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Old April 18th 07, 03:34 AM posted to rec.radio.amateur.antenna
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Default Velocity factor

Does anybody have a velocity factor chart? I need the information for 13
gauge stranded plastic cover?
TIA
Howard W3CQH


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Old April 18th 07, 02:30 PM posted to rec.radio.amateur.antenna
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Default Velocity factor??

John Doe wrote:
At the present time - my MFJ Antenna Analyser has it resonating at approx
10.5Mhz, and I am trying to get it to resonate at 1.8Mhz (160M).


What length and type of feedline are you using? If ladder-
line (or similar) your have a tuned-feeder system and the
resonance frequency may not be anywhere near the stand-
alone antenna resonant frequency.

What does the antenna analyzer say is the resonant
frequency closest to 1.8 MHz?

With the two above pieces of information, we can
estimate what needs to be adjusted to obtain a
system resonance of 1.8 MHz.
--
73, Cecil http://www.w5dxp.com
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Old April 18th 07, 03:20 PM posted to rec.radio.amateur.antenna
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Default Velocity factor??


I have made a indoor/outdoor STEALTH of sorts, a Multiband HF LOOP Antenna,
approximately 540ft long (from center connector back around to the other
side of the connector). I am using 13 gauge - copper - stranded plastic
cover - wire! Does anybody have a velocity factor chart?

At the present time - my MFJ Antenna Analyser has it resonating at approx
10.5Mhz, and I am trying to get it to resonate at 1.8Mhz (160M).

I need the info to try and figure out how much I need to reduce the overall
circumfrence.

73's

Howard W3CQH


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Old April 18th 07, 04:08 PM posted to rec.radio.amateur.antenna
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Posts: 106
Default Velocity factor??

On 18 abr, 16:20, "John Doe" wrote:
I have made a indoor/outdoor STEALTH of sorts, a Multiband HF LOOP Antenna,
approximately 540ft long (from center connector back around to the other
side of the connector). I am using 13 gauge - copper - stranded plastic
cover - wire! Does anybody have a velocity factor chart?

At the present time - my MFJ Antenna Analyser has it resonating at approx
10.5Mhz, and I am trying to get it to resonate at 1.8Mhz (160M).

I need the info to try and figure out how much I need to reduce the overall
circumfrence.

73's

Howard W3CQH


Hello, John,

The effect of a 1mm thick PVC coating on 1.8mm diameter of copper on
phase velocity is less then 2 percent below that of light. So c is
about 0.98...0.99*c0. This is without correction for capacitive fringing
at the ends of the wire and without correction for influence of
ground.

As your wire is about 1 wavelength for 1.8 MHz, your loop should have
a low impedance and therefore you should find a point of resonance
around 160 m band (assuming you did connect the wire directly to the
MJF). Maybe you should use a balun between your MFJ and 1WL loop.
You will get resonance at near multiples also.

Best Regards,

Wim
PA3DJS.

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