For those who believe they are putting 1/4 wave radials on the ground -
it might be important to know/remember that the velocity factor of wire
on the ground is approx. 0.5. Quarter wave radials are actually approx
a half wave electrically - which is why it takes so many of them to get
a monopole down to 35 ohms - each radial presents a high impedance if
its 135 ft long and on the ground. BC stations use quarter wavelength
(mechanical quarter wave) radials because 120 of them will provide a low
impedance when placed in parallel and current share well since each are
a high impedance.
You can easily prove this to yourself. Lay an 80 meter (or higher in
QRG) dipole on the ground and check it with an MFJ. It will be resonant
near 160 meters. Do it quick with a 10M dipole - it will be resonant
around 20M. You can't do that test with a 160 dipole as it will be
resonant around 900 KHz and the MFJ won't go that low.
Want that inverted L impedance down where it should be with very few
radials? Elevate them to eliminate the above effect, or put them on the
ground and make them close to an electrical quarter wave - which is
around 80 feet long - not 135 ft.
Having an inverted L "too long" is just right. It moves the maximum
current up off the ground and is easily tuned out with series C.
73
Hal
N4GG
(Running just great with a low feedpoint impedance from four 80 foot
radials under the vertical, on the ground)
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