External reference oscillator

[KA5BBC]

I have been reading in a lot of places that there are issues with the Pluto drifting due to the poor onboard oscillator and that replacing this with a external reference oscillator is a relatively simple operation, there is no need to do surgery as the onboard can be easily disabled with a jumper or in firmware.
Despite spending many hours searching for a simple plug-in solution I did not quite find what I was looking for. I did find a lot of individual components that would need building onto a board but most were SMDs so I can not use them - none had developer boards available.
So.. what solutions are there that can provide a <0.1ppm (or even ppb) 25MHz 1Vpp sine wave external reference oscillator at a ham friendly price?

[KA5BBC]

I should have added..
Also, what about an option for the LimeSDR?

[g8vpg]

Andy,
I think this might be your best option;
https://plutosdrmods.wordpress.com/
73 Shaun.

[i2NDT]

hi Shaun,
this one is another example:
https://www.ebay.com/itm/TCXO-40-00-MHz ... SwtC1d1qRC

or, if the link doesn't work, item number: 402256301104

73
de
i2NDT Claudio

[YL3AKC]

This is under construction right now. It have internal TCXO, ext osc in and PTT optocoupler with Evariste (F5OEO) GPIO pin logic.
When no signal on ext osc, circuit work from internal tcxo.
When ext appiled it automatically switch to ext osc.
Auto switching between tcxo and ext osc.
When GPIO 0 and 1 is on XOR and optocoupler is off.
When GPIO 0 is on, optocoupler activates.

PCB have 10 pin header with connected GPIO and optional 1.1V input.
Ext supply (1.8V), Ext osc in, clock out and PTT out are on UF.L connectors on PCB.
there is solderpad jumper to select supply source.
ICs are rated to 40 MHz @ 1.1V supply.
TCXO is rated to 1.8V supply.
There is place for mounting screw in future.
I am waiting for components from farnell to test this PCB.
Maybe later this project will go to tindie.

I am planning to use external low phase noise 25 MHZ PLL clock source together with QO-100 LNB.

PS: don't look on component names, they are artefacts form quick and dirty schematic drawing.

adalm-pluto_ext_clk_pcb_2_sch.pdf.png (108.63 KiB) Viewed 3130 times