wrote:
wrote:

I use the ALA 100. The smaller loops may not be as good on MW. It is a
good idea to insure the amplifer is actually doing something. The fuse
could be blown, the wall wart bad, etc. Unplug the power connector and
make sure the signal strength drops. You will get reception from the
loop even if the amp is off since some RF will leak.

Some of the Wellbrook amps were positive ground. The unit is fused and
I would guess there is a reverse biased protection diode. If the wrong
wall wart was used, it would pop the fuse. In my portable set up, I
have red shrink wrap on the connector that goes to the Wellbrook, just
to make it clear the ground is backwards.

As far as the 1530 goes, it may not have a good resale value since they
released the "plus" version, which has response in the FM BCB.

This ALA 1530 requires a reversed, is shell positve and inner negative,
wall wart. But the center conductor of the coax was positive. I left
the
original power injector/diplexer intact and built my own. I verified
the
problem with the stock wall wart/diplexer before trying my own.

With out power I get virtually no signals. A few very strong MW and SW
at way less then S1. So the amp is working. The original owner says
it always behaved like this. OK, but clearly not the do all end all
of antennas.

Terry

If you throw it on ebay, please post the auction here.

wrote:

If you throw it on ebay, please post the auction here.

It is GONE. Traded it off about 3 hours ago.

While John dislikes his AD270, I have found my nearly new, as in
fairly unused, to be a very useful antenna.

Terry

In article .com,
wrote:

Telamon wrote:

1. DC voltage. (DC input) This is connected to the power supply. 2.
AC voltage. (RF output) This is connected to the radio. 3. DC + AC
voltage. (RF input, DC output) This is connected to the
antenna/amplifier.

Port 3 to 2 is connected with a capacitor of very low reactance
(zero) to the signal you want to pass through these two ports.

Port 1 to 3 are connect with an inductor, which passes DC voltage
from port 1 to 3 but blocks RF (high Z) going from 3 to 1 so the RF
only sees a path from 3 to 2.

Port 3 and 2 are coax cable and port one could be two terminals.
One terminal is common grounded with the coax shield grounds. Using
a ground independent power supply to the terminals on port 1 allow
you to have either a positive or negative power supply to the
remote amplifier.

-- Telamon Ventura, California

It is clear you work in the microwave satellite part of electronics.

In the "good old days", circa 1990, most text and other refference
sources reffered to them as "power injectors" or "diplexers". Your
discription of it's function is correct. A power source is isolated
from the RF with an inductor, or strip line version, and a capacitor
blocks the DC from the receiver.

MiniCircuits has very nice, as in wide band, inductors. Since I may
use the same coax for VLF. LF, MW, HF, or VHF my power inject, bias
"T" or diplexer has different inductors in series because I couldn't
find a single inductor to cover from 10KHz through ~500MHz. I found
that by using smaller chokes that were effective at UHF, with larger
chokes for each decade decrease in frequency. One of the changes I am
making is to use the MC wide band inductors to allow a smaller
package to be used. Space is at a premium in my "shack".

My shack is the 2nd bath with the plumbing removed and covered. It is
5' by 10'. I prefer the word cozy over cramped.

Most broadband bias-Ts have several inductors in series. At the RF line
you start with the smallest value inductor and work your way up to
larger values. With several inductors in series you might run into some
problems with the inductors ringing so you may need to have resistors
across some of the larger inductors. Since you are only interested in DC
on the bias port and not modulating the carrier from that bias port you
should be able to do it. You may manage to do it with two inductors in
series and so not have any problems with ringing.

--
Telamon
Ventura, California

Dale Parfitt wrote:
" That was a self defeating test. The idea here is that you will have a
lower noise floor in a locally noisy area with a shielded loop than a
dipole antenna. There is going to be no advantage to using a loop over
a dipole in an electrically quiet area.

A shielded loop is not better at picking up a distant signal than a
dipole but is less sensitive to local noise generators so in an area
with high local noise you would have better signal to noise than a
full size dipole antenna.

Please see:
http://www.w8ji.com/magnetic_receiving_loops.htm

Dale W4OP

Dale [W4OP] - Thanks for the very informative link.
http://www.w8ji.com/magnetic_receiving_loops.htm

Magnetic Loop Antennas Receiving
"Small Receiving Loop Antennas"
http://www.w8ji.com/magnetic_receiving_loops.htm

* Small Loop Antennas are often referred to as "Magnetic Radiators".
Folklore claims a small "Shielded" Loop Antenna behaves like a
sieve, sorting "good magnetic signals" from "bad electrical noise".
http://www.w8ji.com/magnetic_receiving_loops.htm

* Nothing is further from the truth! At relatively small distances a
small Magnetic Loop Antenna is more sensitive to Electric Fields
than a small Electric Field Probe type Antenna.
http://www.w8ji.com/magnetic_receiving_loops.htm

* Field Impedance of the Loop Antenna
http://www.w8ji.com/magnetic_receiving_loops.htm
Loop Antenna Fields - Short Dipole or Vertical Fields - Radiation

* Loop Antenna Shielding and Balance
http://www.w8ji.com/magnetic_receiving_loops.htm

* Examples of Small Loop Antennas
and Analysis of Loop Antenna Construction
http://www.w8ji.com/magnetic_receiving_loops.htm

* Typical Magnetic Loop Antenna
(found on Internet and other places)
http://www.w8ji.com/magnetic_receiving_loops.htm

* Circuit Representations of Shielded Loop Antennas
http://www.w8ji.com/magnetic_receiving_loops.htm

wrote in message
oups.com...

Seeing-I-dawg wrote:
I'll match your dipole against my 70m full-wave horizontal loop for
equal
gain from 70M all they way up to 6M - can you say broadbanded? A dipole
is
not.

Can you rotate your "70M full-wave horizontal loop"?

No need to. It essentially receives equally well in all directions on all
bands, unlike a dipole.

And at 70M, or about 230 feet in "diameter", it is a very different
antenna
then a 1M much touted miracle loop.

No, the circumference is 70 meters = full wave horiz. loop @70M
If you were to transmit into this loop you would see a flat swr from 70M-6M.
No tuner required. Just need to match the ladder line to your tranmitter.
A dipole can't do that without a tuner.

I don't think I was attempting to
compare
3' with 230'. One supposed advantage of the small, fractional
wavelength,
loop is the reported, or should I say reputed, highly directional
charactoristics.
That famous figure "8" pattern.

The dipole to which I am reffering is an amplified, very high IP3 and
IP2 unit with
very good,as in flat gain and very directional, from 100KHz to above
28MHz.

A dipole, any dipole, is cut/tuned for a single band. Any signal outside
that band and its harmonics are attenuated.
Not so with a large loop - equal gain to dipoles at any frequency.

I will
have to connect it to my scanner and see if I can receive any 6M ham
comms,
or more likely around here older 49MHz telephones. I suspect it will
run out of steam somewhere just above 35MHz, but I haven't checked. It
will be later next week before
I can do any tests as my "shack" is in pieces and I am reduced to a
DX398 coupled
to a ~50 random wire out the kitchen window.

Terry


For your perusal:
http://www.cebik.com/wire/hl.html
http://www.cebik.com/fdim/atl1.html
http://www.cebik.com/wire/horloop.html

For your perusal:
http://www.cebik.com/wire/hl.html
http://www.cebik.com/fdim/atl1.html
http://www.cebik.com/wire/horloop.html



Here is a nice horiz loop program from
http://www.smeter.net/antennas/rjeloop4.php

"This program is self-contained and ready to use. It does not require
installation."
Click this link
http://www.smeter.net/software/rjeloop4.exe
then click Open to run from the web or Save to save the program to your hard
drive.

After you have entered the initial values you can vary the frequency up or
down. Then watch how the efficiancy and loss characteristics barely vary.