Here are the "tuning" instructions GEM quad supplied. All elements
except driven elements have a two wire stub hanging down shorted at
bottom. Stub lengths of 15" on 20M, 12" on 15" and 12" on 10M. The
bottom and top of stub are spaced with about 3" insulators. The
bottom of each stub is shorted. Make sure that the calculated lengths
for resonance fall near the middle of the stub. One moves the
shorting stub. These stubs must be made secure so they don't blow
around in the wind and short other elements. GEM quad uses small
nylon ropes attached to each stub and pulls them up to the boom or
hub. Secure them first and then proceed with tuning.
This procedure has assumed you have already "tuned" the driven element
to minimum SWR where you want it.
You need a local ham to help you some distance away.
1) Local transmits a signal around s7-s9. You listen on quad
2) Turn quad so that back is towards the station.
3) Move the shorting stub on reflector until minimum signal is
4) Repeat for all bands.
5) Turn quad towards the s5-s6 local station. Move shorting stub on
director for MAXIMUM signal strength.
Note: Max gain does not occur at freq of max f/b ratio.
On a 5 band 4 element quad you have 15 stubs. Each requires lowering
antenna and raising it several times. Lots of work.
73 de Brian/K3KO
> Hi All,
> I currently am completing construction of my first quad beam antenna. I
> am looking for suggestions about how best to tune the elements. Here are
> a few specifics about my system:
> 1) It is a 2-element, 5-band (10-20M).
> 2) Each element set (driven and reflector) are in the same plane.
> System is using qubex mark2 spiders and spreaders.
> 3) System will switch between bands with the Ameritron RCS-8V remote
> 4) Upon Qubex's suggestion the 10,12,and 15 M bands will have 75 ohm,
> 1/4 wave, (RG11) matching stubs. They say stubs are not necessary for
> 17 and 20M.
> 5) The main feed will be 50 ohm triax (belden 9998).
> 6) At this point I have cut all ten elements extra long before I have
> I did have the foresight to purchase the MFJ 259B ant. analyzer for just
> this project. What I am guessing is that I should (one at a time) tune
> each of the driven elements to resonance at mid-band point. It is at
> this stage I'm not sure about the next step.
> Q1) What is a good method to tune each of the five reflectors? I can
> target a fixed frequency off-set from each of drivers (by percentage).
> If so, what should the off-set be?? I'm not sure how to use the MFJ259B
> to tune the F/B or Gain(max), if it can at all. I could use a field
> strength meter but that's subject to error and my neighbors.
> Q2) Is there a suggested order through the bands to be tuning either
> the dir. or ref.? i.e.- 10>20 or 20>10?
> Q3) And finally, any suggestions about what is a good method to secure
> each of the loop ends to themselves and/or coax? I'm using the diamond
> configuration that provides for a vertical spreader as an anchor point.
> Thanks for input!
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List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
Trylon Titan towers, coax, hardline and more. Also check out our self
supporting towers up to 96 feet for under $1500!! http://www.anwireless.com
FAQ on WWW: http://www.contesting.com/FAQ/towertalk
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