To give you some examples from problems I ran into:
 
No suitable X-tals to build VXO 's or something with an divider, so I decided
to build an VFO on 1.37MHz followed by an 4017 to divide by 10.
VFO worked perfect but the 10-diveder just wouldn't work!!!!
I spend hours and hours to get it running, tried several different IC's
(I expected speed problems etc) all with no result.........
1.37MHz in ......NOTHING out................
It was a sinple circuit : pin 8,13,15 to ground, VCC on 16, 1.37MHz on pin 14,
and output at pin 12...... so stupid simple, that it really is amazing that things are
not working.