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Path: utzoo!watmath!clyde!bonnie!akgua!sdcsvax!sdcrdcf!hplabs!sri-unix!Taylor.WBST@XEROX.ARPA
From: Taylor.WBST@XEROX.ARPA
Newsgroups: net.ham-radio
Subject: Re: antenna tuners for receivers.
Message-ID: <12407@sri-arpa.UUCP>
Date: Wed, 26-Sep-84 10:35:00 EDT
Article-I.D.: sri-arpa.12407
Posted: Wed Sep 26 10:35:00 1984
Date-Received: Sun, 30-Sep-84 04:15:33 EDT
Lines: 31


	There's a distinction which should be considered when choosing an
antenna tuning/matching configuration-- especially when the antenna is
small (ie: less than 1/4 wavelength).  If the antenna proper is adjusted
to resonance first and then a matching network is adjusted one may have
improved signal reception  -- as much as 5 to 10 decibels improvement!

	The reason for this may seem a little subtle.  If the antenna is
resonated first we can control by the method of resonating just where
the current and voltage loops are along the length of the radiator
independently of the subsequent matching process.   For example, by this
procedure one can locate a current loop at a high point on the radiator.
However, if one just peaks the antenna trimmer in the receiver or,
alternatively, peaks an external antenna tuning unit the current loop
may be located at an undesired  point, perhaps deep down in a coil
inside the case of the tuner-- not a good spot to a intercept  incoming
radiation!

	As a practical case, I can get about 6 db higher signal-to-noise at 4
mhz using a 30 foot long loop of wire by  series resonating this, using
a noise bridge for indication, as compared with just using the antenna
trimmer adjustmaent in my Uniden SR-2021!  The latter case picks up much
more electrical noise since only the end of the radiator is exposed-- it
makes a superior electrostatic probe!

		Good luck!


			Jim (W2OZH)