band (mhz) VFO (mhz)
---------------- ---------------
1.8 9.8
3.5 11.5
7.0 15.0
14.0 6.0
21.0 13.0
28.0 20.0


Hmm, did you check those frequencies for spurious responses? Low-side
injection can be a real problem. Remember even if you have a very clean
LO system the mixer itself has to be switching at the LO frequency and
will generate some pretty significant harmonics.

With a 20 MHz VFO on 28 MHz, the second harmonic would be 40 and minus
8 would put a spur response at 32.

At 14.35 you'd have a third harmonic of 6.35*3=19.05 19.05-8=11.05

I guess you might be OK, but you should look at all of that and the
bandwidth of the RF stages between the antenna and mixer.