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
Please do more videos. As a biginner I learned so much from watching this. The way you break down all aspects of the curcuit and show your testing proceadures is monumentaly important to us new players.
Yes, more videos, but move the camera closer to the item being filmed to avoid you putting your hands over the lens, it looks like what used to happen when old people were given cameras to take pictures. They would cover the lens with fingers etc. fingers and hands are solid, we can not see through them, so covering the lens constantly as on this video is quite poor.
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
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.
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.
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 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.
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.
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 🤣
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
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.
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
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. :)
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 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
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.
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.
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.😂👍🙋🇩🇪🗿
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?
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
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?
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
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.
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 .
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.
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.
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.
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 👍
Rfc2 does not store energy it totally blocks all ac/rf current changes. The output coil is the inductor that swaps energy as the transistor is turned off and on. But the rfc is a choke that resists all ac changes
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.
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 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..
I'd like to drive a Lorentz disk** with this because it's simple and low cost - would it do the job to amplify the siggen output enough? **A Lorentz disk creates coherent high (RF) frequency oscillations of the charged particles in thin aluminum layers by way of the Lorentz force as follows: 1) aluminum foil layers each separated by insulation, oriented horizontally on the work bench (foil-insulator-foil-insulator etc) 2) vertically-oriented and axial (centered) magnetic field through the foils lamination 3) small 'eddy current-inducing' coils positioned radially and close to (but not touching) the foils The coils are fed 16.28Mhz because the skin depth of the foil motivates that frequency. Vertical B field, radial and horizontally induced currents in the foil, manifests (right hand rule, recall) the Lorentz force. I'd like to think your design could achieve 100 watts or be modified to reach that - is that feasible? The signal out of the siggen is too weak to see any effect in the Lorentz disk. .
