John, I to am a novice at this stuff. I'm having trouble visualizing your antenna. You said,
>"the fence - of about > 450 feet diameter, and nearly (but not quite) > square." Could you clarify this to me? I too have a horizontal loop. Mine is about 15' off the ground, and has about 240' of wire (roughly 4 X 60'). I feed it with 450 ohm ladder line to the ground. My antenna is resonant at about 3.9 Mhz, and the impedance at SWR minimum (1.5:1) is about 80 ohms. I measure this right on the ground between the ladder line and my DPDT knife switch (I ground it out when not in use). I then use a 1:1 current balun, and RG-8X coax to the shack. My first try was to convert from 450 to 300 ohm tv twin lead at the hole in the wall, and go straight to a Johnson 275 matchbox with 300 ohm twin lead. This was dismal since the Johnson matchbox doesn't seem to have a wide tuning range to feed 80 ohms balanced. It did work unbalanced however, but poorly. So I switched to coax after a 1:1 balun for the run inside. If I do it again, and intend to feed this antenna at resonance, 75 ohm coax straight all the way might be an option. This loop loads up like a SOB, and absolutely NO RF in the shack. The problem though is that my signal reports are usually poor (often) to great (once in a while). It seems that for this to work efficiently as a low horizontal loop (high angle radiator) for short skip, I need good soil conductivity, or counterpoise. Stations beyond 500 miles can hardly copy me, and yet I can sometimes be full scale at 150 to 200 miles out early in the evening. Regards, Jim WD5JKO --- John Lawson <[EMAIL PROTECTED]> wrote: > > > Well - my Valiant is putting out stable rated > power on all bands - this > morning I'll suss out where the audio is > disappearing to - should be ready > for Air then... now to turn to the Radiator. > > > I'm still in the 'steep' part of the EasyNEC > learning curve - and I've > gone through the several ARRL antenna books - so I'm > properly confused. > > I have a loop of 14ga hard copper wire around the > rear of my propery, > attached (with insulators spaced at abt 8' apart) to > the fence - of about > 450 feet diameter, and nearly (but not quite) > square. It is about 5' above > the ground, except for one leg which is attached to > the house, where it is > about 7'. I am feeding it with 450-ohm ladder-line. > My Question to the > Antenna Gurus is this: At the feed-point, should I > maintain the > ladder-line spacing where it joins the loop ends, or > should there be an > angle, ie. should the loop ends be wider than the > feedline pitch - and if > so, what should the included angle of the feedline > 'transistion' be...? > > I've approached this from two or three analytical > directions, and of > course have different (and somewhat exclusive) > "answers".... so I'm > Learning, which is a good thing. > > > Cheers > > John KB6SCO > > > ______________________________________________________________ > AMRadio mailing list > Home: > http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami >
