The TRF radio for LW and MW working on a long wire antenna: final setup demo and front end schematic
Please read the textbox first. Video about the TRF radio for MW and LW. Important: a TRF radio without AVR suffers of fading, etc. and is especially usable for local radio stations, anyway, this circuit works good. Correction: somewhere (say 10.48 in the video) I tell that the earth-electrode is the antenna electrode, that is of course nonsense (! sorry).
I used now a FET amplifier in the front end, connected to the antenna. Used the BF 256 A, general purpose HF FET, a BF 245 B (type a,b,c) is also good usable (obsolete type). That FET lifts up the antenna signal received via the antenna very substantially. HF amplification is realized by giving the FET more voltage to the drain, via the 4K7 potentiometer. It must be limited because, if not, the radio will start to oscillate (=scream) when it is set to its maximum HF amplification, That is the reason for the 2 K resistor in the (+) supply lead to the FET drain.
The amplified radio signal is taken out of the source of the FET (10 K resistor to ground) via a 1N5 capacitor and is coupled via that 1N5 (=1500 pF) capacitor into a standard (classic) first transistor stage with a BC 547 B, with, on its collector, a 1K resistor and between collector and base a 220 K resistor to bias it.
Because there is no emitter resistor in that first BC 547 B stage, the transistor (BC 547 b) amplifies at its maximum, given by its physical amplification (Hfe) properties, that is normally 300 x. Try and test it with a transistor tester before you use it. A too high Hfe can lead to oscillations, but don’t worry.
The next circuit that follows is also classical and is used for HF/AF amplification and AM Radio detection with a Germanium diode. Much more & the best info is here:
On 9.56 in that video is the complete schematic • Trying to make a LW Radio pt 4: stumbled o...
When you compare the schematics now (in this video) and there (old video) you will see that this is a logical continuation. When you have questions and/or don’t understand what happens in these circuits: contact me on radiofun232dotgmaildotcom.
After the classical AM radio detection there is a pre-amplifier:
Schematic is here
Video link
• 1 transistor (BC 547 b) always working aud...
And (after that pre-amp stage) an end-audio amplifier. You can use any audio amplifier that you have/want/like.
When you have questions about my circuits and how to make them: go to my Channel trailer (Radiofun232 on You Tube) and go to the “looking glass”. Type there the keywords that you want/need like: “power supply”, audio amplifier, capacitor tester, oscillator, radio, shortwave, shortwave radio, or any keyword you like to find the essential info & schematics on my YT channel.
Earlier relevant video’s • Trying to make a Long Wave radio converter... Video 3 (impedance transformation radio circuits with a FET, second idea) • Trying to make an Long Wave radio converte... Video 4 (most important) very good practical 2 transistor TRF setup for AM • Trying to make a LW Radio pt 4: stumbled o...
Also more or less not relevant video’s when we look at the TRF principle side paths: trying to make a superheterodyne setup for Long Wave, not succesful, needs more study & experiments. And: radio mixer circuit • Trying to make a Long Wave radio converter... 455 ceramic filter test (part 8) on its bandwidth • Trying to make a LW Radio part 8: a normal... Searching a good quality Germanium radio detection diode • Barrier voltage of diodes Silicium/Germani...
They are all side paths (!). I will work that out later. Next project: a superhet for LW.
My You Tube channel trailer is here: • Radiofun232 on YouTube, find working & tes... 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 electronics books are here:
https://www.lulu.com/search?adult_aud...
I keep all my YT videos constant actual, so the original video’s with the most recent information are always on YouTube. Upload 18 november 2021.