Bill K9HZ who we have already reported had developed a relay control system driven by the Low Pass Filter I/O lines. In addition, Glenn VK3PE has also come up with a circuit that could be adapted using a digital potentiometer module to be driven by the Raduino using a digital I/O line.
Relay drive control
Bill K9HZ has now drawn up the circuit he used to allow for relay switching of drive levels by band grouping, driven by the LPF band grouping I/O lines of the Raduino. No firmware mod is required to deliver even drive power across all of the bands.
RV1 in the yellow circle is the existing drive pot in the uBITx. Remove it and connect the wires from the relay as shown. Q17C, Q18C, and Q19C references connect to the transistor Q17, Q18, and Q19 collectors. Then set RV1A, RV1B, RV1C and RV1D on the basis of the appropriate band grouping selected to keep the power out flat.
Digital drive control
Glenn VK3PE has come up with an old circuit that could be used to work with a digital potentiometer module to use as adrive control set by the NANO firmware on a band by band basis.
The original drive control, RV1, would need to be removed and a few parts added, along with a digital pot (I2C control) in place of R3 below to form an attenuator in the RF path.
With some careful work it should be possible to design a small PCB that fits into the holes vacated by RV1, either vertically or horizontally.
The schematic is from page 62 of the book by Randy L. Henerson on designing a Transveiver. Its a very old book (1997) ISBN 0-07-028263-3