New Nextel DirectTalk service

Hi folks. My first post in the forum.

Nextel has recently rolled out their new DirectTalk service. DirectTalk is push-to-talk, like their famous DirectConnect service, but DirectTalk is not network-dependent. From their press release, the service uses 10 channels and 15 "privacy codes" in the 900Mhz ISM band, it is "digital" (which could mean different things), and they claim "up to" 6 miles range.

So, with one Nextel phone, you could have regular cellular service, DirectConnect, text messaging, I believe email, too, and now DirectTalk (with compatible models). DirectTalk communications can be one-on-one or group broadcast. Seems like this gives you a lot of options when communications are swamped with users or just plain knocked out, and it's all in one phone.

Has anyone used the new DirectTalk feature, particularly in an urban setting?

(I'm not affiliated with Sprint Nextel in any way)

The service itself sounds interesting.

I know that several major clients dropped Nextel like a hot rock in and around Orlando after the hurricanes last year (switch to Sprint). This from a Sprint sales person. Don't know exactly why, but the complaints had to do with availability and coverage.

This may be a non issue now (after the sprint-nextel merger).

<<Seems like this gives you a lot of options when communications are swamped with users or just plain knocked out>>

Not sure what you mean by this, but when communications are knocked out, they are knocked out. One of the few (if not the only) types of communication that is 100% reliable when commercial communications is knocked out are the Amateur (HAM) radio bands. See 9/11and Katrina for example.

That's the appeal of this new DirectTalk service--it's not infrastructure-dependent. DirectConnect is network-dependent, so perhaps that is what you're thinking of.

If the person you want to contact has a compatible phone and is within DirectTalk range, even if phone lines are damaged, cell towers run out of battery backup, you're out of range of a cell tower out in the countryside, etc., you can still contact the person directly, simplex, if I may appropriate some HAM lingo. (I'm not a HAM btw).

For most people, particularly as EDC, it's nice to just carry a phone and get this added capability instead of needing to carry a phone *plus* an FRS/GMRS radio, amateur HT, etc. to have a network-independent way of reaching someone.

For relatively short range use, it seems like a nice option to have. Just wondering if anyone's used it in the real world yet.

This sounds extremely cool. I wonder what exactly is meant by 10 channels and how the channels are shared. Are the signals multiplexed, so multiple conversations happen on a single channel? (This seems doubtful, given the network's point-to-point nature, but I have no idea.)

Is this intended for use where there is no coverage, e.g., in the mountains, or for use in cities, where you might be competing with 1,000,000 other people for those 10 channels?

Anyway, it's very cool and I'd like to find out more. (But for now, I'm not throwing away my Yaesu VX-7R.... <img src="/images/graemlins/smile.gif" alt="" />)

Here is the url to the FAQ sheet for this.

Only those with direct talk can use this. How many other carriers will have this? Won't matter much if it is only Nextel/Sprint.

I do not like the digital stuff either. It only takes a little to for the msg to get garbled. FM is better. You can at least hear some of the msg with static invovled. Even better on SSB.

This feature sounds interesting, but not reliable.

The typical cell phone has around 1/2 watt or so of transmit power. This is about the same power as a cheap FRS radio. So, I would expect about the same performance -- maybe a mile or so in typical circumstances. You might be able to get 5 miles if you are in the middle of a desert.

I would rather use a good GMRS radio.

Harrkev, would you mind elaborating a bit on what you mean by "not reliable"? Do you mean in terms of range?

I just think DirectTalk is an interesting option for people who want to have a means of short-range communications with people who may not want to carry a separate two-way radio as EDC, like a spouse or family members. My wife will not carry a FRS/GMRS radio in her purse, but she probably wouldn't mind carrying a Nextel phone with her, which could prove valuable in a situation where cell service is suddenly down or overwhelmed, like after an earthquake.

Still waiting to see if anyone's had any real world experience using it, though.

Basically the power output of the cell phone/two way is going to be so low that it won't be a viable replacement for the downed communications infrastructure as you will have to be so closw to the person your trying to two way that you might as well jus thow the phone at them to get their attention <img src="/images/graemlins/smile.gif" alt="" />

Already got that covered. My EDC includes a baggy filled with smooth river rocks, just for that purpose. I try not to aim for people's heads. <img src="/images/graemlins/wink.gif" alt="" />

But, to get back to the short range issue, I never expected DirectTalk to fully replace the telecom infrastructure. It's not like I'm going to try and reach my emergency out-of-state contact with DirectTalk! <img src="/images/graemlins/smile.gif" alt="" />

Ok, I was going overboard but basically when you take into account the power output of a cell phone you find that its direct talk range will be much less than a cheap dollar store radio.

Does anyone know the FCC regulations on the max power output of a cell phone? Didn't mobile units (i.e. the old car mounted cell phones) have a higher power output and handheld cell phones?

I'm just asking since the assumption that has developed on this thread is that DirectTalk is broadcast at the usual cellular output. I have no idea, but it's possible that DirectTalk mode is higher power.

Someone with more knowledge, please correct me, but I recall reading that because of Nextel's origins as a mobile radio company (like taxi fleet dispatching) rather than a true telecom/cellular company, it's transmission system and iDen technology is actually more like mobile radio with cellular-like call handling than it is a true cellular service, like Sprint or Verizon. Maybe different FCC regs apply to Nextel phones?

That said, Nextel's claim of "up to six miles" seems satisfactory for short range use, especially compared to the "up to two miles" of FRS.

If I remember correctly, the earliest cell phones were closer to 3-5 watts. Current ones are somewhere between roughly .25 - .5 watts. The FCC generally limits SAR, rather than transmission power, because different frequencies are absorbed differently by the body. Perhaps cell phones have special rules but I would have no idea about that.

You can contrast that with handheld ham radios ("Handi-Talkies"), which can go up to 10 watts, but I wouldn't transmit at 10 watts next to my head unless my brain was feeling cold and needed some toasting.

By the way, it's not uncommon to hit repeaters that are several miles away on .5 watts VHF with a ham radio. (Note I didn't say it's reliable.) Of course, this is apples and oranges to what you're talking about because I'm referring to an analog FM transmission and you've said the Nextel is digital.

Thanks, Fitzoid.

Yeah, it's unclear what Nextel means by "digital". However, the press release also mentions "15 privacy codes," which sounds like CTCSS to me. I would think that if the transmissions were digitally encoded, something like "privacy codes" wouldn't be necessary.

Another part of phone power is size/sexiness. Small phones = small batteries = less power. In general, this works well. You simply add more towers so, on average, you are closer to a tower.

In order to make cell phones cheaper, the receivers are generally half-deaf. Cell towers throw out around 100 times the power of the cell phones themselves. So, while this works well for normal phone calls, it hurts cell-to-cell calls.

There other thing, as I've learned from other FRS/GMRS forums, is that output power is much less important than antenna height. Given that, is would not surprise me that relatively low power cell phones communicate fairly well with cell towers, which are typically positioned at strategic high-point towers in the area. Radio-to-radio reception would be MUCH MUCH worse unless the users are in line-of-sight, such as one of them on a high building or on top of a hill. In an urban area you'll be lucky to get more than a couple of blocks distance.

Heavy duty radio users (GMRS and hams) focus very heavily on antenna height, placement, and design as a first priority for direct transmission (not bouncing the signal). The power is secondary.

Yes, exactly right. Antennas and receiver sensitivity can make all the difference. There's a whole subgroup of hams who do QRP, which is low power, long distance communication, e.g., a thousand miles on a fraction of a watt, but those guys have some fancy radios... <img src="/images/graemlins/grin.gif" alt="" />

Yup. And the members of this forum can really appreciate the fancy case of THIS RADIO.

Nice. If I remember correctly from an old thread I just read a little while ago, if you ground that Altoids tin properly, you've just shielded that puppy from electromagnetic pulse as well! Sweet... <img src="/images/graemlins/smile.gif" alt="" />

If you're going to work CW, you can get by with an even simpler radio. That's a veritable ultra high tech beast compared to the ancient homebrew stuff people used to build.

Arney, that has ICs, so it should be toasted by an EMP. You'll have to move back to vacuum tubes to get something pulse-proof. That would be one hell of a cool Altoids tin, with tubes poking out the top. <img src="/images/graemlins/smile.gif" alt="" />

Fitzoid, yup, you're right, it's toast in an EMP. But I say that because I glanced at the photo again after I posted and realized that there are wires leading into the tin. An EMP would travel right down the wire.

However, the consensus in that old ETS thread did seem to be that if the Altoids can was sealed and properly grounded, it should protect the contents. Yeah...and while we're at it, how many angels can dance on the head of a pin again? <img src="/images/graemlins/tongue.gif" alt="" />

A vacuum tube version of the miniscule RockMite QRP CW rig would be awesome. "Say, is that a vacuum tube QRP rig in your pocket, or are you just glad to see me?" <img src="/images/graemlins/wink.gif" alt="" />