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 => 00000011 (L) > 1A => 00011010 (C) > 01 => 00000001 (network selection) > > Now compare these values to the KXAT3 schematic. 00000011 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 00000001. 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, "AK000000;" 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 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
