[App_rpt-users] RTCM RSSI calibration

Kevin Walsh w8khw1 at gmail.com
Mon Oct 23 11:06:00 EDT 2017


Wow Tim, the Wiki is really taking shape! The section on the RTCM is fantastic. A huge Thank You to you and all who have contributed.

Kevin
W8KHW

> On Oct 22, 2017, at 10:38 PM, Tim Sawyer <tisawyer at gmail.com> wrote:
> 
> Some things to consider:
> 
>  - Install JP1 on the Quantar's RTCM. The squelch should calibrate at around 4 blinks rather than the 12 blinks or so without JP1.
> 
>  - Be sure you've done the diode and squelch calibration with the actual attached radio (no antenna). 
> 
>  - The Quantar firmware should be 20.14.48 as later versions have better noise output. 
> 
>  - Try the "Chuck Squelch" RTCM version. They say it's better. I'm not sure I can tell the difference.
> 
>  - Each RTCM should have 3 to 5 turns past threshold to prevent the squelch form being too loose. Somewhere around the 350 level seems about right. Chuck Squelch seems to need fewer turns but YMMV.
> 
>  - Don't "and" CTCSS with squelch. That may override the RTCM's squelch detection. Compare with CTCSS on and off to see effect if any.
> 
>  - See our new wiki.allstarlink.org. There's a lot of good RTCM information there.
> 
> Hope this helps. 
> 
>> On Sun, Oct 22, 2017 at 12:39 PM, Skyler F <electricity440 at gmail.com> wrote:
>> For one voted site, we are using a Motorola Maxtrac 900 and for the master we are using a quantar receiver. 
>> 
>> Unfortunately, the RSSI levels don't really mean the same thing between the two receivers. The Maxtrac Voter will be almost full quieting and then the Quantar will pick it up relatively very noisy. 
>> 
>> I know it is not the best idea to use two separate models of receivers for voting, but other then the signal strength, the audio seems to sound the same. The problem with the Quantar is that it is a "Virtual Discriminator Audio" which needed BEW mode on the RTCM to be enabled and that is what seems like is messing up the measurements. 
>> 
>> Is there a way to tune these RSSI levels so the perceived signal strength has the same correlation on the numbers 0 - 255. 
>> 
>> In addition, we would like to disable the master receiver at some points, like only have the voter turned on for receive just to test it's coverage. Is this possible? 
>> 
>> Thank you,
>> Skyler
>> 
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> 
> 
> 
> -- 
> --
> Tim
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