On 2022-03-13 3:24 PM, Mickey Baker wrote:
The KW Matchbox that I have is a simple device with a single inductor
with 8 taps that all connect back to a 2 gang band switch.
Those taps/2 gang band switch would be on the secondary coil.
Manual and schematic for the Johnson Matchbox is here:
<https://bama.edebris.com/download/johnson/matchbox/matchbox.pdf>
Unfortunately, the schematic does not give tapping info for the
primary/link coil but if the ratio of tap point to size of the
coil shown is reasonably accurate 1.25 of 5 turns looks about
right. It's likely/common that the T/R relay has been removed
(and along with it the receiver antenna feed/muting contacts).
73,
... Joe, W4TV
On 2022-03-13 3:24 PM, Mickey Baker wrote:
The KW Matchbox that I have is a simple device with a single inductor with
8 taps that all connect back to a 2 gang band switch. I can’t speak to any
mods made.
W0QE has a comprehensive video:
https://youtu.be/OvRI1m4bBjQ
Mickey N4MB
On Sun, Mar 13, 2022 at 1:27 PM Tom Hellem <tom.hellem@gmail.com> wrote:
I have a Johnson KW Matchbox that doesn't seem to be working quite right.
It's very hard to accomplish a perfect match at times even though the load
is well within the claimed capability of the tuner. The RF input from the
TX is injected into an approx. 5 turn coil which surrounds a smaller
diameter coil of many more turns. Looking at the 5 turn coil I can see that
some previous owner had tried tapping different points on it for injecting
the RF.
Question- how critical is the tap point on this coil for proper operation
of the tuner?
The 5 turn coil is grounded on one end and open on the other, and is
currently tapped approx. 1-1/4 turns from the grounded end.
Does anybody know where Johnson tapped this coil when they built the tuner?
Any input gratefully accepted.
Tom
K0SN
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