Trying to make a LW Radio pt 4: stumbled on a very good AM TRF radio schem. & demo

Please read the textbox first. Part 4 of the series, where I try to make a Long Wave radio (converter) that has to work between 150 KC and 280 KC.

Video 1 about the Long Wave radio converter project, started October 2021, is here
Video 2 about the Long Wave converter (Oct. 2021) is here https://youtu.be/flH--5q7zbw
Video 3 About the Long Wave converter is here (Oct. 2021). But the focus is there on “impedance transformation”.

That is also usable for audio circuits & tone control units, say the classic Baxandall circuit. They can be made properly with FETS, info is in this video.

The BF 256A gives a kind of “flabbering” sound. Did some experiments to avoid that, especially by lifting up the supply voltage to the BF256A, that did not work. The BF 245 B worked quite good, but not better compared to the use of a BC 547 B, a NPN mesa transistor with a HFE of (say) 300. By the way: the BF 256 A worked extremely good (!) in an oscillator circuit on (say) 1.2 MHz, I am almost sure it will also work very properly as an oscillator transistor on higher frequencies.

I first made the Front-End. Best results were found with the circuit that I publish now. Tested: the FET BF245, the FET BF 256A, both HF-N Silicon FETS, but nothing worked better (in terms of noise and real radio reception) than this now published circuit.

Have received with this setup and a coil of 820 Micro Henry (50-530 pF tuning capacitor) and a long outdoor antenna (say 10 meters) the BBC on Long Wave, but very faint and very noisy.

Important: in this frequency range (long wave-medium wave) the radio signals can be received very substantially better (say 50 %) when the radio is focused to receive the electromagnetic part of the radio wave. I did not do that now, I have to focus more on that (by making a good quality ferroceptor (=ferrite rod antenna with a typical Long Wave radio coil) or a “window” (=loop) antenna on a wooden frame in the future.

Loop antenna’s on this frequency band can be (too) big and not practical.

But, important, during these experiments I stumbled on this high quality AM radio (TRF type) that can be made with 2 transistors, both the BC547b. They are bipolar transistors and success with these types is scarce, when they are connected in one or another way to a radio coil, because their Base-Emitter resistor normally damps the good properties of the (AM or whatever) radio coil to more or less zero. Though now it was succesfull and thus I had to stand still at this setup/front end/radio circuit. That everyone interested in radio circuits can make.

Important: copy the reception coil on that PVC tube exactly (!) and use the antenna capacitor of 33 pF and the coupling capacitor of 15 P. I received in the Netherlands radio Columbia (1395 KC), Radio Lyca (London, 1458KC) and much more AM stations. Reason to copy the antenna coil exactly: the high Q (=quality factor). You don't have to use the so called "litze wire" to get a high Q. Litze wire is scarce/obsolete. Also important: decide wehther you need that 1 MOhm forward biasing the Germanium detection diode or not. Sometimes not necessary (!).

By the way: the AM band in the Netherlands is more or less “dead”, there are at the moment only 2 private stations: radio Columbia and Radio Paradise. They both have a website.

When you have questions about (certain analog) electronic 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.

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.

My You Tube channel trailer is here: https://youtu.be/xbgQ8T3oqh4 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.

I keep all my YT videos constant actual, so the original video’s with the most recent information are always on YouTube. 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 23 oktober 2021.
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