Topband: Using shielded CAT5 data cable as feedline for active antenna; benefits of multi-turn K9AY loop/SAL/etc?

[Rudy Bakalov]

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 at k9ay.com>
 To: Topband at 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 at contesting.com>
To: topband reflector <Topband at 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 at 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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