[CQ-Contest] SO2R stubs.
callbob at home.com
Tue Nov 13 06:42:34 EST 2001
Dave there is a matching stub table for all freq (+warcs) on my website at
----- Original Message -----
From: "David O Hachadorian" <k6ll at juno.com>
To: <cq-contest at contesting.com>
Sent: Monday, November 12, 2001 8:53 AM
Subject: Re: [CQ-Contest] SO2R stubs.
> On Mon, 12 Nov 2001 17:23:23 +0000 Tom Osborne <w7why at harborside.com>
> > I've been compiling some data to build the stubs here and was
> > wondering, what is the formula for determining the stub length.
> > Is it just cut and try or what.
> > I tried 234/F and for 40 meters came up with 21.75 feet. Most of
> > the posts say 23 feet open or shorted work best. Where did the
> > 23 foot figure come from. I have a bunch of RG-6 CTV coax here
> > that I'd like to use, but it has foam instead of plastic
> > dielectric. How to figure the length of stubs using the foam
> > instead of plastic? Thanks
> > Tom W7WHY
> quarter wave in coax (ft) = (246/F) x (velocity factor)
> where F is freq in MHz
> velocity factor:
> RG 213/8/58 = .66
> RG 6 = .75
> RG 8X, foam RG 8 = .78
> 9913 = .89
> Some of the foam dialectrics may vary from nominal VF.
> I think the best way to put a quarter wave stub exactly on freq is to
> temporarily connect a 1 inch piece of wire from the shell to the center
> pin of the stub's PL-259. Arrange this wire into an "L" shape, making
> a little loop with the center pin and shell of the pl-259. Lightly couple
> a dip meter into this loop. This works on an open stub, which is handy,
> because you'll be cutting little pieces off to bring it up to frequency.
> Dave Hachadorian, K6LL
> Yuma, AZ
> K6LL at juno.com
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