Amateur Radio operators using DMR assist in New Hampshire rescue

Thanks for the explanation. I'm certain others will benefit from the layout.
I am familiar with both the Motorola and EF Johnson trunking, having worked in the LMR/SMR field for years and been an avid 'scanner freak' - also for many years - until dot MIL grade encryption was enacted here some years ago.

My objection to digital V/UHF operations is twofold.
1) The amount of effort required when traveling
2) Lack of range.
To explain.
1) When traveling, an analog FM repeater requires that I enter the frequency pair, offset and tone - if any. Typically, moments work to set up a HT for use where I will travel.
2) Digital works until is dos not. No picket fencing, no indication you are in a fringe area/dead stop until you have nothing.

Happily - we have enough spectrum and plenty of 'legacy' analog machines that I see no impact for where I travel. If digital is something a person wishes to do - great. I chose not to play.

I still use a perfectly working ICOM 28A and would use my now ancient IC2A thumbwheel HTs, except that they have no tone board.

I'm no Luddite. I am, however a noted tighta...frugal person. I do have a rather expensive scanner now nearly useless for monitoring the local PS traffic owing to encryption and not the use of P25 digital technology.

Thanks again for taking the time in your reply.

 

If you think I am trolling you would be highly mistaken. I purposefully didn't explain the reason I said that, as not bring problems here.

73 de Chuck K8CPA

 

Actually the dreaded 'Code Plug' is not much more than a computer spreadsheet that is saved as a comma separated value file then uploaded to the radio. If you know the basics of using a spreadsheet it's a not a problem.

 

The term "code plug" originated from Motorola, Inc (now Motorola Solutions, Inc) very first synthesized LMR radios: the Syntor, and MX-300S radios used a physical PROM (later revisions had EEPROMs) that were on a physical carrier board that was placed in a metal shielded container. It was removed from the radio and placed in a proprietary programming device the size of a small suticase(known as an R1801A) where the radio specific frequency and PL data was written to what the service manuals describe as a "code plug". A physical PLUG that contained CODE one would remove to program the radio. You still had to tune and align the radio "old school". No softpots or tuning data back then.

The term has been carried over to current Motorola Solutions products from the old days. Today's radios are 100 percent software driven, with the "code plug" data residing in an on board EEPROM with megabytes of storage (64MB or more in most APX series radios) versus the less than 1K of yesteryear. Radio firmware does all the work interpreting the "code plug" data. All tuning of RF is done via software pots, and mostly automated via a service monitor running proprietary software that will "auto tune" a radio in around 10-15 minutes on the bench with no technician interaction other than connecting the unit, running the routine, and getting a pass/fail result based on programmed manufacturer provided specifications.

I find the O/P story a great example of how people use whatever they have to get the job done. At least he had a ham DMR rig and not some illicitly programmed trunking radio with a cloned ID. I am glad he was able to be rescued safely.

 

nope nothing you said, I had a reply to a much earlier post in the thread but decided not to be baited in by the negativity lol

 

ah, ok. apologies.

 

I think you are confusing CTCSS, the non-copyrighted term for 'PL' sub-audible squelch with DTMF, the non-copyrighted term for Touch-Tones.

Anyhow:

Many years ago, before cell phones and 911, many ham groups supported "Long Tone Zero" as an emergency signal. Discrete IC decoder designs used 556 chips to listen for the row tone plus the column tone assigned for the telephone zero. A 555 timer chip prevented false alarms on shorter length tones. Today, a micro-controller might be programmed do the job of all the discrete chips.

There was no need to incorporate a light or internal tone signal in the decoder, just install an external speaker muted by the decoder, with the radio's volume turned way up. The decoders would unmute the external speaker after a few seconds of the two correct tones, and the monitoring hams would hear the end of the transmitted Touch-Tones followed by the caller's voice.

An amateur wishing to signal an emergency would send about 5 seconds of the zero Touch-Tone, followed by the assistance request.

Many Touch-Tone encoders at the time were homemade out of old telephones, so the tones would be sent as long as the number was pressed. Touch-Tone pads built into today's radios might not work with this system if pressing keys on the radio produces only short bursts timed by the radio software. We might indeed today need to agree to have a DTMF sequence such as "911" instead of a long tone.

Some business class radios today include alert decoder functions buried in the programming. Some amateur equipment may have the programming option as well.

 

Bottom line : if there is a 'hole' in coverage that looks at the North/West side of the WM range, my site can fill it.

73
Chip W1YW

 

LOL
I actually built one of these for monitoring one of the local (wide area) repeaters. It sat outboard of my ICOM 215 rig.
Once the installed phone patch was operational, no need.
The more technology changes, the pace of change accelerates.

 

DOH! It's been a long time . . . .

The 556 is actually a dual timer IC (two 555s in one package). The decoder chip is a 567.

Thank you to all those of you who did not jump on me for my fading memory.

 

Ed Lawson K1VP

 

I view that as a feature, not a bug.

 

A DSTAR HT would probably send his GPS location...

 

I actually remembered that. Sometimes I think I'm hopelessly old and nerdy.

Tim

 

Hi there,

Nice article. Glad everyone made it home safe.

Anyway, I'd like to suggest another item hikers, and especially four-wheelers, should carry with them any time they go out into the middle of nowhere with no cell or radio service.

A Personal Locator Beacon uses satellite locating, and sends that info to the local S&R group. They're not cheap - mostly in the $200 - $300 range. But on the day you need it, it's priceless.

Hope everyone has a wonderful holiday season!

73 and take care,