Aminos, What sort of a probe are you using? I suspect that you are using a BBFO of or QNP type probe. In these probes, 19F is normally on the inside coil, while 1H is on the outer coil. This will make tuning of 19F more sensitive to sample properties (particularly dielectric constant). Also, the circuitry used to tune the inner coil up to 19F (it is primarily a BB-X coil), might make it more sensitive to capacitive coupling to the sample.

If you use a 1H probe with 1H on the inner coil (e.g. TXI, BBI) then 1H tuning becomes very sensitive to sample properties.

Aminos, What sort of a probe are you using? I suspect that you are using a BBFO or QNP type probe. In these probes, 19F is normally on the inside coil, while 1H is on the outer coil. This will make tuning of 19F more sensitive to sample properties (particularly dielectric constant). Also, the circuitry used to tune the inner coil up to 19F (it is primarily a BB-X coil), might make it more sensitive to capacitive coupling to the sample.

If you use a 1H probe with 1H on the inner coil (e.g. TXI, BBI) then 1H tuning becomes very sensitive to sample properties.

Aminos, Aminos,

What sort of a probe are you using? I suspect that you are using a BBFO or QNP type probe. In these probes, 19F is normally on the inside coil, while 1H is on the outer coil. This will make tuning of 19F more sensitive to sample properties (particularly dielectric constant). Also, the circuitry used to tune the inner coil up to 19F (it is primarily a BB-X coil), might make it more sensitive to capacitive coupling to the sample.

If you use a 1H probe with 1H on the inner coil (e.g. TXI, BBI) then 1H tuning becomes very sensitive to sample properties.

You are doing nothing wrong.