[TowerTalk] Making stubs - questions

[Robert Shohet]

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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