Cqtestk4xs@aol.com wrote:
>
>In a message dated 4/20/2009 10:12:14 PM Greenwich Standard Time,
>garyschafer@comcast.net writes:
>
>A 1/2 wavelength (or multiple of) of 75 ohm hardline could be used and
>when
>hooked to a 50 ohm antenna, 50 ohms will be seen at the other end of the 75
>ohm line.
>
>
>
>That's true, but difficult to do for a tribander. The 1/2 wave xfrmr is
>simple to do for monoband setups, but becomes more complex for triband
>situations, which is what most guys have.
>
>73 Bill KH7XS/K4XS
>
>
A multiple of a 1/2 wave at 3.55 MHz should cover 20, 17, 15, 12, and 10
meters (these bands are approximately 4, 5, 6, 7, and 8 harmonics
respectively). The greater the multiple, the worse the bandwidth. A
more bandwidth independent solution would be:
http://www.arraysolutions.com/Products/baluns.htm#50:75%20ohm%20Xfrm
(see AS-75:50-1)
At $85 a pop this may be the may be the cheapest solution on a "time is
money basis". It has fewer connections to waterproof than the
asynchrounous transformer solution and doesn't suffer from the bandwidth
problems of the multiple of a 1/2 wave line scheme. Which solution is
best depends on the particular circumstances. It is an interesting
system design problem.
73, Mike W4EF..........
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