For my 160m shunt fed tower I had a Rohn 25 - a 60 footer with a few feet buried in concrete...
So I dug out some old articles on how to do it. Now, I DID have a good capacity hat in the form of a 4 element Swan TB4HA beam at the top. AND an 11 element Cushcraft bean on 2m FM above that. I had deliberately installed insulators on the guy wires, so that was not a problem. Ran a piece of #12 gauge solid copper wire up the side about 12" off the tower to a copper pipe standing off at about the 40 or 50 foot level and attached firmly to the tower with two U bolts. This is all from memory. There was a sreries variable capacitor at the bottom of the shunt line, and it worked really well. Flat SWR anywhere I wanted on Top Band! 73 de AF4K, Bry Don K4KYV writes: > I prefer the base insulator and series feed myself. Shunt feed or unipole > feed works great if the tower is close to a resonant length. It becomes > more difficult if the tower is much shorter than natural resonance. > > Sometimes top loading will make shunt feeding easier, since it raises the > resonant frequency of a short tower. Series feed, if you can find an > insulator, gives you a lot more options in tuning up the tower. > > Of course, if you are stuck with a typical ham radio style jury rig where > the bottom section was embedded several feet into the concrete base, you > have no choice. Unless the tower is short enough to stand without guys, > that is about the worst possible way to erect a tower. A tall guyed tower > is subject to much additional stress when the base is rigidly set in > concrete; it cannot sway or rotate in heavy winds, and that can cause > failure of the tower structure. If it is mounted with a base plate and pier > pin, or a ball-and-socket insulator as AM broadcast towers are constructed, > the base of the tower can follow the movements of the tower instead of > having the entire tower bend and twist under high winds. > > Don k4kyv > > > _______________________________________________________________ > > This message was typed using the DVORAK keyboard layout. Try it - you'll > like it. > http://www.mwbrooks.com/dvorak/ > http://gigliwood.com/abcd/ > > > ______________________________________________________________ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:[email protected] > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb >
