Trying to make a Long Wave Radio pt 5: universal Local oscillator for 951KC-1.3 MC or for Shortwave



Published
Please read the textbox first. Video 5 In the process of trying to make a Long Wave Radio between 150 KHz and 280 KC.

My first idea was to make a converter. In that case you need a local oscillator and a mixer. Both units were showed in my earlier videos.

But, after all, the first idea/good thing is to make a so called “front end” (= the first antenna stage with in many cases a HF pre-amplifier) that is especially made to receive the electromagnetic spectrum in this frequency band, 150 KC-280 KC.

That means: a high quality ferrite coil or a loop antenna. I will not focus on the loop antenna, because it is/will too big and/or is not practical. I want to keep it simple by trying to make a Long Wave radio coil on a ferrite rod, perhaps combined with an indoor antenna. Not with litze wire (to expensive & too scarce) but with say “normal” laquered copper wire of (say) 0,4 mm or 0.5 mm.

Anyway & after all: this video shows a Local Oscillator (or a so called VFO = variable frequency oscillator) that works (in this case) between 951 KC and 1.3 MC.

It has a very pure sine wave, works good with the FET BF 256 A. You can surely get to higher oscillator frequencies by changing the inductance of the coil and/or the value of the parallel capacitor (now 500 pF, for SW it will be in the 10 pF-150 pF range). Idea: 1 MC-12 MC sine waves can be generated.

Very important: the capacitive voltage divider in the oscillator has to be changed, when you want to go to higher frequencies (say on Shortwave, from 2 MC-16 MC).

Thus: very important: change the 1000 pF capacitor (gate-source) in this schematic to another value when you want to go to higher frequencies. You want to go to 2 MC-12 MC or even 16 MC?

In that case use a 220 PF for the capacitor between the FET Gate and the Source and a 100 PF between the FET Source and the Ground (-) minus.

Test/try/experiment! Always good.

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.


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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 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 24 october 2021.
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