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Stand-off distance

9

985chicago

Member
Oct 17, 2009
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I want to put a ground plane antenna for 11 meters on the side of my tower.What is a good stand off distance? I will be transmitting with high power if this makes a difference. A 5 element yagi horz postioned is at the top.I have approx 20 feet from the top of the ground plane to this yagi. Is this still ok ?


985chicago.
 

how much power is high power? some people think 100 watts is high power.... others think 1500 watts is.
 
i doubt it, but i am sure there is a difference between 500 vs 5000 as far as the set up is concerned......... why are you banging your head? youre going to need some aspirin if you keep that up.:)
 
I think that if you put that antenna anywhere on the side of a tower for the 11m band; then it is still going to become skewed/directional. Kinda defeats the purpose of a omni-directional antenna. Sure it will work; but not like a omni should.

Why not break down and allow a Sirio Gain Master, A99, or Imax on the top of your beam? It's not going to have problem with being skewed/directional then?
 
I am wondering the same?? Most people just mount their vertical Groundplane on the same mast right above their horizontal or Yagi beams considering they will not in anyway interfere with one another because of the different purpose or radiating patterns.

This is by far the ultimate easiest and best way to do this and get your full use of the vertical groundplane ;)
 
Well, a ground plane antenna will affect the radiation pattern of a beam. Yes. But using an A99 or imax w/o a ground plane will work. These antennas lend themselves to horizontal beams because they will end up using the beam elements as a counterpoise. Just put a choke on the coax that feeds either the Imax or A99.
 
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Thanks Robb, sure i could mount a ground plane at the top, this would be ideal.The planned ground plane verticle is not the primary antenna.Reasons for not putting it on the top... #1. Additional exposure to lighting. #2. I only chase dx. I think a height of 35' is ok. #3. Cost. To have a contractor climb my tower and install a gp. Labor cost est.$ 600.00. I have seen standoffs 7 feet would this not be ok?
 
will the tower be a director decreasing tx/rx behind it from the antenna ? or increasing tx/rx in the direction of the side of the tower the antenna is mounted on ?
if so mount 3 cheap workman 58's with separate coax runs off each side to a 3-way coax switch box inside and use it kinda like a super scanner . LOL
 
985chicago said:
Thanks Robb, sure i could mount a ground plane at the top, this would be ideal.The planned ground plane verticle is not the primary antenna.Reasons for not putting it on the top... #1. Additional exposure to lighting. #2. I only chase dx. I think a height of 35' is ok. #3. Cost. To have a contractor climb my tower and install a gp. Labor cost est.$ 600.00. I have seen standoffs 7 feet would this not be ok?
Click to expand...

Try it and see. What might be "ok" for you might not be for someone else.
 
The tower will add directionality to the antenna in the direction away from the tower. The further away from the tower you can get it the less of an effect it will have.

I would also expect a tower next to an antenna to affect tuning if not throw it off completely. Even if you get an SWR match, the resonant point can be thrown off quite a ways as the tower adds capacitance that needs to be accounted for for best performance. I wouldn't even attempt to tune such a setup without a good antenna analyzer that can read reactance. Again, the further away from the tower you can get the antenna the less of an effect it will have.

I'm guessing 36' plus is a bit much to say to get it away from the tower.
I'm also guessing that 9' would be quite a stretch, but if you can try and get a minimum of 9'.

Any which way, if you mount the antenna alongside the tower get it as far out from the tower as you can.

If you can mount it up above the other antenna as has been suggested that would be even better.


The DB
 

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