STOP!
ISOTRON IS NOT A MAGNETIC LOOP.
It is an electrical antenna just like normal wire antennas. It won't work
indoors. PERIOD
Perhaps I chose the wrong name for it, but it works off of the electrical
component, not the magnetic component of the signal. It will have the same
trouble with house QRN as all of your present antennas.
I suggest you try it as a Receive-Only antenna first.
That way you don't have to worry about losses or anything like that.
It is very easy to build one yourself.
Which band or bands are you interested in?
I had an uncle (now SK) who had to go into assisted living and could have no
outdoor antenna.
He really missed checking daily into his Kadiddlehoppers' net on 40m.
While visiting home (Oklahoma) one year, I learned of that and built him a
40m magnetic loop, using only wood and coax.
With that and his TS-120, he was able to check in daily to his 40m SSB net.
See: http://www.dj0ip.de/my-favorite-antennas/old-folks-antenna/
Of course it would have been better if I had had a variable capacitor, but I
couldn't find one locally, so I just improvised. My uncle was a happy
camper!
For receive only, all you need is the big loop, little loop, and any
variable capacitor with enough capacitance.
The spacing on the capacitor is not important. Important is "how you build
the smaller loop". Many examples found on the Internet are wrong.
Which band or bands are you interested in?
73 - Rick, DJ0IP
(Nr. Frankfurt am Main)
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Lee
Sent: Friday, April 25, 2014 5:02 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] New Jupiter on its Way _ A Few Questions
On Apr 24, 2014 11:50 PM, "Rick - DJ0IP / NJ0IP" <Rick@dj0ip.de> wrote:
>
> One addition to what Stuart has written.
>
> Though we would like to have as large of magnetic loop as possible in
order
> to get good performance on the low bands, large loops do not work well
> indoors. The need to have a distance equal to their radius away from
> the floor, walls, or ceiling. This effectively limits the loop's size
> to about one meter (3 ft.) in diameter.
>
> I had a very expensive commercial loop which was 1.7m in diameter.
> I could get it to work halfway decent indoors on 40m but it just would
> not find a good match on 80m.
> I moved it to the balcony, pushed it up such that it was above the
> edge of the roof a little and it worked great on all bands. Much
> better than when indoors.
>
> Then I moved it to the front yard and raised it such that its lowest
> part was 10 ft. in the air.
> I compared it to a 40m dipole (40 ft. up). There was basically no
> difference, except for some stations, I could rotate the loop and then
> it was a few S-units stronger than the wire dipole.
>
> Don't jump to any false conclusions. My bet is, most loops do not
> work
like
> they should due to poor construction techniques. You have to use the
> best quality of parts and take much care to keep the resistance
> between various components as low as possible. Otherwise the loss will be
too great.
>
> If you open the MFJ mag loop, you'll see that its variable capacitor
> is wielded to the aluminum loop. That's the best way to keep the losses
low.
>
> For 80m indoors, I would suggest a 2 or 3 turn loop. 40m works best
> with
a
> 2 turn loop. It will also work on 40 with a single turn loop, but not
> as well.
>
> One of the guys in my local club lives in a townhouse in the city,
> with a postage stamp size back yard.
> He bought a VERY expensive commercial loop ($1700) and mounted it
> about 10 ft. high on his patio.
> His results have been nothing but astonishing.
> He is as loud as anyone else running similar power, all over Germany.
>
> Again, if you can place it outdoors, it will work a lot better.
> But indoors it will be better than other wire antennas or sticks, "if"
> you build the loop with low loss.
>
> 73 - Rick, DJ0IP
> (Nr. Frankfurt am Main)
>
>
> -----Original Message-----
> From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of
> Stuart Rohre
> Sent: Thursday, April 24, 2014 11:25 PM
> To: tentec@contesting.com
> Subject: Re: [TenTec] New Jupiter on its Way _ A Few Questions
>
> Based on an article on loaded antennas in the latest QEX magazine from
ARRL,
> I would say a magnetic loop, if larger than 0.1 wavelength diameter,
> might have either the same signal as a loaded dipole, (short dipoles
> as I
imagine
> you mean), or the magnetic loop will have BETTER signal to noise on
receive,
> which is very valuable in the indoor environment. Gain in the
> receive, or low noise, may be better than more signal on transmit.
>
> Both types of antennas would give better results if placed in an
> unobstructed attic, (wood house), or placed at least, on the edge of a
roof.
> A larger than 0.1 wave loop could be hidden in a fenced back yard, and
even
> put on a pulley system that would raise it up to hang in a back yard
> tree for after dark operations.
>
> Being indoors as now; you are in a cage or cobweb of electric wires,
> possible metal plaster lath, and obstructions from large appliances on
> the other side of a wall. You are subject to causing TVI to
> electronics
inside
> the home at least, or next door, or the next apartment.
>
> Of all the indoor operating means, the loop offers the best results,
> especially on receive, if shielded, and made of low loss construction.
>
> Use large diameter loop material and low loss connections.
> One of the best loop designs for HF used copper tubing of 1 inch
> diameter
or
> larger, and was octagon shaped, because angled fittings were available.
The
> joints were silver soldered for lowest loss.
>
> The capacitors on the end can be trombone type made from sliding
> copper pipes, with teflon tape as spacer and insulation. Or use
> surplus vacuum variables which turn up at swap meets. Or even large
> metal air spaced variables. while you might spend some money up front
> on material,
> (pipe) and capacitors, those parts and the loop can be used for ANY
> future locations, Field Days, or even mobile on a van.
>
> Locally, Bob, WB5AOH had one on his van that worked HF great on low
> bands like 40 and 75. He would still have it but for a low hanging tree
limb!
> (With big mobile antennas back in bicycle days, I learned you have to
drive
> both the vehicle and the antenna!)
>
> -Stuart Rohre
> K5KVH
> ____________
I have 15 foot ceilings, so I have a lot of space in which to erect a loop
antenna. In fact it would be much less obtrusive than the current antenna I
am using. I think I am going to inquire about some of the commercially
available loops (isotron, Mfj, etc...)___________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
>
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