Frugal Radio: Turning Scrap Wire into an Effective HF Dipole

In this weeks video Rob from his Frugal Radio YouTube channel shows us how he's turned an old piece of scrap electrical extension cord into an effective HF antenna for his Airspy HF+ SDR. The scrap wire is combined with a US$15 NooElec 9:1 balun which helps improve the impedance match of the antenna. He then stretches the dipole out through his backyard and then hooks it up to his Airspy HF+.

The results show good reception across the 20m, 80m, 40m amateur radio bands, as well as on HF ATC aircraft communications, US coast guard weather information broadcasts and the AM broadcast band.

I made an HF Dipole for free! Reception was good on my AirSpy HF+ Discovery SDR!


  1. Nelson

    I am a newbie in SWL listening.
    I live at 13th floor in an apartment building.
    Could I use the wires hanged vertically from a balcony,separated apart from 3 meters and close to the walls of the building ?
    What could be the minimum diameter of the wires (AWG), to keep them stealth ?

    • Bart

      13th floor, then you can make a excellent long wire setup, just try this. Use one long pice of wire and string it to a nearby tree, pole, other building, or whatever is posable. An angel of about 45 degrees is OK, more horizontal is even beter, but just string it to whatever you can find, the angle is not critical. Connect the wire to one terminal of the 1:9 balun, connect the other terminal connection to ground. Experiment with interchanging the two connection’s for best result. Happy SWLing!

      • Nelson

        Thanks Bart for your valuable suggestions, I will think about this, and try to find a way on how to attach the other end of the wire, to keep it stealth..
        Thanks again and stay safe in this difficult time.

  2. Paul PD0SWL

    Thanks for putting all the time&effort into this video. I can confirm a 9:1 RF transformer and 2x10m makes an excellent all round SWL antenna. Performance is quite equal across a wide range and common mode suppression is a big help with SDR. The 9:1 ratio also extends performance doen to the LW/MW/MF range. Easy to judge from behind a keyboard this RX antenna won’t work but it does very well. Great you inspire the experiment and recycling of scrap 😉 Keep on going! 73 Paul PD0SWL

  3. Bart

    $15 spent for nothing

    If the dipole impedance is already a close match to the cable impedance, you don’t need any impedance transformation. In this case impedance transformation only males things worse not better. You’ll better of with a 1:1 balun.

    You can make an effective 1:1 current balun by winding the first two to three meters of the coax to a coil, diameter and length is not that critical. This will prevent almost all current along the outside of the cable, which is the main purpose of a balun (balanced to unbalanced)

    You probably will get away with the impedance mismatch the 1:9 transformation will cause on Rx, but try it on Tx and you quickly find out, what impedance mismatch will do for your radiated signal.

    Remember, impedance matching and preventing what is called ‘common mode’ current along the outside of a coax cable are two distinct different phenomena. Watch a good demonstration on

    As a closing note: There a two fundamental different types of baluns.
    Voltage baluns
    Curent baluns

    Voltage baluns use the voltage transformer principle, the signal runs through the balun windings
    Current baluns use the choke principle to suppress ‘common mode’ currents along the outside of the coax. The opposite and equal currents in the coax don’t generate any magnetic field outside the cable and

  4. snn47

    There seems to be a lack of understanding what impedance transformation on BALUN or UNUN are used for, leeding to a babylonic confusion in terms.
    The video and the statement

    blockquote cite=””The scrap wire is combined with a US$15 NooElec 9:1 balun which helps improve the impedance match of the antenna””

    is completely nonsense!

    A BAL(anced)/UN(balanced) or BALUN is needed if a symetrical antenna is to be connected to an asymetrical/unbalanced distribution/transmission-line e.g. a ~60 Ohm symetrical halfwave dipole to an asymetrical 60 Ohm coax cable.

    Since he said he’d match equal length of the wires to the wave length, the antenna already has a similar impedance to the coax-cable of 50 Ohm he used. The use of a 1/9 transformation in the BALUN is counterproductive, since the dipole is now missmatched in impedance to the distribution/transmission-line. A 1/1 transformation BALAUN would have been the correct choice, using 1/9 provides a major missmatch of impedance.

    For a symetrical ~240 Ohm fullwave dipole a BALUN with 1/4 transformation of impedance factor is the correct choice.

    A UN(balanced)/UN(balanced) transformation of impedance is only needed if the impedance of the antenna and the distribution/transmission-line don’t match, e.g. if a asymetrical antenna is to be conntected to a asymetrical distribution/transmission line.
    The often used 1/4 wavelength groundplane antenna is asymetrical and has similar impedance as most asymetrical distribution/transmission-lines, which is why you connect it directly without the need for a BALAUN or UNUN.

    • K6LJP

      “balance the signal” LOL Wow ok come on Rob I love your videos but please take this one down 🙂
      I think you maybe a bit misinformed on how a balun works
      snn47 is right however a bit hard to understand for most here to understand
      I don’t mean to be rude but the is embarrassing please read a bit more on how things work before posting such a silly video

      Thanks Rob
      Love ya man !

  5. Mike

    The turns ratio is not critical. The main function of the balun/unun in this use is not the impedance matching, but suppressing the common mode interference coming from the cable inside the building.
    I used 4:1, 9:1 and even 1:1 with similar results.

  6. Ladislav OK1UNL

    To be clear: Unun or “Balun” One Nine means transformation ratio 9:1.
    This “Balun” is suitable for Long Wire antenna. Dipole antenna using transformation ratio 1:1.
    Put this antenna wire to high as possible above ground.
    Bulding baluns 9:1 or 1:1 is not too difficult and it is possible make by beginners.
    VY 73! ladislav OK1UNL

    • Ham Killer

      Actually an UNUN is for an unbalanced feed and is suitable for RX, a BALUN is generally for TX with a balanced line.

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