Kostas presents the NR-1 Noise Blanker!

Many thanks to SWLing Post contributor, Kostas (SV3ORA), for sharing the following post which originally appeared on his website:

Update June 1, 2024: Kostas is not currently selling the NR-1 as a product but has, instead, made the entire project open and available for everyone to build their own. You may contact him for more information.

The NR-1, a revolutionary noise blanker that works directly on the antenna!

I designed my own noise blanker because:

    • I was tired of that HF noise that could not be beaten otherwise.
    • I wanted to remove it before it gets into my transceiver.
    • I could not install a separate “noise” antenna/coaxial for diversity.
    • I wanted to remove noise interference from any direction.

NR-1 is a revolutionary Noise Blanker which is the result of two-years of development and extensive testing by Kostas sv3ora.

NR-1 works directly at the antenna. This has significant advantages over the classic noise blankers which work at the intermediate stages of the receivers. It does not require a second “noise” antenna for its operation.

Furthermore, it is not based on cutting-off of amplifiers, unlike common noise blankers

Because of these, the NR-1 is superior, compared tocommon internal Noise blankers of radios:

    • NR-1 removes noise before it even reaches the receiver. Thus, the front-end RF
      stages of the receiver are unaffected by noise, unlike a common noise blanker
      which removes the noise after it has first passed through the internal circuits
      of the receiver.
    • NR-1 removes high-level, high-repetition-rate noises that common noise blankers
      usually cannot cope with.
    • NR-1 is not affected by strong near-by signals. Instead, common noise blankers
      perform poorly when there are strong near-by signals and they distort the signal of the station we want to listen.
    • NR-1 can be used by many radios. Because it is an external device, it can be
      connected to various radios/receivers without the need to modify them.
    • NR-1 has a built-in 8-band preselector and helps eliminate intermodulation (birdies)
      caused by strong local medium and shortwave stations, on RF direct sampling
      radios (eg IC-7300). The preselector is relatively wideband and does not affect
      the sensitivity or the waterfall spectrum in the amateur radio bands.
    • NR-1 has built-in variable gain preamplifier and variable attenuator. Preamplification is
      particularly useful in the high frequency bands, where some radios have limited
      sensitivity. Variable attenuation helps to reduce band noise for more
      comfortable listening to mid/high strength stations.

Comparison of the NR-1 with other noise removal systems (eg. QRM eliminator, X-phase etc):

    • NR-1 does not require a second (noise) antenna/coaxial-line to operate. Unlike QRM
      eliminators, NR-1 does not require an additional “noise” antenna and
      therefore no second coaxial cable out of the shack. The main transmit and
      receive antenna you are already using is sufficient.
    • NR-1 is easy to set up. In contrast, QRM eliminators require systematic testing of
      various noise antennas in different locations to perform satisfactorily.
    • NR-1 removes noise from every direction simultaneously. In contrast, QRM
      eliminators, depending on the noise antenna setup and their configuration,
      remove noise from one direction only each time. If the noise originates or
      “travels” through cables and reaches the antenna from different
      directions, QRM eliminators do not perform well.
    • NR-1 removes more than one noise source simultaneously because its principle of
      operation is not related to the phase of the noise.
    • NR-1 does not require constant adjustment. Once set for one band, it usually does not need to be reset. In contrast, QRM eliminators require resetting every few tens of KHz or so.

Kostas has documented all the details of the NR-1 for his own future reference in his page.

He has also created some YOUTUBE videos as demonstrations of the operation and the effectiveness of this antenna noise blanker.

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21 thoughts on “Kostas presents the NR-1 Noise Blanker!

  1. Richard Zwirko

    Will the NR-1 work on 6 Meters, or does it only work up to 30 MHz?
    Rich – K1HTV

  2. Erick VE2LRZ

    Tikanis Kostas. Thanks for releasing the design and responding to everyone. Looking forward to trying out the circuit.


    1. Kostas

      There is no limit to that. It is an active circuit and it can be set on RX so that it has gain or loss. On TX, it just shorts the plugs, so there is no limit in the minimum power you can use it. There is a limit in the maximum, though which is described in the manual.

      1. Har

        Great. My Timewave requires a minimum to operate the relay, so at very low power levels it fails to switch to TX mode.


  3. BIGOT Jean

    Dear Kostas

    I am interested by the NR1. So I want to know how to order and also the price
    Jean F6CVK

  4. Andy

    Interesting. It seems to achieve about the same NR as my homebrew phasing device, but without the need for a second antenna. I’d love to know how it works!

    1. Andrew (grayhat)

      an x-phaser as they’re called may cure ONE noise source… and then it will REQUIRE a separate “noise antenna”; Kos solved it using a different approach, it took time and a whole lot of “back to the drawing board”, which isn’t exactly nice, but after a lot of “trial and error” he came to the current circuit, which works, and works well, he knows that probably some “big players” may reverse the circuit and adopt it w//o recognizing the origin 😛 but then he decided to give it “unmolded” and allow hams and swl gettting better reception

  5. Jason VE3MAL

    Note that the YouTube videos all demonstrate it running with 20 or 30+ year old radios. This isn’t the same thing as diversity reception or cancelling noise via a noise sample antenna, it’s more akin to the noise blanker that is probably already part of your typical modern DSP radio.

    1. Kostas

      Neither the TS-480HX.
      There are several videos there, based on the rigs I currently have.
      Have a look at the TS-480HX videos and comparisons for example. I believe that people that show interest in it, will eventually upload their own videos to show the performance.
      Each and every noise removal technology (diversity, blankers, DSP, AI) helps towards removing noise, depended on the noise. None of them makes the other obsolete, as explained in the manual.

      1. James

        Good morning Kostas I would love to buy one of these noise reduction units, i tried to email you but it won’t go through hoping you get my message here regards James.

    1. Kostas

      It uses the PTT line of the transceiver, that you normally use to drive a linear amplifier.
      GND on TX, left-open on RX.
      If you intend to use it for reception only and not TX, then you may leave the PTT plug disconnected.
      These things are described in the manual on http://qrp.gr/nr1


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