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Old September 5th 03, 02:02 PM
Richard Cranium
 
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Default Ground plane kit

(Antennahead1) wrote in message . com...
I am thinking about getting a 5/8 wave antenna, most likely the Imax
2000. Does the GPK for it wrap around so that it is centered? I can't
tell from the drawings I have seen posted. If I can get only a bracket
or make one myself, would the performance be better with longer
radials like Francis 8' antennas or something similar? How does the
angle affect gain? I an interested in reducing TVI, improving
groundwave performance and reducing skip as much as possible. What is
the difference if the radials are horizontal vs 45 degrees or some
point in between? Does the bracket need to be below the matching
circuit rings or is there another position that would be better? I am
using a 37' pole and it is well grounded with three 8' rods and
another dedicated rod through the basement floor that attaches to my
radio. TVI has not been a big problem with my A99 but I would like to
improve ground wave performance. With my current setup, I typically
tx/rx out to 40 or 50 miles. Is that good/typical for an omni type
antenna? How much farther can I expect to reach with a 5/8 wave? Has
anyone ever removed the flat mounting plate on the Imax 2000 so the
A99 radial kit can be used?

http://groups.yahoo.com/group/11meteramps/

If you're looking to "reduce skip", then you do not want a 5/8ths-wave
groundplane; they produce a lower angle of radiation which imcreases
"skip". For what you want, it sounds like you've got about the best
antenna. 40 to 50 miles range from an Antron 99 is very good.
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Old September 6th 03, 04:58 AM
Frank Gilliland
 
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In ,
(Antennahead1) wrote:

I am thinking about getting a 5/8 wave antenna, most likely the Imax
2000. Does the GPK for it wrap around so that it is centered? I can't
tell from the drawings I have seen posted. If I can get only a bracket
or make one myself, would the performance be better with longer
radials like Francis 8' antennas or something similar?


I don't know about those specific antennas. I do know that the A99 may or may
not work better with the ground plane kit (mine didn't).

How does the
angle affect gain?


Lower radiation angle improves gain at ground level. A Shakespeare Bigstick is a
vertical coaxial antenna, and it's radiation angle is parallel with the horizon
(ideally). A 5/8 wave antenna will radiate up at a shallow angle, but the lobe
is 'longer' than a half-wave dipole (again, ideally). People using both have
different reports. So it's really a coin-toss.

I an interested in reducing TVI,


You should get your radio tuned up by a legitimate CB shop or ham (not one of
those 'golden screwdriver' techs), and add a low-pass filter.

improving
groundwave performance


Groundwaves at 27MHz are limited mainly by the terrain. If you are in a hilly
area or have lots of buildings, there's not much you can do. If the area is
relatively flat, just mount the antenna as high as possible. But the latter
follows the law of diminishing returns at about 20 to 30 ft.

and reducing skip as much as possible.


There's not much you can do about that either, except to stay away from the
toiletbowl (Channel 6), or use a beam antenna.

What is
the difference if the radials are horizontal vs 45 degrees or some
point in between?


The angle of the ground radials changes the input impedance of the antenna. For
a 1/4 wave vertical, if the ground radials are mounted 45 degrees down, the
input impedance is about 50 ohms, which matches the radio and coax quite nicely.
BTW, that applies for full-length ground radials. I have doubts that those short
little nubs Solarcon claims are ground-plane radials will behave the same.
Actually, I think they are intended to keep RF off the coax, but who knows....

Does the bracket need to be below the matching
circuit rings or is there another position that would be better? I am
using a 37' pole and it is well grounded with three 8' rods and
another dedicated rod through the basement floor that attaches to my
radio. TVI has not been a big problem with my A99 but I would like to
improve ground wave performance. With my current setup, I typically
tx/rx out to 40 or 50 miles. Is that good/typical for an omni type
antenna?


Very good, and much better than typical (assuming you are running legal power).
So well, in fact, you should consider the old proverb, "if it ain't broke, don't
fix it".

How much farther can I expect to reach with a 5/8 wave?


Beats me. People have claimed different results. I don't think you will gain a
whole lot, if any, and definately not as much as a beam antenna. You can make
some BIG gains with a beam.

Has
anyone ever removed the flat mounting plate on the Imax 2000 so the
A99 radial kit can be used?


I dunno.

http://groups.yahoo.com/group/11meteramps/

It's nice to see someone paying more attention to antennas, since they can
provide amplifier-like gains for Tx -and- Rx without the splatter-box.







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Old September 6th 03, 08:11 AM
 
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get a beam antenna

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Old September 8th 03, 07:55 PM
Dino
 
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The "Mastadon" never came to market. Its the INTERCEPTOPR 10K!

http://www.a1antennas.com/

Several sing the praise of the beefed up
version by Jay-in-the-Mojave he calls a Mastadon. Assuming you'll be on
eleven meter, concerning the skip, it's fading until next cycle when it
will return again. When it's running hard, all you can do is change the
freq or get a directional.


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