Someone posting here recently said their SPM-12 did not have a freq
locking facility.
My SPM12 has a phased locked loop, with coarse and fine tuning as well
as the main tuning dial, maybe there are various specifications for the
same models.
It has a 10 khz IF output plus other outputs. I built a product det and
the whole unit works well and is very sensitive and selective down to 25
hz. I also use an ext DSP unit. The whole package makes a great LF
receiver and works well also with my receiving loop antenna.
73 de Mal/G3KEV