Re: [loopantennas] Re: G4HOL horizontal loop aerials
- Hello SteveThanks for the reply. It was only due to reading the Royal Signals article on horizontal loop antennas that led me to your Yahoo group. Up to then I didn't know it existed. I am a member of various groups relating to Ham radio and find them very useful. What I like about the groups is that every question that I have asked is answered in various ways and this has helped to grasp the technical jargon more easily.Your answer to my question was both enlightening and amusing. I will endeavour to read the emails since joining your groupRegards JohnFrom: AlienRelics <alienrelics@...>
Sent: Wednesday, 17 July 2013, 20:24
Subject: [loopantennas] Re: G4HOL horizontal loop aerials
Loop antennas are magnetic loops, and magnetic loops are loop antennas. "Magnetic loop" just references the fact that a loop antenna is mainly sensitive to just the magnetic field and not the electric field of an incoming radio signal.
Sometimes people want a group revolving around a specific type of loop antenna, sometimes they don't understand that a "magnetic" loop is just a loop antenna, sometimes they don't like the moderator, sometimes they just don't search for a group before starting one, sometimes their group starts as a local club's group and expands. Sometimes a person wants to market their own loops or parts, and so starts up a group of their own. Sometimes a person is a little nutty and starts multiple groups, each covering slightly different antennas, just to be in charge of a lot of groups.
Steve Greenfield AE7HD
PS Full disclosure, I'm moderator of this group.
--- In mailto:loopantennas%40yahoogroups.com, "john" <jinwood2@...> wrote:
> Hello Mike and Group
> I am a member of Royal Signals Amateur Radio Club and have been reading the article in this July 2013 journal regarding G4HOL horizontal loop.
> My query is the connection of 300 ohm slotted ribbon to an ATU. It states that one leg should go to the Antenna post and the other leg to the earth tag.
> Does this mean using wire (A) from one end of the cable loop and wire (B) from the other end of the cable? Alternatively should the one end of the cable be short circuited across the two legs and the other end of the cable be used to connect to the ATU?
> My other question (being new to loop antennas) is that a group exists dealing with Magnetic Loops. Are these loops completely different to your loops or would it be better to have just one group to include all types of loop antennas?
> I must apologise for questions of this nature but my tendency is to know precisely how things are done.
> Regards John 2E0KUF
- In my opinion, a "Magnetic Loop" antenna is a distinct species and they are better left alone as a separate group. Contrary to the name, and contrary to intuition, a Magnetic Loop antenna is not one that generates only a magnetic field, or that is sensitive only to a magnetic field. It has even been shown that many Mag Loop antennas are actually the opposite, responding somewhat more greatly to the electric field than the magnetic field.I believe the distinguishing feature of a Magnetic loop is one whose total circumference is much smaller than one wavelength ... perhaps no more than a tenth of a wavelength ... such that the current magnitude and phase around the loop is everywhere nearly the same. This is in contrast to "full size" loops, quad loops, delta loops, horizontal skyloops, and such, where the circumference is usually comparable to a wavelength, or longer. A consequence of this difference, is that a Mag Loop antenna has totally different radiation characteristics to a non-Mag Loop antenna. The directions of maximum radiation, and of the nulls, are reversed!So even though a Magnetic Loop might be considered "just" a loop, I put to you that it isn't, and that it is best treated separately.About your question about the connections, it's a little hard to tell what you mean, and I don't have access to the article. It doesn't make sense to connect wires from opposite ends of the feedline to the ATU and earth. Same end only.Articles about the Skywire horizontal loop describe using it two ways:On higher frequencies (most bands), keep the two ends of the loop separate.On lower frequencies (usually meaning 160 meters), where the loop is too short to be an effective loop antenna, short the ends of the loop together, or the two wires of the feedline together, and drive it against earth. What you really have in this case is not a loop antenna anymore, but a vertical antenna (the feedline), with what was your "loop" acting as a capacity hat. It's a way of "cheating" ... getting an extra band out of that copper where it doesn't make a good loop antenna anymore.Andy