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Topband: Matching Transformer

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Subject: Topband: Matching Transformer
From: "Lee K7TJR" <>
Date: Sun, 28 Dec 2008 11:20:51 -0800
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A couple of observations on matching Bobs Beverage. 
    First I cannot figure out why some are suggesting a Balun in addition to the
 fine Job Bob did making the ISOLATED winding matching transformer. Unless
 I am missing something I would think that the isolated winding would be every
bit as good as any balun and therefore a balun is not needed at the antenna end?
     I agree with Joe that the radials when resonated will not affect the 
of the antenna, however I have measured many radials for surge impedance
referenced to grounds etc and they do indeed show resonant properties. What I
 believe is that resonating radials puts the ground side of the coax connection 
 a low impedance point in the antenna/ground system of radial challenged systems
and you may see less RF voltage on the coax shield in reference to ground. This
 may be helpful for common mode problems. Of course this only occurs when 
 are few and short. The radials are all in parallel at the connection point 
causing a
much lower impedance point with greater numbers and random surge impedances
 of radials. Sound familiar, more radials is better!
    I also think that Bobs Beverage must be very close to his TX antenna if he 
is able
to tie into the radial system. This surely will cause some coupling of noise 
into the
 Beverage antenna. Tying into a radials system is bad news. Not recommended.
Try to keep your Beverage as far away from your TX antenna as you can.
    On the Beverage, signals will come from the end with the termination 
resistor and
 no resistor is needed on the transformer end. Signals will come from the 
that is opposite the transformer not from behind it with a resistor terminated 
Without the resistor signals will come from both ends of your wire.
    Bob mentioned a preamp and so it is hard to judge what his comment means 
 signal levels. It would be best to try the Beverage without a preamp to make 
sure that
 its output is indeed below the level of the TX antenna as it should be.

Lee  K7TJR  OR
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