```Hi Andy, Interesting conundrum that had me scratching my head. These are the conclusions I've come to. Firstly the efficiency has nothing to do with the radiation pattern as you suggest. Since you are now filling in the nulls with radiation; this will steal radiation from the lobes of the single loop system. IE The net radiated power is the same, but the peak field strength has reduced (by say 3dB). Secondly for a small loop you must phase each loop at 90 degrees to obtain the desired omni-directional pattern, as suggested by DJ1ZB. Thirdly the efficiency should be the same as a single loop if you feed them in series or in parallel with 90 degree phase shift. So far it appears that Argument 1 is holding up. Not being conversant with the works of Argument 2 all I can suggest here is that the efficiency does not increase since only one loop is giving it's full radiation every 90 degrees with the other loop contributing nothing. Since the phasing will split power evenly between the 2 loops. Net result same efficiency, hence the Argument 2 model is actually a single loop. Finally since the world is never perfect some loss will occur in the 90 degree phasing so the answer as I see it is the same efficiency as a single loop less the efficiency of the phasing required to feed both loops to give you an omni-direction pattern. 73, Lee M0LMH. -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Andy Talbot Sent: 21 July 2008 12:30 To: [email protected] Subject: LF: Loop Conundrum Was pondering this while out walking the other day, and couldn't come to a satisfactory conclusion either way... A small magnetic loop mounted vertically has a defined radiation resistance that is a function of its diameter, a loss that is function of its conductor and hence a loss or efficiency that is the ratio of the two. It is resonated with a good quality vacuum capacitor, and fed/matched by any suitable metrhod. Lets also leave aside all the myth and folklore about small loops, and also ignore the environment for now. It also as a radiation pattern with nulls. Now, I take two identical such loops and mount then on the same centre line but at right angles to eachother so there should be no coupling between them, whatsoever. Now, I connect the two loops in series and resonate the combination with a single capacitor of half the original value. The resulting radiation pattern should have the nulls filled in, and be a reasonable approximation to omnidirectional in azimuth. BUT... What is the resulting change in efficiency? Argument 1: Two identical loops = two times the loss R, but also two times the radiation resistance (since they don't couple) so net efficiency remains the same. Argument 2 : Chu-Harrington relates efficiency / Q / bandwidth / volume enclosed. Therefore, as the enclosed volume has increased, the effciency ought to rise. Both arguments developed little side trendrils & thoughts as I walked and pondered, and both appear valid in their own way. So the floor is open for discussion :- And where does the net radiation pattern fit into the equation? Does it, at all ? -- Andy G4JNT www.scrbg.org/g4jnt ps. Fascinating paper on EMP btw. - I was up way past midnight last night reading it. No virus found in this incoming message. Checked by AVG - http://www.avg.com Version: 8.0.138 / Virus Database: 270.5.3/1563 - Release Date: 7/20/2008 12:59 PM ```