I agree that folding the low-current parts of an antenna is a good way to make it smaller.
But there are several things at work in the comparison between the Steppir element and the V. Of course the height is one of them. But if you model an inverted V (90 degree angle between wires) and a dipole at the same height you will see that the dipole has significantly more gain. Many inverted V's are constructed with even smaller angles, which are worse. The V pattern also has smaller nulls on the ends. Finally, the Steppir undoubtedly has some kind of balun, and its feedline runs perpendicular to the antenna for 1/2 wavelength. All of these things improve the nulls. They also reduce noise pickup on the feedline. On 6/18/2012 5:26 AM, WILLIS COOKE wrote: > A note on folded back antennae. I have a 3 element SteppIR with the 30/40 > kit. The > antenna is mounted at about 67 feet above the ground. I have compared the > folded > antenna at 67 feet to a full sized inverted V at 40 feet and find it > noticeably > stronger. Even though it is only a dipole which is a little more than half > length it > is noticeably bi-directive with deep nulls off the element ends. It is quite > effective > as a DX antenna and I believe the SteppIR claim that it is only one or two dB > down from > a full sized rotatable dipole. Of course, its improved performance over the > inverted V > is mostly because of the elevation difference, but I would not hesitate to > fold the > ends of a dipole if restricted by lot size or other physical restraints. > > Willis 'Cookie' Cooke K5EWJ& Trustee N5BPS, USS Cavalla, USS Stewart > > > ----- Original Message ----- From: Don Wilhelm<w3...@embarqmail.com> To: Niel > Skousen<nskou...@talisman-intl.com> Cc: Elecraft > Reflector<elecraft@mailman.qth.net>; > qr...@mailman.qth.net Sent: Monday, June 18, 2012 6:18 AM Subject: Re: > [Elecraft] > Antenna Question > > Neil, > > When you see an antenna element folded back on itself like that, think > "linear loading" > (look it up in the ARRL Handbook or similar). There is no "magic", but it is > one way > of shortening an antenna. It is not as efficient as a full length antenna, > but is more > efficient than using loading coils. Everything is relative. If you have the > space to > put up full size half wave dipole antennas, that is the way to go. If you > need > shortened antennas for the lower bands, linear loading is one way to achieve > resonance > with shortened length. > > 73, Don W3FPR > > On 6/17/2012 11:26 PM, Niel Skousen wrote: >> I'm pretty sure I've seen this antenna on the net, but don't recall the name >> nor have >> I been able to find a link to a description / design data. >> >> The county ERC has a 'shortened fan dipole' with three parallel elements, >> spaced >> about 18-24" apart on each side. the longest element folds back around the >> mid-length element toward the shortest element. The antenna end insulator >> / guy >> rope is attached to the long element, where it folds back. There appears >> (from the >> ground) to be a 6~8" insulator / gap between the end of the shortest >> element, and the >> longest element where its been folded back. no traps, loading coils, or >> loading >> resistors that I can see. >> >> I'm assuming three or four band coverage (80, 40, 20, and 15 ??) with a 75m >> dipole, a >> 40m dipole (with 15m as a freebie), and a 20 m dipole. but would be >> interested in >> more technical details if anyone can decipher my text description above… >> >> Thanks Niel -- Vic, K2VCO Fresno CA http://www.qsl.net/k2vco/ ______________________________________________________________ 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
