Is the design feasibility of 160M 625W Class D transmitter?
BA7OMW:
[I'm from a non-native English speaking country and my content is provided by Google Translate]
There isn't enough room where I live to install a full-size 160M band antenna, so I need a more powerful transmitter to make up for the inefficient antenna.
I originally decided to use a Class E amplifier, but a high voltage vacuum variable capacitor suitable for a high power Class E amplifier output tuner was beyond my budget.
Then I discovered W1VD’s Current-Mode Class D power amplifier design on the Internet, which uses a transformer for impedance transformation without the need for tuning components. Seems easier to build too.
After continuing to search for CMCD power amplifier related content, I found the CMCD calculator written by LU5HAH and calculated a design that seemed feasible.
My electronic knowledge is not very rich and I cannot complete the design by myself, so I hope the experts in the forum can help me. Thank you very much.
BA7OMW:
Regarding the outdated MOSFETs used in the design, NOS's FQA11N90 MOSFETs are still readily available where I live for $4.30 each. If there is a better MOSFET option please let me know.
BA7OMW:
It is found from the calculator that the output impedance at 80V carrier voltage and 625W carrier power is exactly 50Ω, which can be output through a simple 1:1 choke. From the Class E website, I learned that the safe operating current of the FQA11N90 should be around 1A, and the total current of 7.9A calculated on the calculator looks fine. But is 80V carrier voltage too high for FQA11N90?
vk3alk:
Hi...
Not sure of your name or country not that it matters....
I am not an expert on CMCD but will give it a go to help...
Tonight will check though whether all your calculations of the tuned circuit are correct using 4 X 11N90s either side etc: and advise soon....
The current balun should be fine and also the DC blocking capacitors locations can be positioned before or after the balun... :)
Using CMCD with 80 volts applied should be OK....
Driving current will be interesting but your operating frequency is 160M so thats in your favour.... :D
Are you using Digital drive or Sinewave drive ?
Wayne
BA7OMW:
Quote from: vk3alk on April 22, 2024, 10:11:22 PM
--
Hi...
Not sure of your name or country not that it matters....
I am not an expert on CMCD but will give it a go to help...
Tonight will check though whether all your calculations of the tuned circuit are correct using 4 X 11N90s either side etc: and advise soon....
The current balun should be fine and also the DC blocking capacitors locations can be positioned before or after the choke... :)
Using CMCD with 80 volts applied should be OK....
Driving current will be interesting but your operating frequency is 160M so thats in your favour.... :D
Are you using Digital drive or Sinewave drive ?
Wayne
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Thank you for your help.
I plan to use digital drivers, using an IXDD614 to drive two FQA11N90s.