```The formula for a single-turn loop I found in the 'Taschenbuch der Hochfrequenztechnik' is the same as Dave's. 73, Rik ON7YD At 07:44 24/11/99 PST, you wrote: ``````Hi Dave, I've been reading your Home Page and came across a formula for the radiation resistance of a loop antenna: Rrad = 320*Pi^4*A^2/L^4 where A is the area of the loop in square metres and L is the wavelength in metres. There is a similar formula in the LF Experimenter's Source Book, in an article on LF Transmitting Loops (page 2.25). No author is given, but it is ```attributed to "Break In" July 1995. The formula given there (page 2.26) is: ```Rr = 7.72E-30*f^4*A^2*n^2 where f is the frequency in Herz, A is the loop area in square metres, and n is the number of turns. Putting n = 1 as in your case and this reduces to: Rr = 7.72E-30*f^4*A^2 The problem is that this formula gives results twice as big as your formula. A factor of 2 appears to have got lost somewhere in one of the two formulae. My question is, which one is right? If the second one is right, your loop is twice as good as you thought it was! One more question. Where can I get 3C85 ferrite rings? I've been through all the catalogues with no success. I hope to be on the air before too much longer. I put up a G5RV a few weeks ago for HF. Because the garden is short, the last 20 feet or so of each arm are turned down to about 8 foot above ground. Having tried a few calls it seems to be working quite well on HF. So now I have provisionally connected the two ends with a good thick multistranded earth type wire and supported it about 2 feet above the ground from one end to the other. The garden is on rather a dramatic slope, rising by over 20 feet at the bottom, so climbing boots were necessary. Like Steve ALG, I quickly found that a 300 ohm conventional feeder has got far too much resistance, so I must change that before I do much more, but I don't want too much weight on the antenna. The total DC resistance was found to be 1.8 ohms and after a few measurements and calculations I found that this is made up of: 34 feet of 300 ohm ribbon 0.7 ohm 15 metres of RG58CU 0.63 ohm 102 feet of 16swg antenna wire 0.3 ohm ```lower loop wire 0.17 ohm ```So the main thing is to replace the feeder and the coax. I don't fancy replacing the 16swg with 14swg, so I may have to live with that, but I may go for even thicker wire for the lower part of the loop. I've got some very heavy gauge 50 ohm coax with a 2.5 mm core, so this may do to connect the bottom of the feeder to the shack, using a balun/matching unit at that point. A loop of this type is attractive for me, because I can't really put up two antennas, one for LF and another for HF. Obviously for HF the lower part of the loop must be disconnected, but that doesn't seem too big a problem. ```73s ```John, G4CNN, Locator: IO91ML ________________________________________________________________ Get FREE voicemail, fax and email at http://voicemail.excite.com Talk online at http://voicechat.excite.com `````` ```