11-02-2021, 05:48 PM
Hello Jeremy.
As you've noted the coupling is altered by bending the coils toward and away from each other, the epcos ones I used (from RS some time ago) are quite sturdy though but I had thought of trying an old technique of putting a small piece of soft foam between them after optimising the adjustment then fixing the foam by soaking with hot beeswax....
Also....
Cut and paste from a PM where I was asked to clarify what load the coil was working into....
IF transformer testing and oscilloscope input loading.....
I think I must have made a pigs ear of explaining
I made the transformers with the 820microhenry chokes with a fixed 100pf//50pf trimmers. The scope input is 1M//25pf (I actually said 20pF ), but that made the transformers unable to tune "up to" 456kHz as I'd wished due to the input capacitance of the 'scope, therefore I used the probe not on times 1 but times 10, so not only giving a load capacitance of ≈2½pF enabling the transformer to tune (?) But also ≈10M load impedance.
Amie
As you've noted the coupling is altered by bending the coils toward and away from each other, the epcos ones I used (from RS some time ago) are quite sturdy though but I had thought of trying an old technique of putting a small piece of soft foam between them after optimising the adjustment then fixing the foam by soaking with hot beeswax....
Also....
Cut and paste from a PM where I was asked to clarify what load the coil was working into....
IF transformer testing and oscilloscope input loading.....
I think I must have made a pigs ear of explaining
I made the transformers with the 820microhenry chokes with a fixed 100pf//50pf trimmers. The scope input is 1M//25pf (I actually said 20pF ), but that made the transformers unable to tune "up to" 456kHz as I'd wished due to the input capacitance of the 'scope, therefore I used the probe not on times 1 but times 10, so not only giving a load capacitance of ≈2½pF enabling the transformer to tune (?) But also ≈10M load impedance. Amie
