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

Tim Sawyer tisawyer at gmail.com
Thu May 11 23:12:59 EDT 2017


The one it comes with.

On Mon, May 8, 2017 at 11:24 PM, Joe Leikhim <rhyolite at leikhim.com> wrote:

> I wonder what kind of enclosure he had it in?
>
> On 5/8/2017 11:10 PM, Tim Sawyer wrote:
>
> 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 <%28727%29%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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> --
> Joe Leikhim
>
>
> Leikhim and Associates
>
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>
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-- 
--
Tim
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