[TowerTalk] Making stubs - questions
Al Williams
alwilliams@olywa.net
Sun, 17 Sep 2000 08:13:19 -0700
For what purpose are the stubs used? Is there a significance in them being
"hardline stubs"?
k7puc
----- Original Message -----
From: "Robert Shohet" <kq2m@mags.net>
To: <towertalk@contesting.com>
Sent: Sunday, September 17, 2000 7:03 AM
Subject: [TowerTalk] Making stubs - questions
>
> Hi Guys,
>
> After poring through the "archives" I have a few more simple (and
possibly
> naive) questions regarding making hardline stubs and would appreciate any
> help.....
>
> 1) When making stubs that require an open at one end, is it necessary to
> terrminate them in a connector or can I just leave it "loose"? Should I
seal
> the end with something if it will be outside? What about if it is inside
> the shack?
>
> 2) If I understand correctly, W8JI suggests that the best place to put a
> stub is 1/4 wave away from the amp. I am having trouble conceptualizing
> this. Each of my antennas comes into a 2 position switch as follows:
>
> Point "Z" Point "Y"
> Amp/Radio B Amp/Radio A----------
> | |
> | ----------------------------------
> | | | | MFJ
> 6-position switch |
> | | | | used
> to select band for |
> | | | |
Radio
> A/Amp A |
> | |
>
> -------|------------------ --------------
--
> -
> |_______________| | | | | |
> | | | | Amp A |
> | | 160 80
40
> 20 15 10 Common to Amp A-----| |
> | |
> | -----------------
> 20 meter antenna switchbox |-----------------------|
> |
> Point "X"
> |
>
> Radio A
>
> Question is ... Where do I put the stub(s)? If I want to use only one set
> of stubs per band then I think that I would use a T Connector put at Point
> "X" with one side as the antenna and the other side as the stub.
>
> If I want to have stubs on each radio/amp then I guess that I would put T
> connectors at Point Y and Point Z with a stub in each of those. Likewise
> for each band on the two position antenna switch. Do I have this
"right"?
> How does one separate the amp from the stub by 1/4 wave? Does one connect
a
> 1/4 wave line at the amp and then use a T connector with one side the
> antenna and the other the stub? If this is correct then I assume that my
> current setup would make this impossible, since each coax jumper between
the
> 2 position antenna switch, 6 position switch and the common are of
different
> lengths (all under 5 feet).
>
> If I am going to use multiple stubs on a given band how do I connect them
to
> each other? With what do I physically separate them?
>
> 3) Does anyone know the approximate Velocity factors for the 1/2" and
3/4"
> CATV hardline? (Not gas-filled) just regular CATV stuff. (1/2" is bare
> aluminum jacket, 3/4" has black PVC jacket).
>
> 4) I assume that the length of the stub should be from the PL259 on the T
> connector end to the far end?
> Or should I just measure the stub without taking into account the stub
> lengthening effect of the hardlineconnector?
>
> 5) Any suggestions on a cheap and accessible supplier of CATV to PL259
> connectors?
>
> These are a lot of questions but I want to so this once and do it "right"
> and I greatly respect the collective experience and wisdom of those on the
> reflector.
>
> Thanks very much for your inerst and your help!
>
> 73
>
> Bob KQ2M
>
>
>
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>
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