Portable Devices for Communications via PSK-31?

yipper asks: "Many amateur radio operators are exploring digital communication modes, one of which is a popular mode is called PSK-31. My local emergency communications volunteer group is thinking about using this mode for off-grid emergency setups. The problem is that a computer with a soundcard is more-or-less a requirement, hence my question: we need a lead on small, portable, battery (preferable 12 volt) powered systems which will run Linux or Windows, be easy on batteries, have audio in/out and a serial port. Recommendations can be older technology, as cost is a factor."

Comments

Laptop

[sigwinch]

The obvious solution is an old laptop. 486 and Pentium laptops can be had cheap, and often have built-in sound. Many models have car adapters available to run off 12V.

Various single-board computers would work too, but there's no way they can beat the price of a used laptop.

iPaq

[baka_boy]

Pick up a bunch of refurb iPaq 3600/3700 handhelds ($350-400 ea.), slap Familiar on them, and you should be ready to go. Oh yeah, they do ad-hoc 802.11, too, so in non-emergency situations you can do normal community networking with them.

laptops the way to go.

[BenTheDewpendent]

Laptops would be the way to go. unless of course you need quality sound.

wich then of course you can consiser lunchbox type computers. I belive that a powersupply in exsiting pc can be modifyed to take 12vDC by bypassing the 1st stage of the powersupply you may want to check up on that.

Attach a solar pannel to what ever solution you use and gain a couple hours on your batteries. and a way to charge them once dead as well.

Or the 3135 for $150 or so

[phr2]

The iPaq 3135 is pretty much the same machine as the 3600 except it has a crappy monochrome display instead of the 3600's fantastic TFT color display. But it's a LOT cheaper. If you just want to use it for audio and don't care about nice graphics, it's a reasonable choice. Note that the regular familiar distribution WON'T run on it directly, because the video driver is incompatible. You have to compile a special kernel for it. There's some info on how to do that in the handhelds.org wiki. It looks like sort of a nuisance but not that big a deal. Maybe they'll fix the Familiar distribution sooner or later to support the 31xx, or maybe they've done it already.

Me, I have a 3135 and was going to run Linux on it but the battery crapped out and I got interested in the Sharp Zaurus which comes preconfigured with Linux. So I think I'll get the battery replaced (it better be covered by the warranty) and then I'll unload the 3135 and buy a Sharp.

Here's my review of the Ipaq 3135.

The trouble with using an ipaq for PSK

[phr2]

is that they have no audio input port except for the microphone. You can't plug your radio receiver audio into it without hacking up the unit somehow, or using some kind of port expander sleeve. Other than that it's a good idea. You might have better luck with the Sharp Zaurus, or if you're really industrious the Agenda handheld PC if you can still find one. Those closed out incredibly cheap.

Sorry I forgot to think of this when posting about the Ipaq 3135 a minute ago.

If all you're building are repeaters, etc

[stienman]

If all you need the device to do is repeating, or simple transmission/reception (to LCD, from keyboard, perhaps), even if you need to log everything to a hard drive, you'd be much better off in the long run making or using a system that uses microcontrollers instead of a full blown computer (where you'd waste 50-90% of your energy).

It appears as though psk31 is simple enough that a micro with a decent A/D would easily handle both reception and transmission. Is there a need for the extra processing power, or is this an issue of rapid development is more important than battery usage?

-Adam

PCMCIA sound and human power

[andaru]

You could throw a real sound card in the PCMCIA slot in the laptop (even run two sound cards if that helps), but the trade-offs are price and power. The decent audio cards for laptops tend to be expensive (Digigram - $500), and adding a PCMCIA card definately sucks down some juice.

As far as power goes, The Register has this article about a foot powered laptop charger (5 min. of vigorous pumping runs a laptop for 20 min.). They are currently selling a hand operated version for $60. The foot powered one will be $150 when it comes out.

I wouldn't use this as a primary source, but it seems like it might be a very usefull device for the emergency communications volunteer group.

On the other hand, if the aliens are invading and you run down into the basement to your radio bench and find that your 12v batteries have all exploded in some freak accident, 5min. of pumping may be way too much latency for an emergency notification.

I think I remember hearing that in the last test of the amateur radio emergency notification system (all volunteers?) they got the test message spread throughout the country in something like 2min.. That's pretty cool. Keep up the good work.

When they run a test like that, what are the criteria for the message being effectively spread - in other words, how do you know when the test is complete?

Actually, It might be nice for you to post a little explanation of how emergency notification using amateur radio volunteer groups works. I think that a lot of people do not even know there is such a system in place. It would also be enlightening from the point of view of how information can be intentionally propogated acroos a wireless human network.... Just a thought.

PSk31 via microcontrollers

[Bishop]

From the official psk31 web page there is a link to psk31 software. At the bottom of that page it mentions a couple of harward implementations of PSK31. I would think that you could hook one of these up to any type of serial terminal (say Dos + telix) and you would be good to go. As mentioned before some old laptops make good serial terminals. Be carefull though. Some of those old laptops have awfull battery times. And just about any laptop that is over 5 years old will need a new battery. There is probably a battery shop in your yellow pages that will rebuild batteries for you.

OT: regarding bypass to 12v on power supply

[Bishop]

I belive that a powersupply in exsiting pc can be modifyed to take 12vDC by bypassing the 1st stage of the powersupply

You probably don't want to do that. First off you probably can't as the transformer probably supplies 12v, 5v, 0v, -5v, -12v not just 12v. Also the transformer plus rectifiers also filter the incomming power. In theory you could use voltage regulator to take 12v and drop it down to 5v. But, you now have a whole lot of power to dissiplate through the voltage regulator.

Re:OT: regarding bypass to 12v on power supply

[rcw-work]

I've done this before.

Go to Maxim IC's web site, and order an evaluation kit with a couple MAX787's to deliver the 5v rail (they handle 5 amps each) and a MAX765 to handle the -12V rail. Most motherboards don't actually need -5V but if yours does the MAX764 will do nicely.

The finished circuit doesn't even get that warm with the IC's bolted to the aluminum case, even when it's delivering 80 watts.

I've tried, but Maxim IC simply will not take your money for small orders, even after you explain to them that you will never ever need 3000 of the things. You have to have them ship you the stuff as an eval kit for free. :)

Re:OT: regarding bypass to 12v on power supply

[Bishop]

Yes. What you are suggesting here is the correct way to do it. (or atleast one of the correct ways) You won't find the MAX chips in your run of the mill power supply though. What I thought the top poster was suggesting was to cannibalize a regular AC to DC power supply and hook the 12v from the car straight into it.

Thanks for the tip on the Maxim parts.

Why not KISS-it with Kenwood's T700D

[ivi]

Look, folks, I really don't understand
why a radio like Kenwood's TM-D700A/E

"FM 2m/70cm Dual-band Mobile Transceiver,
built-in 1200/9600bps TNC for data/visual
communication"

Picture at:

www.kenwood.com.au/comm2.asp?cid=6&gid=3

Spec's at:

www.kenwood.com.au/comm3.asp?gid=3&cid=6&pid=59

(drill down for complete [PDF] manuals, et al.)

I guess I don't see the need for audio-card /
Winmodem-like (i.e. software-based) PSK31 combo

...i.e. when gear like the above Kenwood radio
provides Packet Modems by default... -plus-
there's a -handheld- model that has the same
Packet Functionality

First, you'd need to sell me PSK31... why is
it any better than Packet?

Both seem to work with APRS-protocols - best
with the British UI-View, as seen in Feb QST

If you can't sell me on PSK31, I think you'll
just have to put up with one -less- box (i.e.
the TNC that Kenwood integrated into TM-D700)
and the extra -freedom- e.g. to add a GPS for
Automatic Vehicle Location (AVL) (aka APRS)
and UI-View's inherent digipeater functions.

What do you need, that you don't have here?

73

Re:Why not KISS-it with Kenwood's T700D

[Anonymous Coward]

The TM700D's built-in TNC doesn't do PSK31. Also most PSK31 activity is on the HF bands (below 30 MHz); the TM700D works on 144 Mhz and 440 MHz.

Re: PSK31 vs Packet.

[Bishop]

PSK31 is not better then packet. It is different. It was designed to get 50wpm in 31Hz. The authors don't consider PSK31 a digital mode. Think of PSK31 as an alternative to morse.