The KX2 firmware currently being field tested allows you to determine the ATU’s
LC network settings while in the menu. (This feature will be added to the KX3
as well.)
Below is the information needed to extract the actual L, C, and L-net
configuration values from the information that is flashed on VFO A when you tap
“ATU” in the new ATU DATA menu entry.
Wayne
N6KR
* * *
While in the ATU DATA (or ATU MD) menu entry, tap ‘ATU’ to obtain the L/C/Net
values.
The displayed data format is “LaaCbbNc;”, where:
aa = inductance bitmap in ASCII hex format
bb = capacitance bitmap in ASCII hex format
c = L network relay setting:
A = capacitance on antenna side
T = capacitance on transmitter side
Example: Suppose “L03C12NT” is flashed. The network setting is shown by the
last character (A or T; see above).
Next, convert the L and C hexadecimal quantities to binary:
03 => 00000011 (L)
12 => 00010010 (C)
Compare these values to the lists below, which show approximate L and C values
for each bit of the binary word. In the example above, 00000011 for L means
that two smallest inductors are switched in (.05 and .11 uH). Add these
together to determine the total L value. Similarly, add up the selected
capacitors based on the binary value 00010010.
--------------- Binary Value ----------
0 0 0 0 0 0 0
L, uH: 4.0 2.0 1.0 .5 .23 .11 .05
--------------- Binary Value ----------
0 0 0 0 0 0 0
C, pF: 680 330 164 82 39 18 10
Note on L/C values: The ATU uses industry standard 5 % values for C, and
approximately 5% tolerance on toroidal inductors. L and C are not exact but
will be monotonic over the required range of about 3 to 5 elements for a given
match. In addition, all ATUs have stray L and C that will result in selection
of somewhat different values than expected. This effect becomes more pronounced
as the operating frequency increases.
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