Nice little circuit Rick. I've built similar ones using the commonly available 1Mhz crystal oscillator 4 pin cans before, but I like your design much better. :)
A ( good ? ) use for Medium Wavebands ( ? ) ... now that the ( BIG boys ) have almost fully shut down their transmitters due to their HUGE power needs ( welcome back to young boy's communication in the 1960's ) ... DAVE™🛑
My first plain was to put the antenna on the coil closest to the tap. The RF was at the other end of the coil, so I moved the antenna to the other end of the coil. So I do not think you need the tap. Thanks for your comment.
Is there a video somewhere that explains how that circuit uses the crystal to oscillate? I understand the concept of the crystal, but I've never understood the feedback path that led to it oscillating.
The Crystal produces the signal. The transistor amplifies this signal. Crystal Oscillators for the Beginner ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-xezzwJAZEQY.html
@@AllAmericanFiveRadio All the components are obvious in isolation, I've understood them for 40+ years. It's how they are working together that is a mystery. The crystal is resonating at a particular frequency if it's fed an appropriate signal. The signal seems to be coming from the emitter of the transister through those two 170pF caps. There is also the 68pF cap and the 10mH inductor playing some role. Are there any of these parts we could remove and still have it work? (Ie, muntzing it).
It is not 10 microhenry but 10 MILLI Henry. To get an idea: you can see it in the picture on 2.29 in the video. It is the one with the yellow core. When you want to make it in the same way as Richard did, also use/find such a yellow core ferrite (round) because its inductance, in this case, is related to the ferromagnetic properties of that core. Yellow stands for a certain type of ferrite material, with certain properties. It is a choke coil. When you want to make it on a cylindrical ferrite rod of 1 cm diameter, length 5 cm, you can do that experimentally. Start with 200 windings. When that does not work, make more windings on the coil. Till it works OK.
RFC coils are not critical and 10mH is just a nice round value here. Two or three dozen turns around a small ferrite toroid will do, as you can see just above the crystal in the video at 2:48. But you can buy these for cheap.
