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Old October 7th 06, 01:01 PM posted to rec.radio.shortwave
[email protected] r2000swler@hotmail.com is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 285
Default More loop comments

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