DSE?

[kb9mwr]

The ever popular DSD can record to file. I wish there was a way to play it back into a transmitting radio. Think Digital Speech Encoder!

If it was possible to take this a pipe it back out a sound card (without passing it to mbelib) to a transmitter in theory you could build a P25 repeater using a computer and a couple sound cards with the appropriate discriminator and varactor connections.

The ham radio community would be eternally grateful. I'd be willing to start a crusade to round up a bounty by approaching TAPR and other groups for anyone willing to tackle this project.

There has been a significant displeasure in the ham radio arena when it comes to all the new, but totally non-interoperable digital radios out there. The latest disappointment is Yeasu's System Fusion. Many were hoping it would be either APCO-25 or DMR compatible.

Used P25 radios are fairly cheap and plentiful. The problem is tracking down a Quantar repeater at a decent price.

I suspect that DSD is based on the code from OP25 P25 decoder/analyzer project, that has been around 2009.

Advancing Ham Radio.. different ideas: APCO 25 decoder /analyzer

 

[rjschilder]

op25

Hi,

I'm not sure if dsd is based on op25 but you can definately setup a repeater with op25. It's a treat to get setup, especially since the documentation is a bit dated and GNURadio has been updated. After a few days of getting back into linux I was able to get the latest version of op25 running. I too was mainly interested in building a software p25 repeater. I was able to "transmit" a p25 signal and decode the audio with DSD. Basically I was able to plug a USB headset into the computer and encode the audio into p25, then output it via the soundcard. I then plugged the output from the soundcard into a laptop running dsd, which successfully decoded the audio. I was also able to get this to work in a virtual machine (I believe I did it in vmware and virtualbox). I lost interest in the idea once I realized I needed a USRP or a radio that could transmit (or be modded to transmit) 9600 baud packet radio. It definitely is doable provided you have the right hardware to transmit on RF and time to get op25 working.

-Ryan KC9GMY

 

[kb9mwr]

Thanks for your message. Yes the USRP is kind of the expensive hangup.

Osmocom OP25 operates with app_rpt and asterisk which can provide the PTT and COR signaling needed for interfacing a 9600 baud capable radio. Speaking of the hardware radio interfacing, the URIx by DMK Engineering or dead-bug soldering parts onto an USB audio adapter with a CM108/119 (or compatible) chip are options.

For the I app_rpt and asterisk part, I suggest the AllStar Link ACID distribution, as it has the asterisk source and a working zaptel module. This will save some headaches.