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trying to find radio oscillator to use.

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dl09

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i found a voltage controlled oscillator, on the internet, it generates a sine wave. it has an adjustable frequency of 70 megahertz to 200 megahertz. if i feed the output to an antenna, will the antenna generate radio waves?
 

Yes, it is possible for a simple oscillating circuit to broadcast radio waves. For $10 I purchased a kit to build my own FM broadcasting circuit. Once I adjusted the frequency I could hear my own voice on a radio a short distance away.

Caution, because that is the frequency range used in commercial (fm) radio as well as air-to-ground and mobile communications.

Your circuit should be low power because local laws no doubt require us to avoid interfering with other people's radio reception.
 

it is a prebuilt voltage controlled oscillator. if i buy the item, all i get is a voltage controlled oscillator. then i will build an antenna at home and connect the voltage controlled oscillator to the homemade antenna. will this setup generate radio waves? i am not buying a kit.
 

You'll need to confirm voltage amplitude of signal. And Ampere level.

You need to determine the correct place to attach an antenna.

Also polarity of signal (whether plain AC, or AC riding a DC component).

The antenna can be as simple as a foot or two of wire. For best efficiency the antenna should be tuned to the oscillator, although this is not easy when you apply various frequencies.

The product description might tell you a lot by what it says or doesn't say. Does it mention the ability to broadcast radio waves? Does the seller make it a marketing point by saying 'build your own home-based radio station'?

There is such a thing as legal micro-power fm radio broadcasting (in the US). You should check local regulations, of course.
 

if i feed ac riding dc to the antenna, will the antenna still broadcast radio waves?
 

It will still broadcast but if you short the antenna to anything wired to the unit it may be damaged.

I really should warn you to check the radio transmission regulations for your country. You almost certainly need a license to broadcast and equipment to ensure you only broadcast on authorized frequencies. The frequency range you want to cover includes emergency services, aircraft communication and broadcast bands in most countries and unauthorized use can result in a fine or imprisonment. You should also have filters in the antenna to ensure no harmonics are radiated too.

Brian.
 

i will research laws and regulations, but how do i avoid shorting the antenna to anything wired to the unit?
 

so use magnet wire for the antenna?
 

Is that oscillator 3 octaves ?? 70-200 MHz.. Check it again..
I have never seen an oscillator more than 2 octaves..
 

so use magnet wire for the antenna?
That would work but magnet wire is usually a single copper core so it work harden as it is flexed and eventually break. A multi-strand PVC covered wire would be more practical, the kind used as interconnecting wire or 'hook-up' wire.
Any length will work to some degree but for best radiation there are some lengths that will work better than others. Many factors influence the optimal design but for a straight(ish) wire a good starting point is a half wavelength long. One wavelength is 300 divided by the frequency in MHz, the result is in metres.

Brian.
 

if i feed ac riding dc to the antenna, will the antenna still broadcast radio waves?

I could answer definitely if I were able to fathom the process of how an antenna produces photons.

Here's what I think after giving it some thought...

My understanding is that a radio broadcast consists of a constant stream of photons... dense during peak waveforms, sparse during troughs. At no time does photon count drop to zero. Nor does it make sense to say the photon count is ever negative.

Compare that with the waveforms being positive and negative polarity. In view of this we ask, Are photons likewise positive and negative? Does a photon which is emitted during positive polarity differ from one emitted during negative polarity? I suppose the distinction might have to do with direction of spin, such that they induce a positive or negative charge in a receiving antenna. However the question arises as to what sort of photon (or direction of spin) creates a zero crossing?

In any case there are radio transmitters (such as my mail-order kit) which run on a single polarity power supply. Evidently the antenna can have AC riding a DC component. Such a concept suggests photons don't need to be positive or negative, they are simply abundant or scarce.
I could be wrong.
 

Why do I need to confirm voltage amplitude of signal.

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Why do I need to confirm voltage amplitude?
 

Why do I need to confirm voltage amplitude of signal.

It need not be any particular voltage, however a heavy enough load could cause it to drop. It's a matter of output impedance as well as output voltage.

One time a college professor let me borrow his sine generator, which broke the first day I used it. I took it back to him, and he opened it up and found an output transistor was bad. He easily replaced it.
I guess my point is that it was a professional-looking unit with aluminum housing and graduated dials. Yet that little transistor failed even though I wasn't doing anything to abuse it.
 

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