Batboard

What type of MDC signalling is FDNY using on Fireground ? and if it is MDC1200, why does it sound slighty different then other MDC1200 users ?

[quote]
On 2001-12-27 21:35, Hendu724 wrote:
What type of MDC signalling is FDNY using on Fireground ? and if it is MDC1200, why does it sound slighty different then other MDC1200 users ?
[/"Trying is the first step toward failure"]

That analog sabers for some reason sound a little different then the rest of the MDC1200 cabable radios. My PD uses analog sabers and XTS3000's, and you can tell the difference. I asked this question here before, but no one had an answer. I'll try to grab some wav files in the next couple of days

Correct me if I'm wrong, but I also tried the MDC1200 with both my saber and gp350, against my mt2000, and the gp and saber sounded different. Its like a "higher pitched" (if you will) MDC than my MT. (confused lol) Oh, and speaking of MDC1200, how many departments actually use the MDC1200 DOS ??


<font size=-1>[ This Message was edited by: MT2000 man on 2001-12-27 22:31 ]</font>

Well, with MDC DOS turned on, all that does it must most of the data and turns it into a beep, or click if you will. Turned off, you will hear the entire data burst.

The analog saber sounded lower in pitch then the other radios.

I just recorded tonight the MDC from:
-Analog secure saber I
-Analog secure spectra
-Digital Astro saber with the MDC preamble on

I will setup a quick webpage somewhere and post the wav files there sometime today

<font size=-1>[ This Message was edited by: Pj on 2001-12-28 01:56 ]</font>

We do not use DOS with our HT1250's, simply because I beleive it sounds like crap, and sometimes it will mute for longer than it should, several seconds in some cases... MDC has worked out very well for us though, can tell who's calling when they clip if nothing else...

Here is the website that I put together.

You should be able to click on the links and hear or download the files. I made these tonight at work.

<http://www.geocities.com/packy41/MDC_Sounds.html>
or http://www.geocities.com/packy41/MDC_Sounds.html

Let me know if it does not show up, but it should.

PJ

I couldn't resist trying to decode the files you posted. I dug out my old Captain Midnight Secret Message Decoder Ring (with radioman option) and put it to work. Your MODAT decodes as 698A845 for the seven tones which I think translates into ID#: 6985, but you might let me know for sure, since the printing is a little worn off around the edges of my decoder ring.

Your MDC packets decode as follows:

ASP.WAV = 018000C4 (PTT Pre from unit 00C4)
SaberMDC.WAV = 01000016 (PTT Post from unit 0016)
SpectraMDC.WAV = 01800104 (PTT Pre from unit 0104)

I was really curious how the MDC would hold up being recorded into .wav files and reconstructed hundreds of miles away in a cheap PC sound card. Pretty amazing.

As far as the Saber showing a PTT Post opcode, I am not sure if Saber follows all the rules - Saber wasn't real good at MDC until the 6D & 8D core came out.

Yup, you got all the ID's right.

The one from the saber was a 5D core. However, the pitch or tone of the MDC data on the saber seemed consistant, as I have used 6D's as well, in addition to model II and III's.

Where do you get this magical software program? I could use it to find some sneaky radios in our system

I'd be interested in how that software works too. Anyhow, I tried to decode both MDC's via my computer sound card with two portables and got 0016 for both? I can't tell pre vs. post either.

XMO-

What software are you using to do this? freeware? payware?

-Alex

Pj -

One possible reason for the difference in the sound of the MDC between your radios could be the modulation characteristics of the different units. I have an XTS3000 that the MDC sounded funny on when I got it. It would decode OK on other devices, it just sounded different. I looked at it on a deviation oscope and saw that there was an amplitude difference between the two MDC tones (1200 Hz & 1800 Hz). There is an adjustment for the modulation of high freqs vs. low in the radio alignment of XTS3000's (which was my problem). This kind of modulation difference could account for some of what you have observed.

I went back and looked at your files with an audio oscope and it appears that there is a difference of this type between your units. The analog Spectra appears to have a flatter low to high frequency response than the analog Saber. A skew toward higher deviation at high frequencies will make the packet sound 'harder' or 'sharper' whereas a skew the other way would make a packet sound 'muffled' (which was the problem my radio had).

As far as decoding these things - just hook your PC sound card up to your Centracom Gold Elite console and there you are (JUST KIDDING!)

Decoding the MODAT could probably be done on a PC or with a service monitor - Motorola 2001D or 2600 service monitors have a general sequence decoder that will do the job. I used an HP8920 and created an instrument setup file which has the MODAT frequency table entered. The cool thing about the 8920 is that when it decodes it will match the decoded tone frequency to the table entry number so it shows you the digits without you having to match the freqs manually.

MDC decode is a different animal. I have yet to encounter anyone who has successfully created a PC sound card based MDC decoder. There are a number of hardware devices that decode MDC. The aftermarket ones like CSI & Cimarron just display ID's. One of the best you can get is the old Motorola B1667A MDC console which decodes almost anything. T5620 consoles also do MDC well and can sometimes be found on ebay - I saw one that went for around a hundred bucks.

I use a program called MDC LABTOOL that runs on a PC and looks like RSS. It connects to a T5200 by RS232. The T5200 connects to audio control lines or to a base station or to your test equipment and functions as an MDC modem. This package will decode virtually any MDC including call alerts, emergency, status, message, etc. It will display the name of the decode as well as the raw data (MDC payload - opcodes + ID's) It also encodes the same way, acknowledges emergencies , etc.

Another cool MDC software is Todd Miller's 'Scrutenizer' which you can see at:

http://www.enteract.com/~toddm/STROKE/scrut_view.htm

He uses CCII MDC modem cards with custom firmware - don't bother asking - he won't share. The T5200 I use doesn't need any special firmware so if you can find one of these ....

Gotcha.

In my experience, its only the analog sabers that are different. Playing back the wav's, it really doesn't do it justice. All other MDC1200 units sound the same to me. Even on the radio console with DOS enabled, it sounds a different "beep" then the others, which I think is kinda weird.

What is the purpose of the preamble and which radios are capable of this?

Vince

Interesting. I listened just now to those sound files, and I think that my MT2000(s) sound like the saber. My HT1000, Spectra, and Maxtrac all sound like the spectra sound byte. I found it quite interesting that they sounded completly different, yet both worked.

So is there a way to make them sound the same?

-Alex

My Systems saber III sounded like the Spectra, so did my MT2000 and GP350.

Weird??

what radios are capable of doing the preamble and what is the purpose of it?? I believe a 9150 is but not sure

Preamble? I really don't know. I do know for some repeaters around here that take a bit of work to get into (ie they don't open right away) it gives an extra split second to open the repeater up so your voice isnt front clipped. What the Motorola reason is, I don't know.

I have no idea what exactly the MDC Preamble does, but I know that it sounds different, if added on a spectra, i think it's got a nice sounding ring to it, and only appears to work on "pre" mdc1200 transmissions (no idea about MDC600). If you needed an extra few miliseconds for the repeater to key up and open, that's why there is a "pre-time" setting.

I'd be very curious as to what the specific idea is behind this.

-Alex

MDC preamble sounds much like the MDC RAT FF01.

It there a way to set it on any radio that does mdc 1200, or only select radios capable of it

The MDC preamble is nothing more than a lengthening tool. It's digital 1 and 0 alternating for the set preamble time followed by the requested data. (PTT ID, Status, Msging, Emergency, etc...)

The length is adjusted to accomidate systems that require a longer transmit time to get audio to a required location (MDC modem, Display ID, Actual audio)
IE:
Voted audio system:
A preamble time of 800ms-1000ms is not uncommon. This allows the voting system to vote the best site and pass the audio to the desired location. (MDC Modem)

Repeater with DPL requirement:
A system with DPL where it takes that little extra time to decode the proper DPL, will require a longer preamble so the relevant data doesn't get clipped and refused by the modem.

Hope this helps...
PH

How about the system access tone that was available on the Syntor X9000 MDC1200 boards, which sounded like a high pitched single tone?

Pj

That system access tone on the Syntor X9000 was the same sort of thing as the preamble on the newer radios, it was just one of the MDC modem tones, whereas the new wadios send an alternating pattern. Now - just don't ask me why!

The actual MDC packet is 173 ms. long and consists of 112 bits of codeword preceded by 40 bits of word sync preceded by a 56 bit preamble. Eh? We already have a preamble?Why add a preamble to a preamble? Here is a guess - there are actually two issues here - the other is called pre-time. This is the time that a radio waits after keyup before sending the MDC packet. This gives all the equipment upstream time to unsquelch, key up, etc.

Now here is my guess - if you are sending modem tones during this pretime - the preamble to the preamble - then the Data Operated Squelch circuits can be looking for that and start their muting process concurrent with the regular squelch circuit opening - possibly eliminating (or at least minimizing) the chirp you hear on other radios OR at the console.

Of course, that same preamble to the preamble will give MDC decoders an even better opportunity to sync to the packet.

ok, I have a gp350 and planning on getting a PRO 9150 can any of these radios have a preamble? If so how do I set it. Any help is appreciater

As Elroy would say about MODAT, preamble gets annoying after a bit. Really, it does. I have a use for it, as one of our remote repeaters tends to front clip, and no one wants to spend money to fix it. Once you hear it all the time during an 8 hour shift, 40-60 hours a week, it gets REALLY annoying. As far as I know, just the higher tier radios have it.

Anyone no what the setting is on the radios to get the tone that gets sent over the radio after they rx a message on the fdny radios HT

You mean AFTER they receive the message or BEFORE the send the message. The keyup tone is the digital soft id, but followed by analog voice. It was only available to FDNY when it first released, but I think you can order the option now for XTS5000

The tone thats heard on the radio after someone is done talking you get a short tone on the recieve radio not the tx radio

I came across this Freeware MDC decoder the other day, but haven't had a chance to use it. Does anybody have any experiance with this freeware program?


http://www.antistatic.org/winmdcd/

Thanks

Mikey

Yep, works great.

I've heard FDNY uses ATIS signaling, and I have it in my HT1000, and it is different but sounds similar to MDC.

Here's this article

Read what "SFD_Radio" has to say.

Anyone got a sound file of ATIS signalling?

CGRESQ192 wrote:what radios are capable of doing the preamble and what is the purpose of it?? I believe a 9150 is but not sure

Preamble is a series of tones that instruct the receiving radio to 'stand by' for the actual data transmission. It gives the radio time to stabilize it's squelch before trying decode the data.

Using preamble instead of a plain old carrier only pre-time does two things in my experience:

1- Improves voting because there is actualy audio
2- Makes DOS muting work 100x better.

On the same token, if you do not haev DOS muting, it will drive you nuts.

While we're on this I noticed FDNY used the post MDC on the simplex fireground frequency only and at the time they were using Saber 1's.
So the other radios couldn't decode the burst, was the MDC just for S&G
or did Field Com or some other unit actually decode the MDC ?

I will second that, it is rock solid. Have had great success also with the WinCTCSS offered from the same site.

mancow wrote:Yep, works great.

Mikey wrote:I came across this Freeware MDC decoder the other day, but haven't had a chance to use it. Does anybody have any experiance with this freeware program?


http://www.antistatic.org/winmdcd/

Thanks

Mikey