Improving Reception on the Malachite DSP via USB Grounding

Thank you to Mitsonobu Saitou for writing in and sharing with us a product that he has created which improves reception on of the Malachite DSP software defined radio and other shortwave radios by up to 20dB by improving the grounding. It appears to work by using the negative USB line as a ground via a modified USB cable with grounding clip on the other end. The product is available via Amazon Japan with international shipping.

The Malachite DSP is a portable battery powered software defined radio with built in screen. It is popular amongst shortwave listeners.

Saitou writes the following summary, and full details about the product are available on his blog (link uses Google Translate to translate from Japanese to English): 

Today's item is "Dokodemo Earth KUN". This is an item to pull the ground wire from the charging connector of DCL radios and Mlachite DSPs.

The sensitivity of the receiver will be improved by strengthening the grounding. This is how I applied it.

It is easy to connect by pulling out the ground wire from the charging connector instead of the antenna jack.

It can also be used as a loop antenna by connecting the ground to the antenna.

We have confirmed the effectiveness of this product outdoors. Users who have used this item have experienced a significant increase in sensitivity. 

Malachite DSP and SWL Radio USB Grounding Enhancement Cable
Malahit/Malachite DSP+「どこでもアースくん」

 

15 comments

  1. Fred

    The headline is misleading. The Sensitivity of the Malachite stays the same.

    The offered USB-connected piece of wire is just acting as an antenna counterpoise and improves the signal voltage on the 50 Ohms Input from the Antenna. You can save money and instead use any length of cable and connect it to the shield of the SMA antenna connector. Best ist to connect the Shield of the SMA connector on shortest way with an proper and clean RF-ground.

    • saitou

      Requested to change the title.
      The reason I used USB grounding was to simplify the connection. I made it easy for beginners to use.

    • snn47

      or place it in a 13″ flat frying pan or large metallic table.

      Everything, even touching the receiver can improve or degrade reception, since like a large nail or a wet noodle cooked in salt water, the so called antenna is just a unshielded conductor picking up electromagnetic waves, but NOT a antenna.
      An antenna needs to specfy the frequency range or installation conditions in order to achieve a specified antenna pattern. For more see my other post below.

  2. Saitou

    I came up with this grounding principle based on the fact that touching the ground of a radio or receiver increases its sensitivity. The principle seems to be canterpoise.
    We believe that the sensitivity of the radio or receiver does not change, but the sensitivity of the antenna is improved.
    Thank you.

    • Anonymous

      My short comment did not sufficiently express my approval of snn47 comment. If he has time I would welcome further comment on how increased signal strength is achieved. Perhaps it is due to the increased differential voltage level between a notional ground and a real ground to the voltage at the antenna. Thank you snn47

      • snn47

        Antenna pattern vary with frequency, design and surrounding, (reflecting and obstructing) materials.
        Similar to a light bulb (isotropic antenna = equal in all direction) which provides only a dim light, and the light pattern will change with your surrounding, e.g. if placed on a mirror or black surface. You can use a reflector to get a bright cone but only have minimal light in the other direction, similar to an antenna. You can improve gain of an antenna but limit the antenna pattern in width for elevation and/or azimuth.
        Antenna pattern is only defined if it is sufficiently high in the air (=freespace) and varies with frequency. The real antenna pattern and gain for frequencies will also vary vary with height and distance to reflecting structures, like ground, walls or that will attenuate, e.g. walls of like (steel reenforced) concrete, bricks, metallizes glas windows, solar panel,
        In case of the wire shown that improves reception for this one station and one frequency only, and may have degredaed reception of other stations, again deoending on frequency.
        The posters hand alone will have influenced reception if he would have touch the case.
        There are many factors, since the antenna pattern is frequency/wavelength dependent. Personally I found grounding is only a beneficial for frequencies well below ~30 MHz, while for VHF and higher frequencies radials or reflection surface is better.
        Any stubs of (Telescope) wire or even a nail or noodle cooked in saltwater will provide reception when connected to a receiver. Unlike the RTL-SDR receiver which provides reception over more than 1000 MHz, most antenna types are not wideband, only some provide a “stable” pattern for more a change in frequency of a factor of more than 2 to 8. Again you will receive signals but you cannot apply the antenna pattern for an antenna if you use it at frequencies for which it is not designed. The telescope wire used is not an antenna but some undefined conductor but not an antenna.

  3. snn47

    Misleading title misleads readers and confused cause with effect.
    The antenna pattern of a whip without radials or ground will change its antenna pattern if you connect a wire to ground or when you touch the case (and/or its ground).
    if the signal strength is improving this means the signal that the antenna receives is now stronger, not that the sensitivity of the receiver is improved. No one would built/buy more sensitive/expensive receiver if a single (grounded) wire would improve sensitivity of a receiver as the title suggests.

  4. JTC

    Has anyone tried this with an Airspy or RTL-SDR? I read Mitsonobu’s translated blog and he mentioned grounding the “minus” of the USB connector, I expect he’s referring to the GND and not the D- wires.

    • snn47

      If you have a antenna resonant ath the receive frequency, that also has radials or a metallic/mesh counterpoise, the addition of adding additional ground wires or a wire connected to ground should not vary the antenna pattern/signal reception very much. Due to the impact on the antenna pattern this can improve of one or more signal sources. But there are to many factors, like frequency/wavelength to consider, and I found only a benefit for frequencies below 30 MHz, while for VHF and higher radials are better.

      • JTC

        I’m still poking around in the dark learning the amateur radio world. I’ve got a 30 foot copper wire loop. Not grounded and no counterpoise. I’m going to try grounding the feedline shield to a copper plumbing pipe, since all metal plumbing is grounded and see what that does. Not sure how much noise it’ll pick up through that though. Aiming for better shortwave DXing. Thanks for the tip!

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