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

Pierre Martel petem001 at gmail.com
Fri May 12 17:39:14 EDT 2017


A big thanks Tim. I feel less uneducated ;-) Will have to get a look at
this..

2017-05-12 12:03 GMT-04:00 Tim Sawyer <tisawyer at gmail.com>:

> Political Correctness Gone Mad. 😄
>
> Actually it's Programmable Clock Generator Module.
>
> K
>
> On Thu, May 11, 2017 at 8:38 PM Pierre Martel <petem001 at gmail.com> wrote:
>
>> I know there is always the one that ask the obvious question but, what is
>> a pcgm?
>>
>>
>> Le lun. 8 mai 2017 à 23:10, Tim Sawyer <tisawyer at gmail.com> a écrit :
>>
>>> The PCGM were noisy. I know of a case where a ham using one was shut
>>> down by the site owner. Seems the PCGM was emitting a interfering signal on
>>> high band, around 158 Mhz.
>>>
>>> On Mon, May 8, 2017 at 1:33 PM, Bryan Fields <bryan at bryanfields.net>
>>> wrote:
>>>
>>>> I've been following this with some interest.  One of the fundamental
>>>> issues with the PCGM was the master clock going to the radio was unable to
>>>> be modulated.  This made low frequency signals (PL) distort, and digital PL
>>>> was even worse.
>>>>
>>>> Typically most radios use two point modulation, with modulation on the
>>>> reference oscillator.  When you add an external reference you loose this.
>>>>
>>>> Some base stations are designed to do two point modulation even on an
>>>> external clock, the Quantar for example.  This station will even phase lock
>>>> it's PL and DPL generation if provided a 1 PPS in addition to a clock.
>>>>
>>>> If we could inject modulation into the clock generator simulcast
>>>> performance would vastly improve.  I'd be interested to see your design to
>>>> see if this would be a possibility.
>>>>
>>>> Thoughts?
>>>>
>>>> --
>>>> Bryan Fields
>>>> M: +1-727-409-1194 <(727)%20409-1194>
>>>>
>>>> On May 8, 2017, at 14:15, Reid Brandon <rfpowerguy at yahoo.com> wrote:
>>>>
>>>> Hi Joe,
>>>> I got a page with a pic of a man that rotated  around saying DOWNLOAD
>>>> NOT FOUND.
>>>> Try again!?
>>>> Tks  Reid
>>>>
>>>>
>>>> On Sunday, May 7, 2017 12:25 PM, Pierre Martel <petem001 at gmail.com>
>>>> wrote:
>>>>
>>>>
>>>> I am very interrested in all this project. My email is VE2PF @ VE2MRC
>>>> dot com!
>>>>
>>>> what radio did you used for the project?
>>>>
>>>> Thanks for sharing!
>>>>
>>>> Pierre
>>>> VE2PF
>>>>
>>>>
>>>> 2017-05-07 12:32 GMT-04:00 Kevin Custer <kuggie at kuggie.com>:
>>>>
>>>> Joe,
>>>>
>>>> Why not consider do it as an article for Repeater Builder?
>>>>
>>>> Thanks,
>>>> Kevin
>>>>
>>>>
>>>> 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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>>>
>>>
>>>
>>> --
>>> --
>>> Tim
>>> _______________________________________________
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> --
> --
> Tim
>
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