I may have given the impression that I think that loops have no place
in a radio system.

I am also a ham, extra class, and for the last 18 months I have been
somewhat active
using NVIS in a mobile setup. When you are using a 1991 Honda roof as
your ground
plane, a loop is the only thing that works.

My negative comments about loops should be for broad band, untuned
loops.

My SWL mainly is utility and I often have 2 receivers tuned to very
different frequencies.
For my SWL activities an antenna that must be tuned is not very useful.

A friend pointed out that I had tared all loops with the same brush.

I will stand by the observation that in all of my tests, small,
fractional wavelength
loops have no advantage over, and have proven very inferrior to the
Lankford active
dipole. Even a north country configured in a dipole array worked better
then the Wellbrook.

I will be the first to admit that I have not experimented with larger
loops for broad band
SWL reception. If I every get the time it would be interesting to use a
Dallas "ultra linear"
amplifer with a 50' square horizontal loop. For the time being I will
concentrate my energy
on standard "long" wire antennas with a set of 2 vertical Lankford
active dipoles couple to a
phaser with an additional and rotatable horizontal active dipole. That
should cover my
foreseeable needs.

A Langford "ultra linear amp" makes a very good buffer for ampifing a
signal prior to
power division. In fact it works better, as in much higher IP2, IP3
and simple harmonic
distortion then the 40 year old Nuvistor based unit I had been using
for the last year or
so.

FWIW we got the desk in place, stained and sealed between showers
today. And I
was able to burry the copper tubing that will cary the coax away from
our home. You
can't have too good a ground. The entry bulkhead is ready to mount, and
I am only a
week behind on my planed timeline.

Terry

In article . com,
wrote:

I may have given the impression that I think that loops have no place
in a radio system.

I am also a ham, extra class, and for the last 18 months I have been
somewhat active using NVIS in a mobile setup. When you are using a
1991 Honda roof as your ground plane, a loop is the only thing that
works.

My negative comments about loops should be for broad band, untuned
loops.

My SWL mainly is utility and I often have 2 receivers tuned to very
different frequencies. For my SWL activities an antenna that must be
tuned is not very useful.

A friend pointed out that I had tared all loops with the same brush.

I will stand by the observation that in all of my tests, small,
fractional wavelength loops have no advantage over, and have proven
very inferrior to the Lankford active dipole. Even a north country
configured in a dipole array worked better then the Wellbrook.

I will be the first to admit that I have not experimented with larger
loops for broad band SWL reception. If I every get the time it would
be interesting to use a Dallas "ultra linear" amplifer with a 50'
square horizontal loop. For the time being I will concentrate my
energy on standard "long" wire antennas with a set of 2 vertical
Lankford active dipoles couple to a phaser with an additional and
rotatable horizontal active dipole. That should cover my foreseeable
needs.

A Langford "ultra linear amp" makes a very good buffer for ampifing a
signal prior to power division. In fact it works better, as in much
higher IP2, IP3 and simple harmonic distortion then the 40 year old
Nuvistor based unit I had been using for the last year or so.

FWIW we got the desk in place, stained and sealed between showers
today. And I was able to burry the copper tubing that will cary the
coax away from our home. You can't have too good a ground. The entry
bulkhead is ready to mount, and I am only a week behind on my planed
timeline.

What equipment are you using to make the IP2 and IP3 measurements?

Can you share the comparison data you took on the units?

--
Telamon
Ventura, California

Telamon wrote:

What equipment are you using to make the IP2 and IP3 measurements?

Can you share the comparison data you took on the units?

--
Telamon
Ventura, California

I didn't do the tests, a graduate (PHD) engineering student I know ran
the tests for me.
I will ask for the exact equipment used.As for the exact data that will
take a while, my
"ham shack", communicaitons room radio room is packed in boxes for the
renovation.

I know the people at a local EMI certification lab, full screen room
etc, and I am hoping
to run some tests on all of my active antenna, the "soon" to be
completed WL1030 and the
1530.

Terry

In article om,
wrote:

Telamon wrote:

What equipment are you using to make the IP2 and IP3 measurements?

Can you share the comparison data you took on the units?

-- Telamon Ventura, California

I didn't do the tests, a graduate (PHD) engineering student I know
ran the tests for me. I will ask for the exact equipment used.As for
the exact data that will take a while, my "ham shack", communicaitons
room radio room is packed in boxes for the renovation.

I know the people at a local EMI certification lab, full screen room
etc, and I am hoping to run some tests on all of my active antenna,
the "soon" to be completed WL1030 and the 1530.

Well for the measurements to be meaningful the test conditions must be
known. You must (best) know the tone frequencies and input levels along
with the output tone levels and the levels of all the intermodulation
products you want to report on.

IP2 and IP3 are specifications that are higher the better. If I'm not
confusing you with another thread I think you mean a comparison to the
ALA1530 you you writ "1530". The ALA1530 has very good specifications
and to quote this page:
http://www.wellbrook.uk.com/ALA1530.html

"The Broadband Loop has been specifically designed to reduce
intermodulation products to a minimum. The second order and the third
order intercept points are typically +70dBm (IP2) and +40dBm (IP3)
respectively. Thus the level of the intermodulation products are
generally below the atmospheric and man made noise."

These intermodulation numbers are huge and I don't see the point in
working to get higher numbers than these. I could say that numbers
higher than these are not important unless you sit by some transmitter
in the passband of the antenna/amplifier.

I am I off base?

--
Telamon
Ventura, California

Telamon wrote:


Well for the measurements to be meaningful the test conditions must be
known. You must (best) know the tone frequencies and input levels along
with the output tone levels and the levels of all the intermodulation
products you want to report on.

IP2 and IP3 are specifications that are higher the better. If I'm not
confusing you with another thread I think you mean a comparison to the
ALA1530 you you writ "1530". The ALA1530 has very good specifications
and to quote this page:
http://www.wellbrook.uk.com/ALA1530.html

"The Broadband Loop has been specifically designed to reduce
intermodulation products to a minimum. The second order and the third
order intercept points are typically +70dBm (IP2) and +40dBm (IP3)
respectively. Thus the level of the intermodulation products are
generally below the atmospheric and man made noise."

These intermodulation numbers are huge and I don't see the point in
working to get higher numbers than these. I could say that numbers
higher than these are not important unless you sit by some transmitter
in the passband of the antenna/amplifier.

I am I off base?

--
Telamon
Ventura, California

One reason I want to get the Wellbrook teste, is to verify that it is
fact operating
correctly. The guy I traded if from says the performance now is like
when it was new.
His dissatifaction lead, in part, to his moving on from SWL. Of course
even if everything
had worked perfectly he would have grown bored in a few months to a
couple of years.

My comments regarding Dalla's "ultra linear amplifier" had to do with
its use as a
large loop, non fractional wavelength,amplifier, and as a buffer to
make up the losses
in a 4 way power divider setup. The ancient GE multiset coupler uses
Nuvistors
and Dallas' amplifier has much better IP2/IP3/THD then that unit. Of
course
it still has the original tubes and I am running plates at about 5
volts lower then
the orignal design. Dallas' amplifier being balanced and having a
better handle on
negative feedback should be expected to have lower distortion then a
Nuvistor
triode amplifier.

I completed the WL1030 and, at my home, it behaves very similary to the
Wellbrook
ALA. Slighlty better 3rd harmonic distortion from the local 770KHz MW
station
a few miles away, but still not as good as the stock North Country
active antenna,
a Datong AD370 or stock AMRAD antennas as published in QST. I used a
Kiwa
highpass, BCB reject filter, on the output of all three antennas.
Compared to Dallas'
active dipole all the others are kind of sad.

Receivers used:
R2000
R8B
R392


Hopefully this evening I will get a chance to run the WL1040 and a just
completed
"improved" version of Dallas' active dipole to Jeff's condo for a real
world, nightmare
test.

All of the antennas except for the wellbrook can be easily tested as
one has access
to the amplifiier input. Sadly the Wellbrook is in ?Epoxy making
testing and/or repair
difficult if not impossible.

This thread was meant to define what I consider to be a "good" useage
of small
loops. That is for mobile or other space restricted spaces where a
tuned small
loop can give amazing results. I have been underwealmed by broad band,
untuned
loops. I am not saying they don't work, I just haven't exeperienced a
broadband
loop that works as good as a simple active antenna, much less a proper
active antenna.

Using the small loop on 20 and 40 meters and NVIS I have talked/CWed
mobile
from Knoxville TN to Lexington KY. That is a successfull aplication of
a loop
antenna.

Terry