Joe, 

Did you lock it to a GPSDO?  Jim mentioned this mod to me about a year ago and I never had a chance to give it a try.  My previous overlap area was tolerable but I've added a third transmitter so it may be time to try this finally.

On Sun, May 7, 2017 at 10:00 AM, <app_rpt-users-request@lists.allstarlink.org> wrote:
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Today's Topics:

   1. RTCM Simulcast and 9.6 MHz Phase locking (Joe Moskalski)
   2. Re: RTCM Simulcast and 9.6 MHz Phase locking (Joe Leikhim)


----------------------------------------------------------------------

Message: 1
Date: Sun, 7 May 2017 03:13:26 -0400
From: Joe Moskalski <kc2irv@gmail.com>
To: app_rpt mailing list <App_rpt-users@ohnosec.org>
Subject: [App_rpt-users] RTCM Simulcast and 9.6 MHz Phase locking
Message-ID:
        <CAES28qyXLtJMUoGqAYk5bKU_eE2Nciq_9QQC48rBDSeZigtgHA@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

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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Message: 2
Date: Sun, 7 May 2017 03:42:25 -0400
From: Joe Leikhim <rhyolite@leikhim.com>
To: Users of Asterisk app_rpt <app_rpt-users@lists.allstarlink.org>
Subject: Re: [App_rpt-users] RTCM Simulcast and 9.6 MHz Phase locking
Message-ID: <35ee60f8-a760-363b-0d28-1b6c9967cebd@leikhim.com>
Content-Type: text/plain; charset="utf-8"; Format="flowed"

Thanks Joe;

I would certainly be interested in your documentation. Does this solve
the problem of transmit PL tone jumping phase on key up, as Hayden
encountered?

Joe L

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.
>
> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=icon>
>       Virus-free. www.avast.com
> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=link>
>
>
>
>
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--
Joe Leikhim


Leikhim and Associates

Communications Consultants

Oviedo, Florida

JLeikhim@Leikhim.com

407-982-0446

WWW.LEIKHIM.COM

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