Please Edumacate me...

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Postby ka8ypy » Wed Aug 22, 2007 1:32 pm

r0f wrote:
ka8ypy wrote:
r0f wrote:
tvsjr wrote:DSTAR is for amateur use - no encryption capabilities.

I thought it was some big fancy commercial standard used in Asia?


Right now it is Amateur only, but apparently the Japanese Govt is looking into using it as their form of P25 and making more robust.

If you think about it, it's just another vocoder/dsp combination.

Upgrade the ROS to recognize encryption, add the baord, flip the switch and you are there.


I'd like to see Motorola offer APCO-25 phase II as a host/dsp upgrade in older ASTRO tier products when it's out. The specs call for two-slot TDMA and the AMBE (AMBE+2?) vocoder.

Not sure if the hardware can handle TDMA, but I'm fairly confident it could. So long as the T/R switching is fast enough for TDMA...what's the big deal?

People will be pissed if M makes everyone dump current ASTRO25 products (XTS/XTL 5000, 2500, etc) to buy some new phase II crap :baby:

AMBE+2 does sound quite good. I've used it with iDEN handsets--but it has one major flaw. Certain background noise (specifc audio frequencies at specific amplitudes) completely drown out the desired audio frequencies going into the vocoder. It's almost as if you're muted.

This is one of the main reasons why Nextel/Telus dumped AMBE+2 (The new "6:1" vocoder) out of their products. Car noise mutes your voice traffic!


D-Star is using the AMBE2020 vocoder technology and not AMBE+2.

I haven't read up on them so I'm not sure what the difference is.

On a side note...ICOMs D-Star expansion board for the hammy portables and the P25 expansion board for the commercial portables "appear" to be of the same layout and size. I wonder how hard it would be to hax0r the D-Star ROS and put a P25 board in a 91D and have P25 hammy rig???

Just thinking waaayyyy outside the box.
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Postby KB9SXK » Wed Aug 22, 2007 1:41 pm


On a side note...ICOMs D-Star expansion board for the hammy portables and the P25 expansion board for the commercial portables "appear" to be of the same layout and size. I wonder how hard it would be to hax0r the D-Star ROS and put a P25 board in a 91D and have P25 hammy rig???

Just thinking waaayyyy outside the box.



:anus: :anus: :anus: :anus: :anus: :mjban: :ve4uo: [/quote]
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Postby ka8ypy » Wed Aug 22, 2007 1:53 pm

KB9SXK wrote:

On a side note...ICOMs D-Star expansion board for the hammy portables and the P25 expansion board for the commercial portables "appear" to be of the same layout and size. I wonder how hard it would be to hax0r the D-Star ROS and put a P25 board in a 91D and have P25 hammy rig???

Just thinking waaayyyy outside the box.



:anus: :anus: :anus: :anus: :anus: :mjban: :ve4uo:
[/quote]

Better yet, take it a step further...

Haxor either the D-Star ROS or the ICOM P25 ROS to add another option, then figure out a way to frankenstein both expansion boards together and have a radio the would do conventional/P25/D-Star. :anus:
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Postby smokeybehr » Wed Aug 22, 2007 2:01 pm

ka8ypy wrote:On a side note...ICOMs D-Star expansion board for the hammy portables and the P25 expansion board for the commercial portables "appear" to be of the same layout and size. I wonder how hard it would be to hax0r the D-Star ROS and put a P25 board in a 91D and have P25 hammy rig???

Just thinking waaayyyy outside the box.


I was thinking the same thing, since the model numbers are in the same series (UT-118, UT-119, UT-120, UT-121) for the different flavors of digital operation. Think about it: P25 out of a hammy rig for less than the price of used commercial gear.

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Postby KC9UZB » Wed Aug 22, 2007 2:17 pm

:anus:

That would shut my mate up who keeps asking me if there's a ham p25 rig.

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Postby KB9SXK » Wed Aug 22, 2007 2:20 pm

IIRC,
ICON has a P25 recieve card already
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Postby ka8ypy » Wed Aug 22, 2007 3:38 pm

KB9SXK wrote:IIRC,
ICON has a P25 recieve card already


They also have a P25 Expansion board for their comercial tranceivers(TX/RX). I believe about the same price as a D-Star expansion board as well ($230ish).
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Postby KB9SXK » Wed Aug 22, 2007 4:11 pm

ka8ypy wrote:
KB9SXK wrote:IIRC,
ICON has a P25 recieve card already


They also have a P25 Expansion board for their comercial tranceivers(TX/RX). I believe about the same price as a D-Star expansion board as well ($230ish).


Has anyone.....??????????????? :baby:
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Postby Mong » Wed Aug 22, 2007 4:38 pm

Who wants to chip in money to find out? :baby:

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Postby KB3JUV » Thu Aug 23, 2007 12:56 am

I'll give a dollar.

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Postby Mong » Thu Aug 23, 2007 7:41 am

KB3JUV wrote:I'll give a dollar.




Cheap ass kids :baby:

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Postby KB9SXK » Thu Aug 23, 2007 10:47 am

I think im going to buy my local ICOM shop owner lunch on day this week and bounce an idea off him :baby:
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Postby mr.syntrx » Thu Aug 23, 2007 4:40 pm

I'd rather see P25 Phase II use OFDM rather than the current FM nonsense. You could get 30kbps without much trouble, high spectrum efficiency, and it'd be as robust as hell.

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Postby Wowbagger » Thu Aug 23, 2007 4:55 pm

mr.syntrx wrote:I'd rather see P25 Phase II use OFDM rather than the current FM nonsense. You could get 30kbps without much trouble, high spectrum efficiency, and it'd be as robust as hell.


Yes, and it would require class AB amplifiers for the finals, would piss off about 50% of the PA input as heat and reduce battery life by a corresponding amount.

That's also why they didn't go with CQPSK, which would have been just a physical layer change rather than a protocol layer change.

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Postby tvsjr » Thu Aug 23, 2007 5:01 pm

Wowbagger wrote:
mr.syntrx wrote:I'd rather see P25 Phase II use OFDM rather than the current FM nonsense. You could get 30kbps without much trouble, high spectrum efficiency, and it'd be as robust as hell.


Yes, and it would require class AB amplifiers for the finals, would piss off about 50% of the PA input as heat and reduce battery life by a corresponding amount.

That's also why they didn't go with CQPSK, which would have been just a physical layer change rather than a protocol layer change.


Don't forget the infrastructure changes... bigger power supplies, bigger gensets, etc.

Didn't go with CQPSK? All of the Moto P25 gear supports it... I know of at least one system that uses it for their outlier IRs. ???

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Postby motorola_otaku » Thu Aug 23, 2007 5:15 pm

tvsjr wrote:Didn't go with CQPSK? All of the Moto P25 gear supports it... I know of at least one system that uses it for their outlier IRs. ???

Austin/TC? I thought they used CQPSK on the two simulcast systems and C4FM on the IR sites.
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Postby tvsjr » Thu Aug 23, 2007 7:05 pm

motorola_otaku wrote:
tvsjr wrote:Didn't go with CQPSK? All of the Moto P25 gear supports it... I know of at least one system that uses it for their outlier IRs. ???

Austin/TC? I thought they used CQPSK on the two simulcast systems and C4FM on the IR sites.


Yeah, duh, brainfart. Anyway, they ARE using CQPSK...

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Postby Wowbagger » Thu Aug 23, 2007 7:14 pm

tvsjr wrote:Didn't go with CQPSK? All of the Moto P25 gear supports it... I know of at least one system that uses it for their outlier IRs. ???


By "didn't go with CQPSK" I meant "Didn't adopt CQPSK for the spectral efficiencies mandated." Yes, they use a form of QPSK for simulcast systems, but the modulation parameters are NOT the same as CQPSK - the "eye" of the signal is open quite a bit longer to allow for better operation in the overlap areas between systems, and the mobiles still use C4FM for the inbound link.

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Postby tvsjr » Thu Aug 23, 2007 8:18 pm

Wowbagger wrote:
tvsjr wrote:Didn't go with CQPSK? All of the Moto P25 gear supports it... I know of at least one system that uses it for their outlier IRs. ???


By "didn't go with CQPSK" I meant "Didn't adopt CQPSK for the spectral efficiencies mandated." Yes, they use a form of QPSK for simulcast systems, but the modulation parameters are NOT the same as CQPSK - the "eye" of the signal is open quite a bit longer to allow for better operation in the overlap areas between systems, and the mobiles still use C4FM for the inbound link.


Ah, OK. Thanks for clarifying that... I've never messed with that particular modulation.

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Postby Mong » Sat Sep 15, 2007 3:27 pm

KB9SXK wrote:I think im going to buy my local ICOM shop owner lunch on day this week and bounce an idea off him :baby:



So, have you (or anyone else) found out anything about trying the P-25 board in the :ham: HTs?

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Postby KB9SXK » Sun Sep 16, 2007 12:05 am

He just laughed at me and bought me another beer :baby:
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Postby Rijndael » Tue Oct 02, 2007 10:51 pm

Actually you can get close to 5,000 bps in APCO packet data in IVD. Even peer to peer with a pair of XTS5000 radios you’ll see close to that.

If you location enable the ‘5K the GPS data can be polled via the IVD during voice and carried in the approx 88bps overhead.

But it is more normal to poll the radio periodically with the XML coded GPS data sent at the full packet data rate. In other words the radio can respond to position requests whenever polled without user intervention.

To reduce overheads you can also set the subscriber radios to report positions autonomously at say 5 minute intervals. Looking the transmission it takes a total of 150 ms to send the position report with the 50 ms or so ACK coming in about 50ms later.

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Postby Rijndael » Tue Oct 02, 2007 11:48 pm

Reference Wowbagger’s and other comments the key issue with nonlinear modulation methods is adjacent channel power. While OFDM sounds cool it poos all over the adjacent channels even with a decent class linear amp. Remember that we’re talking land mobile here, that’s neg 60 dB in the adjacent channel (ETSI 12.5 kHz, mileage may vary with FCC rules).

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D-Star is a disappoitment

Postby kb9mwr » Thu Apr 09, 2009 12:48 am

Image

Sorry, but I need to vent:
D-Star is only a 4800 baud total data stream equivalent signal. 2400 baud is reserved for actual digital voice, 1200 baud is reserved for FEC (forward error correction) on the digital voice. (This is for callsign and short message data.) Another 1200 baud is reserved for serial data. (This is for APRS, and text messages/text query's.) The sad part is 1200 baud data is what we were doing in the 1980's.

So if 4800 baud can fit into a 6kHz bandwidth, we could have had a 12800 (12.8k) baud total data stream equivalent signal fit into our existing 16 kHz bandwidth plans. This could have left us with 9.2k left for data. Or at the very least more could have been given for the digital voice codec, so that we could use other license free-codecs that sound more natural.

Ham radio needs narrow band as much as the ARRL needs more aging members.

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Re: D-Star is a disappoitment

Postby Wowbagger » Thu Apr 09, 2009 7:05 am

kb9mwr wrote:Sorry, but I need to vent:
D-Star is only a 4800 bis per second total data stream equivalent signal. 2400 bis per second are reserved for actual digital voice, 1200 bis per second are reserved for FEC (forward error correction) on the igital voice. (This is for callsign and short message data.) Another 1200 bis per second are reserved for serial data. (This is for APRS, and text messages/text query's.) The sad part is 1200 baud data is what we were doing in the 1980's.

So if 4800 bis per second can fit into a 6kHz bandwidth, we could have had a 12800 (12.8k) bis per second total data stream equivalent signal fit into our existing 16 kHz bandwidth plans. This could have left us with 9.2k left for data. Or at the very least more could have been given for the digital voice codec, so that we could use other license free-codecs that sound more natural.

Ham radio needs narrow band as much as the ARRL needs more aging members.


Sorry, but I need to vent:

BAUD != BITS PER SECOND.

Baud rate is the rate of SYMBOL transmission - D-Star, APCO-25, NXDN, and the other systems out there transmit more than on bit per symbol, so the bit rate of the channel is NOT the same as the baud rate of the channel.

Only on a one bit per symbol modulation scheme is bit rate the same as baud rate. So while bits per second and baud may be the same for wired RS-232 or AX-25, it is NOT the same for just about any over the air modulation scheme (e.g. most OFDM systems run about 30 baud or less - they just transmit a WHACKLOAD of bits per symbol).

-------------

But I do agree with you that D-Star should have used a Free vocoder, so that we all could have had it running on our PCs connected to our radios and it would have had greater penetration. And we all want greater penetration, don't we?
These opinions are mine, not Aeroflex's - if you want service info, manual, or other official support please contact Aeroflex directly.

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Re: Please Edumacate me...

Postby kb9mwr » Thu Apr 09, 2009 10:57 am

Sorry about that, thanks for correcting me. Eitherway bps or baud, it's still pathetic and utterly useless


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