Turning RTCM Preemphasis off
I wanted to pose this question in case anyone knows how to do this or not or if its even possible. I currently have a need in a new simulcast system to not have the audio that comes out of the RTCM preemphed. I have done some digging and so far I have not uncovered a solution other than an external deemphasis circuit on the output. Thanks, Joe - KC2IRV
Hey Joe, If you don't specify a PL tone in the voter.conf, the RTCM stops preemphasizing. If you need the PL generation, you're stuck. Hope all is well. On Tue, Jul 11, 2017 at 10:26 AM Joe Moskalski <kc2irv@gmail.com> wrote:
I wanted to pose this question in case anyone knows how to do this or not or if its even possible. I currently have a need in a new simulcast system to not have the audio that comes out of the RTCM preemphed. I have done some digging and so far I have not uncovered a solution other than an external deemphasis circuit on the output.
Thanks, Joe - KC2IRV _______________________________________________ App_rpt-users mailing list App_rpt-users@lists.allstarlink.org http://lists.allstarlink.org/cgi-bin/mailman/listinfo/app_rpt-users
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-- KJ6QFS Sam Skolfield
Yeah, that's what I kept seeing, I was hoping there was a way around that. I am guessing this can be dealt with in the code but I don't really have that ability, external Deemphasis it is then. On Tue, Jul 11, 2017 at 3:42 PM, Sam Skolfield <kj6qfs@gmail.com> wrote:
Hey Joe, If you don't specify a PL tone in the voter.conf, the RTCM stops preemphasizing. If you need the PL generation, you're stuck.
Hope all is well.
On Tue, Jul 11, 2017 at 10:26 AM Joe Moskalski <kc2irv@gmail.com> wrote:
I wanted to pose this question in case anyone knows how to do this or not or if its even possible. I currently have a need in a new simulcast system to not have the audio that comes out of the RTCM preemphed. I have done some digging and so far I have not uncovered a solution other than an external deemphasis circuit on the output.
Thanks, Joe - KC2IRV _______________________________________________ App_rpt-users mailing list App_rpt-users@lists.allstarlink.org http://lists.allstarlink.org/cgi-bin/mailman/listinfo/app_rpt-users
To unsubscribe from this list please visit http://lists.allstarlink.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
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On 7/11/17 3:48 PM, Joe Moskalski wrote:
Yeah, that's what I kept seeing, I was hoping there was a way around that. I am guessing this can be dealt with in the code but I don't really have that ability, external Deemphasis it is then.
A better question, How are you planing to use PL on transmit but not inject into the modulator directly? If you use a de-emphasized input the PL will be distorted on transmit. -- Bryan Fields 727-409-1194 - Voice http://bryanfields.net
I will be separating the voice audio and PL audio using active filters so that I can inject the PL tone and Transmit audio to separate points on the transmitter so that the Transmit audio and PL tone level can be adjusted independently at each transmitter in the simulcast system. Unfortunately this transmitter adds preemphasis to the transmit audio and this cannot be changed in the transmitter. On Tue, Jul 11, 2017 at 4:00 PM, Bryan Fields <Bryan@bryanfields.net> wrote:
On 7/11/17 3:48 PM, Joe Moskalski wrote:
Yeah, that's what I kept seeing, I was hoping there was a way around that. I am guessing this can be dealt with in the code but I don't really have that ability, external Deemphasis it is then.
A better question,
How are you planing to use PL on transmit but not inject into the modulator directly? If you use a de-emphasized input the PL will be distorted on transmit.
-- Bryan Fields
727-409-1194 - Voice http://bryanfields.net _______________________________________________ App_rpt-users mailing list App_rpt-users@lists.allstarlink.org http://lists.allstarlink.org/cgi-bin/mailman/listinfo/app_rpt-users
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On 7/11/17 4:12 PM, Joe Moskalski wrote:
I will be separating the voice audio and PL audio using active filters so that I can inject the PL tone and Transmit audio to separate points on the transmitter so that the Transmit audio and PL tone level can be adjusted independently at each transmitter in the simulcast system. Unfortunately this transmitter adds preemphasis to the transmit audio and this cannot be changed in the transmitter.
You certainly understand it then, and sound like it's under control. Lots of simulcast questions don't quite have the same level of detail understanding. Easiest way is to change the code or do an external filter. Since you're building a board anyways, an external filter would probably be the easy way to do it. I'd (and I'm sure others) be interested in the details of your system when you get it working. 73's -- Bryan Fields 727-409-1194 - Voice http://bryanfields.net
Sure, the two site system I have on the air now works very well. I modified the transmitters to modulate the VCO directly and by luck their frequency response across the audio spectrum happened to be identical. When I went to add a thrid transmitter to this system using an identical model unit I found the frequency response slightly different causing the PL tone audio to be a bit hotter than the rest of the transmitters when i adjust it for 1000 Hz @ 3 KHZ deviation. Its perfectly usable but you can notice the growl of the PL at times due to the level not being within where it needs to. So that's the whole story and why I am going this route. If this works they way i think its going to, I will post the results and the schematic, parts list and gerber files for the board. On Tue, Jul 11, 2017 at 4:16 PM, Bryan Fields <Bryan@bryanfields.net> wrote:
On 7/11/17 4:12 PM, Joe Moskalski wrote:
I will be separating the voice audio and PL audio using active filters so that I can inject the PL tone and Transmit audio to separate points on the transmitter so that the Transmit audio and PL tone level can be adjusted independently at each transmitter in the simulcast system. Unfortunately this transmitter adds preemphasis to the transmit audio and this cannot be changed in the transmitter.
You certainly understand it then, and sound like it's under control. Lots of simulcast questions don't quite have the same level of detail understanding.
Easiest way is to change the code or do an external filter. Since you're building a board anyways, an external filter would probably be the easy way to do it.
I'd (and I'm sure others) be interested in the details of your system when you get it working.
73's -- Bryan Fields
727-409-1194 - Voice http://bryanfields.net _______________________________________________ App_rpt-users mailing list App_rpt-users@lists.allstarlink.org http://lists.allstarlink.org/cgi-bin/mailman/listinfo/app_rpt-users
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On 7/11/2017 3:48 PM, Joe Moskalski wrote:
Yeah, that's what I kept seeing, I was hoping there was a way around that. I am guessing this can be dealt with in the code but I don't really have that ability, external Deemphasis it is then.
What kind of equipment are you using for the transmitter? If it's possible to inject your audio directly into the modulator, and that modulator is FM, then all would be well. Of course, if your transmitter has a phase modulator, then this approach won't help. Kevin
participants (4)
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Bryan Fields -
Joe Moskalski -
Kevin Custer -
Sam Skolfield