"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