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Message |
    
Jd1020
New member
Username: Jd1020
Post Number: 1
Registered: 10-2006
| | Posted on Wednesday, October 11, 2006 - 8:04 pm: | 
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I have been told that these antennas have to be set at an approximate height of 36 ft. to work properly. Is there any way to set the SWR on the antenna before you u-bolt it to a pipe that is 20 ft. in the air? Also, what is the benefit of the ground plane kit at the base of the antennae. I'm new into this and don't understand it. Any information you can give me will be helpful. Thanks! Dale |
Dx431
Senior Member
Username: Dx431
Post Number: 1191
Registered: 2-2002
| | Posted on Thursday, October 12, 2006 - 2:49 am: |
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The SWR is preset from the factory. No tuning necessary. Bolt it to the mast, connect the coax and your done! The A99 works well at any height. |
Tech237
Moderator
Username: Tech237
Post Number: 556
Registered: 4-2004
| | Posted on Thursday, October 12, 2006 - 9:47 am: |
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Actually you can adjust the SWR that is what the two black rings near the bottom are for. I have used mine from 4.5 ft above ground (angled at around 20 degrees from vertical as it was mounted on a Satellite TV Dish bracket and worked over 70 countries between March 99 and September 2000) and then mounted on the vent pipe sitting only 2ft above the roof. Later I mounted it 25ft up on a telescopic mast.
In all cases the SWR (I cut about 6 inches off so that it would work where I wanted it to 28.350MHz) was below 2:1 anywhere bewteen 15MHz and 29.9Mhz.
Right now the exact same antenna (a little beat up after being bashed by tree branches for a couple of years) is sitting in a storage waiting permission to put the mast up and get antennas back into the air.
I never used the groundplane kit in any of my situations and never had any complaints with the antenna. FYI the radios used over the 7 years have included IC-706 (wish I still owned), IC-725, TS-520 and a HTX-10. In all three mounting locations I heard very few stations I could not work and that included several countries worked running less than 5w on 10m.
Now having stated all that I will say that the 36ft height wont hurt. Generally any antenna the rule of thumb is "the higher the better" and 36ft is a wavelength on 11m. Try it at a lower height first and then if you are not happy try at thew 36ft. 18-20ft should work quite well for any 11m antenna. |
Dx431
Senior Member
Username: Dx431
Post Number: 1193
Registered: 2-2002
| | Posted on Thursday, October 12, 2006 - 11:32 am: |
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The A99 is pretuned from the factory for 27.2050
(chnl 20), the center frequecny for 11 meters.There is no tuning, unless of course you plan to use it as Tech237 stated. If for some reason the 99 needs to be tuned, other than stated above, then there is a problem with the coax, pl connectors or the ant is defective. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2150
Registered: 9-2004
| | Posted on Saturday, October 14, 2006 - 10:18 pm: |
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get a 10 foot mast section.
find a spot on the house where there is some dirt or other ground covering below the facia board.
dig a small hole about 6" to 12" deep, put the mast in it, and use a clamp to secure the top to the facia board.
mount antenna to mast, hook up coax that will be used in final installation.
if you have help, hook the SWR meter up at the antenna using a short jumper.
if not, just use the SWR meter in the shack.
check SWR on ch. 1 and 40.
should be approx. 1.5 or less on both.
if SWR is higher on ch.1, lower the rings one full turn, and check again.
if SWR is higher on 40, raise the rings one full turn and check again.
try to balance the two readings.
after adjusted, tighten the two rings against eachother using channel locks so they wont move with wind and vibration.
dont forget the lock washers in between the antenna sections.
the groundplane assy. is to stop any of the signal from firing downward. the idea is to reduce TVI and also lower the angle of radiation a bit.
the extent to which it works is debateable.
when i used one, the groundplane kit made no difference in signal strength or TVI, and just made the antenna look obnoxious to me.
good luck
matt |
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