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Trying to make a simple TRF radio for LW reception part 12: radio propagation on Shortwave & more



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A series of 3 video’s, made today (10 November 2021).Three video’s where I show the developments when trying to make a radio receiver for the Long Wave frequency band. More relevant info in this textbox, read it when you wish.

Say between 150 KC and 280 KC, that was the first aim. Also a slight adaptations to the now and earlier published schematic of this TRF setup. Important: these 3 video’s show an evaluation that distracts (!) from the original Long Wave radio setup idea. But they are interesting and good low selectivity working radio circuits for LW-MW-SW, made with a handful (=2 or 3) of transistors.

This text will be published in all the 3 video’s in this textbox= the 3 video series. Though very different things about radio reception and radio circuits (how to make them) are & will be told in all these specific 3 video’s.

Video 1: focus in general, development further of the LW (but now also MW and SW) TRF setup with all its (sometimes) bad properties

Video 2: making an extra amplifier stage (drawing) + all about simple AM radio detection with a GE (= Germanium) diode

Video 3: focus on Shortwave radio reception with a TRF setup and its (bad) selectivity and more, also with the “fading” phenomenon on SW radio reception

During development I stumbled on a very good simple TRF radio setup, usable between (say) 150 KC and 1.6 MC. And a little bit on Shortwave radio. Made with only 2 transistors, both the BC 547 b. But 1 extra amplifier with a BC 547 b stage is needed, after the diode detection (GE diode, more in the videos). That lifts up the audio amplifier somewhat to its proper (needed) amplification for (say) weak radio stations on Long Wave.

I (thus) also connected in video 3 a typical SW antenna coil (read: not an oscillator coil, thus a typical antenna coil). It had say 12 windings, watch the video (3). And I could of course also receive SW radio stations. Thanks to my YT follower Rob, he inspired me to connect a SW coil to that TRF circuit.
Of course the selectivity on Shortwave is (very) bad with such a TRF setup. The TRF setup works good (= can work good) between 150 KC and 1.6 MC. Say: a (kind of) good selectivity. Study the radio theory why that is a fact with such a TRF type radio reiver.

But, anyway, an interesting circuit to receive Long Wave + Medium wave + Shortwave radio stations with this simple TRF setup (with its bad selectivity on Shortwave).

I have changed the coupling capacitor out of the collector of Transistor 1 (BC 547 b) to the base of the second BC 547 b from 1500 pF (=1N5) to 220 N. That gives a slightly better radio reception on the Long Wave band, only there. Magnitude is 100 x (!).

On SW (and also somewhat on the medium wave from 600 KC up to 1.6 MC) we have to do with the “fading” problem. With such a simple TRF setup sometimes certain radio stations from far away “overrule” the radio station to which you have tuned to…. And after some time (minutes/seconds) they will fade away and the station that you have tuned to is properly audible again….

That is a classical radio problem….anyway.

When you have questions about my 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.

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.

https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=Ko+Tilman

Situation 11november 2021. Contact me when you wish via radiofun232dot gmail dot com.

Earlier relevant video’s https://youtu.be/flH--5q7zbw Video 3 (impedance transformation radio circuits with a FET, second idea) https://youtu.be/vSPQGG4qol8 Video 4 (most important) very good practical 2 transistor TRF setup for AM https://youtu.be/9XK3nGlFQdk Also side paths when trying to make the superheterodyne setup for Long Wave, proved to be not very succesful, needs more study & experiments: Radio mixer circuit https://youtu.be/L7-aoGWQdCk 455 ceramic filter test (part 8) on its bandwidth https://youtu.be/6h9fbAo-vtI Searching a good quality Germanium radio detection diode https://youtu.be/AmcaMFdrLPc Situation 11nov2021
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