2007 1:02 pm

if for some reason it is sending out two, as soon as the 2nd one goes thru it will display the new one and cut off the first.

Spatch713 · Post by **Spatch713** » Tue Feb 20, 2007 1:44 pm

I will try and run that WinMDC program another batlaber made. That should be able to catch both of them.

Lake Effect · Post by **Lake Effect** » Tue Feb 20, 2007 1:45 pm

Possibly nothing more than a bad microphone. I've had several on spectras with a "dead spot" in the ptt switch. As the button is pushed you get ptt then loose contact and then ptt again. On receiving end you hear two mdc bursts. Replaced the switch, no more double mdc.

L.E.

601 · Post by **601** » Tue Feb 20, 2007 3:07 pm

I once progammed my GM300 to ID pre and post, it's an option in the RSS... It lasted a day, when it started getting real annoying....

Not too sure why it would be needed...

Post by Pj » Tue Feb 20, 2007 3:15 pm

There are AVL options for the CDM. I have never seen or knowingly heard one...could be the PTT ID and a location data packet.

ard099 · Post by **ard099** » Tue Feb 20, 2007 4:04 pm

Do you know if they are using Pac-RT's or Pyramid repeaters? I have seen agencies that use Pyramid repeaters and there are signalling systems on the portable along with the mobile. This can create the situation you are hearing.

nmfire10 · Post by **nmfire10** » Fri Feb 23, 2007 7:11 am

Hello boys.... I'M BAAAACK!

I have no clue. I don't know why they would even be using MDC1200 concidering all the consoles at Valley SHore and KX are Zetron and Orbacom... and as far as I know, there is no MDC1200 on those consoles. When one of the dispatchers I know signs onto AIM, I'll ask him.

Is it possible you are hearing the preamble (bit sync packets) and inurpreting it as two seperate ID's? It is either that or he's slipping when he PTT's.

dxon2m · Post by **dxon2m** » Fri Feb 23, 2007 7:59 am

One of the agency in my area uses such MDC setup. Here's an audio sample of how it sounds like without DOS muting

http://rapidshare.com/files/17896423/md ... k.wav.html

Spatch713 · Post by **Spatch713** » Fri Feb 23, 2007 8:18 pm

The more I listen to it seems to be one medic in particular and it seems like he just taps the PTT twice! Very odd.

nhmfire: There is definetly no preamble (our friends in Durham love it!)

The console at KX is made by CCC (pretty much a heaping pile of donkey manure)

muggsy09 · Post by **muggsy09** » Sat Feb 24, 2007 4:26 pm

If there is 2 distinct data bursts, then the person has the radio programmed for MDC Repeater Access, and MDC PTT ID this would cause a duel burst. The first is an ID to open the repeater and the 2nd is the identify the radio (ANI). Very annoying.

nmfire10 · Post by **nmfire10** » Sat Feb 24, 2007 7:57 pm

^^^ Good point. I've never tried the repeater access code on mine so that is probably more likely than hitting the PTT twice.

Valley shore definately does not decode MDC but it sounds like it is in the works. K-Town and D-Town are using it on their radios now. We'll probably be using FleetSync in my town since we use Kenwood.

Post by **PD3090** » Fri Jun 30, 2017 1:05 pm

Does anyone have an audio clip of a twin MDC1200 burst for Repeater access and PTT ID that they could upload? The current audio clip in this thread does not seam to be active.

Twin / Dual MDC1200 PTT ID burst

Twin / Dual MDC1200 PTT ID burst

Re: Twin / Dual MDC1200 PTT ID burst