On Feb 14, 3:22*pm, Cecil Moore wrote:
Richard Clark wrote:
Swoozie Pellegrino wrote:

like a 10-meter long magnet wire hanging from my balcony with a weight
at the bottom. *I could run coax down alongside for 5m and have it
connect there in the center.

Make it 5 meter long wire hanging from the center conductor of a
hanging 5+ meter long coax.

Or fold 1/4WL of the braid back down over itself leaving
1/4WL of the insulated center conductor to hang down.
It's called a sleeve dipole.
--
73, Cecil *http://www.w5dxp.com

What might the impedance of this look like, say, if I
took the last 10 meters of a 100' 50-ohm coax piece
and slice it to split out into a 20-meter sleeve dipole
and hung the dipole part vertically from the balcony?
Can I just screw the other end onto the back of
my transceiver and go? Or....


Thanks,
~swooz

On Fri, 15 Feb 2008 11:40:50 -0800 (PST), Swoozie Pellegrino
wrote:

What might the impedance of this look like, say, if I
took the last 10 meters of a 100' 50-ohm coax piece
and slice it to split out into a 20-meter sleeve dipole
and hung the dipole part vertically from the balcony?
Can I just screw the other end onto the back of
my transceiver and go? Or....

Sure, if you can live with the mismatch. Better if you can tune it
for one band. Or simply stick with my suggestion and run it into a
tuner which you will probably need anyway. The difference between any
of these will be undetectable at the far end of the QSO.

To reduce the chance of a hot chassis due to common mode currents, you
should use a 1:1 W2DU style BalUn (aka choke).

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Fri, 15 Feb 2008 11:40:50 -0800 (PST), Swoozie Pellegrino
wrote:

What might the impedance of this look like, say, if I
took the last 10 meters of a 100' 50-ohm coax piece
and slice it to split out into a 20-meter sleeve dipole
and hung the dipole part vertically from the balcony?
Can I just screw the other end onto the back of
my transceiver and go? Or....

Sure, if you can live with the mismatch. Better if you can tune it
for one band. Or simply stick with my suggestion and run it into a
tuner which you will probably need anyway. The difference between any
of these will be undetectable at the far end of the QSO.

To reduce the chance of a hot chassis due to common mode currents, you
should use a 1:1 W2DU style BalUn (aka choke).

73's
Richard Clark, KB7QHC

I've found that the trick of folding the braid down over the coax does a
very poor job of decoupling the line in an imitation of a "sleeve" or
"bazooka" dipole. It turns out that you really need a high Z0 for the
decoupling sleeve, and the only practical way I know of to do that is
with a larger diameter pipe, and air insulation between the pipe and the
coax. I've also found that a choke balun made of multiple turns on a
single core, by itself, anyway, doesn't provide adequate impedance. I'd
worry that a W2DU style balun would cause a lot of loss in this
application, but it should be possible to model it reasonably well with
a series of loads and find out. (You'd first need to determine the
actual Z of the type of core used, at the operating frequency.) You
might be able to decouple the line adequately with a very high impedance
and low resistance resonant current balun (common mode choke), perhaps
one made by winding coax on a plastic pop bottle. You'd probably need a
second current balun of some type about 1/4 wavelength down the line. My
experience is that it's a trickier problem than most people think.

Roy Lewallen, W7EL

Swoozie Pellegrino wrote:
What might the impedance of this look like, say, if I
took the last 10 meters of a 100' 50-ohm coax piece
and slice it to split out into a 20-meter sleeve dipole
and hung the dipole part vertically from the balcony?
Can I just screw the other end onto the back of
my transceiver and go? Or....

When I plugged it into a 2x6146 transceiver equipped
with a pi-net matching output network, it worked well. :-)
I would guess the SWR will be less than 2:1.
--
73, Cecil http://www.w5dxp.com

On Feb 12, 8:05*am, "Yuri Blanarovich" wrote:
"Swoozie Pellegrino" wrote in message

...





Hi, all.

I'm about to become a General class licensee, and I'm
trying to work out a HF antenna plan for my new apartment.
I have a small balcony on the top (4th) floor, which is good,
but unfortunately there's a roof overhanging it and is
8' over the balcony floor and juts 4' out over the balcony edge,
so a tall vertical is out of the question.

What about a 'vertical' that is angled about 45 deg. down
from vertical? *Will that be good for phone DXing on any
HF band?

Also, sadly, the balcony is all metal and so is the top of
the roof.

What about some kind of loop?

Thanks!

~swooz

Try the Half Sloper if you could.
It is quarter wave wire suspended between balcony and run at about 45 deg
down to a tree or whatever. There is a good chance you will end up with 50
ohm impedance and can be fed directly with a coax, shield connected to metal
railing or door frame and center wire to the antenna. Trim to frequency.
Had one like that from the 9th floor at the hotel in Bahamas, worked very
well.

73 *Yuri, K3BU.us- Hide quoted text -

- Show quoted text -

I think that I'm going to start with this idea, since I have
a radio coming in the mail and would like to do the simplest
and cheapest up front to get the radio tested out. I have
a few questions:

1. After I wire up the antenna & coax as described above,
can I do my trimming to frequency by using only the radio's
SWR meter, or do I need an external tuner at the wire?

2. This radio can output 100W on HF. Can't this setup
with a 10m length of 26-gauge magnet wire handle
this?

3. I may need to run up to 30' of coax. What type should
I buy?

Thanks for all the help!
~swooz

Swoozie Pellegrino wrote:
On Feb 12, 8:05 am, "Yuri Blanarovich" wrote:
Try the Half Sloper if you could.
It is quarter wave wire suspended between balcony and run at about 45 deg
down to a tree or whatever. There is a good chance you will end up with 50
ohm impedance and can be fed directly with a coax, shield connected to metal
railing or door frame and center wire to the antenna. Trim to frequency.
Had one like that from the 9th floor at the hotel in Bahamas, worked very
well.

73 Yuri, K3BU.us- Hide quoted text -

- Show quoted text -

I think that I'm going to start with this idea, since I have
a radio coming in the mail and would like to do the simplest
and cheapest up front to get the radio tested out. I have
a few questions:

1. After I wire up the antenna & coax as described above,
can I do my trimming to frequency by using only the radio's
SWR meter, or do I need an external tuner at the wire?

2. This radio can output 100W on HF. Can't this setup
with a 10m length of 26-gauge magnet wire handle
this?

3. I may need to run up to 30' of coax. What type should
I buy?

Thanks for all the help!
~swooz

One thing you should realize about the half sloper is that it's only
half an antenna. The outside of the coax, in your case, is the other
half of the antenna. If you put one amp into the "antenna" wire, one amp
will flow down the outside of the coax. So don't be surprised if you
find strange effects in your shack, such as electronic keyers which keep
sending, push-to-talk buttons that turn on the transmitter but don't
turn it off, RF burns from the microphone, and an SWR that changes when
you move the feedline around or change its length. You might get lucky
and not see these effects if the length of coax to the antenna and from
the rig to the ground is favorable, or you might not. You'll also need
to take care to keep the feedline as far away as possible from power or
telephone wiring because it's radiating just like the "antenna" part of
the actual antenna.

For those reasons it wouldn't be my choice for an indoor antenna, but
apparently Yuri has gotten lucky and had success with it, and so might
you, too. I'm sure you'll get some other suggestions from people with a
lot of experience.

26 gauge magnet wire is fine for most indoor antennas (about anything
except an electrically small loop). RG-58 is fine for the coax, up to a
few hundred watts, if the SWR is fairly low. If the SWR is fairly high
(say, above 3:1) and you're running 100 watts, you might want to use
RG-59 or RG-58x instead.

Have fun!

Roy Lewallen, W7EL

On Sun, 17 Feb 2008 13:44:05 -0800 (PST), Swoozie Pellegrino
wrote:

Try the Half Sloper if you could.
It is quarter wave wire suspended between balcony and run at about 45 deg
down to a tree or whatever. There is a good chance you will end up with 50
ohm impedance and can be fed directly with a coax, shield connected to metal
railing or door frame and center wire to the antenna. Trim to frequency.

1. After I wire up the antenna & coax as described above,
can I do my trimming to frequency by using only the radio's
SWR meter, or do I need an external tuner at the wire?

Cut the wire long, and trim by small increments. If you are still
trimming well after it is obviously shorter than a quarter wave,
further trimming might find resonance, but you could be bucking up
against unknowns (this is not likely to be big problem however).

2. This radio can output 100W on HF. Can't this setup
with a 10m length of 26-gauge magnet wire handle
this?

And more.

3. I may need to run up to 30' of coax. What type should
I buy?

Common radio shack stuff will work fine. You can spend more,
certainly, but if your antenna is tuned, no one will be able to tell
the difference at the far end between hardline and RG156 (you won't
find that at RS, probably, but there is a lot of RG8X).

However, it you can put up one wire for one band (no tuner? THAT is
odd) you can as easily put up three, four or five as a fan sloper (or
dipole, or monopole...) and not have to worry about SWR for one band
or several. It takes only slightly more construction ingenuity and
effort, but perhaps it may be too much visual exposure that draws the
unwanted eye (which, I suppose, is why you are using magnet wire in
the first place).

73's
Richard Clark, KB7QHC

"Roy Lewallen" wrote in message
...
Swoozie Pellegrino wrote:
On Feb 12, 8:05 am, "Yuri Blanarovich" wrote:
Try the Half Sloper if you could.
It is quarter wave wire suspended between balcony and run at about 45
deg
down to a tree or whatever. There is a good chance you will end up with
50
ohm impedance and can be fed directly with a coax, shield connected to
metal
railing or door frame and center wire to the antenna. Trim to frequency.
Had one like that from the 9th floor at the hotel in Bahamas, worked
very
well.

73 Yuri, K3BU.us- Hide quoted text -

- Show quoted text -

I think that I'm going to start with this idea, since I have
a radio coming in the mail and would like to do the simplest
and cheapest up front to get the radio tested out. I have
a few questions:

1. After I wire up the antenna & coax as described above,
can I do my trimming to frequency by using only the radio's
SWR meter, or do I need an external tuner at the wire?

2. This radio can output 100W on HF. Can't this setup
with a 10m length of 26-gauge magnet wire handle
this?

3. I may need to run up to 30' of coax. What type should
I buy?

Thanks for all the help!
~swooz

One thing you should realize about the half sloper is that it's only half
an antenna. The outside of the coax, in your case, is the other half of
the antenna. If you put one amp into the "antenna" wire, one amp will flow
down the outside of the coax. So don't be surprised if you find strange
effects in your shack, such as electronic keyers which keep sending,
push-to-talk buttons that turn on the transmitter but don't turn it off,
RF burns from the microphone, and an SWR that changes when you move the
feedline around or change its length.

Not as bad as foreseen.
What the HalfSloper is - vertical or ground plane antenna turned on the
side/angle and the pattern then formed between the antenna and the ground
reflection.
It is beneficial to connect as much "iron" as possible as a ground plane -
guardrail, door frame flushing. The RF is then formed between the radiator
wire and the "ground plane" with little getting behind it. Just to
underline that sloping wire goes away from the building, not anywhere
inside.
You can use SWR meter on ic706 to find where the wire resonates and trim it
to frquency. It should be close to 50 ohms, you should not need a tuner. I
was expecting my setup to have lower impedance than 50 ohms and had coil
ready, to be inserted between the guardrail and the wire and then finding
the tap for 50 ohms on the coil, few turns up from the ground connection.
But it turned out to be perect 50 ohms and wire length was original vertical
wire from my baloon vertical working against 4 elevated radials on 160m.

You might get lucky and not see these effects if the length of coax to the
antenna and from the rig to the ground is favorable, or you might not.
You'll also need to take care to keep the feedline as far away as possible
from power or telephone wiring because it's radiating just like the
"antenna" part of the actual antenna.


I had no problem with RF, coax was about 8 feet between balcony and rig and
computer next to it. In case of longer coax and to be safe, you could wind
few turns of coax in a coil at the feed point to form the choke.

For those reasons it wouldn't be my choice for an indoor antenna, but
apparently Yuri has gotten lucky and had success with it, and so might
you, too. I'm sure you'll get some other suggestions from people with a
lot of experience.

It is outdoor antenna with pattern being formed between the radiator wire
and metal mess of the building, RF stays outside with reasonable amount of
"iron" and wiring in the building.

26 gauge magnet wire is fine for most indoor antennas (about anything
except an electrically small loop). RG-58 is fine for the coax, up to a
few hundred watts, if the SWR is fairly low. If the SWR is fairly high
(say, above 3:1) and you're running 100 watts, you might want to use RG-59
or RG-58x instead.

Have fun!

Roy Lewallen, W7EL

I would use 50 ohm coax, RG 58 variety should be OK. 26 gauge wire should
fine.

73 and GL Yuri, K3BU.us