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The power sensor requires a toroid transformer with ten turns and one turn. The next two photos show the transformer mounted on the board.
This is a screen shot of the Quisk Bands screen. The "Tx Level" setting lowers the transmit power to five watts on each band to avoid driving the power amp too hard. Check the power output with a 50 ohm load to check the settings. The HL2 only has 16 power settings even though the "Tx Level" can be adjusted from 0 to 255. The available settings are multiples of 16: 0, 16, 32, ..., 208, 224, 240. Other settings are rounded down to these values. Each setting changes the power output by 0.5 dB.
The "IO Bus" controls a seven bit number sent to the filter board using an I2C interface. Each bit controls one of the seven relays on the filter board. Bits are numbered 6 to 0 from left to right. Bit 6 controls a 3 MHz high pass filter to reject strong AM broadcast band interference on receive. The high pass filter should be used on all bands except 160 meters. The other bits control low pass transmit filters.
The integrated circuits for the I2C interface, the high pass filter, the relays and the SWR bridge all use readily available components. But you may need to find substitutes for the capacitors and inductors in the low pass filters. The specified capacitors are 630 volt NP0 (or C0G) in US 1206 (3216 metric). I used these because I had them available and I knew they had a high Q and good current capacity. Unfortunately, the manufacturers do not specify the Q or current. At 5 watts and 50 ohms, the peak voltage is 22 volts and the peak current is 0.45 amps. But the impedance is not 50 ohms, and we need to allow for open, short and arbitrary antenna impedance. You can try substituting 100 or 200 volt capacitors provided they are the same package (1206), and are NP0 or C0G dielectric. Test by checking for heating.
The inductors are more of a problem. The manufacturers specify the Q but not the RF current capacity. They do specify a DC current, but that is the current at which the inductance starts to decrease. For the low pass filters, the inductors from 220n to 680n are wirewound on non-magnetic cores. You can try to substitute other inductors on non-magnetic cores with the same or better DC current capacity. Inductors of one microhenry and up use ferrite cores, and the characteristics of ferrite at RF can vary. You can try to substitute these, but you will have to test whether they work at RF. A similar or larger DC current spec is a good start.