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RE: Explain the RG62 thing to me, please...



Hello Hamish

> Hmm. The phasing you describe (RG-62 to both dipoles, with additional
> RG-59 section to one) is quite a bit more complicated than that
> described in the ARRL antenna and satellite books.

You're right - I just opened the book up at pp10-16 and 10-17.

The version you describe apparently assumes a 3/8wl distant reflector, which
I wasn't.

I'm not quite sure how the impedances in this example are coming together to
give a 50 ohm impedance, but hey, if it works, don't fix it!

Without the reflector I calculate 75 ohms in parallel with 108 ohms, which
is 44 ohms - not a bad match. With a reflector that's going to drop quite a
bit.

I was going to suggest to Jim that the theory's OK, but messing around with
these matching/power splitting sections may all be a waste of effort: two 75
ohm dipoles in parallel give you a feed impedance which is about 38 ohms. I
wouldn't be too concerned with feeding that with 50 ohms.

On the subject of the balun I got it slightly wrong in that if you're using
a sleeve balun as suggested you don't connect the antenna [unbalanced] end
of the sleeve to anything.

73 Howard G6LVB


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