[App_rpt-users] RTCM Simulcast and 9.6 MHz Phase locking

Kevin Custer kuggie at kuggie.com
Sun May 7 12:32:17 EDT 2017


Why not consider do it as an article for Repeater Builder?


On 5/7/2017 3:13 AM, Joe Moskalski wrote:
> I wanted to throw this email out to the group for all those who want 
> to simulcast with the RTCM. For those who don't know, in order to make 
> the RTCM suitable for simulcast you must have a more accurate 9.6 MHz 
> clock for the RTCM in order to ensure the audio sounds acceptable in 
> the overlap areas. I did this a few months ago using 9.6 MHz OCXO's. 
> This worked reasonably well. Not as well as I would have liked but the 
> system was very usable, but of course I wanted it to be better. Since 
> the PCGM (Programmable Clock Generation Module) is no longer 
> available, I decided to roll my own as some say.
> I created a PLL circuit that can accept a 10 MHz, 1 MHz or 100 KHz 
> reference input and produce a phase locked 9.6 MHz out for the RTCM. I 
> have been testing this over the past few days and it has made an great 
> improvement in the audio quality in the overlap. The quality of the 
> audio in the overlap areas sounds very, very good, it's very similar 
> to what I expect to hear in commercial simulcast systems. My circuit 
> is heavily based off of an old Motorola MSF5000 HSO PLL circuit that I 
> was able to adapt and modify to my needs.  There are other uses for 
> this circuit that make it attractive for simulcasting but I wont get 
> into them here. I am will to share my schematic and bill of materials 
> (digikey) with anyone. Please send me an email and I will be willing 
> to share all of my information on the project.

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