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At the beginning of this thread about modulation level and Ramsey AM25C I posed a question: would a heftier modulation transformer improve peak modulation for this microtransmitter?
The answer is now YES! I replaced L4, the small hand-wound transformer on a toroid form, with a Nortronics T70-T2 bias circuit transformer scavenged from an old magnetic tape recorder, and tried two different wiring patterns, based on the available windings. Both arrangements brought modulation up above the nearby AM stations on the dial with no distortion. The 1st wiring trial had a roll-off above 4500KHz whereas the 2nd trial opens up the high end so that it’s the receiver that rolls off above about 8KHz.