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Re: antennas

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  • jchutch02492
    I briefly considered something like this for 6M & 2M, but decided against it after running some models on EZNEC. I believe you may find log periodic designs
    Message 1 of 3 , Dec 2, 2002
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      I briefly considered something like this for 6M & 2M, but decided
      against it after running some models on EZNEC. I believe you may
      find log periodic designs that could cover both 2M & 70cm, but wonder
      if you would be able to get the gain you want for weak signal work
      (particularly if you're going to try EME - not that I have experience
      there). In my case, I decided just to stack beams for my two bands
      of choice. I'm still in the building phase on one of them, but have
      read (and modelling seems to confirm) that separation of 5 feet or
      more is sufficient, so it doesn't seem to be too much for a small
      rotor. Fro whatever it may be worth, two good 2M designs I've come
      accross: K1FO scalable beams, in both the ARRL Handbook and Antenna
      Handbook (scalable designs are given for both 144 & 440 MHz), and OWA
      design on Cebik's web page -- see "Tales and Technical" link at
      www.cebik.com. You probably can find log periodic designs on cebik,
      as well, but I haven't really looked for them.

      Good luck.

      Joe, KB1CJ

      --- In wsjtgroup@y..., "kenneth" <kenneth@b...> wrote:
      > Can anyone give me some idea on a antenna setup for 2 mtr and 70
      cm . . .
    • Lance Collister, W7GJ
      Hi Ken, MNI TNX - I will certainly add the photo to my web page! Great to see your 2 yagi 6m array with elevation! I am sure others will be very interested
      Message 2 of 3 , Oct 28, 2011
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        Hi Ken,

        MNI TNX - I will certainly add the photo to my web page! Great to see your 2 yagi 6m
        array with elevation! I am sure others will be very interested too!

        As far as comparing different WSJT versions, I know there is a lot of anecdotal
        opinion in support of one version or another. I always monitor signals on two
        separate computers running two different sound cards and sometimes even run two
        different versions of WSJT simultaneously on one of the computers. On all my 3
        computers here, WSJT9 always is superior to other versions. But then, none of them
        are Dell, either, which have had reported problems of various sorts running WSJT
        programs.

        I can't guarantee that you will have the same results as I do, given the sampling
        rate of your sound card and the way you have the program set up at your place, since
        I think those DO make some difference. The only person I can suggest to contact with
        your question is K1JT, although there might be someone else in the WSJT user group
        who could address your question.

        My personal opinion is that you need to:

        1) Use WSJT9
        2) Make sure your 6m feedline is less than 1 dB loss
        3) Install a low noise external preamp in the shack
        4) Use the program and receiver settings as shown on my checklist for JT65:

        http://www.bigskyspaces.com/w7gj/JT65.pdf

        5) Check your QTH and setup for stray noise. You may want to check for general noise
        sources (computers, switcher power supplies, hum on your audio lines, etc.) which
        could be raising your noise floor. Usually when I elevate, the "no signal" JT65A
        decodes show a background noise level of -32 or -33dB. I you are not seeing things
        this quiet, then that may be your problem.

        GL and VY 73, Lance

        On 10/28/2011 1:09 PM, Ken Boston wrote:
        > Lance;
        >
        > I have sent you a picture of my small, elevatable array, on my roof mounted 8 foot
        > glen martin tower. Feel free to add to your ‘rouges gallery’.
        >
        > Also;
        >
        > Just a thought, I have been trying to figure out what works best in order to get the
        > best results decoding the weakest JT65A traces, and came up with the following idea.
        > Somehow, if you have enough computer hardware sitting around, it might work best if
        > you can put JT65A running in TX into a weak signal source, like a transmitter running
        > very low power. In my case, I have an HP8648A synthesized sig gen, that has an
        > external modulation port into which I could drive a JT65A source from a laptop. I can
        > set the generator to create an AM signal, and crank down the output veeeery low, and
        > then radiate from a small whip. (I have done this with carrier to check RX relative
        > sensitivity, and found that trying to do this direct, generator to antenna port,
        > wouldn’t work because the weak signal RX chain picks up signal from inside the
        > generator, going around the attenuator output.) Since the signal is AM, you would
        > ignore the carrier and the opposite sideband.
        >
        > This would allow me to evaluate different radios, front ends, preamp/no preamp, ect.
        >
        > I have also been trying to learn what combination works the best, and have been
        > hearing some of the guys claiming different response thresholds from various release
        > dates of the JT65A software package. I also need to determine if I could do better at
        > decoding using a different (better) sound card, rather than the sound cards built
        > into the laptop(s) I have been using. (Dell Lattitude 610 and the like) I would think
        > the above described test setup will help with this sort of evaluation.
        >
        > As I mentioned earlier, I think I am about 2 dB worse than the other op’s in my RX
        > decode capability, and the front end sensitivity may not be the only hurdle from this
        > regard.
        >
        >
        > Again, Thanks for your help and encouragement.
        >
        > Ken W9GA
        >
        > PS, can you think of anyone else who might add comments to my questions.
        >


        --
        Lance Collister, W7GJ
        (ex WA3GPL, WA1JXN, WA1JXN/C6A, ZF2OC/ZF8, E51SIX, 3D2LR, 5W0GJ)
        P.O. Box 73
        Frenchtown, MT 59834-0073
        USA
        TEL: (406) 626-5728
        QTH: DN27ub
        URL: http://www.bigskyspaces.com/w7gj
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        Skype: lanceW7GJ
        2m DXCC #11/6m DXCC #815

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