Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP 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)