One point to consider, anytime one inserts a tuner in line at the
transmitter, additional loss is also introduced. Additionally the SWR
and related loss on the feedline is not reduced. Some tuners,
depending on load and frequency, can introduce as much as 25% power
loss. In many cases, a 2:1 SWR at the radio is better than using a
tuner to show a 1:1 SWR at the radio due to added loss in the tuner and
the feed line loss remains the same.
73
Bob, K4TAX
On 8/31/2017 5:09 PM, Bill Frantz wrote:
Sorry Jim. You are indeed correct about the feedline SWR. While there
are other SWRs within the radio, they aren't of much interest.
However, these radios do report a SWR in the UI, and that is what I
was referring to. Since a naive user might look at that figure and
say, "The SWR is 2. The antenna must be good.", it is important to
know that the tuners can produce a low figure on that meter with
nothing connected to the antenna connector.
73 Bill AE6JV
On 8/30/17 at 11:25 PM, [email protected] (Jim Brown) wrote:
Please don't perpetuate that myth, Bill. Tuners do NOT reduce the SWR
unless they're at the antenna end of a transmission line. The SWR
exists on the transmission line, and it is determined ENTIRELY by the
match between the transmission line and the load.
What tuners at the rig do is get the rig to put power into the tuner
(and hopefully, onto the transmission line). If the SWR is high
without the tuner, it is equally high WITH the tuner. Depending on
the cable, the frequency, and the SWR, much of the power that the rig
puts into the tuner gets to the transmission line, but is turned into
heat by the SWR in the line and doesn't get to the antenna.
A better way to talk and think about this is to say that the tuner
can match a wide variety of loads to the transmitter sufficiently
well that the rig can pump the maximum power from its output
terminals, whether it's feeding a short wet string or a nice long
wire we've launched into a tree. And if there's no transmission line,
SWR has no meaning! So SWR is the wrong way to talk and think about it.
73, Jim K9YC
On 8/30/2017 10:15 PM, Bill Frantz wrote:
My experience with the tuners in both the K3 and KX3 are that they
will reach an acceptable SWR with anything. I always check the
antenna when they take a long time to reach a match. (I.e. lots of
clicking.) Most of the time I find I am trying to match an open
antenna connection.
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