Wayne wrote:
You can't get L-network information via the menu. But you can send
an AK; (ATU relay settings) command from the KX3 Utility Command
Tester.
The response format is AKaabbcc;, where:
aa = inductance bitmap in ASCII hex format
bb = capacitance bitmap in ASCII hex format
cc = misc relays bitmap in ASCII hex format
At present only bit 0 of byte cc is defined:
00 = capacitance on antenna side
01 = capacitance on transmitter side
Example: Suppose you get back AK031A01;. First convert the hex
quantities to binary:
03 = 0011 (L)
1A = 00011010 (C)
01 = 0001 (network selection)
Now compare these values to the KXAT3 schematic. 0011 for L means
that two smallest inductors are switched in. Add these together to
determine the total L value. Similarly, add up the selected capacitors
based on the binary value 00011010. Finally, you can determine the
network configuration from the value 0001. In this case, the
capacitance is on the transmitter side of the series inductance.
There is a quick way to convert the AKaabbcc word to actual L and C
values and configuration that does not require looking at a binary bit
pattern, correlating each set bit to a specific relay and reactance
on a schematic, and then adding up the connected values.
The KXAT3 has a maximum ATU inductance L = 15.93 uH. The eight ATU
inductance switching relays divide this into 256 (almost) identical
steps. When the ATU has found its best match, a hexadecimal value is
set in aa that is the number of those steps used by the current ATU
inductance setting. So:
1L. The inductance step size is 15.93 uH / 256 = 0.0622 uH.
2L. Convert the hexadecimal value aa to the decimal value AAA.
3L. Total inductance connected is AAA x 0.0622 uH.
The KXAT3 has a maximum ATU capacitance C = 2683 pF. The eight ATU
capacitance switching relays divide this into 256 (almost) identical
steps. When the ATU has found its best match, a hexadecimal value is
set in bb that is the number of those steps used by the current ATU
capacitance setting. So:
1C. The capacitance step size is 2683 pF / 256 = 10.48 pF.
2C. Convert the hexadecimal value bb to the decimal value BBB.
3C. Total capacitance connected is BBB x 10.48 pF.
That's all it takes to compute the effective L and C values. The only
iffy part for a few may be converting a hexadecimal value to its decimal
equivalent.
Once the L and C values are known, all that remains is to determine
if the capacitor is connected on the antenna side (cc = 00) or the
transmitter side (cc = 01).
For Wayne's example of AK031A01:
The ATU inductance byte is 03(hex) = 003(decimal).
The ATU inductance thus is 3 x 0.0622 uH = 0.1866 uH.
The ATU capacitance byte is 1A(hex) = 025(decimal).
The ATU capacitance thus is 25 x 10.48 pF = 262 pF.
The ATU capacitance connection byte is 01(hex).
The ATU capacitor is thus on the transmitter side.
So, the ATU reactance is a series inductance of 0.1866 pF
with a capacitance of 262 pf from the transmitter end of
the inductance to common.
NOTE: Because the eight inductances or capacitances are not
always *exact* factors of 2 from each other due to practical
individual manufacturing or value availability issues, there
will sometimes be very slight differences between the results
from this quick approach, and that from determining which bits
are set in two bytes and applying that to relay configuration
with associated reactance values in the ATU. Applying that
painstaking approach to Wayne's example yields an inductance
value of 0.18 uH (vs. 0.1866 uH) and a capacitance value of
264 pF (vs. 262 pF). Pretty darn close!
Were one very often interested in this detail about KXAT3 settings,
it would be great if firmware did the required work.
If the ATU is not installed, or if the ATU MD menu entry parameter
is set to one of the L/C test values, AK00; is returned.
If the ATU is in bypass mode, quasi-bypass values are shown.
(These were selected to approximately cancel out the ATU's own
stray reactance on each band.)
In AUTO mode, the working auto-tuned values are shown.
I admire the attention to small detail that the description of the
bypass function shows.
73,
Mike / KK5F
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