Hello brains,
Qt the boto; of this page: http://op25.osmocom.org/wiki/wiki/RepeaterPage
I would like to understand the limitation of the USRP transmission:
- Why is the channel spacing arbitrarily 25 kHz (just a SW limitation ?) - Are you transmitting the P25 air interface for voice ?
Thank you,
Has anyone done an intro tutorial for setting up a p25 receiver using the RTL SDR radios and following the trunking channels and decoding p25? I bought two sdr units for my 10 year old ham son. I am trying to see if I can find a tutorial for him to understand how to set it up.
Thanks Brian
Sent from my iPad via Iridium Satellite Data
On Dec 12, 2012, at 9:59 PM, "rosin.f@att.net" rosin.f@att.net wrote:
Hello brains,
Qt the boto; of this page: http://op25.osmocom.org/wiki/wiki/RepeaterPage
I would like to understand the limitation of the USRP transmission:
- Why is the channel spacing arbitrarily 25 kHz (just a SW limitation ?)
- Are you transmitting the P25 air interface for voice ?
Thank you,
--- In op25-dev@yahoogroups.com, Brian Martin <n5kie@...> wrote:
Has anyone done an intro tutorial for setting up a p25 receiver using the RTL SDR radios and following the trunking channels and decoding p25? I bought two sdr units for my 10 year old ham son. I am trying to see if I can find a tutorial for him to understand how to set it up.
Bidding your son welcome to the ham radio hobby! Just to note that (AFAIK) we don't currently have any software to decode in real time the P25 control channel for the purpose of tracking voice channel activity...
73 de KA1RBI
Max
This is true, however as I read the inquiry, he wants to following trunking channels of an unspecified type and decode P25 audio. Using OP25, P25 audio can be decoded, and using gr-smartnet, Motorola SmartNet 3600 baud control channel data can be logged and recorded....so if someone were to spend some time working on merging the functionality of the two, a Motorola 3600 baud control channel could be tracked and the audio decoded.
I for one would love to work on something like this, but my coding skills leave _much_ to be desired. Regardless, I would still help out any way I can.
Jeremy
On Fri, Dec 14, 2012 at 6:43 AM, ikj1234i ikj1234i@yahoo.com wrote:
**
--- In op25-dev@yahoogroups.com, Brian Martin <n5kie@...> wrote:
Has anyone done an intro tutorial for setting up a p25 receiver using
the RTL SDR radios and following the trunking channels and decoding p25? I bought two sdr units for my 10 year old ham son. I am trying to see if I can find a tutorial for him to understand how to set it up.
Bidding your son welcome to the ham radio hobby! Just to note that (AFAIK) we don't currently have any software to decode in real time the P25 control channel for the purpose of tracking voice channel activity...
73 de KA1RBI
Max
--- In op25-dev@yahoogroups.com, "rosin.f@..." <rosin.f@...> wrote:
- Why is the channel spacing arbitrarily 25 kHz (just a SW limitation ?)
No reason for this, it's just behavior inherited from the previous iteration of the p25 transmitter. Would be simple to add code to transmit on specific, discrete frequencies (the selected frequencies would have to fall within the USRP limits, of course).
Please note that the transmitter also supports the use of external hardware to do the actual transmission (that is, standard NBFM transmitter hardware), although this is a difficult problem and we don't have a lot of experience with it. Nonetheless in that case the frequencies would be determined by the external hardware, not the software.
- Are you transmitting the P25 air interface for voice ?
Nominally yes, the transmissions should be compliant with the P25 Common Air Interface (CAI). Early testers found a few nitpicks though, most notably the bit settings for the MI fields weren't being set properly to indicate the proper alg ID. In addition we don't currently prepend HDU's to each transmission.
All of the above are minor omissions and would not take a lot of effort to add.
In addition although we might say that nominally it's transmitting the CAI it has never been certified or even tested for any regulatory compliance, etc...
Best
Max
--- In op25-dev@yahoogroups.com, "ikj1234i" <ikj1234i@...> wrote:
--- In op25-dev@yahoogroups.com, "rosin.f@" <rosin.f@> wrote:
- Why is the channel spacing arbitrarily 25 kHz (just a SW limitation ?)
No reason for this, it's just behavior inherited from the previous iteration of the p25 transmitter.
Which behavior was inherited from its ancestor - the analog NBFM transmitter code that was in GR - written (IIRC) by Jonathan Corgan...
:-)
Max
Hi Max,
Could you send out to me an e-mail at my e-mail @. We are looking for talent for an ambitious project.
Regards, Fred
--- In op25-dev@yahoogroups.com, "ikj1234i" <ikj1234i@...> wrote:
--- In op25-dev@yahoogroups.com, "rosin.f@" <rosin.f@> wrote:
- Why is the channel spacing arbitrarily 25 kHz (just a SW limitation ?)
No reason for this, it's just behavior inherited from the previous iteration of the p25 transmitter. Would be simple to add code to transmit on specific, discrete frequencies (the selected frequencies would have to fall within the USRP limits, of course).
Please note that the transmitter also supports the use of external hardware to do the actual transmission (that is, standard NBFM transmitter hardware), although this is a difficult problem and we don't have a lot of experience with it. Nonetheless in that case the frequencies would be determined by the external hardware, not the software.
- Are you transmitting the P25 air interface for voice ?
Nominally yes, the transmissions should be compliant with the P25 Common Air Interface (CAI). Early testers found a few nitpicks though, most notably the bit settings for the MI fields weren't being set properly to indicate the proper alg ID. In addition we don't currently prepend HDU's to each transmission.
All of the above are minor omissions and would not take a lot of effort to add.
In addition although we might say that nominally it's transmitting the CAI it has never been certified or even tested for any regulatory compliance, etc...
Best
Max
tried - the email bounced
My address is ikj1234i at yahoo dot com - you can send email to that addr
Best
Max
p.s. apols to the list for the OT
________________________________ From: fredofaiduvelo rostard@yopmail.com To: op25-dev@yahoogroups.com Sent: Friday, December 14, 2012 9:52 PM Subject: [op25-dev] Re: P25 Transmission
Hi Max,
Could you send out to me an e-mail at my e-mail @. We are looking for talent for an ambitious project.
Regards, Fred
--- In op25-dev@yahoogroups.com, "ikj1234i" <ikj1234i@...> wrote:
--- In op25-dev@yahoogroups.com, "rosin.f@" <rosin.f@> wrote:
- Why is the channel spacing arbitrarily 25 kHz (just a SW limitation ?)
No reason for this, it's just behavior inherited from the previous iteration of the p25 transmitter. Would be simple to add code to transmit on specific, discrete frequencies (the selected frequencies would have to fall within the USRP limits, of course).
Please note that the transmitter also supports the use of external hardware to do the actual transmission (that is, standard NBFM transmitter hardware), although this is a difficult problem and we don't have a lot of experience with it. Nonetheless in that case the frequencies would be determined by the external hardware, not the software.
- Are you transmitting the P25 air interface for voice ?
Nominally yes, the transmissions should be compliant with the P25 Common Air Interface (CAI). Early testers found a few nitpicks though, most notably the bit settings for the MI fields weren't being set properly to indicate the proper alg ID. In addition we don't currently prepend HDU's to each transmission.
All of the above are minor omissions and would not take a lot of effort to add.
In addition although we might say that nominally it's transmitting the CAI it has never been certified or even tested for any regulatory compliance, etc...
Best
Max
-
Brian Martin -
fredofaiduvelo -
ikj1234i -
ikjtel
-
Jeremy Neal -
rosin.f＠att.net