Hello, the village idiot has returned.
Time for stupid questions round 2.
To save you the time of answering my questions in my "wireless electric current" thread, I watched YouTube tutorials about spark gap transmitters and AM transmitters for the past 3 hours.
I found out that a transformer is NOT used in a spark gap transmitter to create radio waves, rather the transformer is used to STEP UP THE VOLTAGE.
The high voltage is connected to a tank circuit consisting of an inductor and a capacitor (of course it is tuned before you start transmitting so you don't electrocute yourself!).
Early spark gap transmitters did not have oscillators. Later spark gap transmitters used tank circuits to create the oscillator as the radio spectrum became more crowded with transmissions and also since resonance greatly amplifies a signal to be picked up by a reciever at the same resonance so the transmission distance is much further than with unmodulated spark gap transmitters.
The spark gap is used because it was the first practical way to transmit before amplification components were invented since the gas breakdown makes an audible sound.
I wonder what would happen if I touched the antenna of a spark gap transmitter?
I think a spark gap transmitter looks dangerous to build and it unfortunately only works for on-off morse code and neither CW nor AM.
I wonder if I could build an AM transmitter using spark gap transmitter principles, with the major change of there being no spark gap so AM is possible, and the transformer used to step up the voltage and current is a 500 W PA output transformer.
So a 500 W transmitter?
The audio signal is connected to the PA, amplified by the transistors in the PA, and the voltage is stepped up by the output transformer (the PA is solid state, so that means it doesn't actually have an output transformer, but it still has something to step up the voltage performing the same function) from the low line level (about 0.3 volts for consumer audio gear) to 8 ohm speaker level for a 500 watt amp (63.2 volts).
V=IR
P=IV
P=(I squared)(R)
500 watts = (I squared)(8 ohms)
62.5 amperes = (I squared)
square root (62.5 amperes) = I
7.9 ampere = I
V= (7.9 ampere)(8 ohm)
V= 63.2 volts
Increasing the load of the speaker increases the voltage, but decreases the current.
Decreasing the load of the speaker decreases the voltage, but increases the current.
Power can be increased by either increasing current or increasing voltage.
Since my threads were locked, I went to this forum and found this thread about what happens if I touch an antenna.
The thread linked to this page.
So if I touch the end of a speaker cable with my finger connected to the output transformer of that PA, will that really give me RF burn, since we have already discussed that current in a wire creates a magnetic field?
Or does RF burn only apply at radio frequencies and does not apply at audio frequencies?
I don't want to try at home, because I don't want to burn a hole in my finger to see if RF burn applies to audio frequencies.
Well if I connected a tank circuit consisting of a loop with a vari-cap and an inductor to the speaker cable and connected an antenna wire to the other end of the tank circuit, would 500 W of RF give me an RF burn from touching the antenna wire?
Edit: Well actually, that wouldn't be AM RF either, that would just be base band at radio frequency, which is used for the spark gap transmitter, but is not used for the AM transmitter. but it would still be RF because the frequency is higher than audio frequency and lower than microwave frequency. just the RF has the base band at RF carrier wave that can be turned on and off by a morse key so it only works for morse code (which the morse code can be made to be heard as CW with my regenerative detector feedback loop).
The AM transmitter uses a voltage controlled oscillator adding some resistors into the tank circuit so the base band at radio frequency carrier wave has the signal modulated into its amplitude peaks at a small voltage difference.
Here I found a good link for FM transmitter that explains base band at radio frequency (this is how FM can be stereo and mono on the same carrier wave frequency for backwards compatibility with mono FM receivers) and explains voltage controlled oscillators (VCO):http://ibahceci.etu.edu.tr/ele474/fmradio/FMTutorial.pdf
Time for stupid questions round 2.
To save you the time of answering my questions in my "wireless electric current" thread, I watched YouTube tutorials about spark gap transmitters and AM transmitters for the past 3 hours.
I found out that a transformer is NOT used in a spark gap transmitter to create radio waves, rather the transformer is used to STEP UP THE VOLTAGE.
The high voltage is connected to a tank circuit consisting of an inductor and a capacitor (of course it is tuned before you start transmitting so you don't electrocute yourself!).
Early spark gap transmitters did not have oscillators. Later spark gap transmitters used tank circuits to create the oscillator as the radio spectrum became more crowded with transmissions and also since resonance greatly amplifies a signal to be picked up by a reciever at the same resonance so the transmission distance is much further than with unmodulated spark gap transmitters.
The spark gap is used because it was the first practical way to transmit before amplification components were invented since the gas breakdown makes an audible sound.
I wonder what would happen if I touched the antenna of a spark gap transmitter?
I think a spark gap transmitter looks dangerous to build and it unfortunately only works for on-off morse code and neither CW nor AM.
I wonder if I could build an AM transmitter using spark gap transmitter principles, with the major change of there being no spark gap so AM is possible, and the transformer used to step up the voltage and current is a 500 W PA output transformer.
So a 500 W transmitter?
The audio signal is connected to the PA, amplified by the transistors in the PA, and the voltage is stepped up by the output transformer (the PA is solid state, so that means it doesn't actually have an output transformer, but it still has something to step up the voltage performing the same function) from the low line level (about 0.3 volts for consumer audio gear) to 8 ohm speaker level for a 500 watt amp (63.2 volts).
V=IR
P=IV
P=(I squared)(R)
500 watts = (I squared)(8 ohms)
62.5 amperes = (I squared)
square root (62.5 amperes) = I
7.9 ampere = I
V= (7.9 ampere)(8 ohm)
V= 63.2 volts
Increasing the load of the speaker increases the voltage, but decreases the current.
Decreasing the load of the speaker decreases the voltage, but increases the current.
Power can be increased by either increasing current or increasing voltage.
Since my threads were locked, I went to this forum and found this thread about what happens if I touch an antenna.
The thread linked to this page.
So if I touch the end of a speaker cable with my finger connected to the output transformer of that PA, will that really give me RF burn, since we have already discussed that current in a wire creates a magnetic field?
Or does RF burn only apply at radio frequencies and does not apply at audio frequencies?
I don't want to try at home, because I don't want to burn a hole in my finger to see if RF burn applies to audio frequencies.
Well if I connected a tank circuit consisting of a loop with a vari-cap and an inductor to the speaker cable and connected an antenna wire to the other end of the tank circuit, would 500 W of RF give me an RF burn from touching the antenna wire?
Edit: Well actually, that wouldn't be AM RF either, that would just be base band at radio frequency, which is used for the spark gap transmitter, but is not used for the AM transmitter. but it would still be RF because the frequency is higher than audio frequency and lower than microwave frequency. just the RF has the base band at RF carrier wave that can be turned on and off by a morse key so it only works for morse code (which the morse code can be made to be heard as CW with my regenerative detector feedback loop).
The AM transmitter uses a voltage controlled oscillator adding some resistors into the tank circuit so the base band at radio frequency carrier wave has the signal modulated into its amplitude peaks at a small voltage difference.
Here I found a good link for FM transmitter that explains base band at radio frequency (this is how FM can be stereo and mono on the same carrier wave frequency for backwards compatibility with mono FM receivers) and explains voltage controlled oscillators (VCO):http://ibahceci.etu.edu.tr/ele474/fmradio/FMTutorial.pdf
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