Portsdown and Langstone external GPSDO

[g0mjw]

For the Portsdown, it appears that you need to use the F5OEO firmware but then switching back to Langstone you would need to reload the original Pluto Firmware if you want to be anywhere near your intended txrx frequency otherwise is uses the internal clock which is miles away from true it drifts like mad so no good for qo-100

73s Greg G4CST

Or, you could use Evariste's 0303 firmware

https://www.f5uii.net/wp-content/upload ... /pluto.zip

and the F5UII patch for the Pluto Rev C/D

https://www.f5uii.net/wp-content/upload ... e-0303.zip

In passive mode this works with most SDR applications including SDR console. For DATV you can use it with a script and OBS. This doesn't resolve your Portsdown/Langstone dilemma.

If you plan to always use an external reference, perhaps just fix it in hardware.

https://wiki.analog.com/_media/universi ... vd_0.1.pdf page 7

The clock is selected by a GPIO line PS-GPIO6. Low is the internal clock, high is the internal clock. There is a resistor, R102 39 ohms that connects this line to the clock select line. This line controls two FETs. Q2 and Q3 that actually select the clock. Then the line is low, both FETs are off. When the line is high, both are on.

It looks like if you were to remove R102 you could control the line via a 39 ohm resistor to 1.8V. Note it is on the back of the PCB. You could even add a physical switch.

If that's too much, R102 is fairly small, you could force it by connecting the source and drain of Q2 to disable the internal reference and connecting the source and drain of Q3 to enable the external clock. Q2 and Q3 are huge devices, BSS138

Mike