[App_rpt-users] Voted Simulcast Configuration Questions

[Chuck Henderson]

...
3.) Thunderbolt to RTCM:  This is both serial data and 1PPS.  (receive
data, ground, and 1PPS)
4.) Latency/Jitter:  By configuring buffers properly you can deal with more
than normal Internet latency and jitter.  The only limitation is that you
could run out of buffer memory in the RTCM if you go beyond several hundred
milliseconds.
5.) Processor Requirements: I don't know what the minimum is but I use an
Intel Atom D510MO and it is more than enough to run 2 repeaters with a
total of 7 RTCM/Voter boards, 3 on one repeater and 4 on the other repeater.
6.)  Internet/VPN/Vlan/NAT:  I have had no problems using any combination
of these.  As long as you understand the technology and take into account
MTU limitations.  If you do not already understand those requirements then
you are better off to just use standard Internet access without VPN/Vlan.
 NAT is no problem.
7.) Simulcast transmitter clock:  This is independent of the RTCM.  Using
the 10MHz GPSDO to control the transmitter frequency requires additional
hardware between the GPS and the transmitter.  Micro-node did at one time
sell a device for that but it is still not listed on their web site. Did
you already read this?
http://ohnosec.org/pipermail/app_rpt-users/2012-May/004463.html
 Some transmitters that are built for simulcast may be able to take the
10MHz signal direct from the GPSDO, but most are not able to directly
interface to it.

Chuck,  WB9UUS,  CCIE2285



On Thu, Feb 27, 2014 at 1:05 PM, Steve Wright <stevewrightnz at gmail.com>
 wrote:

> Re: Voted Simulcast Configuration Questions (Caleb Pal)
>>
>>
>> 3.) Thunderbolt to RTCM: Is there documentation on this interface? Is it
>> serial between the two or is there a 1 PPS signal as well?
>>
>
> Ask @micronode.com.  The 10MHz signal from the GPSDO either phase-locks
> the transcievers' clock, or replaces the clock completely.  There are
> circuit diagrams of the RTCM online if you google them..
>
>
>
>> 4.) Latency/Jitter: What is the top end of the latency the
>> Voting/Simulcast system can handle? We are working on getting a private
>> VLAN over Fiber between our two sites, but until the funding for that
>> becomes available, we will be working over the internet and a VPN.
>
>
> You can add a fixed delay in the config that will be greater than the
> networks' latency, so as to mask problems so they don't appear at on the
> repeaters as "problems".
>
>  My prediction is the VLAN will be sufficient, but the VPN will suffer
> connectivity problems.  I've never really seen a reliable PPP based VPN -
> they are regularly up and down for seemingly no reason at all.  Cue regular
> unexplained dropouts for some 2-200 seconds with no real chance at
> diagnosis.  Frankly, I don't like VLANs either - rather plain ol' ethernet
> or directly routed IP is best, and avoid all the trickery-doo on top of the
> real thing.
>
>  Sounds like you're having fun with that. ;)
>
> Steve
>
>


On Thu, Feb 27, 2014 at 1:17 AM, Caleb Pal <cleb at defcon-3.net> wrote:

> Hello All,
>
> We are working on setting up a Voted Simulcast system on 70cm, and wanted
> to get ya'lls input on a few things. Excuse me for being a little new to
> this!
>
> We have two existing repeaters, both Motorola Quantars, with 4 wire
> Wireline cards. They are currently both on the same frequency, with
> different PL's to access. The Quantars have pretty diverse coverage areas,
> but there is definitely some overlap. I have ordered, and hope to have
> shortly Trimble Thunderbolts as well as RTCM's for both machines. I have a
> few questions about setting this all up.
>
> 1.) Quantar to RTCM interface and Quantar Programming: Can someone provide
> pinouts or diagrams for interfacing the RTCM to the Quantar? Is audio off
> of the 4W connector, and COR/TX via the MRTI? How is the Quantar Programmed
> for operation with the RTCM?
>
> 2.) Tuning: Is it OK to have the Quantars tuned before bringing the RTCM
> into the mix, or is it best to do it all on the service monitor with the
> RTCM controlling the Quantar? What are the important points to hit when
> tuning the Quantar/RTCM?
>
> 3.) Thunderbolt to RTCM: Is there documentation on this interface? Is it
> serial between the two or is there a 1 PPS signal as well?
>
> 4.) Latency/Jitter: What is the top end of the latency the
> Voting/Simulcast system can handle? We are working on getting a private
> VLAN over Fiber between our two sites, but until the funding for that
> becomes available, we will be working over the internet and a VPN. How does
> the system handle Jitter, and how much jitter can the system handle before
> things start behaving poorly?
>
> 5.) Processor Requirements: We currently have 2 TX/RX sites, and plan to
> have a 3rd in the future. Will something like a BeagleBone Black handle the
> load? Our alternative would be an Fit PC 2, running an 1.6GHz  Atom. Open
> to suggestions.
>
>
> Thanks Much!
>
> Caleb
>
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