Batboard

Posted: **Mon Jun 19, 2006 8:51 pm**

I'm using WinMDCD (from antistatic.org) to decode MDC1200 PTT IDs. I love it, but I've found a strange quirk: the pre-ID decodes as a post-ID. This happens only when it's my radio transmitting, though; everyone else's decodes right. It's not the end of the world (I really have no need to be running MDC, I just like tinkering).

My Saber is set up for pre-ID. In RSS (07.01.00), I have

Code: Select all

H959 - Unit ID - MDC 1200 (Unit ID=1234) Before Call.

selected. When I key up, the burst occurs first.

However, it doesn't decode this way in WinMDCD. It shows my ID fine (100% of the time), but always has an OP/ARG of 01/00, which is a post ID. Local public safety is always either 01/80 or 00/80 (I forget which is right?), pre ID.

Since the program is calling everyone else's pre-ID a pre-ID, I'm pretty sure that it's my radio that's at fault. I've tried disabling MDC, writing that codeplug, reading it back in, adding MDC, and writing that back, but it's still coming across this way. Am I doing something stupid? Is this a know bug? (A quick search revealed nothing.)

Because everyone else in the world that uses MDC is correctly showing up as a pre-ID, I'm pretty sure the problem does not lie with the WinMDCD software or the receiving setup. I'm almost positive it's the Saber (H43QXN7139CN). I just can't figure out what's wrong.

Sidenote: Are 3-digit PTT IDs valid? I assumed 4 characters were required (and, indeed, I'm using a 4-character ID), but listening to local fire, one of the commander's HTs was consistenly showing up as 204.

Posted: **Mon Jun 19, 2006 10:42 pm**

I doubt your radio is at fault, if your model is the secure one, then post ID is all you will be able to use.

As for the digits, it's got to be 4...IE..0011, or 0123, or 0001 or 1000.

It can also be AEC1 or 652A or any combination of ABCDEF, 0-9

I suspect your decoding program is incorrectly identifying the preamble as well as the ID string.

Posted: **Tue Jun 20, 2006 5:03 am**

WinMDCD doesn't display the zero in the program itself, but in the log it would show "0204".

Posted: **Tue Jun 20, 2006 7:19 am**

AEC wrote:if your model is the secure one, then post ID is all you will be able to use.

I'm not using secure mode (I've got the switch disabled and every channel 'strapped' as clear), but I haven't even found a way to select post ID, just pre.

Is the Pretime Delay option (H770, etc.) how one configures the preamble length?

Posted: **Tue Jun 20, 2006 9:54 am**

You can make the actual burst longer (it will kinda sound like a phone ring), it's called "Bit-Sync" packets. Just enable Bit Sync to something like 5 or 10.

There should be a time to configure the pre-amble length, i.e. the time before the MDC burst that is silent. I think default is something like 250ms (miliseconds), and it is adjustable.

You can try either of the 2 above methods or both, if that helps.

Posted: **Tue Jun 20, 2006 8:24 pm**

fogster wrote:
AEC wrote:if your model is the secure one, then post ID is all you will be able to use.
I'm not using secure mode (I've got the switch disabled and every channel 'strapped' as clear), but I haven't even found a way to select post ID, just pre.

Is the Pretime Delay option (H770, etc.) how one configures the preamble length?

It's not about 'using' secure, it's a function of the RSS for secure capable radios, you get no choices with secure radios, it's pre or nothing.

This is designed to allow passage of the encrypted voice traffic so that no data bits are lost along with the MDC data.

Even setting the preamble time to minimum or maximum does not change or alter the encrypted audio, the radio is designed to oeprate with those in mind, and adjusts for those as well.

The preamble allows the receivers to open, then decode the MDC data as many have a lag time that may clip the incoming data prior to it being decoded, the preamble 'pre-time' is supposed to prevent this from occurring.

Batboard

Saber's MDC1200 Pre-ID is a Post ID

Saber's MDC1200 Pre-ID is a Post ID