Should I run a Sky-wire loop?
 

Should I run a Sky-wire loop?


I currently have a dipole hung by two trees about 30 feet off the
ground.


I would replace the dipole and run the Skywire loop off the same
trees, along with two more trees at the same height as the current
dipole.

This antenna would only be used for receiving, and never for
transmitting, the same for the dipole.

My question is, does anybody think it will make enough of a difference
over the dipole to warrant running it?

I would also like to know what your views are on "grounding" either
my current dipole, or the Sky-wire.

Currently, I have the coax center wire soldered onto one end of the
dipole, and the braid soldered onto the other end. I was told that I
should also ground the braid before it comes into the house and into
the radio.

I do have a ground wire attached to GND screw on the back of the
radio, going outside to a piece of copper pipe pounded into the
ground. Is this enough, or do I need to also ground the braid, and if
so, how? Will grounding help my reception, or decrease the noise on
the line?

Thanks.

A Horizontal Loop will pickup less vertically polarized atmospheric noise. I
am very satisfied with my 480 ft loop that is up 35 ft. For receive only, an
ATU would not be necessary, but it will improve the signal strength at some
frequencies.

My feedline is open line from the corner of the loop to the earth where
there is a 1:1 current type balun. I connect the shield of the coax to a 8
ft ground rod. If your area is prone to lightning, I would install a
polyphazer. The coax runs underground to the shack. The coax is only
connected to the rig when I am actually using the antenna.

This reconfiguration is relatively inexpensive. Go for it and compare the
results.

Joe O, KI5FJ

"Walter" wrote in message
om...
Should I run a Sky-wire loop?


I currently have a dipole hung by two trees about 30 feet off the
ground.


I would replace the dipole and run the Skywire loop off the same
trees, along with two more trees at the same height as the current
dipole.

This antenna would only be used for receiving, and never for
transmitting, the same for the dipole.

My question is, does anybody think it will make enough of a difference
over the dipole to warrant running it?

I would also like to know what your views are on "grounding" either
my current dipole, or the Sky-wire.

Currently, I have the coax center wire soldered onto one end of the
dipole, and the braid soldered onto the other end. I was told that I
should also ground the braid before it comes into the house and into
the radio.

I do have a ground wire attached to GND screw on the back of the
radio, going outside to a piece of copper pipe pounded into the
ground. Is this enough, or do I need to also ground the braid, and if
so, how? Will grounding help my reception, or decrease the noise on
the line?

Thanks.

Walter,
It depends a lot on what type of feed line you use. If
you use coax to feed the loop, performance will probably
be about the same or worse than the dipole. If you use an
open wire or ladder line feed line through a tuner, you will
probably see ~some~ difference between the two antennas. How
much is anyone's guess. I like large loop antennas. I've
found that using ladder line and a tuner will make them usable
on more than one band and usually performs better than a dipole
used the same way (I don't have the best place to put up an
antenna to start with). Every installation is different so
what works great for me, here, may not work very well at your
location. Having said that, try the loop. If you don't like
how it performs, change back.
'Doc

Joe O wrote:

A Horizontal Loop will pickup less vertically polarized atmospheric noise.

Could you give an explaination for why this is?

Dale W4OP

If I use a Polyphaser lightning arrestor, that is grounded to a
grounding rod, and hooked to the feed line, and the radio, will that
do the same job as grounding the coax feed line braid?

or are we talking about two different grounding steps?

thanks for the help!!!

I have created a new group on yahoo about skywires.

please visit and add your comments.

thanks

http://groups.yahoo.com/group/SkyWires/

Dale, W4OP wrote:
"Could you give an explanation of why this is?"

Joe O. had written:
"A Horizontal Loop will pickup less vertically polarized atmospheric
noise."

ON4UN wrote on page 10-7 of "Low-Band DXing":
"The loop will act as any horizontally polarized antenna over real
ground; its wave angle will depend on the height of the antenna over the
ground."

So, the short answer is "cross-polarization".

Most noise is local and reaches a receiver through ground-wave
propagation. Horizontally polarized waves have zero ground-wave
propagation. Their low-angle reflections are out-of-phase with the
direct wave.

Horzontal antennas are in general quieter than vertical antennas.
Cross-polarization loss has been often reported as about 20 db.

Loops, small in terms of wavelength, tend to have the same volts and
amps induced into all their increments. This helps reduce sensitivity to
overloads from high-power signals at frequencies far below the desired
reception, as might be received on a voltage-probe antenna.

Best regards, Richard Harrison, KB5WZI

Should I run a Sky-wire loop?

Walter,

Give the Skywire loop a try....I put one up almost a year ago and it
definitely is better than my other wire antenna ( a 40m dipole). Mine
is approx 440' long and is shaped more like a rectangle than a perfect
round (or square) loop. Each corner is at a different elevation, the
higest 35' , the lowest 20'. I feed it with RG8X, no balun, and my
K2's autotuner permits effective operation on all HF bands at less
than 2-1 SWR, except on 160 where it only tunes down to 3.5 to 1. I
haven't done it yet but I've worked out a way to enlarge it another
100', so the 160m swr should come down. I also plan to try switching
to 450 ohm ladder line feed.....everyone says it will work even
better. Did I mention it is the "quietest' recieving antenna I've
used?.... But don't limit its use to only recieving....the horizontal
loop is a great transmitting antenna too. My first contact with mine
was on 20m to Tierra del Fuego at the southern tip of Argentina ( 5
watts ssb, got a 5x5 sig report!). Seems to be somewhat omni
directional too as I've worked dx in all directions. I don't claim it
will outperform a good beam on a tower but the price is right (cheap)
and its realatively easy to make. Go for it!

Regards,

Rich K2CPE

Rich,

It is much more of an advantage to run open wire line for multiband operation
due to the much lower losses.

73s,

Evan

Rich, K2CPE wrote:
"My first contact with mine (large horizontal loop) was on 20 m to
Tierra del Fuego at the southern tip of Argentina (5 watts ssb, got a
5x5 sig report!)."

That`s great performance. It helps that Tierra del Fuego is cold and
quiet. I made 2 triops there and spent a total of more than a year there
on the Argentine side of the island about 40 years ago.

I was able to listen to a Houston MW 740 KHz station during Hurricane
Carla on my little Hitachi transistor radio which was about the size of
a package of cigarettes. This does not mean that Rich`s 20m contact
wasn`t special. Ionospheric conditions were probably much different on
separate occations so widely separated in time. Dan Rather came in loud
and clear on 740 KHz from about 1/3 the distance around the globe. I was
very interested in what the hurricane was doing in my absence.

The MUF was pretty high when I was in Tierra del Fuego because when I
connected a 5W Motorola 33 MHz FM walkie talkie to a vertical dipole at
about 20 ft I raised a Midland, Texas oilfield supply company.

I put up a rhombic on the island to communicate with an Argentine public
correspondence station which operated between 80 m and 40 m near Buenos
Aires. The post office in Rio Grande on the Island had a BC-610 that
they used to contact that station, Radio Pacheco, near Buenos Aires. Our
transmitter was a Hallicrafters HT-20, surplus from our Bolivian
oilfield operations. It had been replaced with a Collins 30K-5. We
needed our own radio contact with Buenos Aires because the post office
on the island closed during the frequent postal worker strikes.

When we gave Radio Pacheco a call and told them we were calling from
Tierra del Fuego, they were incredulous. The rhombic was really rattling
their cans.

The only ham active at the time on Tierra del Fuego was Padre Munoz who
presided over the local mission. He tried to use equipment in nearly all
cases identical with ours to assure a source of replacements for
anything that failed. We had Land Rovers. Padre Munoz got a Land Rover
for himself. Same with radios, etc. He was a wise old guy.

My assistant was a nuclear physicist but there was no work for his
specialty at the time in Argentina. So he accepted a job in the oil
patch working with electronics. He was a ham after all and had an
excellent scientific preparation. His name was Alex Eusler. Don`t know
where he is now or what he is doing. Hope he is doing great things with
atoms.

If Bill happened to contact someone on Tierra del Fuego who was using
something like the rhombic erected there 40 years ago, he might expect
good communications. Its gain at 20m is likely 15 or 20 dBd in the
direction of the USA. Even a dipole isn`t bad as evidenced by my
Midland, Texas contact. I was probably right at the MUF at the time, and
Bill was probably well below the MUF on 20m at the time he made his
contact with Tierra del Fuego. His contact was probably much harder to
make and keep working if he were far below the MUF at the time.

Best regards, Richard Harrison, KB5WZI

Mark Keith wrote:
"As far as noise, if the dipole and loop are both horizontal, there
should be little if any difference in noise received, unless the pattern
of the particular antenna favors the noise source."

I wrote that the loop was small at lower frequenciues such as those used
with power mains and BC band transmitters. This can be equalized by an
r-f choke across the receiver input to short out the low-frequency
interference. A folded dipole or loop antenna doesn`t need a choke.
Their configurations provide a short at low frequencies.

I noticed the hum pickup of car radios using untuned r-f anmplifiers
back in the 1940`s. They had no low-frequency, low-impedance path for
noise intercepted by the conventional whip antenna. Radios with a
conventional antenna coil had bo antenna hum problem.

Best regards, Richard Harrison, KB5WZI