This is without a doubt one of the best tutorial presentations on youtube. It's the equivalent of a 1st semester course in RF engineering. As students we are lucky to have folks like "RFman" create these type videos. When you compile how much information and learning this 6 part video series provides, it's enormous.
The question is related to the RF push-pull amplifier. What will be the result, if we assembled a push-pull RF amplifier circuit of 7 RF same transistors like 2N3866 ? Consider there are 7 RF transistors 2N3866 as A, B,C,D,E,F,G. Transistor A is a driver transistor of output transistors B and C, whose conduction angle is 180 degree. Transistor B is a driver transistor of D and E, as well as transistor C is a driver transistor of the transistors F and G. And the each output transistors D,E,F,G are conducted at an angle of 90 degree , ok ? Can this configuration of 7 RF transistors works well ? And the efficiency of this amplifier will increase well ? Because each output transistors has conduction angle of 90 degree. Please explain with great affection and lovely approach.
One question please, my friend. The nano vna is not damaged or it does not produce autoosilation when applying it at the entrance to the shelf. I want to do the same with a pallet that has a blf188xr. Thank you. I await your response. Thank you
I want to check impedance of last binocular core. If I put a dummy load to out and connect nanovna to primer side of core, can I check it? Thanks a lot!
Rf man great videos for radio amateurs. At minute 7 of the video you show c6 and c5, but how are these values calculated , from the primary and secondary leakage inductance of the output transformer? Another question would be Can I have access to those wonderful slides from this series of videos? greetings from Spain.
You can try using the leakage inductance to determine the value of C. The problem is all the other parasitics in the circuit. Its easier and more accurate to use a trimmer capacitor and adjust it to find the optimal value to lower SWR's and increase power output.
There are some transformer designs that use that technique. I have never tried it. I have used conventional transformers and a number of different TLT.s in my designs. Regards
Hello, I have a basic question, I would love to hear your opinion, I have an amplifier for the range 87 to 108 that is supposed to produce 150 watts, it is based on a blf177 resistor, but in practice it outputs a maximum of 50 watts, I added circuits to adjust the input and output impedance of the amplifier, and the meter shows 1.2, which is In my opinion, swr. The antenna adjustment is at a reasonable level, but still the maximum power is 50 watts instead of 150 watts, a smaller transmitter is connected that outputs up to 7 watts at the input as requested, it was said that power between 3 and 7 watts should be provided at the input, but the output receives 50 watts instead of 150 watts, what else should be checked In your opinion ? Thank you in advance.
I noticed the mistake at first glance. You made a mistake in calculating the RF choke. The output impedance of the transistor is 6.25 ohms with a transformer ratio of 1:4, not 50 ohms as you stated. Additionally, the RF chokes should be bifilar wound on a single ferrite core for symmetry, which is important for further attenuation of even harmonics.
This is without a doubt one of the best tutorial presentations on youtube. It's the equivalent of a 1st semester course in RF engineering. As students we are lucky to have folks like "RFman" create these type videos. When you compile how much information and learning this 6 part video series provides, it's enormous.
I agree, brilliant.
⁰
From an old GE Mobile Radio engineer: well done, sir.
Thank you for your positive feedback...RF Man
Great series. Love it.
Another excellent vidio RF man. Thx
Hello rf man pls make/add video where u had challenges and how u resolved them for our better understanding
The question is related to the RF push-pull amplifier.
What will be the result, if we assembled a push-pull RF amplifier circuit of 7 RF same transistors like 2N3866 ?
Consider there are 7 RF transistors 2N3866 as A, B,C,D,E,F,G. Transistor A is a driver transistor of output transistors B and C, whose conduction angle is 180 degree. Transistor B is a driver transistor of D and E, as well as transistor C is a driver transistor of the transistors F and G. And the each output transistors D,E,F,G are conducted at an angle of 90 degree , ok ?
Can this configuration of 7 RF transistors works well ?
And the efficiency of this amplifier will increase well ? Because each output transistors has conduction angle of 90 degree. Please explain with great affection and lovely approach.
One question please, my friend. The nano vna is not damaged or it does not produce autoosilation when applying it at the entrance to the shelf. I want to do the same with a pallet that has a blf188xr. Thank you. I await your response. Thank you
I have a video on my channel which shows the same measurement for a BLF188XR device.
On your video about RF chokes how do you have your nano VNA setup. I'm not using the PC version but hand held
I am using port 1 and port 2 and measuring S21 (Gain). LOGMAG on NanoVNA. Regards
I want to check impedance of last binocular core. If I put a dummy load to out and connect nanovna to primer side of core, can I check it? Thanks a lot!
Yes, just use 50 ohms for you load. Regard RF Man
Rf man great videos for radio amateurs. At minute 7 of the video you show c6 and c5, but how are these values calculated , from the primary and secondary leakage inductance of the output transformer? Another question would be
Can I have access to those wonderful slides from this series of videos?
greetings from Spain.
You can try using the leakage inductance to determine the value of C. The problem is all the other parasitics in the circuit. Its easier and more accurate to use a trimmer capacitor and adjust it to find the optimal value to lower SWR's and increase power output.
Have you tried the output transformers in parallel run the winding from one transformer to the other then out.. 1.5 turns each
There are some transformer designs that use that technique. I have never tried it. I have used conventional transformers and a number of different TLT.s in my designs. Regards
Muy bien explicado
I was wondering were do you get your ferrite beads/cores from
Any electronic distributor like Arrow, Digikey, Mouser, Newark, etc. will have a good assortment available in stock. Regards
can u up load your spice file so i can get used to using it thank you
If you PM me on facebook, I would be happy to send it to you. Search on Rob Campo.
Do you make a full hd video or DVD
Hello David, I'm only posting on You Tube right now. Thanks
Hello, I have a basic question, I would love to hear your opinion, I have an amplifier for the range 87 to 108 that is supposed to produce 150 watts, it is based on a blf177 resistor, but in practice it outputs a maximum of 50 watts, I added circuits to adjust the input and output impedance of the amplifier, and the meter shows 1.2, which is In my opinion, swr. The antenna adjustment is at a reasonable level, but still the maximum power is 50 watts instead of 150 watts, a smaller transmitter is connected that outputs up to 7 watts at the input as requested, it was said that power between 3 and 7 watts should be provided at the input, but the output receives 50 watts instead of 150 watts, what else should be checked In your opinion ? Thank you in advance.
Please send me a photo or schematic and I will take a look. If you have a video, please attach the link. Regards carmine2962@gmail.com
U win my subsribe dude
Everything looks good but I bought three of them and after a month they didn't charge anymore, "disappointed"
I noticed the mistake at first glance. You made a mistake in calculating the RF choke. The output impedance of the transistor is 6.25 ohms with a transformer ratio of 1:4, not 50 ohms as you stated. Additionally, the RF chokes should be bifilar wound on a single ferrite core for symmetry, which is important for further attenuation of even harmonics.
Can I email you please I am having an issue with simulating this circuit. I have a distorted waveform.