----- Original Message -----
From: <steve_lacourse@agilent.com>
To: <towertalk@contesting.com>
Sent: Wednesday, September 24, 2003 5:48 PM
Subject: [TowerTalk] Ferrite Bead Balun Impedence Req'ts for Quad
There's no need for the 1/4 w/l 75 Ohm traffos Steve.. With all of those
elements, and if your using the standard Gem Quad spacing, you'll find the
feed impedance will vary from 40 to 80 Ohms approx, depending on band.. L B
Cebik has a good writeup on that whole subject.. Take a peek at
http://www.cebik.com/quad/quad7.html
I use wider spacing than the Gem Quad, and use 50 Ohm feeds, which gives an
excellent match.
http://www.iol.ie/~bravo/
I was using 6 beads on each of the RG213 lines, but now I use 12 turns of
RG58 wound on a T200-2 iron dust core.. I find that arrangement lighter, and
easier to handle.
73
John EI7BA
>
> > I'm putting up a multi-band (20,17,15,12,10 & 6) quad antenna (2 el Gem
spider quad) and will be feeding each band wire with a separate feedline
through a switchbox (Ameritron). Each feedline between the switch & antenna
will be a 1/4 wave stub of RG62 or RG11 cut to length. At each feedpoint, I
intend to put a ferrite bead balun on the coax to help minimize wire
interaction.
> >
> > While I think the right bead mix is #77 (or maybe #43) to suppress 10 -
50 MHz, what I don't know is how much impedence do I need and thus, how many
beads to put on the line. Somewhere along the way, I read that the balun
impedence should be 5x the load impedence.
> >
> > If the quad is at 100 - 130 ohms, should I design for 600 ohms of balun
impedence? Why 5x and is this a valid rule of thumb?
> >
> > 73's
> > Steve KD7NTK
> >
> >
> >
> >
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
>
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>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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