02-12-2016, 05:02 PM
Ideally a transformer from the same type of set, for reasons already given.
Sometimes the IFT which drives the detector has a different turns ratio than the one between frequency changer and IF amplifier.
It might be important too, that not only can the cores tune the thing to the right IF, but also that they are in approximately the right position. Because not only does moving a core affect the inductance of the coil that it's in, it affects the coupling to the other coil, and that determines IF bandwidth and gain. IFT's with trimmer capacitors rather than core slugs obviously are immune to this effect!
You also need to be sure that you have enough inductance, with your parallel capacitance, to tune to the IF. Otherwise, you might find that you get a peak in response when the core is right in the middle of a coil, further screwing reducing the signal - but all that's happened is you got nearly on tune and then started to go off tune in the same direction, rather than passing right through resonance.
These are most of the pitfalls. But in practice, have a play - a bit like usual big a mains transformer as a single-end output transformer, you may not be optimum, but you'll still find yourself with something useable!
Sometimes the IFT which drives the detector has a different turns ratio than the one between frequency changer and IF amplifier.
It might be important too, that not only can the cores tune the thing to the right IF, but also that they are in approximately the right position. Because not only does moving a core affect the inductance of the coil that it's in, it affects the coupling to the other coil, and that determines IF bandwidth and gain. IFT's with trimmer capacitors rather than core slugs obviously are immune to this effect!
You also need to be sure that you have enough inductance, with your parallel capacitance, to tune to the IF. Otherwise, you might find that you get a peak in response when the core is right in the middle of a coil, further screwing reducing the signal - but all that's happened is you got nearly on tune and then started to go off tune in the same direction, rather than passing right through resonance.
These are most of the pitfalls. But in practice, have a play - a bit like usual big a mains transformer as a single-end output transformer, you may not be optimum, but you'll still find yourself with something useable!
