[App_rpt-users] Non-RTCM voter, where?

Joe Leikhim rhyolite at leikhim.com
Wed Mar 30 16:53:38 EDT 2016

What is the problem with the RTCM and simulcast?

Analog simulcast may never sound as good as a single site, because it 
does experience/cause time differential interference and noise and 
therefore requires some very specific design constraints. However, for 
some applications it still is the way to go. Moving forward 5-10 years, 
two slot DMR with IP connectivity will be the way to go. Before I get 
flamed, TETRA never got a foothold in the US and because FCC eliminated 
most 25KHz channels, getting TETRA to play in the US is reserved for 
those few who have the contiguous spectrum.

I will confess to being a lurker here, primarily because I have 
interests both in the commercial LMR and the "ham radio". The RTCM and 
IP Simulcast support interests me because I have done a lot of simulcast 
design work in Public Safety and the  commercial support of analog 
simulcast is becoming threatened with the loss of Raytheon JPS SNV-12 
product.  Also the commercial products are very pricey and complex. That 
being said, I see the RTCM as having some potential niche in the 
commercial LMR world.


On 3/30/2016 2:52 PM, Steve Wright wrote:
> On 31/03/16 05:28, Jeff Ackerman wrote:
>> XIPAR does not do GPS timing of the audio so there will be no timing 
>> of audio.  Its called "simple voter", no frills.  XIPAR simply 
>> selects the best receiver based on DSP signal strength measurements.
> Obviously the 'no timing' situation is not completely traumatic for 
> the conversational use of the repeater, as there is no widespread 
> comments or negativity about it.
> The RTCM is a good idea and a good design, but with the Simulcast 
> transmit not functioning, and no apparent developer activity there's 
> just not enough light at the end of the tunnel to commission it 
> everywhere.
> It seems to me that analog simulcast transmit is never really going to 
> sound right.  I feel uneasy about the relentless approach of digital 
> audio into ham radio, but maybe the dream of zero-handoff multi-rx 
> multi-tx systems means 'digital' and we're stuck with it. I'd like to 
> be proven wrong on that.
> Steve
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Joe Leikhim

Leikhim and Associates

Communications Consultants

Oviedo, Florida

JLeikhim at Leikhim.com



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