Pete
We installed and I used exactly such an antenna at VE3/N2WQ this past year.
The loops were easy to construct, and the project was built around 3x3"
pieces
of wood. The loops were located around 400ft from the shack; one thing we
did find was that, even doubling up on the power and ground wires of the
Cat5
cable, we had to feed about 18.5V into the coax at the shack end to get
enough
voltage at the loops to run the amps. As we turned the voltage up past
the 13.8V,
you could hear the output go up greatly.
The loops were erected last April; preliminary use showed there was enough
directivity that switching directions on the AM band (on the proper
frequency)
resulted in different stations being received on the radio. I can't say
there was
a great deal of directivity, but there was some. I also used the loops
in the WPX
CW contest as VA3CCO; their biggest contribution was the reduction in noise
picked up by the antenna. There was a thunderstorm 50 miles south of us
during
the contest; the 80M delta loop on Europe picked up too much noise and Qs on
80M required several repeats due to the static crashes. Using the
loops, the static
crashes were minimized and I was able to get the SN with only one
transmission.
I didn't make a lot of 80M Qs- it was almost summer and in WPX 80/160M
usage is pretty light- but it did help.
In my mind, the effectiveness of the loops is still an open question,
particularly if
you weighed their performance against that of other reduced size Rx
antennas.
I would not rule them out, either.
LZ1AQ also recommended constructing both the loops and the short vertical
elements, as the short vertical elements were better for low angle
arriving signals.
We did get the loops built, but the wx was bad and we never did get the
vertical
elements added on. The preamps all included the switching to go between the
two antennas at the touch of a switch.
Dennis W1UE
On 1/2/2016 10:45 AM, Pete Smith N4ZR wrote:
I was recently reading a web page by LZ1AQ
<http://www.lz1aq.signacor.com/>. It is full of fascinating data and
design equations for the use of small magnetic loop antennas. There
were two points, in particular, that caught my layman's attention:
1. He recommends using shielded CAT5 data cable with RJ-45 connectors
as feedline. The obvious advantage is having three pairs left over
for voltage supply and control. See
<http://active-antenna.eu/amplifier-kit/> for more information.
2. He cites experimental data showing that coplanar crossed loops and
multi-turn quad loops both offer very significant improvement in the
recovered signalcompared with a single loop. See
<http://www.lz1aq.signacor.com/docs/experimental-comparison-v10.pdf>
to check whether I got this right. Anyway, it occurred to me to ask if
anyone has ever tried multiturn K9AY, SAL or flag/pennant receiving
antennas, and did you see something similar?
Any other critiques of his design would be appreciated. The price is
certainly right, and the construction looks good. A couple of 1-meter
coplanar loops wouldn't be at all hard to construct.
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