Please read the description/textbox. Part 2 of the series where I show my radio experiments, in this case making an IF filter via 4 simple (cheap, in my case 50 cents) ceramic IF resonance filters that were made (originally) as a kind of crystals/resonators on 1 frequency (of course with a certain bandwidth!) in an oscillator/remote control unit.
Go to the www. to see more properties of the here used IF 455 ceramic resonators.
Be it between 440 KC and 470 KC this circuit (and the preceding circuit) is usable. In the earlier video (link will follow) I showed how I could change these filters to make a resonance “peak” (instead of a dip) with the help of a 2 transistor circuit, I used 2 x the BC 547 b, NPN Silicon.
Such a “peak” resonance on an IF frequency is (of course) necessary in an IF filter in a radio. The setup/idea is here to make a superheterodyne radio to receive Long Wave radio signals in the (say) 1200 meters band.
Of course in such a case sharp filtering is necessary to shift out the different radio stations on Long Wave, via that superheterodyne principle. That means that the IF filter for such a superheterodyne LW radio must be sharp, say have a 8 KC or 10 KC bandwidth.
That is what I am developing now experimentally with (say) simple electronic components, available everywhere in the world.
So here I show more considerations (following video 1) about how to make such a sharp IF filter (bandwidth 10 KC) and how to use a Field Effect Transistor (BF 256 A, a N-FET, comparable to the BF 245 A,B, or C, they are obsolete) to hold this filter sharp on its peak resonance, say in a 10 KC bandwidth. Be it somewhere between 440 KC and 600 KC (the standard values).
For more info: go to my first video. There I showed how to use these “single” (2-wire) ceramic filters that were made to resonate on 440 KC, 450 KC, 455 KC, 460 KC in this 2 transistor electronic HF setup IF filter.
When you know about electronics: the term “impedance transformation” must be common. Good, in this case, the best idea to connect the output of that ceramic 455 KC (or whatever ceramic) filter on its peak resonance frequency will be via the grid of a tube (triode) or the Gate of a FET.
I had to add a 1 Mega Ohm resistor from the Gate of the FET to ground, otherwise the circuit was not stable. So the IF ceramic filter at its extremely high impedance output is shut off with a 1 Mega Ohm resistor to ground, that is (in general) a good high value that does not deteriorate the resonance filter properties and its peak resonance.
All these things are now showed. You can contact me via email when you have questions about my published circuits. I always ask for a picture of what you have made + a problem description; I ask to communicate.
Part 1 of the series is here • Making a sharp 455 KC ...
Part 2 of the series is here • Making a sharp 455 KC ...
Part 3 of the series is here • The Grounded Emitter 1...
Part 4 of the series is here • Making a sharp IF filt...
My You Tube channel trailer is here: • Radiofun232 on RU-vid... When you search, search always “NEWEST FIRST” to get the right overview. You can also search via the “looking glass” on my Channel trailer via keywords like ”audio”, “radio”, “amplifier”, “filter”, “Shortwave”, “transistor”, “FET”, “oscillator”, “generator”, “switch”, “schmitt trigger” etc; so the electronic subject you are interested in. My books about electronics & analog radio technology are available via the website of "LULU”, search for author “Ko Tilman” there.
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I keep all my YT videos constant actual, so the original video’s with the most recent information are always on RU-vid. Search there, and avoid my circuits that are republished, re-arranged, re-edited on other websites, giving not probable re-wiring, etc. Some persons try to find gold via my circuits. I take distance from all these fake claims. I cannot help that these things happen. Upload 22 november 2021.
12 сен 2024
