If we use round numbers...
45mhz - dial frequency= spur
For 28 to 29mhz the spur is 17 to 16mhz
For 24.830 to 24.990mhz the spur is 20.17 to 20.01 mhz
For 21.2 to 21.45mhz the spur is 23.8 to 23.55mhz
For 10 and 12 if one can devise a suitable high pass that attenuates
everything below 21mhz it can work.... I ran a 9pole filter and it did not
work well enough as in it either kills 24.9 or it doesn't kill the 20.17
spur much. Possibly a Caur or elliptical filter would but they will
be touchy to make.
Not matter what one filter can't do it all. Though 28mhz is the easiest
as the spur is further away.
Triple tuned band pass can, models were tried and maybe a double tuned might.
I do know that a triple tuned filter for 28 to 29 mhz was effective. Phone (SSB)
is frm 28.3 to not much over 28.8 and for techs its only 28.3 to 28.5. It would
have to pass down to 28.0 for CW.
The 15M filter is a tough nut as the spur is close at 23.55 when at 21.45.
That would require a triple tuned filter of some quality. If it lowers the
spur by 20db it would do the job with a little excess. It would be a very
good filter to do that.