Topband: Using shielded CAT5 data cable as feedline for active antenna; benefits of multi-turn K9AY loop/SAL/etc?
4cx250b at miamioh.edu
Sat Jan 2 12:03:26 EST 2016
I did some tests a few years ago on unshielded CAT6 (UTP) cable. The
twisted pairs in the cable are rated at 100 ohm nominal impedance, so I
paralleled two sets of twisted pairs together and measured their VSWR.
Surprisinlgy I found the cable handled 100W at 20m, with negligible VSWR. I
thought about using the CAT6 for the feedline of portable antennas, but
found that the noise pickup was very high. To do this properly (which I
didn't do in my esperiement) one would use a simple 1:2
unbalanced-to-balanced balun for a single twisted pair, as well as STP
cable, but I don't see any problems doing so.
> -----Original Message-----
> From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of PA3CSG
> Sent: Saturday, January 02, 2016 09:53 AM
> To: Topband at contesting.com
> Subject: Re: Topband: Using shielded CAT5 data cable as feedline for
> benefits of multi-turn K9AY loop/SAL/etc?
> I tried to measure this UTP cable as a receive line. For the results see:
> The plan is only slowly moving forward:
> To use one twisted pair as a receive line
> One pair as the supply voltage
> One pair to communicate via a RS485 protocol to control a several RX
> antennas / K9AY and to control the gain of the preamp as well.
> One pair left.
> Since the discussion is going this way, how about the above idea?
> I have not tried it but would be interested in your comments.
> Regards & HNY!
> Geert PA3CSG
> Op 02-01-16 om 16:45 schreef Pete Smith N4ZR:
> > 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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