Sounds like you, Tom, and LZ1AQ are saying the same: in order for loops to be
effective (low SNR and high signal levels), they must have large area and low
reactance (inductance to be exact). Parallel loops or fat conduits increase the
signal levels, while the CP configuration and other similar measures are aimed
at lowering the loop's inductance. All this of course is paired with a
designed-for-purpose amp that does match the low loop impedance.
Rudy N2WQ
From: K9AY <k9ay@k9ay.com>
To: Topband@contesting.com
Sent: Sunday, January 3, 2016 8:50 PM
Subject: Re: Topband: Using shielded CAT5 data cable as feedline for active
antenna; benefits of multi-turn K9AY loop/SAL/etc?
Pete & all:
I have done a number of experiments with multi-turn K9AY Loops and flags. I
have only made brief mentions in print, mainly in last year's NCJ article.
Still sorting out the most useful data from a number of observations.
In short, what W8JI says is true -- larger conductors increase the signal
level, and parallel multiple loops do the same. The mechanism is more
complicated than simply reducing losses, involving the interactions with the
fields. I'm still working on that analysis.
One piece of data is that increasing the spacing between multiple, parallel
loops also increases signal level (gain). This is on a scale of inches to a
couple feet, so it's not array gain.
73, Gary
K9AY
Message: 9
Date: Sat, 2 Jan 2016 10:45:43 -0500
From: Pete Smith N4ZR <n4zr@contesting.com>
To: topband reflector <Topband@contesting.com>
Subject: Topband: Using shielded CAT5 data cable as feedline for
active antenna; benefits of multi-turn K9AY loop/SAL/etc?
Message-ID: <5687F0A7.6030401@contesting.com>
Content-Type: text/plain; charset=utf-8; format=flowed
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.
--
73, Pete N4ZR
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