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Author Topic: dimond cp6  (Read 3409 times)
2E0ALL
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Posts: 2




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« on: January 02, 2004, 04:47:23 PM »

hi all ..
i have a dimond cp6 vert antenna  it covers 80-10 meters bands...
im haveing a problem with this,,, swr is ok but it doesnt seem to perform well,,, has any one got one of these antenna i would like to know how hight u hve this  and maybe any tips on getting this antenna working better   thanks all the best 73,s andy
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WB2WIK
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Posts: 21836




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« Reply #1 on: January 05, 2004, 06:16:48 PM »

The CP6 is very small, very narrowband and only rated for low power operation, which is a certain clue that its traps dissipate power (otherwise, the antenna could be rated for 1500W PEP easily)...as such, although there are many in service, it's not much of an HF antenna.

I installed a CP6 for a local ham a few years ago, placing the base of the antenna up about 45 feet above ground on a small tower installed on the roof of a 3-story condominium building.  At that vantage point it worked pretty well for its diminutive size (15' tall or so), but the antenna was the highest thing in the neighborhood for several blocks around, so it had nothing to couple to or to interfere with its ability to radiate.

When I tuned the CP6 at ground level, I had it "dipped" in the center of each band; when I moved the antenna to the rooftop, I had to start all over again, and adjust *everything* to re-resonate it in each band.  That's a sure sign that the antenna is extremely high-Q and easily detuned by surrounding structures, which I had at ground level but not at rooftop level.

It is a critical antenna to tune, for sure.  It's an "electrical quarter wavelength" on each band, but let's face it: On 80 meters it only measures 0.06 wavelengths long, which means it cannot be more than 23.8% efficient, compared with a quarter-wave on that band.  Since it also has trap losses, I'd downgrade that 23.8% to maybe 10%.

Another example of an antenna having a nice, low SWR but not actually working particularly well.  Still, for its size, weight and cost, the CP6 does about what it should do and it's not a bad deal for those who really can't install anything larger.

WB2WIK/6
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