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Why this AC to DC SMPS is not producing noises on this basic TV transmitter?

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Willen

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This is simple AV to RF modulator. It has no ICs, has no regulators, has bad rectifier (single or double diode only). I am showing this device because I don't have schematic. It looks very basic circuitry. It has simple power supply from 220V AC to DC may be 9V (see left down side). There are three '9018' UHF small transistors as an oscillator for audio and video.

So it is a basic transmitter just like my basic FM transmitter. When I received the signals from this device on TV, it was very clear in sound and video without AC noises, how?

But If I used this type of AC to DC SMPS to power my basic FM transmitter, it produced horrible noises.

Seeing this simpler device I guessed I can use this type of SMPS to power my basic FM Tx without having any AC noises with little tricky circuit.

Do you know anything? Please!
 

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I don't see your problem?, a correctly designed and built SMPS doesn't cause interference, and provides a reliable smooth DC.

and can I compare this DC with battery's DC? Using battery on my hand made FM transmitter (actually an oscillator with a small buffer) produces 0% noise while receiving it on FM receiver. But if I used such SMPS as a power source, my FM tx starts to trsansmit 70% noise with 30% poor audio.

Linear transformer with bridge rectified with capacitor gave same noise on transmitted signal. :(
 
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But If I used this type of AC to DC SMPS to power my basic FM transmitter, it produced horrible noises.
By 'this type' do you mean exactly that particular SMPS or something vaguely like it? I'm guessing if it's two non-identical supplies then the one causing problems has insufficient smoothing. Likewise the linear supply.
 
Actually I used cell phone charger as a power supply for my basic FM oscilllator (lets say transmitter) gussing (by seeing its components) that is same type of SMPS.

Really does SMPS peoduce pure DC like battery? And can I use it to power my simple one ar two transistor FM transmitter? Wow!
 
An SMPS will not produce pure DC like a battery. There will always be ripple on the output. How much ripple will depend on the smoothing efficiency (which may be low for a phone charger, if the phone can tolerate significant ripple).
 
OK then I will try with few SMPS by using it as a source of power supply for my basic FM oscillator. And will listen noise level (due to AC ripple). My oscillator has 7805 regulator with 1nf and 100uF decoupler filter capacitor.

How can I increase smoothing efficiency of SMPS simply? Adding more decoupler capacitor? Or high value? Or has tricky circuitry?
 
A series resistor or inductor, followed by a shunt capacitor, should help.
BTW, your 7805 reg needs a supply of at least 7V or so to work properly.
 
Are there any simpler SMPS design which has almost no AC ripple?
 
Simpler than what?
 
Simpler than what?

Simpler than my skill :D

Ok just I want to know that- can I use AC to DC SMPS on my oscillator without any noise like batttery? Even if used Battery, the Oscillator catches AC noise from audio line connected with computer (Computer's AC). (audio line connected with cell phone is very clear transmission through oscillator transmitter)
 
No SMPS or linear power supply is totally noise-free. You should filter/decouple the supply to your oscillator.
 
Are there any simpler SMPS design which has almost no AC ripple?

Use SMPS with more current rating like laptop chargers. if voltage is more use 78XX regulator with a capacitor with it.

another way to filter the noise is to keep a battery inline and it will act like a big capacitor
 
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