[App_rpt-users] RTCM Simulcast and 9.6 MHz Phase locking
Joe Leikhim
rhyolite at leikhim.com
Tue May 9 06:24:46 UTC 2017
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
> <mailto: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 <tel:%28727%29%20409-1194>
>
> On May 8, 2017, at 14:15, Reid Brandon <rfpowerguy at yahoo.com
> <mailto: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 <mailto: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
>> <mailto: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
WWW.LEIKHIM.COM
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