Slinky antennas
Patrick
trying the Slinky beverage and maybe a Vertical, dipole or just
straight..has anyone had experience with outdooor vertical slinkies?
W5LZ
Patrick,
If you just want to 'play' with a 'slinky' antenna,
have fun withit. They make an almost good back-up
antenna. Or, if you just can't use a 'real' antenna, they
make an almost good substitute (better than nothing).
If you put one outside, it's difficult to keep the SWR
constant because of a constant change in the 'bounce' of
the 'slinky'. You can stabilize it, but it's a pain. The
one good thing about a 'slinky' antenna, if you get tired of
it you can always 'play' with it.
'Doc
Yuri Blanarovich
3 to 5 slinkies, thread the rope through it for support, stretch it over 100 to
200 feet, put matching transformer (600 - 1000 ohm to 50 ohm) and terminating
resistor (if unidirectional pattern desired). Comes very close to Beverage that
is two to three times the length.
GL Yuri, K3BU, VE3BMV
Reg Edwards
is continuously inductively loaded which increases the characteristic
impedance of the single-wire transmission line above ground. But
probably will make no difference whether the termination is connected
or not.
Likewise the impedance step-down ratio to the receiver is about 100 to
1. Better to use a FET source follower.
Happy experimenting.
--
Regards, Reg.
================================
http://www.btinternet.com/~g4fgq.regp
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Yuri Blanarovich <k3...@aol.com> wrote in message
news:20000518085413...@ng-cl1.aol.com...
W5LZ
Yuri,
Ok, but a beverage is a rotten transmitting antenna, too.
'Doc
Patrick
length of stranded soldered to the end and running down to a 9:1
transformer..
Yuri Blanarovich
>The correct value of termination is several thousand ohms. The antenna
>is continuously inductively loaded which increases the characteristic
>impedance of the single-wire transmission line above ground. But
>probably will make no difference whether the termination is connected
>or not.
>
>Likewise the impedance step-down ratio to the receiver is about 100 to
>1. Better to use a FET source follower.
>
>Happy experimenting.
>--
>Regards, Reg.
The impedance is around 1000 ohms according to KM1H and W8JI measurements,
regular beverage transformers are just fine. Here I use 600:50 ohm transformer
and it is just fine. I connect termination resistor if I need Eu enhancement,
or leave it open for NE - SW bidirectional use. Mine is made from 5 slinkies
and is stretched over 180 feet on the rope tied between the trees, with one
wooden support in the middle.
Ground here is quite good and moist, I use just copper pipes for grounds at
both ends. With dry or poor ground it helps to use quarter wave "radials." KM1H
uses 3 wires fanned out at the termination end with around 1k ohm resistors.
(Use carbon type 2W or more to prevent damage by static from lightning.)
K6SE found that using steel wire with some resistance for Beverages helps the
unidirectional pattern, letting the slinkies rust a bit might actually help :-)
You need to be careful with slinkies when stretching or contracting, they tend
to go wild if jump out of hand. You need to slowly "unwind" it (let it rotate
on the rope) as it stretches. Otherwise thing has its own mind and likes to
turn into a puzzle of wild artistic bundles.
I also use "Dog Loop" receiving antenna, which is about 800 ft insulated wire
loop (almost square) around the property, burried abt 1 inch. This originally
was supposed to be the electric fence for the dog, but doggie got smart without
it, so I put 600 ohm tranformer on it and use it for receive, it needs abt 20
dB preamp, signals are low, but discrimination against the neighborhood garbage
from TVs and dimmers is great.
Other "clandestine" low band receiving antennas I used was "street beverage" -
wire running in the gutter on the street (overnight) or AC wiring ("ground"
side is fine) through HV blocking capacitor through a tuner.
Yuri K3BU, VE3BMV