Re: [amsat-bb] Cheap Yagi Antennas for VHF/UHF: experiences?

[K5OE@xxxxxxx]

Achim,
These have been around for a number of years.  After seeing one built by Howard, G6LVB, at AMSAT-UK last year, I decided to try one out.  Howard bragged like a new father about how easy it was to build and how flat an SWR it had--and he brought along an MFJ SWR meter to prove it!  See:  http://www.g6lvb.com/

I recently built a 10-element version in "cross-Yagi" style with orthogonally oriented elements.  I used 1" PVC pipe and #10 AWG Cu wire.  Unlike Howard's though, I did not offset the elements--I arranged the perpendicular elements adjacent to each and brought each feedpoint down to a coaxial relay on the mast for polarity switching.  Howard's version is fixed RHCP.

The design is indeed broadbanded and easy to tune.  The "J" feed element is novel in a Yagi configuration, but works very well as a nice balance between the too-touchy folded dipole and the too-low-impedance dipole.  I spoke to Kent about the design at the time I was building it.  I modeled it in YagiMax and NEC4Win95 but got different results... thus contacted Kent to discuss.  I subsequently learned an important lesson about modeling sharp turns (90 degrees) in NEC.  Anyway, I digress...  the design works as advertised and I have been using it succesfully on AO-40 (and LEO's) for about 4 months now.

In correspndence with NC7I, Norm, he just built one and has it in his attic on a TV rotor.  He seems pretty happy with it as well.
73,
Jerry, K5OE


In a message dated Thu, 14 Feb 2002  2:00:00 PM Eastern Standard Time, Achim Vollhardt <avollhar@physik.unizh.ch> writes:

> Hi all,
> 
> I want to construct a UHF cross yagi for 70cm AO-40 ops. the Yagis on
> the website of Kent Britain, WA5JIB
> 
> http://www.clarc.org/Articles/uhf.htm
> 
> are quoted with something around 12dbi for the 435 MHz Amsat Versions.
> Has anyone experience with this antennas? particulary the quite 'flat'
> and unconventional driven element seems funny to me.. I have NO
> experience on Yagi design..
> 
> How much ERP do you need for apogee?
> 
> 73s Achim, DH2VA
> 
> 
> -- 
> 
> -------------------------------------
>     Achim Vollhardt
>     Universitaet Zuerich
>     Physik Institut, 36H24
>     Winterthurerstrasse 190
>     CH-8057 Zuerich
>  
>     tel: 0041-1-6355742
>     0041-1-6355704 (fax)
>  
>     email: avollhar@physik.unizh.ch
> 
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