It's difficult to tell, probably 5.1k. The pin at the bottom of the attached photo is pin 6 of the ADF4351 which seems to be connected to the resistor marked 510 although it is indistinct.

On Sun, 3 Jan 2021 at 23:26, Robin Szemeti - G1YFG <robin@...> wrote:

Glad it is working, out of interest, what value did you find for the charge pump resistor on your board?

On Sun, 3 Jan 2021 at 21:48, G0FCU <simon@...> wrote:

Thanks for your help Robin, all working fine now. I had to amend F1CJN's Arduino sketch to set the charge pump value as you suggested. The recharge pump resistor is not R7 as far as I can work out but could be a seemingly unlabelled resistor next to R3.

Thanks

Simon.

On Sun, 3 Jan 2021 at 08:26, G0FCU <simon@...> wrote:

That's the one. So I need to remove R5 and L1 and thanks for the heads up about the charge pump resistor.

Many thanks

Simon.

G0FCU.

On Sun, 3 Jan 2021, 07:44 Robin Szemeti - G1YFG, <robin@...> wrote:

This one?

https://img.fasttechcdn.com/935/9355700/9355700-7.jpg

R5 is the signal from the onboard xtal

R8 is the signal from the SMA socket

L1 is the power to the onboard xtal

Check also the value of the charge pump resistor and make sure it matches the value set in the software you use to calculate the numbers ... I *think* it is R7 on that board, but please check.  It connects between pins 7 and 20.  Most of the software is set up to expect a value of 1K ... these boards often have 5.1K  in that position ...  if the numbers don't match the software, you'll run out of tuning range.

On Sun, 3 Jan 2021 at 07:14, G0FCU <simon@...> wrote:

Could someone tell me the components that need to be changed on the ADF4351 (black eBay) board to enable a 10 MHz reference input?

I can't find a circuit diagram on-line. Earlier in this thread Andy mentioned an inductor to be removed (L1?) and some other links to be changed.

Thanks
Simon
G0FCU (new to microwaves so bear with me!)

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Robin Szemeti - G1YFG

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Robin Szemeti - G1YFG