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+--- Thread: FT991 drift on digital modes (/thread-681.html)
FT991 drift on digital modes - VK7HH - 12-11-2018
Here is an interesting one for you.
I have an FT991 radio which I've been using a lot on WSPR - mainly 6 metres. I have noticed through testing that it seems to drift. I have had several spots from stations that indicate up to 4Hz drift. Usually it's about 2-3 maximum.
With that in mind, you'd think that 2m and 70cm would be bad. Not so. I did testing on the bench and confirmed that drift at 70cm seems to be 2-3Hz too, at worst when compared with another GPS locked radio.
I located the 30.225MHz reference in the radio, it sits underneath a plug in PLL board, on the main board. I placed a small piece of styrofoam over the TCXO in case it was getting some air flow over it. This seemed to make things more stable at 70cm, yet I still have the drift at 6 metres. I can't imagine it using a different reference. Perhaps the 6 metre PA is located directly underneath?
Anyone got any other ideas. Wish these rigs came with GPS locking as standard..