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

Tim Sawyer tisawyer at gmail.com
Fri May 12 15:53:17 EDT 2017


The PCGM used to be manufactured by micro-node.com which came with an
enclosure similar to the RTCM http://micro-node.com/_img/rtcm1-750.jpg but
smaller.

Mark at micro-node.com said he was thinking of building another batch (25
or so) of PCGMs as he is seeing some demand.

On Fri, May 12, 2017 at 12:08 PM, Joe Leikhim <rhyolite at leikhim.com> wrote:

> I have searched for documentation on the PCGM. can you point me to the
> enclosure?
>
> On 5/11/2017 11:12 PM, Tim Sawyer wrote:
>
> 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
>>
>> Communications Consultants
>>
>> Oviedo, Florida
>> JLeikhim at Leikhim.com
>> 407-982-0446 <%28407%29%20982-0446>
>> WWW.LEIKHIM.COM
>>
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> --
> --
> Tim
>
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> --
> Joe Leikhim
>
>
> Leikhim and Associates
>
> Communications Consultants
>
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> JLeikhim at Leikhim.com
> 407-982-0446 <(407)%20982-0446>
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>
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-- 
--
Tim
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