Jim,
I stand by what I said (and we don't disagree, it's semantics). For
further (group, noob) understanding; an improved definition...
A 'tuner' is a variable impedance matching network; interfacing the
input impedance to the output impedance to allow the most possible flow
of energy between them. (Too many words for a noob.)
It doesn't need to take into consideration of the impedances along the
feed; it matches what it gets (as best it can).
It does zip for any antenna except (once adjusted correctly) allow the
most energy between input and output of the tuner to be exchanged.
THAT is the main benefit, more throughput while the secondary benefit is
less heat and longer life from an 'irritable' RF power source (i.e.
transistors) from mismatch. [You cannot expect long life of any final
of any kind at high power into a gross mismatch of impedance load. Some
devices allow you to learn instantly😮, that you've made a mistake;
others take time to inform you.]
A tuner does NOT make any antenna more efficient; it makes it louder
because the max energy is exchanged. Antenna efficiency, involves a few
more aspects not covered here.
WHAT impedances are being matched, depends on where the tuner (or even
fixed tuned circuit) is placed; at the antenna is usually optimal (less
feed losses); but it can be at any place along the path between rig and
antenna; making the downstream feed, part of the antenna network (some
designs require that feed for impedance matching). (Rig internal
tuners/matching are still AFTER the final.)
I too recall the tube days where one loaded the rig into a 50 ohm dummy
load for max output (peak, dip, repeat) then into a tuner (repeat the
same process on the tuner elements); where it went into the entire
antenna network (which was almost any impedance in those days). [I
still have that rig, but it's been so long without power, it could be
'exciting' to apply power now.]
And in those days, I also came up with configuration of (unboxed, open
on a board, DO NOT TOUCH the parts) tuner and antenna that 200 watts
went in and nothing reached the antenna (connected directly to the
tuner); but it sure warmed the room nicely (happy tube rig AND tuner
warmed up). "Why am I not being heard?" hi hi... Yep the tuner
happily absorbed ALL the output of that rig (a Knight as I recall).
I do not miss those days but they did teach (sometimes painfully). I'm
much happier with power on (boot) the (no tube) rig while the antenna
tunes (in the case of a SteppIR, it actually tunes, is always resonant)
and turns to the location direction I wish to work. Simpler, just ROCKS.
By the time the station has done those things (for me); I have the
refreshment at hand, seat adjusted then... get to work.
73,
Rick nk7i
On 9/30/2024 2:10 PM, Jim Brown wrote:
On 9/30/2024 1:39 PM, Rick nk7i wrote:
In the simplest sense, what a tuner does, is (attempt to) adapt the
impedance of the antenna to that of the source so that the max energy
is exchanged between the two (what works for TX, works for RX).
Hi Rick,
I disagree with this analysis and that proposed by AB7E, primarily
because it ignores the match between the antenna feedpoint Z and the
transmission line, which is what determines voltage and current
distribution along the line, and its loss. The tuner does NOT change
that.
What a tuner does is transform the antenna's impedance as seen at the
shack end of the line to a value that the transmitter's output stage
can supply power and operate optimally. For most modern transmitters
and solid state amps, that's 50 ohms resistive.
Those of us long enough in the tooth to remember hollow-state
amplifiers and output stages may have learned that they come equipped
with variably tuned output networks to do what antenna tuners do, but
usually over a much less-wide range. My Ten Tec Titan 425, 1978
vintage, could be happy with mismatches in the range of 3:1. Ten Tec
sold one of the best (greater efficiency over a wider range) tuners to
cover a much wider range.
BTW -- I know that you know all this stuff -- this post is for those
who don't. :)
73, Jim K9YC
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