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Digital in GMRS - which mode is most appropriate?

digital nxdn p25 dpmr idas mototrbo dmr

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#41 intermod

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Posted 14 December 2019 - 01:13 AM

Fighting against change is the surest way to failure.

 

Well said.   

 

Digital will eventually happen.  The question is whether we (GMRS licensees) what to propose the rules, or let the manufacturer's propose the rules.   



#42 gman1971

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Posted 14 December 2019 - 02:31 AM

Well said.   

 

Digital will eventually happen.  The question is whether we (GMRS licensees) what to propose the rules, or let the manufacturer's propose the rules.   

 

Maybe it should be we, the users, who propose the rules. Manufacturers usually don't care about anything else but revenue... 

 

G.



#43 gman1971

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Posted 14 December 2019 - 02:47 AM

Yes, however, I suspect that a lot of the cheap radios used for GMRS are not even type accepted, and they put out spurious RFI emissions off the charts.

 

For example, I can hear my cheapie GD77ss like 1000 channels away when operating on DMR.... now you crank the power of that CCR with one of those CCPA  (cheap Chinese power amplifier) like the BTech one, up to 50W, and now you have spurious RFI crap and IMD all over the band. I have a similar situation (not caused by 50W CCR, but kilowatt TV stations and whatever crap is on the giant tower) and I am certainly not a happy camper... but I've taken extensive measures with cavities and LNAs to get the situation somewhat under control. While its not as good as a remote location with little RFI, or noise, but its certainly better than 3 miles on receive with a triple collinear 5/8 over 5/8, when I know that antenna was easily capable of 20+ before... 

 

Again, its also about using the proper equipment, and unfortunately for us, licensed operators, not everybody cares, and the CCRs, for all their virtues to help people get in the hobby, they also have a lot of downsides. Most new folks (like I did) just want the darn thing to work reliable as a cellphone, and when they can't reach 5 miles with 50W they immediately assume they need to run 500W, or more power until the dang thing works (or smokes). Radio range, as explained by marcspaz is not about more power, is about location, antenna and feedline + filtering.

 

 

G.

 

dPMR-like 6.25 might have been the approach if no other common digital mode existed.  But we have many now.  

 

You may have missed the earlier discussions here - interference has to do with signal level & proximity, not technology to any significant degree.  And the assumption that the number of users and interference sources would grow and cause overcrowding has no basis.  

 

In the end, changes in radio services and rules are always much simpler than you portray.  If the Commission simply permitted the typical digital emissions and made no change to analog operations or anything else - new digital radios would operate on existing channel centers.  Bandwidth is a don't-care.   And like today, if an analog direct-mode operation was interfered with, the victim would simply change channels until it went away.  Despite what the Commission believes, I have never seen one user call another and coordinate channel usage (FCC pipe-dream).  They can't - they are all in tone squelch, and if they could hear, they would just start spewing expletives at each other. 

 

Repeater operations would be the same as they are today - a new repeater owner would usually listen, select a channel, and work with the other co-channel repeater owners to arrive on a good (or least bad) channel.   In the beginning, most digital repeaters would be replacing existing analog repeaters - so the interference environment would remain unchanged.  Having the option to operate a digital repeater would not necessarily increase the total number of GMRS repeaters.  Digital repeaters are expensive enough that I cannot see many going up initially anyway.  User equipment is also slightly more expensive. 

 

What if a new digital repeater owner does not coordinate?  You listen for his (analog) Morse Code IDer, or buy the $90 digital radio with Promiscuous Mode and talk to them directly if you want to save time. 

 

Also - all the new digital equipment have an extremely good "busy-channel-lockout" features if it came down to it.   But like analog, nobody would want to use it. They would simply move their repeater to a different channel and avoid the headache (and likely jamming/self-policing). 

 

Would digital complicate the GMRS? Only for those who wanted to use digital.   If I don't want to understand it, then I could save money and just buy analog.      

 

Really - its just that simple. 






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