BEST ANTENNA FOR MY LOCATION?

[N6WDR]

Ok... I have my mind set and I am going to shunt feed my tower.

I went to my storage unit yesterday and got a 500ft roll of 10 gauge wire to add some more radials to my towers grounding system.  The towers guy system is no problem since I have phillystran cables in place.  As I mentioned before it is a rohn 25 at 50ft with a 43ft boomed 10M beam at around 58ft on a hazer system.  I have the Hazer grounded to the tower and I am working on grounding the mast to the tower for added measure.

The question I have is.... If I use my MFJ 259B to find the 50 ohm feed point on the tower for the shunt line, Can I hook up the center conducter of my 1/2" Heliax to the shunt line and of course the ground to the shield, and be able to use my Nye Viking Tuna? . This system will be used with a Henry 2K so I want to make sure everthing is done right so things don't go up in smoke.  Or would it be safer to add a vaccuum variable out at the base of the tower?

Richard

[Steve - WB3HUZ]

If you found the 50 Ohm point, you wouldn't need a tuner.

[WA1GFZ]

Be careful with all cables running up the tower including rotator cable. Attach coax shield of beam to the base of the tower. Bypass all rotor cable leads to the baes of the tower. You will fry the rotor cable and maybe the rotor if you do not bypass the leads. It might be a good idea to bypass the rotor cable leads at the rotator. All cables running up the tower lege will get RF coupled to them when you shunt feed the tower and if they are not terminated to the tower could generate some high voltage RF due to the length. You can assume zero volts at the grounded base and very high voltage above the shunt connection.

[N6WDR]

The 7/8 Heliax to the beam I have grounded at the base of the tower and at the entrance to the shack so that is taken care of.

How would I bypass the rotor cable? This is all new to me, so I am in stupid mode right now lol. I was just planning on disonnecting the rotor from the control box when I was going to transmit, but I see what you are saying.  What do I need to do to bypass it?

Richard

[WA1GFZ]

.01uf disc ceramics at the highest voltage you can find. I bet a common mode choke at the rotator would also be a good idea to keep RF out of the innards. Tom Vu played with shunt feeding so maybe he can add some ideas.
I would terminate the 7//8 in a few places to keep it from becoming a radiating extra element.

[N6WDR]

Ok... I will break the 7/8's up as well.  How big on the voltage should I go on the caps?  I think I have a bunch of 5k lying around, I will have to make sure though, is that high enough or will the voltage need to be higher?

On the rotor cable I am guessing that you ground all eight wires?  If so I will do that prbably at the top and bottom just incase.  I have a weather station on the tower as well so I will ground those leads as well while I am at it.

Sorry for all the questions, Just would rather ask then learn the hard way by burning something up.


Richard

[WA1GFZ]

I think they are very good questions. You want the tower leg voltage the same as the cable voltage. as you go up the tower voltage increases until you hit the quarter wave length.