[TowerTalk] Mosley discussion

[Dave Thompson]

When I lost my homebrew W5HVV Quad (QST 1966) I put up a TA-36 and later added a 40 meter element.  The antenna did very well on 10 but was not nearly as good as the quad on 15 and 20,  I bought a Swan TB-4H for a song from Swan and that antenna did OK but when the KT-34X (early KT-34XA) came along W3TMZ got me one.  I had 5 el KLM beams for 10, 15, and 20 and the KT-34X seemed to do just as well with a lot less aluminum on the tower.  I put up a Cushcraft 2 el 40 which was and is a killer antenna on that band for the size.

The Mosley antennas that Carl Mosley designed use old technology and traps.  My TA-36 was on a par with most TH-6 antennas except on 15.  When Hy-Gain switched to the TH7DXX design the improvement was evident.  I have the Engineering paper on the differences between the TH6 and TH7.  For one thing the Log Cell adds some gain to the antenna.  K4EWG and Oliver Swan's work on the log cell showed clearly the log cell had gain and adding parasitic elements to the boom made an effective antenna. Oliver Swan's designs are in the KLM/M2 antennas.

I think the older designs that Mosley, Hy-gain, and even Telrex used were not optimum and the antenna modeling programs showed this.  W6SAI's equal spacing worked Ok but certainly was not optimum.  Years ago there was no comparison so most of us believed the old designs worked well. The W2PV and OWA designs are certainly steps forward in yagi beam design.  I also built a 7 el Razor beam (a quad-yagi) for 10 meters and made the high North America Score in the 1970 CQ SSB (now WPX) contest.  SM5BLA told me he got tired of tuning across me.   With my 71 foot crank up I could not put up razor beams for 20, 15, and 10 so finally settled for the KT-34X (now XA). 

There are several new Mosley designs (by K0VUW) that seem to work well.  We just need to  discuss antennas in relation to technology.  The Mosley TA-33 sold over 100K units and the hams who used them were head and shoulders above verticals and dipoles.     

Dave K4JRB