This is the best video on amplifier design andtest that I have ever seen. For people that are serious about learning to build RF power amplifiers without EE level mathematics I recommend the following: 1. RF Circuit Design -Chris Bowick 2. Practical RF Design Manual - Doug Demaw 3. Ferromagnetic Core Design and Application -Doug Demaw 3. Solid State Design for the Radio Amatuer - ARRL 4. Simplified Solid State Design - John Lenk.
Thank you for adding this comment I have been looking for literature to learn some theory of why builders do what they do. I was able to find all these books in pdf form for free. I can't wait to dig in
I watched the whole video. But I can assure you..... I'll be watching it ohhh.... Another 5 or 6 times a day until I know it word for word. Your very smart and I have a very high respect for what your doing here. As a member of the Amp building community I would like to sincerely Thank you for what I just witnessed. I could literally pay you for this info and totally justify it. Seriously man. Thank you so much. I just spent the 75 bucks on Amazon before the video even finished lol got one of the vna tools and all the connectors. I'm stoked
DUDE DUDE DUDE DUDE.... DUUUUUUUUDDDE......THANK YOU SOOOOOOO MUCH!!!! This is hands down the most informative and well put together video on this topic and the most well explained and informative
learned alot with this video. I like how you soldered the nano vna connectors to the input and output for amp circuit. thx for explaining everything with great detail.
New subscriber here and I never comment but I just had to thank you for sharing your knowledge. This is the info that holds a lot of us back and most amp builders absolutely will not share with you. Thanks again bro.
this was a fantastic video, i hope when you get your new shop setup in your new home you will one day make a video of a push pull amp and explain in detail how you obtain your input and output impedances with the data sheets and vna with the 2 transistor design, you may consider yourself a novice or beginner at this but you are way smarter than most other amp builders on youtube, plus you share information which is greatly appreciated and are excellent at explaining the design and theory, my hat is off to you. just watching this video alone gives me ideas on how to further fine tune inputs and outputs on texas star, boomer solid state amps that usually have horrible input tunes out of the box. thanks again and looking foward to your new shop and more experimenting / teaching videos.
This is my kinda channel. Love the “ugly” construction. Usually the uglier stuff works better with RF at least with my feeble attempts at home builds. Really appreciate the walk through of the circuit.
This is eaxctly the video I needed to watch today! I've been getting into building audio amplifyers and compressors with amp circuits within them etc. recently and have been trying to learn more and more about how they do what they do on a deeper level. I've been tracing the signal through the circuit with my scope and playing about trying to understand certain things ... and being a tube circuit (although not much differant to a transistor circuit in what I was trying to figure out) I couldn't work out why the HV power was being supplied to what appeared to be the tube signal output .... but this makes that make perfect sense, and was kind of what I assumed it must be, but had no way to know for sure without this vid! It's just taking an elevated AC voltage from the change due to what the tube lets through from the grid signal on the annode plate side, rather than taking it from the cathode and the output being only what the tube lets through like I initially thought (untill I looked at the circuit and was like well it's attached directly to ground through a resistor, so it can't be that). Thanks for uploading this!
The first 5 seconds I see that it’s already AB biased! I love that for purity! As I’m an all mode operator! Not just an AM stripped down no trash collection caps or feedback resistors in a class C! 🤮Great job and work! Yes, I’ve been into this since the early 90’s and throughout the Toshiba years. These DEI and huaggo HG transistors are tuning differently than the old stuff they do tune differently. The C’s are bad ass as the MRF421’s too! 😊 I now work as an electronic engineer and love RF and radio! CB and HAM both! I don’t forget where I started and love it all! Keep it up! 👍🏼 the input RF coupling should be 910-1200pf for a low ac rf resistance and impedance. Everything so far I’ve heard has been correct! But for gain, the LD mos fet is a multi junction transistor. They naturally have more gain! But a higher beta bipolar transistor will have greater gain at the expense of stability. But stability comes with bias and bias it into class A if you need stability and or purity but then linearity gain dwindles. So, what gives? Thats where a curve tracer or even a peak 75 to test the transistors and matching…. Thats another time.
This has helped me to understand amp construction more than anything on youtube! I was curious as to why this circuit does not have input and output transformers.
I definitely appreciate your informational video, I have finally put it to use. I managed to put together a pair of 2879 @13.8 vdc and achieved about 300 w out and that definitely put a smile on my face 😁 although not fully understanding all of the information yet I guess it's a start. Not quite sure if I have the confidence yet to put together six or eight of these. But I guess eventually I'm gonna try ? I am definitely interested in LDMOS, but not liking the hassle of 65 vdc while mobile ! Thank You And Please Keep Building And Making Videos If Possible 😁 Again, Thank You For All You Do ! My poor old eyes aren't what they used to be but with the proper enhancements I'm sure I will be able to throw something together 🤣
Fun video. My construction projects look a lot like yours. Two suggestions: one you might want to add a series variable capacitor between the connector and the shunt capacitor to be able to adjust for optimum match should the transistor not present the published impedance. The same holds for the output. Usually it is best to be able to have two variable components to be get the ideal match. It's easier to adjust a capacitor than an inductor. Second point. If the output power of an RF power transistor doesn't produce the expected output, all else being correct, it is probably not fully good. This was a typical problem for earlier (1970s) VHF and UHF transistors in mobile radio applications. With an ohmmeter they measured like a good device, but had little to no power gain.
Eh Sharky. Thank you very much for your informative video and for all that you have contributed to the hobby. There aren't may people doing what you're doing.....especially not as clear and concise in their videos. I truly appreciate a logical, obviously very intelligent and humble approach to your content. It's certainly a breath of fresh air compared to other conceited loud mouths. Lol........my dogs drink alot too!!!
I saw the lead on the input bias choke bouncing up and down as you were tapping on the choke and I wanted to yell that to you - 3 years after the fact. :)
Thanks for sharing your knowledge, saves me lots of time digging through the application notes. Measuring the transformer with nanovna is a good idea. I don't know if it matters that the transformer is balanced where as the nano is unbalanced. Also I will take my time to read the datasheet. Thanks
Fantastic video! You took 40 years of mystery out of my tinkering. Wondering what value your "high value" blocking caps were? Also what diode did you use to stabilize the bias supply? ... if I may ask.
I think those caps were 5.6nF. Enough to pass 27mhz with little reactance. As for the diode I don't remember... just a random one from the junk pile. Didn't matter much for what I was testing.
Howdy. Nice. I would suggest the second capacitor in both input and output are loading capacitors. These serve the purpose of matching the impedances. I think these need be adjustable too to get max. gain. One starts with a random setting of these. Then tunes the others for resonance. Slightly increase or decrease the loading cap.s, retune to resonance and observe if the gain increased or decreased. Switching back and forth one should find max. gain. Observe that the circuit may jump into oscillation in peak tuning. A slight over or under tuning may be needed for stable operation. Regards.
That is almost the same test circuit used in the Motorola RF transistor hand book. will be very clean but wont brood band much with out re tuning . for singe band use that's fine. for VHF smaller inductors and 80 meter HF will need longer coil. depending on transistor. MRF 492 works 50 MHz . That is best bias circuit. to build this into working amp place diode on heatsink with thermal compound. My book in storage think 1N4997 is press fit into heat sink for bias .will help with thermal run away. you are right the 2sc2290 has less input drive needed . makes great driver for low dead key radio . 73's
MD Sharky, g'day mate, that was very done your explanation AMPS theory. Like" BBI said go over to his site learn more". Good presentation for a happy bloke. Cheers & Beers.73.
Man very very smart and good at what he does just wait tell u see what he has done ..check out his channel and videos ...smart dude .works as I grew up in a machine shop he.. is very good with metals heat sinks disapation and cooling banks and much more on ldmos
Hi matey. There was an article in either Practical Wireless or another magazine over 20years ago showing how to make a 2metre VHF amplifier is used similiar construction to yours .Double sided copper clad board glued on board as capacitors and inductors. I built one and surprised how well it worked and easy to build all dimensions was included in design no ferrites. Maybe worth researching. George
Really appreciate your explaination. Would you mind sharing the device model of your high Q tunable capacitor (which seems quite compact there)? I am thinking of tuning the circuit myself for high power amplifier, would really appreciate your help. - Yuanchen
You would not happen to have a board layout for this amp would you? I'd have a go at a build but I need a place to start. It would also give me justification for the Nano VNA I bought. Thanks.
That network on both the input & output of the test circuit was used to lower the Q of those networks to achieve more bandwidth. With a simple L-network you're using... you have no control over the network Q. Let me also say that controlling the Q may or may not be necessary... depending on application requirements.
Thanks for the video it was really interesting to watch especially the use of the nano VNA to measure the input and output circuits. I'm looking to build an amp that can be driven with about 200mw from a GRC-106A to some reasonable output of 20 or 30w or more. Do you have a suggestion for a high-gain transistor that may be good to start with for experimentation?
You need to do a two-tone test on any RF power amp, particularly an external linear amplifier. If you don't do the test you won't know the linearity and the in-band intermod products. You will quickly find that you need to back off the drive to get reasonable linearity. For SSB operation your 3rd order products should be at least 26dB below your carrier. These 3rd order intermod products are what causes "splatter" on adjacent channels. All ssb tranceiver's output power is limited by the 3rd order products and they run them below their peak output capability. That's why it's always possible to overdrive the PA and get more output power.
Wow,das geht schnell ins Auge.Ich habe immer nur die halbe Wattleistung abverlangt um den armen Transistor nicht Strom oder Hitzetod sterben zu lassen.😂👍🙋🇩🇪🗿
Ducky i have a nano vna also..I can use it to tune a amp right? I have a 1x2 in transitioning back into a base and might might it a 1x4. I would like to swap it to a c box the tuning is what I kinda am having trouble with .
Hi. First off all, thanks for your great informative wideos Let mee know if my thoug process is wrong, the output rfc choke is there for two reasons, blocking the rf from the power supply and keeping an relative constant current, when the fet or transistor is on, the current slightly increases and goes to ground, when the transition is off the "constant current" will increases the voltage on top off the transistor, abaut Doble the supply voltage in a perfect world, depending on the output tune, in case you don't have matching network connected the voltage wuld in theory spike to infinity. At least if you are driving with Square wave Litle like a switching powers supply works. So in my theory the the transformer kind a output will be more forgiven for higher antenna inpedans, this is due to the transformer "self limiting propeys" when in a lc kind of a "pump and dump" network a higher antenna inpedans will result in a higher source to drain voltage, and might go over the break down voltage character or your feet / transistor All the best and keep up the great work 👍
At what point would it be beneficial to switch over to the longer tube shaped shotgun looking transformers? And why. Heat dissipation? Better impedance match? ?
I am so glad I found your channel Mister mud duck, although I do not understand every word that you are saying not that your English leaves anything to desire just my vocabulary of electronic components is very limited, I'm hoping by watching and listening and maybe soldering occasionally I can figure it out, I must confess I feel more comfortable with tubes have you ever done anything like a tube type modulator or something in that line, once again thank you for your time I really appreciate it GL lake Cumberland Kentucky.
Awesome. Really lays it down on how it's working. Takes a lot of the mystery out of it. I know electronics but now RF. I want to learn. I want one of your kits too. How much current for the ab bias?
I really appreciate this info. Maybe you can help me with my linear amp. It has 2 of these. Pull amp works great, tx led aluminates with about 3 watts dead carrier. No rf power out. One of the transistors is cold, the other heats up super fast. Out of circuit, each transistor measures as it should in diode mode. Very strange. They both measure good yet 1 or both might have no gain. Any clues? Thanks!
If your radio has a 10 watt carrier and 30 watts peak, your already in compression at the radio!. For experimenting you really need to start with a clean radio..
what is the patrs and detail eahch one or value of all parts/ could you pls sir show the complete diagram and material needed thank and god bless ..keep it up boss.
gud day sir,,, im a first starter assembler electronics graduate, that i want to assemble like n rf amplifier booster for a fm transmitter exciter sir, do you have a chematic diagram for an rf amplifier booster, and how to adjust and align the tuning capacitors on this amplifier you assembled?
![Gain block RF Amplifiers - Theory and Design [1/2]](/img/1.gif)
That is a great explanation with simplicity, straight to the point, no ego, no sarcasm, no arrogance, and what matters most. Thanks.
This is the best video on amplifier design andtest that I have ever seen.
For people that are serious about learning to build RF power amplifiers without EE level mathematics I recommend the following:
1. RF Circuit Design -Chris Bowick
2. Practical RF Design Manual - Doug Demaw
3. Ferromagnetic Core Design and Application -Doug Demaw
3. Solid State Design for the Radio Amatuer - ARRL
4. Simplified Solid State Design - John Lenk.
Thank you for adding this comment I have been looking for literature to learn some theory of why builders do what they do. I was able to find all these books in pdf form for free. I can't wait to dig in
I watched the whole video. But I can assure you..... I'll be watching it ohhh.... Another 5 or 6 times a day until I know it word for word. Your very smart and I have a very high respect for what your doing here. As a member of the Amp building community I would like to sincerely Thank you for what I just witnessed. I could literally pay you for this info and totally justify it. Seriously man. Thank you so much. I just spent the 75 bucks on Amazon before the video even finished lol got one of the vna tools and all the connectors. I'm stoked
Check out 440 cb shop on Facebook if you like amps
Ma brain hertz...
DUDE DUDE DUDE DUDE.... DUUUUUUUUDDDE......THANK YOU SOOOOOOO MUCH!!!! This is hands down the most informative and well put together video on this topic and the most well explained and informative
learned alot with this video. I like how you soldered the nano vna connectors to the input and output for amp circuit. thx for explaining everything with great detail.
New subscriber here and I never comment but I just had to thank you for sharing your knowledge. This is the info that holds a lot of us back and most amp builders absolutely will not share with you. Thanks again bro.
Mr MudDuckSharky, excellent informative video. You answered so many of my questions. Many Thanks!!
Thanks for taking the time to show this, Finding out what the transistor needs has always seemed to be a mystery.
this was a fantastic video, i hope when you get your new shop setup in your new home you will one day make a video of a push pull amp and explain in detail how you obtain your input and output impedances with the data sheets and vna with the 2 transistor design, you may consider yourself a novice or beginner at this but you are way smarter than most other amp builders on youtube, plus you share information which is greatly appreciated and are excellent at explaining the design and theory, my hat is off to you. just watching this video alone gives me ideas on how to further fine tune inputs and outputs on texas star, boomer solid state amps that usually have horrible input tunes out of the box. thanks again and looking foward to your new shop and more experimenting / teaching videos.
Very nice I learned today as you explain. Also you have a voice easy to listen to that kept me on board.
This is my kinda channel. Love the “ugly” construction. Usually the uglier stuff works better with RF at least with my feeble attempts at home builds. Really appreciate the walk through of the circuit.
This is eaxctly the video I needed to watch today!
I've been getting into building audio amplifyers and compressors with amp circuits within them etc. recently and have been trying to learn more and more about how they do what they do on a deeper level. I've been tracing the signal through the circuit with my scope and playing about trying to understand certain things ... and being a tube circuit (although not much differant to a transistor circuit in what I was trying to figure out) I couldn't work out why the HV power was being supplied to what appeared to be the tube signal output .... but this makes that make perfect sense, and was kind of what I assumed it must be, but had no way to know for sure without this vid! It's just taking an elevated AC voltage from the change due to what the tube lets through from the grid signal on the annode plate side, rather than taking it from the cathode and the output being only what the tube lets through like I initially thought (untill I looked at the circuit and was like well it's attached directly to ground through a resistor, so it can't be that).
Thanks for uploading this!
Time for more videos...
Love thee information you have packed into this video.
Looking forward to seeing morr
So well explained, this beginner was able to follow it all. Thank-you.
The first 5 seconds I see that it’s already AB biased! I love that for purity! As I’m an all mode operator! Not just an AM stripped down no trash collection caps or feedback resistors in a class C! 🤮Great job and work! Yes, I’ve been into this since the early 90’s and throughout the Toshiba years. These DEI and huaggo HG transistors are tuning differently than the old stuff they do tune differently. The C’s are bad ass as the MRF421’s too! 😊 I now work as an electronic engineer and love RF and radio! CB and HAM both! I don’t forget where I started and love it all! Keep it up! 👍🏼 the input RF coupling should be 910-1200pf for a low ac rf resistance and impedance. Everything so far I’ve heard has been correct! But for gain, the LD mos fet is a multi junction transistor. They naturally have more gain! But a higher beta bipolar transistor will have greater gain at the expense of stability. But stability comes with bias and bias it into class A if you need stability and or purity but then linearity gain dwindles. So, what gives? Thats where a curve tracer or even a peak 75 to test the transistors and matching…. Thats another time.
Your shack looks the same as mine, we follow the same paths. But your have a great gift in explaining matters. Thank you!
Concur with Mike and Skywave. Just what we have been looking for in regards to impedance matching for input and output of a transistor. Thanks Cale
Greetings from Toronto! That was indeed an in-depth analysis - and an equally in-depth (great) explanation. Thank you! 73.
This has helped me to understand amp construction more than anything on youtube!
I was curious as to why this circuit does not have input and output transformers.
Very good little video. Very similar to tje motorola manual on the MRF454. That has been a staple for 40 years
Great job in explaining this theory and board lay out according to the Schematic, very good job, well done.
I definitely appreciate your informational video, I have finally put it to use. I managed to put together a pair of 2879 @13.8 vdc and achieved about 300 w out and that definitely put a smile on my face 😁 although not fully understanding all of the information yet I guess it's a start. Not quite sure if I have the confidence yet to put together six or eight of these. But I guess eventually I'm gonna try ?
I am definitely interested in LDMOS, but not liking the hassle of 65 vdc while mobile !
Thank You And Please Keep Building And Making Videos If Possible 😁
Again, Thank You For All You Do !
My poor old eyes aren't what they used to be but with the proper enhancements I'm sure I will be able to throw something together 🤣
Fun video. My construction projects look a lot like yours. Two suggestions: one you might want to add a series variable capacitor between the connector and the shunt capacitor to be able to adjust for optimum match should the transistor not present the published impedance. The same holds for the output. Usually it is best to be able to have two variable components to be get the ideal match. It's easier to adjust a capacitor than an inductor. Second point. If the output power of an RF power transistor doesn't produce the expected output, all else being correct, it is probably not fully good. This was a typical problem for earlier (1970s) VHF and UHF transistors in mobile radio applications. With an ohmmeter they measured like a good device, but had little to no power gain.
Eh Sharky. Thank you very much for your informative video and for all that you have contributed to the hobby. There aren't may people doing what you're doing.....especially not as clear and concise in their videos. I truly appreciate a logical, obviously very intelligent and humble approach to your content. It's certainly a breath of fresh air compared to other conceited loud mouths. Lol........my dogs drink alot too!!!
I saw the lead on the input bias choke bouncing up and down as you were tapping on the choke and I wanted to yell that to you - 3 years after the fact. :)
Very useful to see how the NanoVNA is used. Compared with just looking at a diagram, much better!
I have a lot of fun and learning !! Thank you very much for sharing !!!
Great Test Layout !
Keep On Keepin' On Sharkey
Thanks for sharing your knowledge, saves me lots of time digging through the application notes. Measuring the transformer with nanovna is a good idea. I don't know if it matters that the transformer is balanced where as the nano is unbalanced. Also I will take my time to read the datasheet. Thanks
Nice single transistor design. Doesnt need matching transformers thetefore very simple and easy. The MRF 454. MRF 455 work nicely too
Fantastic video! You took 40 years of mystery out of my tinkering. Wondering what value your "high value" blocking caps were? Also what diode did you use to stabilize the bias supply? ... if I may ask.
I think those caps were 5.6nF. Enough to pass 27mhz with little reactance. As for the diode I don't remember... just a random one from the junk pile. Didn't matter much for what I was testing.
@@MudDuckSharky thank you! You should have 100K subscribers with this type of content.
Great informational video.
Howdy. Nice.
I would suggest the second capacitor in both input and output are loading capacitors. These serve the purpose of matching the impedances.
I think these need be adjustable too to get max. gain.
One starts with a random setting of these. Then tunes the others for resonance.
Slightly increase or decrease the loading cap.s, retune to resonance and observe if the gain increased or decreased. Switching back and forth one should find max. gain.
Observe that the circuit may jump into oscillation in peak tuning. A slight over or under tuning may be needed for stable operation.
Regards.
what a crystal clear explanation, thank you very much !!
Good video, pay attention to have the shunt resistor connected, without it you can have stability issues leading to transistor destruction
That is almost the same test circuit used in the Motorola RF transistor hand book. will be very clean but wont brood band much with out re tuning . for singe band use that's fine. for VHF smaller inductors and 80 meter HF will need longer coil. depending on transistor. MRF 492 works 50 MHz . That is best bias circuit. to build this into working amp place diode on heatsink with thermal compound. My book in storage think 1N4997 is press fit into heat sink for bias .will help with thermal run away. you are right the 2sc2290 has less input drive needed . makes great driver for low dead key radio . 73's
Hey question, where can I find those connectors that connect the coax cable to the circuit board?
Keep it going bro! Thank you!!
You are happy with ur construction and results...
MD Sharky, g'day mate, that was very done your explanation AMPS theory. Like" BBI said go over to his site learn more". Good presentation for a happy bloke. Cheers & Beers.73.
Man very very smart and good at what he does just wait tell u see what he has done ..check out his channel and videos ...smart dude
.works as I grew up in a machine shop he.. is very good with metals heat sinks disapation and cooling banks and much more on ldmos
where did you hook your powersupply to on the circuitboard
Hi matey. There was an article in either Practical Wireless or another magazine over 20years ago showing how to make a 2metre VHF amplifier is used similiar construction to yours .Double sided copper clad board glued on board as capacitors and inductors. I built one and surprised how well it worked and easy to build all dimensions was included in design no ferrites. Maybe worth researching. George
Really appreciate your explaination. Would you mind sharing the device model of your high Q tunable capacitor (which seems quite compact there)? I am thinking of tuning the circuit myself for high power amplifier, would really appreciate your help. - Yuanchen
Hi at what frequency did you tune the amplifier?
You would not happen to have a board layout for this amp would you? I'd have a go at a build but I need a place to start. It would also give me justification for the Nano VNA I bought. Thanks.
How about a schematic? What's the value of C1 & C4?
You are the man. Great work.
I need to build this to test some transistors from a Kenwood TS50 2sc2879. PA deck has very strange response
Excellent Video ! Thanks
That network on both the input & output of the test circuit was used to lower the Q of those networks to achieve more bandwidth. With a simple L-network you're using... you have no control over the network Q. Let me also say that controlling the Q may or may not be necessary... depending on application requirements.
Thanks for the video it was really interesting to watch especially the use of the nano VNA to measure the input and output circuits. I'm looking to build an amp that can be driven with about 200mw from a GRC-106A to some reasonable output of 20 or 30w or more. Do you have a suggestion for a high-gain transistor that may be good to start with for experimentation?
I would expect you can use a RigExpert on all parameters or it's smith chart features to see the Z in place of the NaNo VNA??
Why no standard transformer with the wire wrap going through it?
Decent performance for a single-ended amp. Push-pull offers 2nd harmonic cancellation, better linearity, and better efficiency.
Why such a high dead key ? Why not a 1-2 in then a modulate the radio?
Great video,,,,,,, thanks man❤❤❤
Excellent video.
Most intelligent man on the Internet
Good Stuff Sharkey 👍🏻
You need to do a two-tone test on any RF power amp, particularly an external linear amplifier. If you don't do the test you won't know the linearity and the in-band intermod products. You will quickly find that you need to back off the drive to get reasonable linearity. For SSB operation your 3rd order products should be at least 26dB below your carrier. These 3rd order intermod products are what causes "splatter" on adjacent channels. All ssb tranceiver's output power is limited by the 3rd order products and they run them below their peak output capability. That's why it's always possible to overdrive the PA and get more output power.
Hi, On Page 2 of the Toshiba 2SC2879 Data Sheet (Test Circuit Schematic, What Voltage are you feeding VBB ? Thank You
the measurement you made with the transistor disconnected?
Wow,das geht schnell ins Auge.Ich habe immer nur die halbe Wattleistung abverlangt um den armen Transistor nicht Strom oder Hitzetod sterben zu lassen.😂👍🙋🇩🇪🗿
How are you achieving class AB with a single transistor? I see it has two emitter flanges. Is this really two in one?
Ducky i have a nano vna also..I can use it to tune a amp right? I have a 1x2 in transitioning back into a base and might might it a 1x4. I would like to swap it to a c box the tuning is what I kinda am having trouble with .
QUESTION if i drive 5 watts in around 35 peek,, in a 2 pill amp with 2x2879's will i get around 300 watts out?
what is the carrier freq that you used? :)
Cool 🤩 Thanks 👍
What about an IRF version of transistor your are testing.
MDS!! I have become one of your major fans! Some advice: Where may I be able to source some compression trim caps as used in this video?
Donde puedo adquirir los transistores?
Hi. First off all, thanks for your great informative wideos
Let mee know if my thoug process is wrong, the output rfc choke is there for two reasons, blocking the rf from the power supply and keeping an relative constant current, when the fet or transistor is on, the current slightly increases and goes to ground, when the transition is off the "constant current" will increases the voltage on top off the transistor, abaut Doble the supply voltage in a perfect world, depending on the output tune, in case you don't have matching network connected the voltage wuld in theory spike to infinity. At least if you are driving with Square wave
Litle like a switching powers supply works.
So in my theory the the transformer kind a output will be more forgiven for higher antenna inpedans, this is due to the transformer "self limiting propeys" when in a lc kind of a "pump and dump" network a higher antenna inpedans will result in a higher source to drain voltage, and might go over the break down voltage character or your feet / transistor
All the best and keep up the great work 👍
No the only purpose of that inductor Is to avoid any rf going back to the power supply, ot ha nothing to do with switching power supply
At around 8:00 the choke solder connection is bad :) Great video!
Pretty bad ass little dude...Way smarter than me...
hey Sharky , can you post the link on the Motorola application note on how to obtain the impedance numbers? Please
At what point would it be beneficial to switch over to the longer tube shaped shotgun looking transformers? And why. Heat dissipation? Better impedance match? ?
You should check the choke RFC2 with the final current to see if this choke saturate.
I am so glad I found your channel Mister mud duck, although I do not understand every word that you are saying not that your English leaves anything to desire just my vocabulary of electronic components is very limited, I'm hoping by watching and listening and maybe soldering occasionally I can figure it out, I must confess I feel more comfortable with tubes have you ever done anything like a tube type modulator or something in that line, once again thank you for your time I really appreciate it GL lake Cumberland Kentucky.
Awesome. Really lays it down on how it's working. Takes a lot of the mystery out of it. I know electronics but now RF. I want to learn. I want one of your kits too. How much current for the ab bias?
🏆🏆🏆 73 my friend I from BRAZIL
I really appreciate this info. Maybe you can help me with my linear amp. It has 2 of these. Pull amp works great, tx led aluminates with about 3 watts dead carrier. No rf power out. One of the transistors is cold, the other heats up super fast. Out of circuit, each transistor measures as it should in diode mode. Very strange. They both measure good yet 1 or both might have no gain. Any clues? Thanks!
I’ve had RF transistors that test fine with a diode test & DC HFE, but won’t work at RF
That hound is THIRSTY! 19:33 😂
It will be broadband, but still the question,
For what frequency?
Thanks sharky.. I'm going to try this just for fun maybe lol
Baising the base with DC could increases the risk of the TR and reduce it's age especially on high power RF, but seems to be you are professional
Your choke become unsoldered? 😅
Id like to buy a kit for this...
Awesome I understand,thank you 💪🏾
If your radio has a 10 watt carrier and 30 watts peak, your already in compression at the radio!.
For experimenting you really need to start with a clean radio..
Whats a tool?
Thank you for your info
what is the patrs and detail eahch one or value of all parts/ could you pls sir show the complete diagram and material needed thank and god bless ..keep it up boss.
Do you do repairs?
gud day sir,,, im a first starter assembler electronics graduate, that i want to assemble like n rf amplifier booster for a fm transmitter exciter sir, do you have a chematic diagram for an rf amplifier booster, and how to adjust and align the tuning capacitors on this amplifier you assembled?
try 15 volts DC to the power input and that really wakes up the transistor
The diagram at 30mins is class c correct?
great content dude
How can u rely upon s parameters in such nonlinear circuit? Even large signal s parameters wont fit and wont give accurate Z meassurements
Beautiful