They are overweight and underoptimized. And the design inherently prevents
proper optimization. They were supposedly based on an nbs standard yagi
with a fixed element spacing and simple taper, and I doubt that the element
diameters were properly accounted for. Their big 10m one that I modeled
would have made a decent 11m beam it was so far off. Their 6 ele 20m
optimized down to 5 elements, as did the 8 element 15m. Also, the older
ones were decent mechanically, though heavy... newer ones had vibration
problems because the aluminum was made stiffer and lighter, but the element
to boom attachments weren't changed so they tended to vibrate loose and
break off the boom.
David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
> -----Original Message-----
> From: Steve Baughn [mailto:baughn@wowway.com]
> Sent: Saturday, November 15, 2008 02:15
> To: towertalk@contesting.com
> Subject: [TowerTalk] telrex question
>
> I am contemplating an antenna farm utilizing Telrex yagis for 20-10
> meters. I have never owned one and only know about them through their
> reputation. Afte hearing some of their advertised gain figures, I have to
> wonder if they are as good as their legend would lead one to believe. I
> was looking at a 20M646-6el 20 on a 46' boom and the advertised gain was
> 14DB, when in fact it should probably be somewhere in the 8-9db range.
> They also appear in some cases to use an extra element or so given a
> particular boom length i.e., the 20m646 uses 6 elements on a boom length
> that would typically have 5 based on modeling.Can someone enlighten me as
> to Telrexs' claims? I am also looking for some of their antennas if anyone
> out there has any for sale at a decent price. Thanks es 73,
>
> Steve, WD8NPL
> _______________________________________________
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