[Antennas] increased antenna bandwidths through a tuner, why?

Sun Apr 30 01:06:31 EDT 2006

 Sam,
 In a word you are reducing the Q of the apparent load, your
 antenna. In all actuality you are padding the load , as to create a
 more desireable load for the transmitter. You really are not changing
 the antenna characteristics of the antenna.
 The only way to do that is to insert a network at the antenna end of
 the transmission line, in which case you wont need a tuner, if you do
 it right.
 This is the most difficult aspect of an efficient antenna, and the
 least understood. The modeling programs make the solution simple, by
 providing the network to use with a 50 ohm transmission line. And we
 all thought all there was to an antenna, was an equation to calculate
 the resonant length.
 Gene KZ5V
 ______________________________________________________________
 From: Sam Morgan <ka5oai at cox.net>
 To: "antennas - qth.net" <antennas at mailman.qth.net>
 Subject: [Antennas] increased antenna bandwidths through a tuner,
 why?
 Date: 2006年4月29日 07:27:08 -0500
 I have a bugcatcher set with 1:1 at center frequency of 7.09 with
 no tuner.
 It has a base coil taped for minimum swr.
 When I check the 2:1 to 2:1 bandwidth it is about 76kc.
 If I run it through my home brew T-tuner, and set the tuner to have
 the same 1:1 at that same 7.09 frequency, I then get a bandwidth of
 151kc. (not touching up the tuner further than when I set it to 1:1
 initially).
 The tuner is set with both caps @ 50% and the (small) roller
 inductor is set at about 7 of 17 turns out from minimum inductance.
 It makes me happy, sure, but I'm wondering if someone would explain
 it to me.
 How does it increase the bandwidth if the same 50ohm feed point is
 there with or with out the tuner.
 --
 GB & 73's
 KA5OAI
 Sam Morgan
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