Mast Material / Metal ?

[jrd426]

Hi guys. For a fiberglass type base antenna big stick, antron etc, is a metal mast pipe needed vs say a finerglass pole. Is the typical metal mast needed for this type antenna for counterpoise ? Lets use a antron type antenna without groundplane / kit. Would the coax coming straight down attached to a fiberglass pole work ok compared to a metal pipe. Any difference with swr or anyrhing ? Thx!

 

[loosecannon]

they would actually perform better on a fiberglass mast.

metal masts create a "leaky capacitor" to ground and can mess with radiation patterns.

strength could be an issue.

with the antron 99 in particular, you would want to make sure the first 9 feet of coax coming down from the feedpoint runs straight down vertically as this antenna uses the first 9 feet or so of the coax for a counterpoise.
that would also mean that if you wanted to use a choke balun, you'd want to put that 9 feet down from the feedpoint as well.

not sure about the big stick but i believe you could choke at the feedpoint of that one.

now here's something SUPER important to know. to achieve this improved performance you can't run a long ground wire down from the feedpoint as this would essentially be recreating the metal mast.
this means that you MUST have a lightning arrestor (a real one) connected to a ground rod (or more than one) before the coax enters the shack.


this subject has been covered a lot here on the forum, and many of the discussions centered around the avanti astroplane design so search those terms to find good threads.
there is also a thread about isolating end fed antennas from their support structures that is a good read.

hope this helps!
LC

 

[jrd426]

they would actually perform better on a fiberglass mast.

metal masts create a "leaky capacitor" to ground and can mess with radiation patterns.

strength could be an issue.

with the antron 99 in particular, you would want to make sure the first 9 feet of coax coming down from the feedpoint runs straight down vertically as this antenna uses the first 9 feet or so of the coax for a counterpoise.
that would also mean that if you wanted to use a choke balun, you'd want to put that 9 feet down from the feedpoint as well.

not sure about the big stick but i believe you could choke at the feedpoint of that one.

now here's something SUPER important to know. to achieve this improved performance you can't run a long ground wire down from the feedpoint as this would essentially be recreating the metal mast.
this means that you MUST have a lightning arrestor (a real one) connected to a ground rod (or more than one) before the coax enters the shack.


this subject has been covered a lot here on the forum, and many of the discussions centered around the avanti astroplane design so search those terms to find good threads.
there is also a thread about isolating end fed antennas from their support structures that is a good read.

hope this helps!
LC

Thanks LC. Helps allot. 73

 

[sp5it]

It is enough to insulate antenna from mast.
Mike

 

[Alexis Mercado]

Do I need to isolate an A99 if I install it on top of a 3 element Mosley TA-33 Yagi antenna ? A99 will be around 4-5 feet above the yagi .