If You Are Considering Buying A Linear Amplifier, A Linear Amplifier With Tubes May Be a Good Deal
HTML-код
- Опубликовано: 23 июл 2024
- Jim explains the schematic for a tube linear amplifier and shows some of the parts he had on the shelf. Keep in mind that some used amps sell for $800 to $1500 which is about 1/4 the price of some new amps.
Наука
This is one of the best, easy to understand videos I have seen explaining linear amps. Thank you.
I've had my Drake L4B for over 35 years and absolutely love it.
DE K6PA
Thanks for the information on amps and I am still learning how all of this ham radio works and still studying my tech test and yes I am still learning
Excellent explanation of how an amp works. Thanks
Just for a moment, I was back in US Navy Fire Control Technician A school, learning electronic theory. That was 55 years ago, Jim. You’re a time machine magician.
Bob Runge W1LSZ
Thanks. I feel more like an old machine! 73, Jim
Smiling!
Thanks Jim, I have 2 home brew amps a pair of 3-400z and a 4-1000A. Run a Clipperton L I bought off of a good friend W0JLC about 35 years ago or so mostly.
Thanks for the education Jim. Finding a tube amp basics video like this has long been in the back of my mind.
Thanks, Jim
Hi Jim,
I have an SB-221 I built in 1979 which was purchased just after Heathkit stopped supplying the SB-220 to the amateur community due to FCC regulations. It is currently being converted to an SB-220 by the addition of 10m. I had purchased the conversion kit from Heathkit, but decided to buy components off Ebay from SB-220's there were being parted out when I resumed the conversion. I had started the conversion in the early 90's, but life intervened and the project was shelved. I think I will finish sometime next month. I'm keeping fingers crossed the original Eimac 3-500Z's are still in good shape. Hope you are well and stay safe. 73 WJ3U
Miss Heathkit Start As Kid The Kits Where So Good To learn From Did the 25" CRT TV Love There Tech. Last Forever Sold It Miss It Now Grandkids To See How It All Started...
Hello Jim: I hope you are doing better and feeling better 😊 ????? Thank you for your video on linear amps. I think the be t topic of discussion after this video should be on feedilne coax & SWR. I'VE seen so many amps go up in flames due to poor antennas, high SWR, & low grade or defective coax / feedline. Great job sir & I'm praying for you for a speedy recovery, 73's , TMP from N.J.
In the last couple of years, I've built myself three monoband linear amplifiers (all ceramic/metal tubes). I've learned a lot in the process...
Excellent! Thanks Jim. A fine presentation.
Excellent information Jim… hope your heath improves. Amazed you manage to fit your excellent videos in😏. I have an immaculate L4B with solid state mains switching. Must preserve those power switches..psu rebuilt as well. I use your technique to tune the amp.. never have any problems.. when you guys are gone, where will we get all this critical information!
Would be useful to drop all your videos on CD for future generations.
Many thanks once again for your teaching on RUclips, fingers crossed for your health problems.. many Kind Regards and 73 from the UK
Jim, as a new ham these parts are very interesting to see. Schematics are one thing, actual parts are something else. Thanks again for all you don for the community.
Cool, thanks Stewie! 73, Jim
Thank you for the easy to grasp lesson, Jim. Regards from Oz.
Very welcome and thanks for commenting. I do appreciate the feedback. Some comments in the video got edited out by me and by mistake. I will do a follow up video in a few days and fill in some more information. Thanks, Jim
Hey Jim, I use an Ameritron ALS-600 I bought used from QRZ which I use on 80 meters mainly with a full legal limit manual tuner (MFJ-989D). I use a 80 to 10 meter end fed half wave. I haven't had any issues with it. of course I don't over drive it, I only use it for around 300 watts at most even though it can do 600.
Okay, good information. We need to keep in mind that a reduction in power may be very good for the equipment and still have a potent signal. 73, Jm
Thanks Jim .. Always helpful! :)
Interesting! I'm very familiar with tube audio amplifiers but I've not looked at tube RF amps before this! Thank you for video!
Thanks for watching Steve. RF amps can be very basic and still have a very clean signal. Thanks Steve and 73, Jim
Where was this video 25+ years ago when I was a teenager trying to figure out this stuff with no elmer!? Great info, Jim! Very good job at presenting the info in an easy-to-follow lesson! Thanks & best 73, Tom KG8Y
Glad it was helpful! I would have done a follow up video but became ill with MDS and Neutropenia. I spent much of the last two days isolated and in bed. 73, Jim
Great video , Thanks Jim
Glad you enjoyed it Dave. 73, Jim
THANK YOU MR JIM !!!!
Great Stuff Jim! I still love my Natural Amplifier, The Great Atlantic Ocean! 73!
Ya ya, Mark, I would move to your neighborhood if I could. You hear better and get out better than I do! I hear you working DX that is zero copy here. There needs to be a law! 73, Jim your Elmer
I am a brazilian tecnician .Today I HAD MY subscribe um your Y T Channel.THANK you for clarify about triodes in RF Linear amplifier.
Welcome Sir and thank you. If you need some help just let me know. 73, Jim in Rocklin CA
Jim please can you talk how I make T1 for a diferents band? Thank you so much and very very nice the video.
Thank you Jim, another very well done video..as usual, good to see you -n2qfk
Many thanks! 73, Jim
Nice video Jim!
Thanks! 73, Jim
Jim:
Thank You for a clear explanation.
I have an old Yaesu 2100 series amp that has served me well for years. The unit uses a Pi-network for tuning/line balancing. I think the Pi-network is active when the amplifier is on stand-by mode or completely off. Is my assumption correct?. Is there a way to disable the Pi-network to avoid conflict with the Automatic Antenna Tuner that tunes my Ciro Mazzoni Loop antenna?.
FYI, the Automatic Tuner can only handle 200 watts input, consequently the amp needs to be between the antenna and the tuner.
Any thoughts?
Another excellent video.
Glad you enjoyed it Tim. I have been ill. Spent yesterday and today mostly sleeping. We can talk when I feel better. Thanks Tim! 73, Jim
G'day Jim...hope the health is improving.
Tnx again for our qso the other day. Was a great pleasure for me. I hope our further discussion on audio and subtractive eq was of interest.
We briefly touched on 'tuning for max out'. I am still somewhat confused by the concept, but I wonder if it is the chosen terminology that is where the confusion lies. Does it mean 'tune for the maximum the exciter is capable of' or 'tune for max output based on what the exciter is set at'? I ask for a few reasons:
1. Licence conditions in VK are for 400w PEP....a TL922 will do that with 25-30w in depending upon the band.
2. Doesnt key down tuning with 100w of drive impact on the tubes more than 30w of drive? I usually do the latter and wind some extra load in to stay linear and to cover for any possibility (although thankfully rare nowadays) of overshoot.
3. What if you have a QRP radio? If tuning with 100w ensures tube longevity by achieving optimal plate and load capacitance for the band, what are QRP folks to do?
We did speak about it, and you assured me my method (point 2 above) was a sound one....but I wonder if I communicated it well enough at the time. From what I have read about the net, the jury seems out on this, as I am sure you are aware, and I wonder if that is because of some confusion the arises from the phrase 'tune for max out'. As you mention in this video, these finals are not getting any cheaper, and in the 922, they are not directly cooled either...so care is important to me. Max Q output with the caps with additional load and never overdriven has been my method for both the 922 and for my old SB230 with the rare as hen's teeth 8873 (I have a spare which is fortunate).
Your clarifying thoughts kind sir....many thanks again for your videos....take good care. 73 de Aaron VK2ON
Thanks Jim
Thanks again. They put me on a different medicine I have been in bed much of the time. So, I stopped it and went back to the old medicine and will contact the doctor about what happened. Boy, I was sick and weak. I'm better today and hope that I continue to improve. Friday is infusion day so I need to feel better to get there and then get home to the recliner. I don't drive and I should not drive. I gave up the license and the car. 73, Jim
I wish I could find one of my most favorite liner amps. You could key it with a portable low power transmitter. Great foe field days. It used one horizontal amp tube and instead of a tube to drive it, it used hand wound coil to trigger it. Someone modified a ferrous coil core in place of a tube. It worked verry good. you could drive it with ten watts and get 85 out. was very simple to make.
Thanks for the info! 73, Jim
Another excellent video Jim. Regarding another comment about harmonic output. I compared an ancient QST review of a TL922 with the current standard required by the FCC and seems to be compliant even if manufactured//installed post 2003. (All a bit ambiguous). I guess a few simple checks might be worthwhile if someone purchases a similar amplifier used. Some may have damaged resistors in the parasitic stoppers, and fan bearings might need lubrication. Of course many of the older amplifiers may need an interface to cater with the high demands of the PTT line.
(I am sure you have covered these points in other videos). Good to see you making videos, I know it is a difficult time. 73
Also, we need to look at the bandswitch very closely. That switch can be easily damaged. ALSO, timing of the relay is critical. It is slow to close on the transmit side and the transceiver may be very fast. So RF gets to the amp before the relay is closed and it arcs at the tank circuit. Thanks, Jim
@@ham-radio sage advice Jim, as you mentioned in your video the bandswitches are a nightmare to replace even if you can source a replacement. As for sequencing of the relays you are obviously correct again. The TL922 uses DPDT relay in the RF path so a simple bend to one contact can take care of the hot-switching issue. An issue with amplifiers that have been unused for a while can be flaky receive due to dirty bypass contacts. Half an hour spent on inexpensive maintenance should pay rewards.
Much improved audio over your older videos, thank you. I never took the time to learn vacuum tube operation so this video was certainly informative. Please correct me but it seems to me the abbreviated circuit you describe would be running class C and hence not linear. So does the amp require biasing for class AB?
It is B class, zero bias. My other amps have zeners or a diode string for Class AB1. These amps very very linear IF properly loaded. Thanks Rob, 73, Jim
Sb-220 here! Took three months to rebuild as it was my first time and I would let it bleed off for hours.
Good idea. Lethal voltages in that box with lots of MFD's. 73, Jim
Got a Henry 2kd classic with 2 3500zg tubes and built like a battleship
Jim. Will you go over basics of a tube amp power supply? These are getting more and more scarce…
amazing! are there many people these days that have the knowledge to work them? or even get parts?
Back in the late-1970s, my HF rig was a horrific Eico 753 vacuum tube baby that required Plate-Tune-Load 'tuning-up' after any significant QSY, and my antenna was a random wire that required an "antenna tuner" (homebrew Pi network) that also required 'tuning-up' after any significant QSY. By the time I was ready to jump in and make a call, the DXpedition had already packed up and flown back home LOL. Since then, my goal has been to get as far away from systems needing 'tuning-up' as possible. I'll buy an amp when I can afford something solid state and as close to 'No Tune' as I can get. My goal is instant QSY, even band to band.
On the bands even today, one can hear Hams tuning-up their kw linear, either right on the frequency or near enough to cause an audible beat note. Then, after a minute, their powerful signal arrives on the pile-up. None of this 'tuning-up' on the bands nonsense is anything to be particularly proud of. Perhaps such amps should have a built-in dummy load (use enforced with a Tune-Up mode), provided that at least their antenna system is already pre-matched to 50 ohms. Even with that, there is a delay. 100 watts operators might be in and out before the kW is ready to go.
I do have a large dummy. There's a joke in that sentence but I will pass on that. Tuning up on the air should be the final small adjustment. And, doing that near or on top of someone is wrong as you point out. Thanks for your help and 73, Jim
Shouldn't there be an RFC on the output to short the supply if the blocking cap fails so as to prevent HV at the antenna connector?
There is. It is a must and somehow I did not mention the safety choke. I had several on my desk at the time. Thanks Mister Hat, 73, Jim
is it correct to say/think that for 100% Out, you need 10% in ? I typed another way, what kinda ratio in power ? If the grid wasnt at ground potential, say fixed at 1 or 2 volts, would it just become an oscillator ? N9IZX
You didn't mention harmonic output at all. FCC rules on harmonics are stricter now than they were back when that amp was designed and used. Simply tuning for max and not monitoring harmonic output will certainly lead to incorrect operation. A spectrum analyzer is definitely recommended if not mandatory if using a circuit like that in the video to keep from splattering all over.
Hi and thanks for writing,
You wrote: "FCC rules on harmonics are stricter now than they were back when that amp was designed and used." Please tell us what the FCC rules are that you say are now stricter. By the way, those amps are still being used today.
You wrote: "Simply tuning for max and not monitoring harmonic output will certainly lead to incorrect operation." Can you tell us more about the harmonic output? Also, what do you mean by "incorrect operation"? I have no idea what that means.
How would a spectrum analyzer keep a linear amplifier from "splattering all over"?
Please do educate us all by answering the questions above in detail. Clearly you know more than I do. Thanks in advance for your help. 73, Jim Heath W6LG licensed in 1964
@@ham-radio When a "linear" amplifier is over driven it will produce all kinds of spurious frequencies. The spectrum analyzer will clearly show when this begins to be excessive so you can adjust the drive level to keep a clean signal. You may find the optimum clean signal occurs at considerably less than at maximum power output. After purchasing a "100 watt" linear amplifier I used a spectrum analyzer to find that it would only put out about 30 watts before splatter and harmonics began to exceed FCC requirements. At 100 watts output the second harmonic was only 10db down from the carrier! That's 10 watts of harmonic being radiated on the wrong frequency! Not polite to others at all!
I finally almost understand an amp now. 😂
Vacuum tubes are a tough act to follow. The music industry is starting to integrate old vacuum tube designs with modern technology making some of the best sound systems available like McKintosh, Audio research, Rogue and many more.
As for Ham radio, nothing beats a good vacuum tube linear.
Just as I was finishing that last statement. My notifications bell rang, its almost time for Saturday nights "Old Tube Radio Network" show here on YT. This is a show that Hams and CB'ers alike join together and showcase their vacuum tube CB's from the 50's 60's and 70's radios like Browning, Robyn, Teaberry, Helicrafters, Heathkits and many more!!!.
I think a new company is opening in the USA to start making tubes again
I hope so. Let us all know if you confirm a tube manufacturer for glass tubes and ceramic tubes. 73, Jim
Thank You, Jim Well Done , Tube Tech.Too Know & Show The Components Thank YOU ! Take Care, & Be Well Prayers Your Way Same As You 2 Times.. Working Though It Too...
Drake made high quality top of the line equipment. I'm sure an L 4b is a great amp, problem is where do you find one now?
I just sold one. Estate ssles, radio clubs, askng local guys are the best ways that I know. Ebay is not the place to buy one unless it is a local sale. 73, Jim
Not anymore 😁 now everyone will drive the price up trying to buy one.
skematik final tabung. ..
Jim what do you think of the Mercury 3 amplifier? N9NVU hope you’re feeling well!
It's good from what I can see and from guys who bought it. So all I have heard is that it is excellent and well worth the price for that level of performance and design. 73, Jim
Jim what do you think of the Mercury 3 amplifier? N9NVU hope you’re feeling well!
It's good. I spent the last two days in bed. I think one of my meds is causing the problem. I am hugely anemic because of the MDS. 73, Jim