May I add to Don's comment by noting that other benefits to be gained from
the use of a properly designed link coupled tuner (we used to call them
Antenna Matching Units or AMUs) are:
1) This type of tuner being a bandpass circuit helps to reduce the level of
unwanted signals reaching the receiver, e.g. Medium and Shortwave broadcast
signals, which if not reduced in level could result in receiver
generated intermodulation products being heard. This type of tuner also
reduces the level of the transmitter's harmonics reaching the antenna.
2) That if a ferrite or iron cored balun (sorry Jim) is used with this type
of tuner, it would be placed in the link circuit where the impedance is 50
+j0 ohms - or close to this value, and it would not be exposed to
large values of reactance.
3) Placing a balun at the end of a feeder exposes the balun to all of the
signals arriving down the feeder, which in some situations could be strong
e.g. Medium Wave and / or Shortwave BC signals. This could result in
numerous intermodulation products being generated by the balun's core, some
of which might end up in our bands. One has to careful
as well that a ferrite/ iron cored balun connected to the feeder or
antenna's feedpoint does not increase the level of radiated transmitter
harmonics.
73,
Geoff
LX2AO
On Dec.09, 2011 at 3:53 AM, Don Wilhelm wrote:
> For those who want a really high efficiency balanced tuner, go to ARRL
> publications back several years to find a link coupled tuner.
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