UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Building the 'Minimod' AM modulator-questions!

Restoration73 · 28th Sep 2018, 9:20 pm

Dividing R3 and adding a zener may stabilise the oscillator. The highest value Toko 10K was 45uH, so the Spectrum ones are specials. All inductors recover from adjustment
but if this is inconvenient put a small foil trimmer say 30p across the 270p.
6408 coil is 360uH with a tapped primary and low-Z secondary and may tune with a
lower C. I have a few for the receivers I designed using TDA1072A so let me know if
you would like any.
I prefer a Colpitts oscillator with a quartz crystal in my own modulators.

28th Sep 2018, 9:20 pm	#46
Restoration73 Nonode Join Date: Jun 2013 Location: Surbiton, SW London, UK. Posts: 2,801	Re: Building the 'Minimod' AM modulator-questions! Dividing R3 and adding a zener may stabilise the oscillator. The highest value Toko 10K was 45uH, so the Spectrum ones are specials. All inductors recover from adjustment but if this is inconvenient put a small foil trimmer say 30p across the 270p. 6408 coil is 360uH with a tapped primary and low-Z secondary and may tune with a lower C. I have a few for the receivers I designed using TDA1072A so let me know if you would like any. I prefer a Colpitts oscillator with a quartz crystal in my own modulators.