>>>
>>> Does the ARRL book really recommend a 4:1 balun with a hairpin
>>> match? I'd expect this to be a 1:1 balun.
>>
>>Yes, read section 18 of the ARRL Antenna Book. It is the
>>'Optimized Yagi' for 6 meters
>
>I'll look at the book eventually. But I'm willing to take your
>word for it now. It must be a folded dipole driven element or
>something. A "normal" simple dipole split driven element will
>usually be below 50 ohms at resonance in a yagi of 3 or more
>elements. The hairpin (or its cousin the "beta") match is used
>to bring the feedpoint up to 50 ohms for the feedline.
It indeed uses a hairpin match, almost a clone of the HiGain 66 which has
been described in several VHF pubs as a rather inefficient performer.
Changing the DE to an all metal T Match as used by CC and the highly
rated K1FO designs would be a better choice and less prone to wx related
VSWR problems.
SNIP
>>I'm not sure what difference this makes.
>
>If they aren't intended for operation above 30 MHz, they may not
>work all that well at 54 MHz.
A lot of the reasons behind balun problems in general and the W2AU 4:1
type in particular were covered in Sevick's book and magazine articles. I
dont have specific details handy.
Going to an optimized toroid core design rather than a lossy ferrite rod
can give excellent performance up thru microwave. However, the best
materials are not always available in sizes suitable for QRO.
A FairRite 67 ferrite mix or a Micrometals 6 and 7 powdered iron mixes
might be decent starting points for 50MHz.
GL Carl KM1H
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