How is MDC preamble on keyup possible?

dxon2m · Post by **dxon2m** » Mon Feb 28, 2005 8:31 pm

I just heard one of the news agency here that does that. The radio transmits MDC with preamble enabled after keyup. Isn't the preamble option available only for keydown? What radio is capable of this?

AEC · Post by **AEC** » Mon Feb 28, 2005 9:03 pm

Depends on RSS version, the older ver. 5, like I have, is keyup only, but my version 7XXX has the option in the radio options menu, when MDC is selected, you are directed to enter ID and then you will see the selection listed as follows: 1-keyup, 2-Both, 3-dekey.

Enter your ID and how you want MDC to actuate.

I've tried Ver. 4 and earlier as well, and only Ver. 7XXX appears to have the option to select MDC keying options.

My SysSaber has the option/s as well, and I have one of the latest and a few of the earlier also.

I'm in debt by .05C after this post......And my check hasn't cleared yet.

HOWARD · Post by **HOWARD** » Mon Feb 28, 2005 9:13 pm

Most radios have the option of keying up before, after or both. The Jedi series, the Astro radios, the Pro Series all key up that way.

HOWARD · Post by **HOWARD** » Mon Feb 28, 2005 9:20 pm

The older radios have the key/dekey selection and most of the newer ones say pre/post.

JOHN 1807 · Post by **JOHN 1807** » Tue Mar 01, 2005 5:18 am

True, most radios have the option of MDC pre/post,

However, this refers to MDC ID only, not preamble which I'm sure is available "pre" only.

Preamble would serve no purpose post ID

apco25 · Post by **apco25** » Tue Mar 01, 2005 11:06 am

I think its a question of confusing terms

Key-up, Key-Down, Pre or Pre-key all mean the same thing

PTT-ID (with or without preamble) inserted after PTT is pressed and before voice comms begin.

preamble was designed to allow faster and more complete muting of MDC data packets.

dxon2m · Post by **dxon2m** » Tue Mar 01, 2005 12:02 pm

So since preamble is designed for a higher decoding rate, is it correct that inserting preamble on keyup serves no purpose?

Post by Pj » Tue Mar 01, 2005 6:39 pm

No, the other way around. Turning on preamble will help mute hearing any MDC packets when recieved by the other radios.

jedi_saber · Post by **jedi_saber** » Tue Mar 01, 2005 7:51 pm

Interesting too that only the pro series radios (CDMs, Waris) insert preambles in pre- as well as post PTT IDs. As AS/XTS/Jedi etc only show "preamble during pre-PTTid".

apco25 · Post by **apco25** » Wed Mar 02, 2005 12:35 am

How is that possible - preamble is inserted in the dead air pre time before the ID packet is sent.

Rayjk110 · Post by **Rayjk110** » Wed Mar 02, 2005 4:52 am

Correct me if I'm wrong, but is it the "BitSync" packets that have to be enabled to where the PreKey MDC Sounds more like a phone ring??

-Ray

nmfire10 · Post by **nmfire10** » Wed Mar 02, 2005 6:17 am

The jedi's call it pre-able. The CDM/HT's call it "Bitsync packets" It's the same thing.

The CDM/HT's will send the preamble on a Post-ID (dekey) and it is quite pointless. Other radios will only use the preamble on Pre-ID where is a very underused and useful option.

The act of pressing the transmit button can be refered to as keyup or keydown. The act of releasing the transmit button would be de-key or unkey. I think there is a lot of backwards interchangement of these terms in this thread.

JOHN 1807 · Post by **JOHN 1807** » Sat Mar 05, 2005 8:02 am

Pj wrote:No, the other way around. Turning on preamble will help mute hearing any MDC packets when recieved by the other radios.

PJ,

I thought the digitally operated squelch (dos) settings determined how much of the MDC packet you would hear on the receiving radio- basically all you would hear is a "chirp" if anything at all - as opposed to the full MDC packet. I'm still sure that "preamble" settings have no bearing on what a receiving radio mutes.

-John

apco25 · Post by **apco25** » Sat Mar 05, 2005 11:48 am

Preamble causes the radio to mute faster with or without DOS settings enabled.

You can basically set DOS to 0 with preamble enabled and get none of the MDC chrip coming through. This is especially nice because DOS if not set exactly right can clip off the first part of a transmission

JOHN 1807 · Post by **JOHN 1807** » Sat Mar 05, 2005 4:09 pm

Ahhhhhhh,

Makes sense , like they say- you learn something new everyday.

How is MDC preamble on keyup possible?

How is MDC preamble on keyup possible?

MDC on dekey....

Most radios