Posted by
Ron D'Eau Claire-2 on
Feb 01, 2006; 6:19pm
URL: http://elecraft.85.s1.nabble.com/PAR-antenna-on-80-meters-tp386245p386247.html
You can often get a match to a difficult antenna system by making it LESS
efficient. Many have posted how they have been able to load up this or that
antenna after using fewer radials in the counterpoise or through some
similar means.
That raises the resistance of the system which helps the tuner. The bad news
is that the added resistance is loss resistance, not RF being radiated. But
as Eric observed, it can make a system usable in a pinch.
Of course low SWR is *not* an indication of antenna efficiency. As others
have pointed out many times, were that true our dummy loads would be the
best antennas ever!
Probably the best indicator is the "Q" or sharpness with which our antenna
systems tune, especially when using an antenna that is less than 1/2 wave
long. Efficient short antennas have high "Q", tuning sharper and sharper
(have less bandwidth at the 2:1 SWR points) as they get shorter. For
example, I have a doublet that is only about 80 feet overall. It works FB
on 80 meters, but I have to retune if I move more than 5 or 10 kHz to keep
the SWR down below 2:1. That is a sign that it is working efficiently.
If you have a short antenna that seems to work over a broad range in the
band, you can be sure that there is a lot of loss resistance in the system.
Be happy if your short antenna requires that you to wait while the tuner
finds a new match after moving a few kHz!
Ron AC7AC
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