Open Loop aka Dipole bent into a square
 

Priz wrote:
"I`m working with attic antennas and need some help."

The attic is a poor place for antennas but a good place to experiment.

A 60-ft. perimeter is over one wavelength at 15 meters.

According to Arnold B. Bailey`s "TV and Other Receiving Antennas" Fig.
8-14 on page 408, an open-circuit large loop has a radiation resistance
of less than 80 ohms. A closed-circuit large loop has a radiation
resistance of over 40 ohms.

A closed-loop`s radiation resistance varies less with frequency than
does the open loop.

Borrow the book. Look at the chart. Pick the radiation resistance you
want and proceed.

Best regards, Richard Harrison, KB5WZI

Open Loop aka Dipole bent into a square
 

I've got an update on my antenna experiment. I decided to buy a new
tuner, the MFJ 902H to see if that would help. It was priced low
enough and had a built in balun. I tested it out using my SWR
analyzer and this tuner was able to find matching points in the 80,
40, 30, 20, 17, 15, 12, and 10 meter bands. I did try to find a
matching point on 160 meters but wasn't able to do so which is OK,
since I've never worked 160 and the manual says not to try it on 160
anyway.

I plan to put this antenna on the air over the weekend to see what it
can do. I know it will be a compromise antenna but I'm hoping it will
allow me to do what many other hams in my situation aren't doing,
getting on the air. I also know all the jokes about MFJ, Mighty Fine
Junk, Made from Junk or my personal favorite, Mississippi's Finest
Junk, but it was priced right and when I got it, it appeared to be
well put together. I'll let everyone know how it works out.

Later...

Priz

Open Loop aka Dipole bent into a square
 

On Nov 16, 8:54 am, Priz wrote:
I've got an update on my antenna experiment. I decided to buy a new
tuner, the MFJ 902H to see if that would help. It was priced low
enough and had a built in balun. I tested it out using my SWR
analyzer and this tuner was able to find matching points in the 80,
40, 30, 20, 17, 15, 12, and 10 meter bands. I did try to find a
matching point on 160 meters but wasn't able to do so which is OK,
since I've never worked 160 and the manual says not to try it on 160
anyway.

I plan to put this antenna on the air over the weekend to see what it
can do. I know it will be a compromise antenna but I'm hoping it will
allow me to do what many other hams in my situation aren't doing,
getting on the air. I also know all the jokes about MFJ, Mighty Fine
Junk, Made from Junk or my personal favorite, Mississippi's Finest
Junk, but it was priced right and when I got it, it appeared to be
well put together. I'll let everyone know how it works out.

Later...

Priz

The MFJ tuners are ok as long as you don't abuse them..
And on some , you probably should take the power ratings
with a small bit of salt depending on the load you are matching.
I've got a small MFJ random wire tuner that I've had since 1977.
It still works, and I often use it as a mobile matcher. Also
handy as a "line flattener" when running coax to a solid
state rig.
I've got a 989C that I got free from a guy that fried the coil.
He was ignoring the instructions and running high power
into a nearly half size dipole. I'm talking 8877 power.. :/
Started melting the coil form. Went through two of them.
So he went out and bought a big Nye Viking, and gave
me the 989C as basically junk.. To him anyway..
I messed with it a couple of hours getting the wires
back in the right positions, and then resetting the
roller tension, etc, and got it working again. I've been
using it ever since. Well, when I use a tuner anyway..
I use the watt meter and antenna switch more than
anything.
It's rated 3KW, "dash of salt", but it will handle and
tune about anything I will ever be messing with.
Being it's a T network tuner, it's lousy for feeding
half size dipoles though.. :( It will do 160m though.
MK

Open Loop aka Dipole bent into a square
 

wrote in message
...

snip

The MFJ tuners are ok as long as you don't abuse them..
And on some , you probably should take the power ratings
with a small bit of salt depending on the load you are matching.
I've got a small MFJ random wire tuner that I've had since 1977.
It still works, and I often use it as a mobile matcher. Also
handy as a "line flattener" when running coax to a solid
state rig.

snip

I picked up a used MFJ tuner at a local ham swap meet. As is my wont, I
took off the cover to give it the visual once-over before dumping any 'trons
into it. Good thing. About six mounting and/or connection points - screws
or nut/bolt combos -- were so loose as to guarantee problems.

It's anybody's guess how long that stuff needed tightening. Was it ever
tight? (hint-hint)

"Sal"

PS: The thing works pretty good, overall.

Open Loop aka Dipole bent into a square
 

"Sal M. Onella" wrote in message
...
snip

I picked up a used MFJ tuner at a local ham swap meet. As is my wont, I
took off the cover to give it the visual once-over before dumping any
'trons
into it. Good thing. About six mounting and/or connection points -
screws
or nut/bolt combos -- were so loose as to guarantee problems.

It's anybody's guess how long that stuff needed tightening. Was it ever
tight? (hint-hint)

"Sal"

PS: The thing works pretty good, overall.

The few MFJ items I have remind me of an old Ford Bronco II that I once
owned. It was a piece of junk from day one, extremely useful, and reliable.
With a little TLC it ran forever, and was the second best car I ever had.
For example, my old MFJ CW audio filter is great, and has given over 20
years of service. But you don't want to look inside at the construction.

Open Loop aka Dipole bent into a square
 

I put the antenna on the air last night and this morning and did make
a couple of CW QSOs. From Louisiana, I worked Virginia on 40meters
with around 40 watts and Missorui on 30meters with 5 watts. Not
great, but I'm getting on the air!

Open Loop aka Dipole bent into a square
 

Priz wrote:
I've got an update on my antenna experiment. I decided to buy a new
tuner, the MFJ 902H to see if that would help. It was priced low
enough and had a built in balun. I tested it out using my SWR
analyzer and this tuner was able to find matching points in the 80,
40, 30, 20, 17, 15, 12, and 10 meter bands. I did try to find a
matching point on 160 meters but wasn't able to do so which is OK,
since I've never worked 160 and the manual says not to try it on 160
anyway.
=========================
You highly likely find a matching point for the 160 m band when you
extend the twin feeder . The extension length to be such that from any
end of the dipole to the matching unit the total length is roughly 1 or
3 or 5 etc quarter wavelengths .Any part of that feeder which is inside
the shack can be coiled -up (kept away from a metal clad area).

Frank GM0CSZ / KN6WH

Open Loop aka Dipole bent into a square
 

Highland Ham wrote:
You highly likely find a matching point for the 160 m band when you
extend the twin feeder .

Sorry, with a feedpoint impedance with R in the units
and X in the thousands, there is probably no length of
feedline that will come close to being compatible with
a tuner. No matter what feedline is used the SWR is way
up in the hundreds to thousands.
--
73, Cecil http://www.w5dxp.com