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Thread: Körner 19.3 FM Yagi

  1. #11
    k6sti Guest

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    Peter deserves all the credit for designing this great antenna. All I did was tell people about it. I believe a commercial version of the design is now available from VHF Teknik in Sweden.

    Glad to hear you're using a preamp with the XDR-F1HD. Its adaptive noise reduction greatly reduces noise in stereo, but it doesn't function in mono and can't benefit mono DXing. The tuner does not have an RF amplifier stage so its noise figure is rather high (8.5 dB, about the same as a Technics ST-9030). Adding a low-noise preamp can really improve S/N for weak signals. As you note, the preamp gain covers up the soft-muting, which can be annoying at low signal levels. It also holds off the high-cut noise filter and this can improve intelligibility when trying to ID a weak station.

    Brian

  2. #12
    Boško Igić Guest

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    Konrad, you have great equipement. You can also try to catch radio-stations from Serbia:
    Radios from Crveni Čot near Novi Sad (824 km to Plock):
    94.5 RTS - Radio Beograd 1
    96.5 Beograd 2
    101.8 Beograd 202
    Radios from Avala near Belgrade (876 km to Plock):
    95.3 Beograd 1
    97.6 Beograd 2
    104.0 Beograd 202

  3. #13
    Todd Emslie Guest

    Default Körner 19.3 FM Yagi

    Konrad,

    A 4 dB RF preamplifier contributes too much noise considering you are living in a semi-rural environment. Rural or semi-rural environments often (but not always) feature relatively low ambient noise levels. I know of two DXers who are receiving significant S/N improvement when using the following 87-108 MHz PHEMT design LNA with their Sony XDR-F1HD tuners:

    http://cgi.ebay.com/LNA-FM-Radio-UKW...item19bf586972

    The AMIWINA PHEMT FM LNA is rated as having ~ 0.5 dB noise figure, which is competitive with other high-end EME installations. Use RG6 (or ideally RG11) type low loss 75-ohm coax when the RF LNA is used near the XDR-F1HD tuner.

    With the AMIWIMA LNA in line, you may be able to hear out to 800 km FM on a daily basis using aircraft reflection.

    DXers living in metro / city areas will not benefit from this preamp, unless they are situated at least 20-25 km (12-15 miles) from high powered band 2 FM transmitters. For example, Peter Korner and myself both tried one AMIWIMA LNA, but IMD / overload was excessive.

    Regards,

    Todd

  4. #14
    Join Date
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    Welcome to WTFDA Forums, Todd.
    Danny
    Shreveport, LA
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  5. #15
    k6sti Guest

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    Peter has made some very minor changes to the 19.3 design and I've updated my writeup and performance curves:

    http://ham-radio.com/k6sti/korn193.htm

    http://ham-radio.com/k6sti/curves.htm

    I include a photo of the prototype installed well above ground for testing with broadcast signals. Peter reports improved reception of difficult signals as far away as 520 km. He says distant weak signals that previously suffered interference from the rear are now free of it.

    Brian

  6. #16
    k6sti Guest

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    Peter has measured F/B for the prototype 19.3 Yagi in a city environment. I've added his measurements to my writeup. I also included a model of a distant unwanted reflection to see how it might affect F/B. The results astonished me.

    http://ham-radio.com/k6sti/korn193.htm

    Brian

  7. #17
    k6sti Guest

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    Below is a message I received from VHF Teknik AB. Looks like I was a bit premature thinking the 19.3 might be commercially available. I was surprised how many of the smaller 15.11 design they have sold.

    Brian

    ------------------------------------------------

    > By the way, I've been telling people that VHF Teknik AB would probably
    > be offering the 19.3 for sale. Is that true?


    We haven't decided yet Brian it is quite costly to make a kit and no one
    have been asking for it, 26 of the 15.11 are mounted around the globe
    mostly Europe but also Canada, Australia and Brazil is on the map.
    Sven
    Last edited by k6sti; 10-08-2010 at 08:06 AM.

  8. #18
    Join Date
    Jul 2005
    Location
    Enfield, CT
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    There's not much of a demand for FM antennas these days, I guess. Ed Hanlon found that out. He sold as many of his APS9bs and 13s as he could and now he's out of business.

    What I heard was that Ed dumped his remaining antennas on eBay and got what he could for them. VHF Teknik is probably wise to not offer it commercially.

    FWIW, anyway.
    Mike B.
    Enfield, CT
    -72° 30' W/41° 59' N
    FN31RX

    Mike's TV and FM DX Page
    Online since 1999 and still going!

  9. #19
    k6sti Guest

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    Peter made some additional F/B measurements on the 19.3 over the weekend. I've added them to my writeup here:

    http://ham-radio.com/k6sti/korn193.htm

    Here are some comments from Peter:

    "In practical tests, which is what counts, like when receiving the 420 km distant BFBS in Germany, the 19.3 gets it cleanly, whereas with the old 14 element antenna there is considerable breakthrough from a Swedish transmitter from behind, often taking over completely.
    So when switching antennas, a new transmitter is heard although both antennas point in the same direction! - Thanks to the improved F/B.

    Going by car to the summer house yesterday afternoon, I could get BBC from the UK on the car radio!
    Having arrived I turned the 15.9 west, and easily got BBC on 13 frequencies, most of which achieved three signal strength bars with RDS on the XDR-F1HD. Distances are around 980km across the North Sea. Also from Germany some 500km distant stations produced similar levels."

    The 15.9 is an earlier version of the 15.11 described here:

    http://ham-radio.com/k6sti/korn1511.htm

    I've attached a photo showing the 19.3 and the 14-element antenna, both aimed south toward Germany. The four guy wires on the mast are made of nonconductive, pre-stretched polyester (what we call Phillystran).

    Brian

  10. #20
    Join Date
    Jul 2005
    Location
    Enfield, CT
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    Going by car to the summer house yesterday afternoon, I could get BBC from the UK on the car radio!
    Having arrived I turned the 15.9 west, and easily got BBC on 13 frequencies, most of which achieved three signal strength bars with RDS on the XDR-F1HD. Distances are around 980km across the North Sea. Also from Germany some 500km distant stations produced similar levels."

    Those receptions are because there's a HUGE tropo opening going on over there from the UK to Germany and all points in between as I type this.
    Mike B.
    Enfield, CT
    -72° 30' W/41° 59' N
    FN31RX

    Mike's TV and FM DX Page
    Online since 1999 and still going!

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