An Opensource Mini-Whip Antenna and Upconverter Design for RTL-SDRs

Thank you to Igor Yatsevich for submitting news about an open source Mini-Whip and Upconverter design that he's created and released for free on GitHub. An upconverter converts HF frequencies into VHF frequencies so that they can be received by RTL-SDRs in their quadrature mode, and a Mini-Whip is a small active antenna for receiving HF signals.

The designs include the PCB Gerber files for manufacturing, the components list and assembly and usage guides. Also both through-hole and SMD designs are provided.

The Mini-Whip design has a frequency range of 10 kHz - 30 MHz and to power it you'll need a 5 - 13V bias tee. You will need to install it up high and preferably away from the house as Mini-Whips are quite susceptible to local noise pickup. Another very important point is that Mini-Whips need to have a good ground connection. The upconverter is based on the ADE-1 mixer, and uses a 125 MHz local oscillator.

Igor's documentation on the project is excellent, and is a good read for getting more information about upconverters and Mini-Whips. He has noted that he is sending us some samples of units that he's built, so when we receive them we'll post again with test results. It looks as if he's put a lot of research into these designs so we're looking forward to seeing how well they work. 

Diagram on how to ground a miniwhip connected to a metal mast.
Diagram from Igor's documentation about how to properly ground a Mini-Whip connected to a metal mast.

15 comments

  1. Richard Zed

    I realize this an old thread but interesting none the less, I see there are a number of people who are to say the least very skeptical about the mini whip antenna I used to be one of them even after reading through a number of forums.
    I’m a short wave/BCB DXer from way back and have had an antenna up in almost all my residences over 47 years .
    We recently moved and I put up a long wire properly earthed through a balun as I did in the past but the noise here is atrocious , during the day the number of solar inverters in the area made impossible plus also a power transformer not far from us was spewing out noise across the broadcast band which I got fixed by calling the local power company, I have done this in the past and they are always very helpful and repair the issue in good time .
    During the evening I also had some other local noise that a friend and I called the Romper Stomper it traveled across the HF band killing all in it’s path and occasionally settle but always return within a day or two, I was never able to find the cause of this noise even after a few late night jaunts roaming around with a portable receiver.
    I removed the antenna giving up disheartened only to put it back up some months later and remembered something I read regards a twisted pair counterpoise so I went about winding one round for the first 10 meters of the long wire .The result was a much lowered noise floor making dxing a possibility still not the best but workable.

    Knowing how successful some Miniwhip installations have been for many people I decided to give it a go and purchased one bare bones from Ebay which came as two components the main antenna and the power injector , I installed the antenna inside a short piece 30mm pvc pipe.
    I then attached it to a 1 mtr of pvc pipe which was attached to 4.5 meters of gal pipe which was earthed at the base by a 1.8 mtr earth rod.The Miniwhip was also earthed where the pvc pipe connected to the gal pipe.
    The coax runs from the top of the gal pipe 10 meters across to a j pole on the car port then routed under the first floor back outside earthed through another rod and up into my shack , I use a 12v Battery for the power.in the house a total of approx 28 mtrs.
    The results a just short of a miracle the noise floor is so low it amazed me , Romper Stomper is now just a 1khz fuzzy line causing no more than the occasional bother if it happen to rest on a frequency I wanted to listen to.
    LW is a beauty to behold and have logged over 45 beacons all over Australia , I live on the north coast of Tasmania.Am DXing is a reality for me again and the first station I logged on the BCB with the Miniwhip was KBLA USA .The short wave bands are plump with signals and the waterfall is a beauty to behold.
    Same on the Ham bands from 160m through to 20m ,I can enjoy HF air traffic control also skip on the 27mhz CB band.
    The Miniwhip has made it possible for me to fully enjoy my hobby again in the evening and drastically reduced the noise level from the Solar installations during the day. My SDR, FRG7000 and FRG 7700 love the Miniwhip. If you are in a similiar situation I would say give it a go.

  2. John

    The J310 is getting a bit expensive these days, I have tried a 2N5486 which works just the same and is much cheaper ($0.98)

  3. jlc66

    Ah, the mini-whip. It always seemed to me like soup from a stone. You only need this very small piece of metal. It just has to be high up, at the top of a long piece of wire. People have modeled it, and, indeed, the long wire (coax) serves as the antenna.

  4. Dan

    I don’t suppose any of the people slamming the PA0RDT will care to point to some case studies?

    At any rate, the article is also about the upconverter. There are many diode mixer designs like this out there and they do work. It’s very convenient these can be ordered from jclpcb for very cheap straight from the public EasyEDA project.

    • Mike

      Ok, here I am “publishing” a study anyone can reproduce.
      Setup 1 is a vertical 24AWG wire going up along a 30ft fiberglass pole. There is a 8ft ground rod near the base of the pole. The wire and the ground are connected to a 1:1 transformer (4 turns bifillar on BN43-202 binocular ferrite core). The other side of the transformer is connected to coax going to the shack. The coax shield is also tied to the ground rod.
      Setup 2 is a mini-whip mounted on top of the same pole. The coax from the mini-whip is connected at the base to the coax going to the shack, without the transformer, but with the shield grounded at the base to the same rod.
      I claim that there is no observable difference in the S/N ratio of these 2 setups. Prove me wrong.
      For completeness, setup 3: FT-817 radio on the asphalt shingle / wood frame house roof, 6m up, connected to a battery supplied mini-whip with a 1ft piece of coax. No connection to any kind of ground. This setup can only receive the strongest signals and is basically unusable. I claim (and mini-whip proponents don’t deny) that mini-whip REQUIRES a long vertical feedline grounded at the base to work at all.

  5. Kerteszradio

    It is really incredible. Here is a shematics : http://radioaficion.com/cms/pa0rdt-mini-whip/ Suggest replace the J310 to MPF102. This slightly better (lower) noise. All data in millimeter. I replace the “probe” antenna to 60cm wire antenna but not much better. Of contrary ! These setup in occasional overloaded the V3 dongle direct sampling input.

  6. Rusty

    Stop spruiking this snake oil. It has been repeatedly proven that mini whips are no more effective than the length of the feedline.

    • Max

      This is partially true but if somebody can turn a vertical feedline into a good receiving antenna just using a simple amplifier he is already a genius.
      The results can be seen at Twente websdr, it’s true, not a metropolitan legend.

      • Anonymous

        When in a quiet place, mini-whip works similar to a vertical (wire, not coax) of the same length as the feedline. This is my real experience. The amplifier doesn’t change the S/N ratio on most of HF bands, and is prone to overload. So the simple vertical without the amplifier has some advantage when strong signals are present. Both systems require good clean ground.
        So yes, mini-whip really works, and no, it doesn’t work better than a piece of wire in the same location. The only situation where it works better is with a deaf receiver which benefits from the preamp gain.

      • Adam

        If I do remember well, the antenna on Twente websdr is placed on top of the uilding where the roof is flat and completely covered with the metal sheet. This brings another dimension to this antenna but comparing it to the proper wire antennas is out of the question.

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