10-06-2014, 09:20 AM
Fields, do not confuse the 455 kHz IF offset with the proper osc frequency. The osc will ALWAYS be 455 kHz higher than the actual receive freq in your radio, provided the IF was aligned properly. What is important is that the osc covers the full range necessary. Did you set the osc to 955 kHz as you mentioned for the low end or the correct 540 + 455 = 995 kHz?
It is very important to rewind the osc tuning coil EXACTLY as the original, because any difference in geometry will affect its inductance and therefore its tuning range and accuracy. It is not like rewinding the usual tickler coil as in most Philco coils. The tickler coil is not very critical as to wire size, number of turns, etc, but the resonant tuning coil is critical in your case.
To me it seems as if the inductance of your coil is low. I get this impression because for you to get the osc to operate at the right freq at the low end, you have to screw the J padder trimmer in completely. This indicates that more capacity is needed to make the coil tune because the inductance of the coil is too low. If I were working on it, I would try adding another 10 turns to the existing winding, and see how it then behaves.
It is very important to rewind the osc tuning coil EXACTLY as the original, because any difference in geometry will affect its inductance and therefore its tuning range and accuracy. It is not like rewinding the usual tickler coil as in most Philco coils. The tickler coil is not very critical as to wire size, number of turns, etc, but the resonant tuning coil is critical in your case.
To me it seems as if the inductance of your coil is low. I get this impression because for you to get the osc to operate at the right freq at the low end, you have to screw the J padder trimmer in completely. This indicates that more capacity is needed to make the coil tune because the inductance of the coil is too low. If I were working on it, I would try adding another 10 turns to the existing winding, and see how it then behaves.
