Which Devices For Caravanning Communications? (Nextel Direct Talk Or FRS/GMRS)

nanZor

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We recently performed a test with these units - amongst a handful of others and it should come as no surprise as the two most important criteria regardless of power:

Unobstructed line of sight
Good receiver front end

Direct-talk was first - 8 miles los was no problem although we *did* use the little pull-out antenna. I'm on top of a 6 story building, and the other end was free and clear about 3 stories up. Nothing between us. Units stationary, not mobile. Worked just fine, like he was standing next to me, although once in a blue moon, a little fec took place.

FRS - Moto T200's with stubby built-in antennas. RF made the trip just fine. The limiting factor was the weak receiver front end which made it nearly unusable.

Amateur - various amateur freq were tried, and with better front ends (using low power, and very small ducks to try and emulate the frs environment ) - no problem for the rf. Receivers were better, but still nothing like the go / no-go of digital.

CCR's - various rigs were tried on amateur freqs, and again, rf had no problem at half a watt. Being sdr in nature, the noise floor was better than an analog transceiver, but was still limited by not having much front-end in my dense rf environment. So similar to frs, but not quite as bad. CCR murs specific radio a bit quieter actually since VHF isn't as dense as UHF where I'm at.

The trick is to actually get to an unobstructed line of sight environment, and have a good receiver front end.
 

nanZor

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The crux of the issue between frs / direct talk is not just frequency and power. It is the *receiver* quality that is vitally important often overlooked.

Jasii - I know you miss direct-talk greatly. Attempts to shoe-horn an frs/gmrs/murs radio into a cellphone as a replacement just isn't going to fly - why? Unless a carrier actually designs in a good receiver, and consumers are willing to pay for that, then one is most likely looking at the incorporation of an inexpensive direct-conversion sdr, which at times is just as bad as a cheap analog frs radio. And when in the great outdoors, one often gets even closer to mountaintops in which repeater and other high powered rf live, crushing your weak front end.

Moral - if one wants to get serious about it, you'll need a serious radio to bring along with you. Budget attempts, no matter what band or power, will get budget results.
 

n1das

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We recently performed a test with these units - amongst a handful of others and it should come as no surprise as the two most important criteria regardless of power:

Unobstructed line of sight
Good receiver front end

Direct-talk was first - 8 miles los was no problem although we *did* use the little pull-out antenna. I'm on top of a 6 story building, and the other end was free and clear about 3 stories up. Nothing between us. Units stationary, not mobile. Worked just fine, like he was standing next to me, although once in a blue moon, a little fec took place.

FRS - Moto T200's with stubby built-in antennas. RF made the trip just fine. The limiting factor was the weak receiver front end which made it nearly unusable.

Amateur - various amateur freq were tried, and with better front ends (using low power, and very small ducks to try and emulate the frs environment ) - no problem for the rf. Receivers were better, but still nothing like the go / no-go of digital.

CCR's - various rigs were tried on amateur freqs, and again, rf had no problem at half a watt. Being sdr in nature, the noise floor was better than an analog transceiver, but was still limited by not having much front-end in my dense rf environment. So similar to frs, but not quite as bad. CCR murs specific radio a bit quieter actually since VHF isn't as dense as UHF where I'm at.

The trick is to actually get to an unobstructed line of sight environment, and have a good receiver front end.
This more or less matches my experiences over the years.

The modern version of Direct Talk (DT) is the DTR series, consisting of the DTR 410/550/650 models now discontinued, and the new DTR 600/700 models. Another recent addition in 2015 is the DLR series with the DLR1020 and DLR1060 models. The DTRs and the DLRs are based on the MOTOTALK platform that Direct Talk used but were coded differently such that DT is not compatible with the DTRs and DLRs. Direct Talk appears to be an early implementation of MOTOTALK. I think the DTRs and DLRs became incompatible with DT when more features were added to the DTRs starting with the DTR 410/550/650 models.


I have become totally hooked on the DTRs and DLRs for my local on-site simplex type use with family and friends. They are my digital replacement for my local GMRS/FRS and MURS type use because they work so well and are all digital. And while not encrypted they can be made VERY secure. I don't use analog at all anymore for my non-ham use of 2-way radio. I still have GMRS/FRS and MURS as backups and for interoperability (and I even use PL 156.7) but they are no longer my go-to modes for local simplex ops with family and friends. We much prefer to use the DTRs and DLRs because they work so well for our needs.

I saw in a DTR brochure that the receiver sensitivity is spec'd at -125 dBm @ 5% BER. -125 dBm is 0.126 uV. That's better than the common 0.25 uV 12dB SINAD sensitivity for an analog receiver.

I recommend JAS II stick with Direct Talk for the family caravan trip to address the immediate need. Then later on replace them with DTR or DLR series radios. DT capable NEXTEL phones are ancient and plans should be made for their replacement. I recommend the DLR series and the DLR1060 model. The DLR1020 is a 2-channel radio and not expandable. The DLR1060 is marketed as a 6-channel radio but is expandable to 10 channels with the latest CPS. The DLRs are super convenient because they are so damn small and smaller than most FRS bubble pack radios. They are insanely easy to use. A little more money gets you into the DTR 600/700 models. I sold my fleet of DLR1060 radios after getting my fleet of DTR700 radios. I still have my fleet of DTR650 radios.

The crux of the issue between frs / direct talk is not just frequency and power. It is the *receiver* quality that is vitally important often overlooked.

Jasii - I know you miss direct-talk greatly. Attempts to shoe-horn an frs/gmrs/murs radio into a cellphone as a replacement just isn't going to fly - why? Unless a carrier actually designs in a good receiver, and consumers are willing to pay for that, then one is most likely looking at the incorporation of an inexpensive direct-conversion sdr, which at times is just as bad as a cheap analog frs radio. And when in the great outdoors, one often gets even closer to mountaintops in which repeater and other high powered rf live, crushing your weak front end.

Moral - if one wants to get serious about it, you'll need a serious radio to bring along with you. Budget attempts, no matter what band or power, will get budget results.
I agree here too. My wife and I have used i355 DT capable NEXTEL phones years ago and used the DT feature. That's when I first learned of the DTR series digital on-site business radios. I don't bother with any DT capable NEXTEL phones on the used market because I already moved on to the DTRs and DLRs. I have settled on using DTRs and DLRs as my digital replacement for GMRS/FRS and MURS for my local on-site simplex type use with family and friends. A coworker asked me why not use FRS? My answer was that I have already been doing that since FRS was created in 1996 and longer than that as a GMRS licensee since 1992. I want an all-digital solution that is higher quality and more professional than FRS. Being able to make them reasonably secure by using private groups and 1 to 1 calling and not having to worry about FCC licensing and frequency coordination are bonuses. They work amazingly well from my experiences with them.
 
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nanZor

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n1das - Your excellent write-ups got me hooked with a DTR700 pair of my own.

Sure enough, building penetration is exceptional, and I was especially interested compared to my amateur conventional 927 mhz operations - the fhss does seem to do a bit better in that regard. Thanks for the tip.

For caravanning, as long as the vehicle isn't totally shielded with metal-film type glass, 900 mhz is easy to squeak out mobile, but of course the end of the caravan can't be totally blocked either. Thing is, in reality most impromptu caravans don't take the time to use external antennas, so you can bet that 99% of the time, people are going to use it from the drivers seat inside. 900mhz squeaks out better under these real-world conditions. :)

And yep - the vocoder is vastly improved over the old direct-talk units. When we get a chance, we're going to run some "dx" if you will with them and have some fun. Heh, 8 miles line of sight is child's play.

So I'm with you. I think the expense is worth it if one is serious about their simplex comms for all the reasons you stated above. While I dug into it like I do with my amateur dmr radios, the "out of box" operations should suffice for most.
 

n1das

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Excellent! I really like my DTR700 radios. The DTR 600/700 models added AGC to the transmit audio and it really cleans it up and handles loud and soft talkers and people practically eating the mic as they talk. The DLRs and old DTR 410/550/650 and Direct Talk in old NEXTEL phones don't have AGC in the Tx audio. I want Motorola to add AGC to the Tx audio in the DLRs to clean them up.

There is a firmware update available for the DTR 600/700 models if you don't already have the latest FW and CPS. The updated FW adds scan capability and fixes a couple of bugs. A stubby antenna (PMAF4025) is now available for them. I am using the PMAF4025 stubby antenna on my DTR700 fleet.

The same CPS cable used to program the DTR 600/700 is used to apply the FW update. It is an easy plug and play upgrade.
Original 1/2 wave antenna: PMAF4024
New stubby antenna: PMAF4025
The new CPS is R07.01 to program the scan capability in the updated FW.


I regularly check Motorola's website for updates and haven't seen any. Moto's site still has R07.00 CPS and doesn't show the PMAF4025 stubby antenna on the accessories tab.

The DLRs are getting popular and I expect DTR 600/700 models will be popular too. Rest assured that the DTRs and DLRs won't be going away anytime soon.
 
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nanZor

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And thanks again for that upgrade info! I don't really need scan, but it might come in handy in the future.

The sad thing, is despite all this, there are those that no matter what, don't hold a radio properly or get others in the group to do likewise - vertically.

I just laugh when I see all the "distance test" videos online, and inevitably see operators hold them horizontally like harmonicas, or like a cellphone at a 45 degree angle to each other. Not realizing that doing that on both ends tends to do a -60db cross-polarization problem ....

Whether frs, or DTR, holding the radio correctly goes a long way. :)
 
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