Class E Amplifiers are hard to modulate in general, since the input waveform is a square wave (ie no amplitude information at all). As-is you could use it for frequency modulation or on/off modulation like CW. Getting amplitude modulation requires modulating the voltage supplied to the amplifier to match the rf envelope. To get SSB you need to combine the amplitude tricks with changing the phase of the square wave sent to the input, which is pretty complicated. This is actually what the uSDX / truSDX projects do using an arduino and controlling the phase of the rf oscilator over i2c.
You can look at the shape of the voltage waveform to determine how well your wave shaping circuit is working. Remember you are trying to achieve Zero Volt Switching (ZVS), so the rise and fall times should be very fast. You should also see a significant reduction in the transistors case temperature if the transistor is switching more efficiently. Regards
Hello Sir, can you make a video about how to safely measure the output impedance of a RF Amplifier circuit with attenuator, there are already many videos covering how to measure input impedance of a RF Amplifier circuit using a Nano VNA. Especially for non-50ohm amps, how do I measure the output impedance on the VNA?
It's hard to quibble with the highly efficient result you measured, but if the goal is to have a high Q 700 nH inductor, an air core should produce a better result than a powered iron core, with the reduced core losses more than making up for the increased wire losses. An air core with 700nH and a Q of 300 is pretty straightforward. I'm curious what you are achieving with the powdered iron core...
Powdered iron cores (T68-6 in my circuit) can be used to design high Q inductors at frequencies below 200 MHz. The core must be large enough to ensure it does not saturate. Using an on-line calculator the Q value for my inductor is just over 100. I agree, an air core inductor would have a higher Q and less losses. This might yield a small increase in efficiency. With the current inductor, I found the circuit performance to be acceptable and the temperature rise of the inductor to be quite low. Thanks for your comments. RF Man
I retested with an air core inductor (OD .625", L .750", #Turns 8) and basically saw the same results 89 - 90% efficiency. I can made a video update if you like.
Interest video series, thanks. I see you drove it by a square wave. Sokal claims designs have been made up to GHz. Even at 144MHz a square wave would be difficult to achieve, so can you drive with less-than perfect square to switch the amplifier. Secondly NBFM would not problem, but what about DSB or SSB.
Class E Amplifiers are hard to modulate in general, since the input waveform is a square wave (ie no amplitude information at all). As-is you could use it for frequency modulation or on/off modulation like CW. Getting amplitude modulation requires modulating the voltage supplied to the amplifier to match the rf envelope. To get SSB you need to combine the amplitude tricks with changing the phase of the square wave sent to the input, which is pretty complicated. This is actually what the uSDX / truSDX projects do using an arduino and controlling the phase of the rf oscilator over i2c.
Great information
Great work. Thanks for the effort. I wonder how this class E amplifier would do for AM and SSB where linearity is required.
Class E Amplifiers are hard to modulate in general, since the input waveform is a square wave (ie no amplitude information at all). As-is you could use it for frequency modulation or on/off modulation like CW. Getting amplitude modulation requires modulating the voltage supplied to the amplifier to match the rf envelope. To get SSB you need to combine the amplitude tricks with changing the phase of the square wave sent to the input, which is pretty complicated. This is actually what the uSDX / truSDX projects do using an arduino and controlling the phase of the rf oscilator over i2c.
What is the preamplifier you are using? Thanks for the great video!
www.ebay.com/itm/395155655328?chn=ps&mkevt=1&mkcid=28&srsltid=AfmBOorZkYme5NQ1m-M_8zEyQrhEjcBcasnGRsEaA0LikwUnalfVMxLCRIw&com_cvv=8fb3d522dc163aeadb66e08cd7450cbbdddc64c6cf2e8891f6d48747c6d56d2c
@@rfmanchannel6915 thanks!
Hello ... Great stuff. I've enjoyed your channel for a few years. I would really appreciate your spreadsheet. How would one get in touch ??
Thank you
Are there UHF signal repeater circuits?
Is it possible to align a class E amp without having a current probe attached?
You can look at the shape of the voltage waveform to determine how well your wave shaping circuit is working. Remember you are trying to achieve Zero Volt Switching (ZVS), so the rise and fall times should be very fast. You should also see a significant reduction in the transistors case temperature if the transistor is switching more efficiently. Regards
Hello Sir, can you make a video about how to safely measure the output impedance of a RF Amplifier circuit with attenuator, there are already many videos covering how to measure input impedance of a RF Amplifier circuit using a Nano VNA. Especially for non-50ohm amps, how do I measure the output impedance on the VNA?
I already have a video on my channel that discusses this topic. This is the method I use.
ruclips.net/video/byivod5HxDc/видео.html
It's hard to quibble with the highly efficient result you measured, but if the goal is to have a high Q 700 nH inductor, an air core should produce a better result than a powered iron core, with the reduced core losses more than making up for the increased wire losses. An air core with 700nH and a Q of 300 is pretty straightforward. I'm curious what you are achieving with the powdered iron core...
Powdered iron cores (T68-6 in my circuit) can be used to design high Q inductors at frequencies below 200 MHz. The core must be large enough to ensure it does not saturate. Using an on-line calculator the Q value for my inductor is just over 100. I agree, an air core inductor would have a higher Q and less losses. This might yield a small increase in efficiency. With the current inductor, I found the circuit performance to be acceptable and the temperature rise of the inductor to be quite low. Thanks for your comments. RF Man
I retested with an air core inductor (OD .625", L .750", #Turns 8) and basically saw the same results 89 - 90% efficiency. I can made a video update if you like.
Interest video series, thanks. I see you drove it by a square wave. Sokal claims designs have been made up to GHz. Even at 144MHz a square wave would be difficult to achieve, so can you drive with less-than perfect square to switch the amplifier. Secondly NBFM would not problem, but what about DSB or SSB.
I didn’t test SSB only AM. I will consider this for future videos. Thanks for your feedback. RF Man
Ok that would be interesting. When I finish my current project Im going to look into a 145MHz Class E amp.
You do not talk much about what modes this will work for? SSB? Seems like other Class E amps focus on AM.
Class E Amplifiers are hard to modulate in general, since the input waveform is a square wave (ie no amplitude information at all). As-is you could use it for frequency modulation or on/off modulation like CW. Getting amplitude modulation requires modulating the voltage supplied to the amplifier to match the rf envelope. To get SSB you need to combine the amplitude tricks with changing the phase of the square wave sent to the input, which is pretty complicated. This is actually what the uSDX / truSDX projects do using an arduino and controlling the phase of the rf oscilator over i2c.
@@MobiusHorizons Thanks, that is kind of what I thought, but wanted to verify. Will checkout the uSDX/truSDX projects...sounds interesting