Re: [App_rpt-users] App_rpt-users Digest, Vol 88, Issue 16
The RTCM and simulcast DOES work. As mentioned before, you have to be using a transmitter that can accept a 10 mHz (or whatever) reference signal. You also need 1 PPS for your receivers and transmitter. You also need to sync the RTCM to your GPSDO (which I have not done). If you have not done all this you WILL hear some "funk" in the overlap areas. That "funk" can go from usable to un-usable depending on how strong the transmitters are in the overlap region. Pardon the "non-technical" terms. It does work but the law of physics do apply here. de K0JSC On Mon, Jun 6, 2016 at 9:54 AM, <app_rpt-users-request@ohnosec.org> wrote:
Send App_rpt-users mailing list submissions to app_rpt-users@ohnosec.org
To subscribe or unsubscribe via the World Wide Web, visit http://ohnosec.org/cgi-bin/mailman/listinfo/app_rpt-users or, via email, send a message with subject or body 'help' to app_rpt-users-request@ohnosec.org
You can reach the person managing the list at app_rpt-users-owner@ohnosec.org
When replying, please edit your Subject line so it is more specific than "Re: Contents of App_rpt-users digest..."
Today's Topics:
1. Re: audio for direct VCO FM (Joe Leikhim) (Steve Wright) 2. Re: RTCM Simulcast question (Steve Wright) 3. Re: audio for direct VCO FM: Si5351B (David McGough) 4. Re: RTCM Simulcast question (Joe Moskalski) 5. Re: RTCM Simulcast question (David McGough) 6. Re: RTCM Simulcast question (Joe Moskalski)
----------------------------------------------------------------------
Message: 1 Date: Mon, 6 Jun 2016 19:40:50 +1200 From: Steve Wright <info@meshnetworks.co.nz> To: app_rpt-users@ohnosec.org Subject: Re: [App_rpt-users] audio for direct VCO FM (Joe Leikhim) Message-ID: <57552902.9070008@meshnetworks.co.nz> Content-Type: text/plain; charset=windows-1252; format=flowed
On 04/06/16 04:00, Joe Leikhim <rhyolite@leikhim.com> wrote:
Assuming the VCO is part of a PLL, the PLL will tend to "correct" the modulation, [....]
Was planning to use the Si5351B - has VCO input.
S
------------------------------
Message: 2 Date: Mon, 6 Jun 2016 20:22:36 +1200 From: Steve Wright <info@meshnetworks.co.nz> To: app_rpt-users@ohnosec.org Subject: Re: [App_rpt-users] RTCM Simulcast question Message-ID: <575532CC.2020304@meshnetworks.co.nz> Content-Type: text/plain; charset=windows-1252; format=flowed
On Sat, Jun 4, 2016 at 6:03 PM, Joe Moskalski <kc2irv@gmail.com> wrote:
I will be setting up a 2 site UHF simulcast system in the coming months
Huh? I was told (on this list) that simulcast TX "doesn't work".
S
------------------------------
Message: 3 Date: Mon, 6 Jun 2016 10:46:38 -0400 (EDT) From: David McGough <kb4fxc@inttek.net> To: app_rpt-users@ohnosec.org Subject: Re: [App_rpt-users] audio for direct VCO FM: Si5351B Message-ID: <Pine.LNX.4.44.1606060946450.4196-100000@goliath.inttek.net> Content-Type: TEXT/PLAIN; charset=US-ASCII
Hi Steve,
We're getting way off topic for the mailing list, but, I thought I'd post this reply here if there are any other interested hams out there, perhaps who are also experimenting in this area.
I haven't played with the Si5351B version of this interesting chip, yet. I wonder whether the voltage control input of this chip would be suitable for AF FM modulation? Assuming that you could modulate the VCXO at audio frequencies (the datasheet isn't completely clear to me about that), an immediate issue would be that everytime you change the fractional-N division ratio, you'll change the modulation index. This will have to be compensated for, one way or another.
I've been playing with several boards with Si5351 chips. They're pretty neat. They're also pretty noisy! ...With both spurious and phase noise. The phase noise can be improved somewhat with a better external crystal oscillator, the spurs seem more challenging. Using the on-board VCXO with the 5351B, you can't use a high quality external oscillator, so phase noise and overall frequency stability could be an issue, too.
Anyhow, for my applications, I'm following the Si5351 with a secondary clean-up VCO/PLL, which was already in the radios. I just needed a frequency-agile reference oscillator, so to speak. I think the Si5351 will work well for this, based on my preliminary tests! (I'd certainly like to hear the experiences from anyone who has already been down this road!)
I guess you're not finding any local sources of surplus radios? Do you have any 6m power amps available?
73, David KB4FXC
On Mon, 6 Jun 2016, Steve Wright wrote:
On 04/06/16 04:00, Joe Leikhim <rhyolite@leikhim.com> wrote:
Assuming the VCO is part of a PLL, the PLL will tend to "correct" the modulation, [....]
Was planning to use the Si5351B - has VCO input.
S
------------------------------
Message: 4 Date: Mon, 6 Jun 2016 11:03:11 -0400 From: Joe Moskalski <kc2irv@gmail.com> To: App_rpt-users@ohnosec.org Subject: Re: [App_rpt-users] RTCM Simulcast question Message-ID: <CAES28qxB06niu+nL4Y5QfUvgZFf-y8s= uZdH2afzxKnwr0HV+w@mail.gmail.com> Content-Type: text/plain; charset="utf-8"
It seems clear that in order for simulcast to work properly with the RTCM I will need to clock the CPU to the GPSDO. Is there a device available to give you the 9.6 mhz reference from the 10 mhz out from the GPSDO or does anyone have a schematic available so that I can build them myself?
< https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaig...
Virus-free. www.avast.com < https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaig...
<#DDB4FAA8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
There was mention on this board that drift of the 9.6 MHz clock causes the CTCSS phase to shift. If this is the case, you will have audible noise and possibly receiver CTCSS drop outs in overlap areas. You will have distortion of audio frequencies as well. Whatever solution to the 9.6 MHz clock must be phase coherent between RTCM nodes . I have no experience with RTCM, but am quite familiar with commercial simulcast in the LMR world. I am lurking here because I see the RTCM as a very affordable contender to the commercial products that exist today. Joe K4SAT On 6/6/2016 12:23 PM, Jeff Carrier wrote:
The RTCM and simulcast DOES work. As mentioned before, you have to be using a transmitter that can accept a 10 mHz (or whatever) reference signal. You also need 1 PPS for your receivers and transmitter. You also need to sync the RTCM to your GPSDO (which I have not done). If you have not done all this you WILL hear some "funk" in the overlap areas.
That "funk" can go from usable to un-usable depending on how strong the transmitters are in the overlap region.
Pardon the "non-technical" terms. It does work but the law of physics do apply here.
de K0JSC
On Mon, Jun 6, 2016 at 9:54 AM, <app_rpt-users-request@ohnosec.org <mailto:app_rpt-users-request@ohnosec.org>> wrote:
Send App_rpt-users mailing list submissions to app_rpt-users@ohnosec.org <mailto:app_rpt-users@ohnosec.org>
To subscribe or unsubscribe via the World Wide Web, visit http://ohnosec.org/cgi-bin/mailman/listinfo/app_rpt-users or, via email, send a message with subject or body 'help' to app_rpt-users-request@ohnosec.org <mailto:app_rpt-users-request@ohnosec.org>
You can reach the person managing the list at app_rpt-users-owner@ohnosec.org <mailto:app_rpt-users-owner@ohnosec.org>
When replying, please edit your Subject line so it is more specific than "Re: Contents of App_rpt-users digest..."
Today's Topics:
1. Re: audio for direct VCO FM (Joe Leikhim) (Steve Wright) 2. Re: RTCM Simulcast question (Steve Wright) 3. Re: audio for direct VCO FM: Si5351B (David McGough) 4. Re: RTCM Simulcast question (Joe Moskalski) 5. Re: RTCM Simulcast question (David McGough) 6. Re: RTCM Simulcast question (Joe Moskalski)
----------------------------------------------------------------------
Message: 1 Date: Mon, 6 Jun 2016 19:40:50 +1200 From: Steve Wright <info@meshnetworks.co.nz <mailto:info@meshnetworks.co.nz>> To: app_rpt-users@ohnosec.org <mailto:app_rpt-users@ohnosec.org> Subject: Re: [App_rpt-users] audio for direct VCO FM (Joe Leikhim) Message-ID: <57552902.9070008@meshnetworks.co.nz <mailto:57552902.9070008@meshnetworks.co.nz>> Content-Type: text/plain; charset=windows-1252; format=flowed
On 04/06/16 04:00, Joe Leikhim <rhyolite@leikhim.com <mailto:rhyolite@leikhim.com>> wrote: > Assuming the VCO is part of a PLL, the PLL will tend to "correct" the > modulation, [....]
Was planning to use the Si5351B - has VCO input.
S
------------------------------
Message: 2 Date: Mon, 6 Jun 2016 20:22:36 +1200 From: Steve Wright <info@meshnetworks.co.nz <mailto:info@meshnetworks.co.nz>> To: app_rpt-users@ohnosec.org <mailto:app_rpt-users@ohnosec.org> Subject: Re: [App_rpt-users] RTCM Simulcast question Message-ID: <575532CC.2020304@meshnetworks.co.nz <mailto:575532CC.2020304@meshnetworks.co.nz>> Content-Type: text/plain; charset=windows-1252; format=flowed
On Sat, Jun 4, 2016 at 6:03 PM, Joe Moskalski <kc2irv@gmail.com <mailto:kc2irv@gmail.com>> wrote:
> I will be setting up a 2 site UHF simulcast system in the coming months
Huh? I was told (on this list) that simulcast TX "doesn't work".
S
------------------------------
Message: 3 Date: Mon, 6 Jun 2016 10:46:38 -0400 (EDT) From: David McGough <kb4fxc@inttek.net <mailto:kb4fxc@inttek.net>> To: app_rpt-users@ohnosec.org <mailto:app_rpt-users@ohnosec.org> Subject: Re: [App_rpt-users] audio for direct VCO FM: Si5351B Message-ID:
<Pine.LNX.4.44.1606060946450.4196-100000@goliath.inttek.net <mailto:Pine.LNX.4.44.1606060946450.4196-100000@goliath.inttek.net>> Content-Type: TEXT/PLAIN; charset=US-ASCII
Hi Steve,
We're getting way off topic for the mailing list, but, I thought I'd post this reply here if there are any other interested hams out there, perhaps who are also experimenting in this area.
I haven't played with the Si5351B version of this interesting chip, yet. I wonder whether the voltage control input of this chip would be suitable for AF FM modulation? Assuming that you could modulate the VCXO at audio frequencies (the datasheet isn't completely clear to me about that), an immediate issue would be that everytime you change the fractional-N division ratio, you'll change the modulation index. This will have to be compensated for, one way or another.
I've been playing with several boards with Si5351 chips. They're pretty neat. They're also pretty noisy! ...With both spurious and phase noise. The phase noise can be improved somewhat with a better external crystal oscillator, the spurs seem more challenging. Using the on-board VCXO with the 5351B, you can't use a high quality external oscillator, so phase noise and overall frequency stability could be an issue, too.
Anyhow, for my applications, I'm following the Si5351 with a secondary clean-up VCO/PLL, which was already in the radios. I just needed a frequency-agile reference oscillator, so to speak. I think the Si5351 will work well for this, based on my preliminary tests! (I'd certainly like to hear the experiences from anyone who has already been down this road!)
I guess you're not finding any local sources of surplus radios? Do you have any 6m power amps available?
73, David KB4FXC
On Mon, 6 Jun 2016, Steve Wright wrote:
> On 04/06/16 04:00, Joe Leikhim <rhyolite@leikhim.com <mailto:rhyolite@leikhim.com>> wrote: > > Assuming the VCO is part of a PLL, the PLL will tend to "correct" the > > modulation, [....] > > Was planning to use the Si5351B - has VCO input. > > S >
------------------------------
Message: 4 Date: Mon, 6 Jun 2016 11:03:11 -0400 From: Joe Moskalski <kc2irv@gmail.com <mailto:kc2irv@gmail.com>> To: App_rpt-users@ohnosec.org <mailto:App_rpt-users@ohnosec.org> Subject: Re: [App_rpt-users] RTCM Simulcast question Message-ID:
<CAES28qxB06niu+nL4Y5QfUvgZFf-y8s=uZdH2afzxKnwr0HV+w@mail.gmail.com <mailto:uZdH2afzxKnwr0HV%2Bw@mail.gmail.com>> Content-Type: text/plain; charset="utf-8"
> It seems clear that in order for simulcast to work properly with the RTCM > I will need to clock the CPU to the GPSDO. Is there a device available to > give you the 9.6 mhz reference from the 10 mhz out from the GPSDO or does > anyone have a schematic available so that I can build them myself? > > <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 <http://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> <#DDB4FAA8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
Hi Joe, I'm not sure how you would pull off phase-coherence between nodes, even if you could phase-lock all the 9.6MHz clocks....You have to remember that the software on each node would have to be in perfect sync between each node as well. I think the bigger issue in overlap areas, with moving users, will be Doppler shift between the transmitter sites. With analog systems, Doppler shift is going to be a hard issue to resolve. 73, David KB4FXC On Mon, 6 Jun 2016, Joe Leikhim wrote:
There was mention on this board that drift of the 9.6 MHz clock causes the CTCSS phase to shift. If this is the case, you will have audible noise and possibly receiver CTCSS drop outs in overlap areas. You will have distortion of audio frequencies as well.
Whatever solution to the 9.6 MHz clock must be phase coherent between RTCM nodes .
I have no experience with RTCM, but am quite familiar with commercial simulcast in the LMR world. I am lurking here because I see the RTCM as a very affordable contender to the commercial products that exist today.
Joe K4SAT
On 6/6/2016 12:23 PM, Jeff Carrier wrote:
The RTCM and simulcast DOES work. As mentioned before, you have to be using a transmitter that can accept a 10 mHz (or whatever) reference signal. You also need 1 PPS for your receivers and transmitter. You also need to sync the RTCM to your GPSDO (which I have not done). If you have not done all this you WILL hear some "funk" in the overlap areas.
That "funk" can go from usable to un-usable depending on how strong the transmitters are in the overlap region.
Pardon the "non-technical" terms. It does work but the law of physics do apply here.
de K0JSC
David, all the simulcasting RTCMs are driven by one node. On Monday, June 6, 2016, David McGough <kb4fxc@inttek.net> wrote:
Hi Joe,
I'm not sure how you would pull off phase-coherence between nodes, even if you could phase-lock all the 9.6MHz clocks....You have to remember that the software on each node would have to be in perfect sync between each node as well.
I think the bigger issue in overlap areas, with moving users, will be Doppler shift between the transmitter sites. With analog systems, Doppler shift is going to be a hard issue to resolve.
73, David KB4FXC
On Mon, 6 Jun 2016, Joe Leikhim wrote:
There was mention on this board that drift of the 9.6 MHz clock causes the CTCSS phase to shift. If this is the case, you will have audible noise and possibly receiver CTCSS drop outs in overlap areas. You will have distortion of audio frequencies as well.
Whatever solution to the 9.6 MHz clock must be phase coherent between RTCM nodes .
I have no experience with RTCM, but am quite familiar with commercial simulcast in the LMR world. I am lurking here because I see the RTCM as a very affordable contender to the commercial products that exist today.
Joe K4SAT
On 6/6/2016 12:23 PM, Jeff Carrier wrote:
The RTCM and simulcast DOES work. As mentioned before, you have to be using a transmitter that can accept a 10 mHz (or whatever) reference signal. You also need 1 PPS for your receivers and transmitter. You also need to sync the RTCM to your GPSDO (which I have not done). If you have not done all this you WILL hear some "funk" in the overlap areas.
That "funk" can go from usable to un-usable depending on how strong the transmitters are in the overlap region.
Pardon the "non-technical" terms. It does work but the law of physics do apply here.
de K0JSC
_______________________________________________ App_rpt-users mailing list App_rpt-users@ohnosec.org <javascript:;> http://ohnosec.org/cgi-bin/mailman/listinfo/app_rpt-users
To unsubscribe from this list please visit http://ohnosec.org/cgi-bin/mailman/listinfo/app_rpt-users and scroll down to the bottom of the page. Enter your email address and press the "Unsubscribe or edit options button" You do not need a password to unsubscribe, you can do it via email confirmation. If you have trouble unsubscribing, please send a message to the list detailing the problem.
-- KJ6QFS Sam Skolfield
participants (4)
-
David McGough -
Jeff Carrier -
Joe Leikhim -
Sam Skolfield