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To: <towertalk@contesting.com>
>Date: Mon, 12 Apr 1999 17:58:04 -0400
>From: Joe Shuey NE3H <ne3h@access.webcombo.net>
>
>Eric Gustafson wrote:
>
To: <towertalk@contesting.com>
>>>Date: Sun, 11 Apr 1999 17:12:27 -0400
>>>From: Joe Shuey NE3H <ne3h@access.webcombo.net>
>>>
>>>I am building a 6 meter beam. I decided on the Antenna book
>>>arraingement of feeding this Yagi with a Hairpin match and a
>>>4:1 balun.
>>
>> 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.
Snip... Discussion of measuring the baluns with different
instruments
>> >Is it unreasonable to expect a decent reading with such low
>> >power?
>>
>> Yes.
>> Why is the answer 'Yes'?
Because if the system is linear and capable of handling more
power than your test instruments expose it to, it should measure
good if it is in fact good at any level of excitation that is
adequate to produce valid readings on the test instrument. I'm
assuming that test instruments that provide their own excitation
provide enough to make valid measurements.
Snip...
>> Have you tried them with truly balanced (as opposed to
>> floating) loads? For example, referenced to a conductive
>> plane, ground the coax shield at the balun input and connect
>> 100 ohms from each wire of the balun output to ground?
This was a serious question.
>>
>> Are any of them designed for operation above 30 MHz?
>
>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.
>I swept the baluns from 1 to 100 mhz and reported the results at
>the best point.. abt 30mhz for most. Worse at all others within
>that spectrum.
What are you using for a load?
73, Eric N7CL
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