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Open-Hardware Licensed Handheld Software-Defined Radio In the Works 50

Posted by timothy
from the good-speculation dept.
An anonymous reader writes "Chris Testa recently presented at TAPR Digital Communications Conference and annouced his development work on a hand-held software defined radio. Running uClinux on an ARM Corex-M3 coupled to a Flash-based FPGA, it will be capable of receiving and transmitting from 100MHz to 1GHz. Designed to be low power, Chris has designed the radio primarily with the Amateur 2m and 70cm bands in mind. Currently in early prototyping stage, Chris intends to release the design under the TAPR Open Hardware License."
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Open-Hardware Licensed Handheld Software-Defined Radio In the Works

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  • Why is he designing it primarily for 2m and 70cm (better known in amateur radio land as 440)? 2m is kinda crowded around here and 70cm doesn't seem to like the hills and trees around here. Our local ham group (in particular our ARES/RACES subgroup) is thinking about going to 6m.

    I'd be more interested in something like this if it went down to 50MHz. But I don't know enough about designing this kind of thing to know if that is feasible.

    • by atrus (73476) <atrus@nosPAM.atrustrivalie.org> on Thursday January 03, 2013 @03:54PM (#42465815) Homepage
      The only real limits are: RF front end/IF section (if any, could be a direct conversion) FPGA speed The latter really only comes into play for high datarate/frequency work, so its all in the (hopefully replaceable) front end.
    • by dtmos (447842) * on Thursday January 03, 2013 @04:01PM (#42465895)

      But I don't know enough about designing this kind of thing to know if that is feasible.

      The SDR is feasible, in fact, easier, but the problem is the "handheld" part -- "emphasis on the word, 'handheld.'" The physical size of the antenna starts becoming uncomfortably large as the frequency goes down -- or, said another way, the efficiency of the antenna goes down with frequency if the physical size is held constant. A full-size 50 MHz quarter-wave whip antenna is 1.5 meters (or metres, if you prefer; about 59 inches) long; that's pretty unwieldy for a handheld radio.

      • Yeah hardly anyone uses quaterwave whip antennas on a hand held radio. In all the radios I've ever used - easily a dozen they've all had loaded coils. Which are not all that efficient sure, but they work well enough - especially with an infrastructure which there is plenty of on 2m and 70cm (and 6m as in your example).

        • by dtmos (447842) *

          Yes. And if one makes a 6m antenna the same physical size as a handheld 2m antenna the 6m loading coil will be larger, its series resistance will be higher, and the 6m antenna will be significantly less efficient than the 2m antenna. It will work "well enough", for suitably generous definitions of "well enough."

          The optimum operating frequency for a given service can be determined (in the absence of regulatory restrictions, of course) analytically, taking atmospheric noise, antenna performance, and receive

    • Re: (Score:2, Interesting)

      by Anonymous Coward

      The 2 meter and 70cm bands are by far and away the most popular amateur radio bands, and they are the most accessible. All license tiers can use them, and equipment can be had for reasonable prices.

      These sorts of considerations are very important if you want to kick off something you want to see widespread use. HF can always be added later, once a project develops traction.

    • by maird (699535) on Thursday January 03, 2013 @04:08PM (#42465977) Homepage
      Then if the future of 2m, 70cm is narrower channel bandwidth than is currently used (how could it not be given the public service channel bandwidth now used) the nice thing here is that you only have to install the ROM image with the new modulation, keeping the old bandwidth as a feature anyway. Leading to more space for local groups in the long term from free software. I'd bet the lack of 6m comes from one of the chips at the RF end being limited to 100MHz. It's quite easy to fill-in the 0-100MHz block for receive with a cheap mixer (see the article in this month's QST, pg 30 I think).
      • by CC12123 (443428)

        Chris Testa KD2BMH here. marid, your suspicion is correct, the CMX991 transceiver I'm using has a low-end cutoff of 100MHz.

        The HF converter w/ a NE-602 mixer in the latest QST looks like an attractive solution to support the missing lower frequencies receive, I'm guessing 2 would allow me to build a full duplex transceiver.

        I'm using a 40MHz ADC & DAC, so at least some of the HF bands should be possible using direct conversion.

        Either way, HF wasn't part of my initial plan, I'm focusing on exactly what I

        • by maird (699535)
          Hi Chris, thanks for the response! It's maird rather than marid BTW but AD7GH or David works too ;-) I have the parts for a pair of 125MHz NE-602 mixers en-route from Mouser as I write and they should be here on Monday. The ultimate goal is to extend a RTL2832 USB receiver that should get here in early February. So hoping for a nice little project for fun and some spare parts in case I blow it. I might just build it before the USB device gets here and test it on one of my other receivers. I watched the show
    • by tlhIngan (30335)

      Why is he designing it primarily for 2m and 70cm (better known in amateur radio land as 440)? 2m is kinda crowded around here and 70cm doesn't seem to like the hills and trees around here. Our local ham group (in particular our ARES/RACES subgroup) is thinking about going to 6m.

      I'd be more interested in something like this if it went down to 50MHz. But I don't know enough about designing this kind of thing to know if that is feasible.

      Probably because the RF power amplifiers needed - just because you

      • Like 6M and 1.25M? They are both pretty dead where I live (DFW). I have a radio that will do 6M but no antenna yet. I have yet to hear anything on it while spinning the dial. I do have a 220MHz receive-only radio but all the repeaters in my area are linked to either 2M or 70cM repeaters and serve no real purpose...

        • by Muad'Dave (255648)

          Bob,

          Keep an eye on www.dxmaps.com [dxmaps.com] and when you see QSOs near you, fire up your 6m rig using your HF antenna. I've worked over 100 grid squares using a 756 PRO, 100W and my multiband HF dipole (that isn't cut for 6m) and is only 15 feet off the ground. If your rig has an antenna tuner, I bet it can find a match for 6m. I think part of why I can load up that antenna is that the coax is so bad it presents enough raw resistance so that the SWR is under 3:1 regardless of the actual antenna impedance!

          See you on t

  • by ickleberry (864871) <web@pineapple.vg> on Thursday January 03, 2013 @04:07PM (#42465955) Homepage
    I want! Imagine a mesh network of these, put the evil telco's out of business :)
  • I just started using Gqrx and a rtl device for $20 to get started in software radio.
    Grabbing the APT images from polar orbiting satellites.

    http://www.oz9aec.net/index.php/gnu-radio/gnu-radio-blog/477-noaa-apt-reception-with-gqrx-and-rtlsdr [oz9aec.net]

    There is also the Funcube USB Dongle you can use but its more $$$$.
  • But perhaps there's a text article somebody could link to instead? Video is an unbearable format when it comes to technical news - just stop doing that (although the fact that reading (and writing) is hard is understandable...).

  • by westlake (615356) on Thursday January 03, 2013 @04:55PM (#42466773)
    Correct me if I am wrong.

    But is there any shortage of openly published and easily accessible hardware designs for amateur radio?

    • Are you saying there are too many? You can always sign off and go get some fresh air.

      I happen to be kind of excited about his work, it's compact, it has a nice frequency range, and it can transmit, which is a bit novel. To each their own.

      • by westlake (615356)

        I happen to be kind of excited about his work, it's compact, it has a nice frequency range, and it can transmit, which is a bit novel. To each their own.

        It's not the project I object to.

        It is the ridiculous "open hardware" hype applied to radio enthusiasts who were sharing designs, techniques, etc., long before the invention of the vacuum tube.

  • by Anonymous Coward

    It would be even better if it covered the HF bands.

    I've had this fantasy about designing a very low bitrate (short messages only may take minutes to hours to send one message) massivly multiple access self organizing messaging protocol using GPS ref with ability to operate way way way way below the noise floor leveraging only ISM bands and effective power limits.

    The ultimate would be a tablet sized (mostly antennas) device able to communicate short text messages directly to others (P-T-P ONLY no meshing or

    • by Muad'Dave (255648)

      Look here [princeton.edu]. I've used WSPR to send a small message from Richmond, VA to New Zealand using a 0.1 Watts on 30m (about 10.1 MHz). Dr. Taylor is a weak signal nut, and has done an amazing job of creating modulation schemes that work well for a lot of very weak signal scenarios. Want to bounce signals off of the ion trails left by meteors that are so small you can't even see them? Done - it's called FSK441 [princeton.edu].

      His newest JT9-x schemes [princeton.edu] can detect signals 40 dB _below_ the noise floor - that's 1/10,000th the noise powe

  • by no_such_user (196771) <jd-slashdot-20071008@@@dreamallday...com> on Friday January 04, 2013 @03:40AM (#42472865)

    12 hours and only 37 comments? The response to a device like this should be far greater on a site like Slashdot. *Sigh*.

    Anyway, I've always felt TAPR kits were not entirely within my grasp due to either high prices or high complexity. I hope this will be an affordable kit which doesn't require a ton of SMD soldering. Take the lead from Raspberry Pi - small, simple, affordable hardware.

    Good luck! I'll see you guys at Dayton!

    • I see these articles occasionally, but I don't know the significance. Can you outline *why* I should be excited about this?

      • by CC12123 (443428)

        Chris Testa KD2BMH here...

        This is one of the most interesting and challenging questions to answer. Here's a blurb excerpt from Eric Blossom, an early innovator in software radio as to why this stuff is so valuable:

        "Software radio is a revolution in radio design due to its ability to create radios that change on the fly, creating new choices for users Perhaps most exciting of all is the potential to build decentralized communication systems. A centralized system limits the rate of innovation. We could take

    • by CC12123 (443428)

      Thanks no_such_user... see you at Dayton! I'll hopefully be helping out at the TAPR booth.

      73,
      Testa KD2BMH

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