More on this: Exciter Modulation Signals Digitized audio/data intended to be transmitted from the station is output from the DSP circuitry to a D/A converter via the TX/Voice Audio signal (p/o the Serial Synchronous Interface bus, connected between the DSP and the DSP ASIC). The digitized signal is converted to analog, level shifted and amplified, and fed to a 0-6 kHz filter. The output of the filter is then fed to one of the inputs of a multiplexer. The output of the multiplexer is fed to two individual digitally controlled potentiometers (each of which is adjusted by the Host uP via the SPI Bus) and output to the Exciter Module as modulation signals VCO MOD AUDIO and REF MOD AUDIO. On 5/8/2017 5:26 PM, Joe Leikhim wrote:
I think it is a bit more complicated than that. If you dither the reference oscillator of a repeater, it will also have an effect on the demodulated PL/DPL from the receiver. Some half duplex transceivers indeed apply modulation compensation directly to the reference oscillators, and others do not, but employ alternative compensation techniques.
This from a Quantar Manual
Modulation The active VCO receives an audio/data modulation signal from the Station Control Module via two low-pass filters. This modulation signal modulates the active VCO to produce a modulated low-level rf carrier signal.
Low-frequency modulation signals (below the loop filter corner) tend to be interpreted by the PLL as VCO frequency error. A modulation compensation signal is added to the PLL _control voltage_ to cancel out this effect and allow for low frequency modulation.
The trick I believe, is in the way the PL/DPL is presented to the station and if the modulation compensation adjustment is sufficient to track out the PLL's tendency to cancel the low frequency tones.
Joe Leikhim
On 5/8/2017 4:33 PM, Bryan Fields 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
On May 8, 2017, at 14:15, Reid Brandon <rfpowerguy@yahoo.com <mailto:rfpowerguy@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@gmail.com <mailto:petem001@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@kuggie.com <mailto:kuggie@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.
______________________________ _________________ App_rpt-users mailing list App_rpt-users@lists.allstarlin k.org <mailto:App_rpt-users@lists.allstarlink.org> http://lists.allstarlink.org/c gi-bin/mailman/listinfo/app_rp t-users <http://lists.allstarlink.org/cgi-bin/mailman/listinfo/app_rpt-users>
To unsubscribe from this list please visit http://lists.allstarlink.org/c gi-bin/mailman/listinfo/app_rp t-users <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.
_______________________________________________ App_rpt-users mailing list App_rpt-users@lists.allstarlink.org <mailto: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.
_______________________________________________ App_rpt-users mailing list App_rpt-users@lists.allstarlink.org <mailto: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.
_______________________________________________ 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 visithttp://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.
-- Joe Leikhim
Leikhim and Associates
Communications Consultants
Oviedo, Florida
JLeikhim@Leikhim.com
407-982-0446
WWW.LEIKHIM.COM
_______________________________________________ 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.
-- Joe Leikhim Leikhim and Associates Communications Consultants Oviedo, Florida JLeikhim@Leikhim.com 407-982-0446 WWW.LEIKHIM.COM