wrote in message
oups.com...

Dale Parfitt wrote:
Has anyone had a "bad", as in less then stellar performance, with a
Wellbrook ALA 1530
loop antenna?

Hi Terry,

I have a homebrew version of the Wellbrook shielded loop 7' in diameter.
It
is in my woods on a short tower and rotator.
On 160M and 75M it is the same as my 80M inverted vee. It's a good
performer
on MW/LW but not any real difference between it and a homebrew voltage
probe
antenna with a 4' whip.

Loops are most useful where there is a single noise source that can be
nulled with the loop- other than that, it's a toss up.
There is still the wive's tale making the rounds that shielded loop are
immune to the E field noise - rubbish and well disproven in the
literature.

So, in summary, I like mine for being a compact RX antenna for MW/LW,
but at
least in my environment, not sure I would go to the trouble next time.

Dale W4OP
for PAR Electronics, Inc.

I am begining to think that many people over rate a loop because it has
lower over
all gain and therefore is quiter. Based on my experience with improved
detector and
audio chains I have come to understand that the signal to noise is the
only variable
that really matters. I wish my fancy HiFer beacon/test source had not
been fried
by Thor. Even the 13.xxMHz crsytal was toast! It would be interesting
to run some
real experiments to compare antennas the way I compared detectors and
post detection amplifiers.

BTW I have completly ripped out all of my coax and pulled down my
antennas.
Since I got rid of my desktop PC and I have gone to a laptop I found I
really needed
to redesign my radio desk. Since my antennas and coax have been up for
over 15
years, I decided to redo the whole mess.

Fall is a very good time to errect new antennas and I am going to
reroute all my coax
through 1/2" copper tubing that will be bonded to my perimeter ground
ring. An
electrician friend used his mini Ditch Witch to dig me a couple of
trenches. I hope
to have the antennas back up by Monday evening.

I typically research and build devcies in the summer, think about
antennas in teh
fall and do serious listening over the winter.

Terry


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.

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"?

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

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

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.

Apples and oranges. The current discussion is about electrically small,
rotatable loops.

Dale W4OP

In article VD8Tg.9636$422.6849@trnddc03,
"Dale Parfitt" wrote:

Snip

There is still the wive's tale making the rounds that shielded loop are
immune to the E field noise - rubbish and well disproven in the literature.

Snip

Old "wives tale" is a rec.radio.amateur.antenna trash talk phrase.

Were have you been reading that an electrically small shielded or
unshielded loop is sensitive to E field?

--
Telamon
Ventura, California

wrote:
Has anyone had a "bad", as in less then stellar performance, with a
Wellbrook ALA 1530
loop antenna?

Given the almost sacred refference the Wellbrook is held in I have
debated asking
this question. I have a ALA 1530 that is part of a trade that I am
looking at and
guys I just don't get it. This antenna is reputed to be the cat's meow,
but I have
found it marginal at best. A north country active antenna is nearly
it's match
and the 3rd harmonic of a local MW (770KHz) is S3 on the Wellbrook. A
Lankford Active Dipole stomps it in gain, IP2 and IP3 and for
directivity.

I am wondering if this antenna is defective or if it is a case of the
Emperors New
Clothes. I have tried loops several times in the last 30 years and
always give up
becuase I have never found the reported imunity against local QRM to be
true.
I am building a copy of the WL1030 (http://wl1030.com/), but I don't
understand
the fascination with loops. What am I missing?

For MW DX "big" air loops make sense. Good directivity to null out an
offending
signal. I notice Ron Harding uses McKay 100E with a phaser to achieve
good
nulls. For HF the sky wave "smears" both the desired and unwanted
signals
making a null very iffy.

Receivers used in this test:
R2000
R8B
R390
R392
The R390 and R392 where not tested at my home but at a friend's home
where I have them stored. While I like both the R390 and R392, they are
somewhat awkward to rapidly tune from one frequency to a wildly
seperated
one.

Terry

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.

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.

Checking that fuse is a very good idea. I once blew mine by accident
when a piece of coax I was using turned out to have a short. I didn't
immediately realize what had happened and went a few days simply
thinking that conditions were terrible. LOL.

Steve

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

In article . com,
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.

What you are calling a "power injector/diplexer" would probably be best
described as a bias-T. This is a three port device:

Sample schematic:
http://www.smelectronics.us/biast.htm

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

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.

Terry