In article . com,
wrote:

Telamon wrote:
In article . com,
wrote:

Telamon wrote:
In article
. com,
wrote:

Telamon wrote:
In article
. com,
wrote:

Telamon wrote:
In article
.com,
"R390A" wrote:


Telamon wrote:
In article
.c
om,
"R390A" wrote:

To Whom It May Concern: Additions and revisions
have been made to two of my articles about
vertical antennas and the ALA 100 on the
www.kongsfjord.com web site. The articles are
(1) "Measurements Of Some Antennas Signal To Man
Made Noise Ratios In The Daytime MW And LW
Bands," and (2) "Some Of My Favorite Small
Antennas For MW And LW." In the first article an
additional comparison of the ALA 100 was made
with an active whip antenna. The ALA 100 and
active whip had about the same signal to man made
noise ratio. In the second article some
information was added about reducing noise in
active whip antennas due to what are believed to
be ground loops in the DC feed.

The link is dead.
http://www.kongsfjord.no/dl/Antennas/Measurements%2
0Of%20So me%2 0Antenna s
%20Signal%20To%20Man%20Made%20Noise%20Ratio.pdf


Try www.kongsfjord.no and then click on The Dallas
Files.

That link worked.

Looking at your data I'm at a disadvantage not knowing
which are radio stations and which are computer noise
other than KNOE 540 kHz you specifically pointed out.
Another problem for me is the loop antenna gain looks
to be about 10 dB less than the other antennas. While
actually not a problem for signal to noise measurements
it does make the sweep look different to a person that
did not make the measurement.

Antennas in different locations around your house is
not exactly apples to apples comparison.

If your spectrum analyzer has a max hold on the trace
that would be a help in measuring the top of the noise
floor.

A clear difference in S/N would be the last pair on
page three 1500 to 2000 KHz where the ALA-100 looks to
be 22 dB (-42 S to -60 N) compared to the vertical 33
dB (-32 S to -65 N). One problem for me here is I don't
know what the analyzer noise floor itself is at this
point and I can see that the loop has 10 dB less gain
than the other antennas. Assuming that the analyzer
noise floor is -70 dBm and lower would make this
comparison valid. A simple check of just disconnecting
the cable from the analyzer at those settings would
show the instrument noise floor. Using max hold would
make the noise floor less ambiguous.

Due to my disadvantages noted I can't draw any firm
conclusions based on the analyzer pictures.

I'm an audio person, but noise should be measured in
terms of root hertz. Thus the noise floor you see is a
function of the bandwidth of the tracking filter. As you
go narrower, the noise floor should drop.


*************

I have to take exception to the wording you ascribe to
other people such as myself about a "belief in magnetic
field sensitive antennas". I rely on belief only when I
have no other choice as a fall back to no being able to
test a thesis empirically.

An electrically small shielded loop antenna will
respond very poorly to a local electric induction field
and very well to a magnetic one. An electrically small
dipole would be just the opposite in response to
induction fields. This is theoretically and empirically
correct. I have much experience using these types of
antennas monitoring for induction fields and they
behaved as theory predicted.

When poorly designed electronic devices generate
induction fields the electric fields have the tendency
to spread farther from the source than the magnetic
fields. This is a generalization but knowing this leads
to the conclusion that a loop would pick up less of the
locally generated noise most of the time or in other
words it would be an advantage to use over a dipole.

Most people that have local noise problems and purchase
a loop antenna such as the Wellbrook find that their
listening situation is greatly improved.

I use a non-amplified folded dipole and non-amplified
shielded loop. The loop picks up much less of the local
noise and picks up as much signal as the folded dipole
depending on the band.

Notice that belief is not required for any of the
foregoing.

************

You have the right idea about field impedance vs
distance but that relationship is appropriate for
transmitting antennas that are efficient. Here the
subject is inefficient noise sources. Here the
induction fields fall off rapidly compared to an
efficient antenna.

*************

I just noticed that your ALA 100 is pretty big and not
electrically small at SW frequencies. This means it
will also respond to electric fields and being
broadband will raise the noise floor. Your 60 foot
amplified loop is 10 feet bigger than my passive loop.
Why do you need an amplifier with a 60 foot loop?
Normally when I consider an amplified loop it more like
1 to 3 foot in diameter.

Here again, I believe being broadband increases the
integrated noise, but not necessarily the noise measured
per root Hz. The final bandwidth of the filter of the
radio determines the integrated noise.

Say the noise was 1nV/root Hz. Say the filter bandwidth
was 6Khz. Multiply the square root of 6Khz times 1nV/Root
Hz to get 77.5nV.

That's why even if I know the model number of the spectrum
analyzer I can not easily know the instrument noise floor
in the sweep. The sweep settings will modify the noise
floor.

I took another look at the measurement pdf and I think it
likely that the analyzer noise floor at those settings is
lower than the measurement noise in the sweeps and so at
least in the last pair of comparison photos on page 3
clearly show that the ALA-100 has a poorer signal to noise
than the vertical he is comparing it with.

I still don't know about the other sweeps as I don't know
what is a radio station and what is the local noise in the
sweep. When I did work on a range I would turn the DUT on
and off to see what actually popped up on the sweep when
the DUT is turned on. You had to do this on a range where
you can't have a large enough screen room due to cost. I'm
sure the author knows what is being generated by the stuff
in his house and what is a radio station.

It looks to me that although the Wellbrook amplifiers have
very good intermodulation numbers but that the noise floor
may be high. You would have to put in a larger signal into
the Wellbrook to measure the intermodulation products
relative to the other antenna amplifiers in the pdf
document.

Wellbrook does not appear to give a noise figure for the
amplifier. The author of the pdf could easily make that
measurement since he has an analyzer. Maybe noise is coming
in through the power supply connection for the amplifier,
the amplifier has a poor noise floor, or the antenna is
picking it up.


The difficulty in making measurements on the ALA 100 with
test instruments is you need a differential drive. I don't
know if grounding one side is kosher.

Grounding one side would not be acceptable. I would use a
simple test BALUN to drive the input.

-- Telamon Ventura, California

Yeah, but then what are you testing. The ALA 100 or the balun.
Good instrumentation isn't simple.

The BALUN would be simple and you would test it first. It would be
no problem at all.

-- Telamon Ventura, California

Not really. You need the balun to "act" like the wire antenna, which
means you need to characterize the wire antenna first, so you know
the impedance you need for each frequency tested.

There is a reason why Welbrook has no competition. I wish they did
since that would lower the price of the gear. I'm sure ANdy Ikin is
just snickering at this thread.

No you do not want the BALUN to "act" like the antenna wire. The BALUN
is to couple the generators single ended output to the differential
amplifier input so the amplifier can be tested. This is trivial thing to
do to test the amplifier. I'm not going to argue about this.

Amplified loop outdoor antennas have a number of costs associated with
them and I don't expect prices to lower.

--
Telamon
Ventura, California