[App_rpt-users] Turning RTCM Preemphasis off

Joe Moskalski kc2irv at gmail.com
Tue Jul 11 16:23:28 EDT 2017


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 at 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
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