Great antenna for software defined radio is really easy to make

800px-Ezcap_EzTV668

The University of Kent’s hackerspace, TinkerSoc, recently had a talk on software-defined radio using an incredibly inexpensive USB TV tuner. Of course this is nothing new to Hackaday readers, but they did manage to build one of the best antennas for their TV dongle. It’s a discone antenna, and is perfectly suited for tuning into a whole bunch of really cool things such as weather balloons and aircraft transponders.

The idea discone antenna looks exactly like its namesake; a metal disk attached to a metal cone. Of course with the frequencies the RTL software-defined radio deals with, it’s rarely necessary to build antennas out of sheet metal. The team at TinkerSoc built their discone out of galvanized garden wire and attached it to the input of their TV tuner.

All the dimensions for their discone antenna were gleaned from [ve3sqb]‘s antenna design programs. Since TinkerSoc designed their antenna for 110 MHz, it ended up being pretty large. For higher frequencies, though, a discone antenna become fairly small and more than portable enough for a mobile rig.

Comments

  1. strider_mt2k says:

    Vermillion Hells yes!
    Discone antennas rock for their versatility, as long as you understand that you don’t really get any gain from them.

    I bought a Radio Shack model years ago and mounted it in my attic connected with some over-speced hardline. It’s still my go-to for those times when I needed a quick antenna solution within it’s extremely wide frequency range.
    There are also ham radio-oriented models with an additional vertical element that will let them operate down into the 10 meter band.
    Ghod knows there are plenty of DIY designs for these awesome antennas too.

    I was away from HAD for a while, but have wandered back again.
    Good to see stuff that brings out my enthusiasm…thanks!

  2. geekmaster says:

    tinkersoc web server is offline. :-(

  3. geekmaster says:

    Not on Google cache or Coral Cache or the archive.org Wayback Machine.

  4. ejonesss says:

    did you call tinkersoc to tell his site is down?

  5. ejonesss says:

    “Side note, for us students, TV licensing is a tricky thing, but as long as you don’t use the device to tune into TV you won’t have a problem”

    can you transmit with the device too?

    • Mex says:

      Nope receive only.

    • radion39 says:

      In some places the world you need a license or pay a tax to receive free over the air TV.

      • Bacchus says:

        Yes, but at least we get the BBC, which means no ads… well, only ads for BBC products… the BBC turns out to have lots of products…

        The best thing about the BBC is, of course, the news. I thought politics, wars, and economics were the very staple of news until the BBC showed me that most news involves people with regional accents waving embarrassingly shaped vegetables around. Still – at least it’s only 24 hours per day.

  6. zibri says:

    Oops! Google Chrome could not find tinkersoc.org

  7. zibri says:

    ” a metal disk ” ==> ” a metal disc ” :)
    disk is a computer term, short for DISKETTE, disc is the geometric figure :)

  8. daniel says:

    We are just propagating the DNS to a different server now and we should be back up. It was our first foray into SDR, so any tips for us, or any questions we are happy to have them.

    • geekmaster says:

      Bummer. If your DNS server had the typical 7-day TTL, it could take up to a week for those of us how tried to visit the old site to properly resolve the new IP address for your domain name.

      We have to wait for our ISP to flush your old IP address from its DNS cache before we can resolve the new IP address.

      Could you please post its IP address so we can visit the site by IP instead of domain name? Hopefully you are not on a virtual hosting service with many domains sharing an IP…

      • geekmaster says:

        I seen that 72 hour DNS propogation is common these days. My domain names still have the older 7 day propogation for the TTL setting in their zone records. You can edit your zone records to change that at your DNS service provider.

        What was the TTL setting in the tinkersoc DNS zone record?

      • WhyTheLongTTL says:

        What’s the reason people keep their TTL so high? On my domains I keep them at 800. Usually it seems that my changes propagate almost instantly. My site doesn’t seem any slower with the low TTLs.

        I’m on Namecheap’s DNS service for my domains and use Google DNS for my client machines.

    • Rob says:

      Daniel, adsb mapping can be done with google earth. Lots of fun (particularly if you live near Heathrow!!): http://www.irrational.net/2012/08/06/tracking-planes-for-20-or-less/

  9. Roklobsta says:

    In the meantime y’all can read an earlier HaD incarnation of the same project here: http://hackaday.com/2012/05/14/improving-a-software-defined-radio-with-a-few-bits-of-wire/

  10. ejonesss says:

    then why would they say about tv licensing if you cant transmit on it?

  11. M4CGYV3R says:

    “100 Mhz and below that the military seems to start appearing. It’s likely encrypted and not something we want to be arrested for listening in to.”

    1. Nobody can really tell if you are listening. Radio broadcasts(aside from things like radar) are fire-and-forget. If you don’t obstruct or interfere with the wave by listening, nobody will know you even heard it.

    2. If it’s encrypted, you won’t have a clue what they’re transmitting. Hearing an encrypted transmission is not a crime. Decrypting it without permission, however, IS a serious crime.

    The nature of radio and the rules the FCC has in place say that if you can receive it, you are allowed to. Understanding the message is a whole different matter.

  12. ejonesss says:

    i think the only way that they can know if you are monitoring the channels is.

    1. if the device is putting out emf sort of like the van eck effect. ( i think is why moning companies say no radios during blasting (because the maybe the van eck effect can set off the charges)) as is.

    2. if the modifications to the device causes it to put out more emf than specified or change it’s emf signature ( sort of like what cable co called the cuckoo tone used to detect cable theft or theft of scrambled content) because most of the theft of premium content required the modification of the descrambler box to get more channels than what you paid for.

    so the cable would drive up and down the streets with some sort of radio detector and if the cuckoo tone was detected they would cut the cable or report the theft or even charge them the max amount.

  13. radion39 says:

    Making a discone is NOT a hack by my book. But something like this are http://www.emrg.ca/EMRG-202_Tape_Measure_Discone.pdf

    Also discone is prone to get everything from air, from powerfull FM broadcast to near Cellular Towers, not a good thing with these very small dynamic range SDR.

  14. Ryan7777 says:

    Yeah, the UK is whack with their lame TV licensing rules. Lots of stories i’ve heard over the years of them driving around in vans, sniffing around for rouge TVs.

    AND yes you absolutely can sniff out a radio receiver. The police have been doing it for years with radar detector-detectors like the VG-2 and spectre/stalcar series. They sniff for the local oscillator leakage from your radio receiver (or radar detector). Easier for that application because up in the microwave frequencies, its easier to build smaller, more directional antennas, but it can be done with other frequencies as well using pseudo doppler direction finding and other techniques.

  15. Ren says:

    I bought a Radio Shack discone antenna for my workplace back in the ’90′s to listen to aircraft radio. The some of the ground plane elements (the cone) fell out after a number of months, maybe loosened by wind. I wasn’t sure if using a Loctite compound would work, maybe it would insulate the rods from their base.

  16. I Made a jpole antenna that i set for 160Mhz and it works great with my gm300 tx and rx and swr for tx was fantastic would that be ok for sdr ?? I have not got sdr yet but it’s a must for me I have played with scanners and pmr radio for over 30 years now.

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