Just for kicks, I will try to explain the thought process that led up to my question.
Although it is generally accepted that GRE provides some of the best digital audio quality of digital scanners on the market, I am not particularly satisfied with it. Others on this forum have stated that digital audio quality on the radios professionals use approaches if not surpasses the audio quality of analog. That is certainly not the case with any scanner I have owned or heard. I have verified the disparity between professional radio and scanner performance through monitoring P-25 scanner audio and comparing that to scanner audio of a P-25 patch to analog that a local agency uses.
I wanted to know the technical reasons why this disparity exists, so I asked
several questions in the General Scanning forum. None of the responses were quite as specific as what I was looking for, although I got the general idea that scanner audio will not be significantly improving anytime soon.
With many local agencies actively pursuing digital systems, I started thinking of possible solutions. Reading
this file from the Wiki gave me the idea that perhaps I could use one of DVSI's products (like the
VC-55-PR or the
Net-2000-P25, provided there is a way for me to purchase one) connected to a scanner. If the scanner would output the 7200 bps voice bits, perhaps there was a way of feeding the bits into the vocoder to attain the audio. Of course, if scanners already use DVSI's vocoder, then I couldn't expect the resulting audio to be any better than that of a scanner.
I assume that the PSR-500 and 600 at some point in the digital signal processing have to obtain the 7200 bps voice bits before constructing the analog voice, so if I could extract the bits, a connection to a DVSI vocoder might work. I know that the voice bits can be attained through a discriminator tap, but I don't have the capacity to even begin to understand the steps necessary to accomplish this.
With so many uncertainties, I began to see that what I wanted to do was way over my head. Since I can't drop $20,000 for the method described in
this Wiki page, I guess I will have to be content with what I have.