Hi All, A friend of mine here locally once did quite a bit of modeling for loops. He determined that setting up a loop vertically was easier than he expected. Horizontal loops are difficult here in the desert. Anyway, his modeling disclosed that the horizontal height of a vertical loop (full wave) only needed to be about 30 degrees to start being quite effective. In other words, a 40 meter vertical loop only needed to be about 11 or 12 feet high on each end, with the rest of the loop run horizontally. This is not all that difficult to do with readily available supports. Of course, the bottom of the loop should be off the ground as much as possible, so the total vertical height should be something more than just 11 or 12 feet. Vertical loops are quite directional, but they have a lower take-off angle for DXing.
Smaller magnetic loops may have similar tendencies. I know it is important to get them up off the ground as much as possible, and I have always had much better results using them vertically as opposed to horizontally. I built a couple of these things from magazine articles, and they do work. It's hard though, to imagine the efficiency being all that great. Nevertheless, they are fun to play with, and not too difficult to make yourself. Bill Jones, KD7S, had a very good article in QST some years back which really gives you a lot of important info about doing various things to make the antenna as efficient as possible. His "trombone" capacitor was very interesting, but I haven't tried that yet. I would think that apartment dwellers, hopefully having a balcony, might have some real fun tinkering with these antennas. If you are high enough off the ground you might get decent results using the loop horizontally. A low RPM motor to tune the capacitor makes life easier too. I bought one from Edmund Scientific, and it worked very well. The tuning will be extremely sharp however. I was never able to go more than a few khz without having to retune. Dave W7AQK ----- Original Message ----- From: "Julian, G4ILO" <julian.g4...@gmail.com> To: <elecraft@mailman.qth.net> Sent: Tuesday, August 04, 2009 1:35 AM Subject: Re: [Elecraft] Magnetic Loops > > > > Gary Hinson wrote: >> >> By the way, I don't know if it's the same with magnetic loops but the >> fullwave loops radiate mostly "broadside" to the plane of the loop. >> If the loop is vertically oriented (e.g hanging between two trees), >> the polarization of the signal is determined by whether the loop is >> fed at a horizontal or vertical section of wire. If the entire loop >> is laid 'flat on its back', most of the radiation heats the ground, >> some heats the clouds but I'm uncertain what polarization the signal >> would be - probably horizontal I guess since all the wire is parallel >> to the ground but I may be wrong. >> >> > > With magnetic loops most of the radiation is in the plane of the loop, and > it's vertical polarization if the loop is vertical. But there is not much > directivity. There are nulls axially through the centre of the loop but > they > are extremely sharp. The polarization also changes to the horizontal as > you > move round to the side too. > > According to MFJ if you can get it up high enough you can mount their > magnetic loops horizontal and get omnidirectional horizontal polarization > with nulls straight up and down. > > It's interesting switching between the magnetic loop and a dipole, > sometimes > the dipole has the stronger signal and sometimes the loop. A receive > magnetic loop would make an inexpensive and easy to make antenna for > diversity reception for those who have the 2nd RX in their K3. > > ----- > Julian, G4ILO. K2 #392 K3 #222. > * G4ILO's Shack - http://www.g4ilo.com > * KComm - http://www.g4ilo.com/kcomm.html > * KTune - http://www.g4ilo.com/ktune.html > > -- > View this message in context: > http://n2.nabble.com/Re%3A-Magnetic-Loops---Stan-tp3378914p3383267.html > Sent from the Elecraft mailing list archive at Nabble.com. > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
