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Old March 8th 06, 08:55 PM posted to rec.radio.amateur.antenna
Dave Oldridge
 
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Default Q. about height of the ends of a doublet

Big Endian wrote in
:


My center of a 3.8 Mhz doublet is at about 35 feet and am going to
drop the ends from 30 feet to about 10 to 15 feet. Just wondering if
it will make all that much difference if any?


There will be a marked improvement in the low angle performance in the
direction off the ends of the antenna (the flattop is very poor at this).
This will come at the expense of a sight loss (about .8db) off the
pattern's top (where you can most afford it). You will also experience a
slight deterioration in the SWR (based on 50 ohm coax) from about 1.34 to
2.05, easily managed by any tuner, including those built into many radios.
You will also find that you need to shorten the antenna very slightly to
maintain the same resonant frequency.

This won't make it into a superior DX antenna but it may allow you to hear
things you missed before. Basically, Bob Heinlein was right. There ain't
any such thing as a free lunch.

--
Dave Oldridge+
ICQ 1800667
 
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