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Design question, from just a hobbyist

Discussion in 'Electronic Design' started by Dave, Nov 2, 2007.

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  1. Dave

    Dave Guest

    I am wanting to take my (homebrew) tunable, active antenna for shortwave
    reception to the next level, and make it independant of an external antenna.
    To do this I have installed two 43" whips which I would like to have working
    in tandem. They are spaced approx. 5.5 inches apart, and capable of being
    spread to any angle through hinge-joints (sorry, I don't know what that is
    called.) Question is, just for plain-vanilla operation, can I attach both
    of their leads to my RF input and expect some sort of useful result? I am
    planning on using an impedance-matching setup such as was described in the
    July 2001 QST article about the Miracle Whip antenna (The Miracle Whip: A
    Multiband QRP Antenna, PP 32-35) . I am wondering if I need something like
    an NE/SA602 or 612 mixer to condition the antenna inputs before feeding them
    to my RF amplification stages, in case the two signals are out of phase with
    each other (a distinct probability, I suspect.)

    If anyone would care to comment, I'm all ears.

    Thanks for any input.

  2. Eeyore

    Eeyore Guest

    Rabbit's ears ? ;~)

  3. Dave

    Dave Guest

    Yeah, basically. :) And it almost works!

    Seriously, I've hooked it up and tried it out, and am able to pick up a
    couple of stations, weakly and with a lot of noise. Although current
    conditions appear to be less than optimal. The external antenna doesn't do
    much better, and it is usually a gangbuster. Will have to give it a couple
    days, and then maybe try out my other ace-in-the hole, a different toroid
    for the tank circuit with better coupling and response to the Q-multiplier.
    I took it out because it made the device too sensitive, without being able
    to tune the antenna. Don't know if it'll help, but it'll be interesting to
    see what it does.


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