The VFO's on the HW-100 and 101 were terribly unstable, no matter how well
you built-rebuilt them. To many structural stress points that changed with
temprature, defective coils, a transistor junction as a VR, improper drive
coupling

The SB-101 used a brick solid temprature compensated factory built TRW LMO
on a pinch drive that could expand and contract with temprature.

For the SB-102 Heathkit dropped the good TRW's and went back to a cheap
flimsy thing marketed as the "New and improved FET LMO".
Most of these LMO's aligned with the tuning capacitor trimmer screws all the
way out so if you put you coffie or D-104 down to hard the set would jump a
couple hundred Hz.

Keep the SB-101, Id say its the best HF tranceiver kit they put out
-Joe