FT-8x7 Rig Locking

[VK7HH]

with the XRef-FT no longer in production, I wonder what others have used to lock their FT-8x7 rigs to an external reference, most likely GPS?

I have a 897D running an XRef but now have a FT-857 which I'd like to do the same too.

I've had a couple of thoughts - 
Use a Leo Bodnar programmable GPS reference - he makes two versions, one with a single output and one with a dual output.
The dual output is limited in generating different frequencies on it's respective outputs as it uses the one PLL chip, but if you wanted to lock two Yaesu radios using the same reference it should be possible.

http://www.leobodnar.com/shop/index.php?...cts_id=301
http://www.leobodnar.com/shop/index.php?...cts_id=234

The Ref-Unit in the radios just have 5V, GND and REF. I imagine it's as easy as that, feed in the reference directly from the GPS via a cap and away you go? Whilst a workable solution, it's not the cheapest. 

I noticed another thread on here using the ProgRock and a 1PPS signal from GPS. This would be an incredibly cheap way of locking a rig.

https://www.qrp-labs.com/progrock.html
https://www.qrp-labs.com/qlg1.html

How have others gone about this with their rigs?

[VK5ZD]

I bought a ProgRock to see what they're like. Of marginal use for HF only. The 'locking' method is a reprogram the PLL to compensate for drift. By default this happens if the 27MHz reference is off by more than 5Hz (can be changed to 1Hz). When it does a correction there is a sudden jump in output frequency.

[VK7HH]

I bought a ProgRock to see what they're like. Of marginal use for HF only.  The 'locking' method is a reprogram the PLL to compensate for drift. By default this happens if the 27MHz reference is off by more than 5Hz (can be changed to 1Hz). When it does a correction there is a sudden jump in output frequency.

Thanks for the reply Iain.

Yeah not suitable when running digital modes on the higher bands then... I might need to try the Leo Bodnar design. The TCXO he has in that GPS unit stays stable using historical data if GPS is lost, then once signal is received again it seamlessly corrects itself. Seeing as though the XRef-FT's are hard to come by now it's probably my only option.

[VK2JDS]

I bought a ProgRock to see what they're like. Of marginal use for HF only.  The 'locking' method is a reprogram the PLL to compensate for drift. By default this happens if the 27MHz reference is off by more than 5Hz (can be changed to 1Hz). When it does a correction there is a sudden jump in output frequency.

Thanks for the reply Iain.

Yeah not suitable when running digital modes on the higher bands then... I might need to try the Leo Bodnar design. The TCXO he has in that GPS unit stays stable using historical data if GPS is lost, then once signal is received again it seamlessly corrects itself. Seeing as though the XRef-FT's are hard to come by now it's probably my only option.

---

Yes it is true the way it works is to make a change to the N division of the pll, which is a cunning way to do it, rather than varying the dc voltage to a multioven expensive sinewave ocxo.
You can use this technique on the high bands for digital modes, if you assist the stabilisation of the progrock by thermally insulating the existing circuit, or better still , replacing the existing 27MHz crystal with a ebay tcxo. 
For field day microwave use on the bands up to 76 GHz I built mine into a diecast box with plenty of foam packing and its been great.
Also I have used it on 23cm moonbounce JT65C locking a IC910h. Its the backup for the expensive 10 MHz GPS locked source and xref I usually use.
You get what you pay for.
73 Dave vk2jds