Getting ready to get back on the air after a 10 year layoff and I was wondering about using 572-Bs in my 30L-1. I think that when I put it all to bed I had just put a new set of 811-As in, but it's nice to know I can do the switch when those get used up. Thanks!
Very nice video and after watching this, I bought preowned 30L-1! I am interested in how 30L-1 works with 10, 18 and 24MHz WARC bands. How would be SWR between Transceiver and 30L-1.
Your numbers don't add up. At approximately 15 min of the video you said that you have 800 watts of carrier at 20 meters with 1700 volts and 0.6 Amps. 1700 volts times 0.6Amps equals 1020 watts of input and the rf output is 800 watts. That translates to an efficiency of 78%, something impossible unless you work at class C.
Hello, excellent. I have a 30L-1 with 4 811s, but I know of people that replace the 4 811s y 4 572Bs. Is that ok? Better or worst than 2 572Bs? Also, the mods shown at the begining are still valid is using 4 811s? Thanks
The problem with four tubes like the 811 or 572B is they really should be neutralized for stable operation above 20 MHz. Four tubes have too much feed through capacitance to be stable above ~20 Mhz at 1500Vdc, and this problem is proportionally worse as the anode voltage is increased. Almost everyone, such as the Heathkit Warrior, the Gonset four-tube 811 amplifier, and the Ameritron four-811 tube, neutralize. Yaesu in the FL2100 eventually had to add a rather poor implementation of neutralization with just two tubes, but this is because of the voltage. Ameritron, in the AL572 amplifier, has to neutralize the four 572. If proper stability tests are run on the 30L-1 as-manufactured, it will fail miserably. The Dentron Clipperton will fail also. If the neutralization is removed from the AL811H, Heathkit Warrior, or Gonset, they will miserably fail proper stability tests. I likely have some videos of this. With that in mind, and because the 30L-1 amplifier components can never make use of the full power of four 572's, it makes absolutely no sense to run tube cost up and amplifier stability down by adding two extra tubes that will not increase useful output significantly but will significantly decrease stability. Maybe three tubes, not four. Three tubes are on the edge of needing neutralization but are more stable than using four. I personally would never use four.
@@Jerrythenerdful Tom, very thorough reply. Highly appreciated. I'll start by adding the bracket on the back of the variable cap. It makes a lot of sense and can't see any problems. Thanks.
@@CH_Pechiar I have not documented the electrical advantage by actual measurements because they would be so involved. But if the amplifier is shipped, not having the air variable weight hanging on the front sub-panel, and also having that capacitor supporting some of the tank coils, is reason enough. This is the third 30L-1 we have received with a loose tuning capacitor (out of maybe ten or eleven). I have documented in other amplifiers that wider and shorter grounding paths result in improved upper-frequency performance. It is almost always the sum of many small things that makes the difference in performance, and not just one single major thing.
@@Jerrythenerdful I have here 2 of mine and the club's one. I'll check in the three of them. I agree that, unless a big design flaw stands out, improvement is the sum of small issues, sometimes related to cost of production at the time.
I have this amplifier with the same modification, but I get the same power output as you are getting with the four valves and you said that your only using two, can you please explain?
The 572 and the 811 both have a good bit of reserve emission, the 572 which has always been oxide coated (by Cetron and from China) and the modern 811 even more than the early 811 tubes. The real limit in 811 tubes is the anode dissipation of 65 watts, not the emission current or peak power. You need four tubes to get around 260W of dissipation so the anodes do not melt down, not because of emission or peak power limits. Collins beats the death out of 811 tubes by high voltage. They are up near the 2000-volt area. The Collins is also not neutralized and that makes it unstable on 10M and 15M with four tubes. Everything gets better by dropping back to two 572B. The amp is more stable, and the dissipation becomes 320 watts with two 572 tubes instead of 260W with four 811s, plus 572s like the nearly 2kV anode a whole lot better than 811 tubes do. Plus everything can be converted back to make it a museum amp instead of a workhorse.
I have thousands of new RF components. Either email me at my ctrengineeringinc.com email or I think I have them listed on eBay if that listing is still up.
My question is do you perhaps have a written upgrade procedure for this mod and a parts list? or better yet can you provide the needed parts. Thanks 73 de K2AES
Bogus. Two 572B tubes does not equal the same power output as four 811A's. The Mu of a 811a is 150, the 572b is only 160, and the last 10 points is above the 1500 volts that the 811a is rated two.
Your comment doesn't make sense. The mu makes very little difference in output power in a cathode driven amp. The output and input are out-of-phase and in series in a cathode driven amp. This gives it a high level of negative feedback. Because of that, the major determinant of gain in a cathode driven is the ratio of driving impedance at the cathode and load line at the anode. So much for mu and gain, if that was what you were trying to say. As for power limits, Collins uses much higher anode voltage than 811 tubes should be operated at. Because the voltage is so high the gain is up from normal voltages of 1500 volts. The 811 tubes would make a great deal of power at that voltage, but they are grossly dissipation limited. The anodes are so frail the 811s cannot be used anywhere near full emission without melting the anodes down. The 572s cure that.
@Jerrythenerdful Sorry. Two 572's are not going to produce 1000 watts of RF. If that were true, every Linear manufacturer would have done it. Ameritron had their AL-811 HD with four 572's and stated a maximum output of 1000 watts. No one has a two tube 572 with that much gain, unless you are driving it with over 100 watts in and exceeding plate voltage. IF Collins had higher plate voltage than the 811A's would allow, wouldn't that shorten their life? Yet, many are still in service with near original sets. Try presenting your entire test setup so everyone can see what you are doing. I have seen too many people make claims with black boxes.
@@Ferret488 The gain of a cathode driven amplifier is largely set by the ratio of anode operating loading impedance to the cathode drive impedance. You seem to either not understand that, or be unwilling to accept a common well-known engineering fact. I designed the 811 amplifier series in 1991. The AL811 uses 1500Vdc on the anode. The voltage and power determine the impedance of the loadline, the cathode drive impedance hovers around 220 ohms per tube regardless of high voltage. Thus gain is set by the high voltage and desired power level. This is why we have to re-tune an non-class A RF amplifier at increased drive, the increased power and fixed voltage moves the loadline lower. That also decreases gain. There were no tricks involved. The typical 30L1 I see is about 2000 volts or so operating voltage on a normal 120V or 240V main. That is 25% higher than an AL811 and far higher than the fragile 811 tube should be run. It makes the gain of the 30L1 too high for the anode dissipation in the 811 tubes. But one 572 is almost the dissipation of THREE 811 tubes. The 572 solves the severe anode dissipation problem and gives good safety at the Collins 2kV or so. The filament emission is more than enough in any of those tubes to not saturate. Emission limits are not a factor at these cathode current levels. Instead of wasting time and making up conspiracy theories in your head, run the test yourself and get some data.
Hello Jerry - there is always a keyboard warrior, UA-cam seems to attract them. I carried out the upgrades recommended by you on my AL-811HXCE and fitted 4x572B's, delighted with the results. As a matter of interest which of the 572B valves do you recommend, i.e.' from which manufacturer. 73 & Happy New Year.
@EI6DPToo bad you didn't listen to what he said before you also made a comment. He specifically said that TWO 572's would output over 1000 watts, not four. It is hilarious that the person credited with helping to design the AL-811 amp is also criticizing the design.
Ohmite OY series 100 ohm 2W is also a composition resistor and can be used in the parasitic suppressors; available from stock at DigiKey
Great video. We miss watching your videos .
Thanks Tony! We stopped taking in so much service. I need more time for fun things.
@Tom W8JI Yes.
Let me know when you're ready to go fishing. I will take you to West point lake.
Hay Tom nice to see you back in the amp service
A year later . How is she holding up? Any events? Thanks for posting.
Getting ready to get back on the air after a 10 year layoff and I was wondering about using 572-Bs in my 30L-1. I think that when I put it all to bed I had just put a new set of 811-As in, but it's nice to know I can do the switch when those get used up. Thanks!
Please tell me how to run this amplifier with only two valves!
thank you for sharing your knowledge, I'm from Brazil and I will implement these modifications. 73 PY5NC
Very nice video and after watching this, I bought preowned 30L-1! I am interested in how 30L-1 works with 10, 18 and 24MHz WARC bands. How would be SWR between Transceiver and 30L-1.
Comment connecter un transceiver moderne relais tampon etc? Merci 73
anyone have part number for those GDTs?
How are you getting that output if you're only using two valves? I'm confused because doesn't it use four?
Outstanding!
2 x 572b i'm going to do this...
Many thanks...
73 de K4WRF
I just got one of these that have the 572s installed. Why don't they put 4 of the 572s in since theres room? Sorry, I'm clueless about this amp.
Read the replies above yours and all will be clear.
Your numbers don't add up.
At approximately 15 min of the video you said that you have 800 watts of carrier at 20 meters with 1700 volts and 0.6 Amps.
1700 volts times 0.6Amps equals 1020 watts of input and the rf output is 800 watts.
That translates to an efficiency of 78%, something impossible unless you work at class C.
Hello, excellent. I have a 30L-1 with 4 811s, but I know of people that replace the 4 811s y 4 572Bs. Is that ok? Better or worst than 2 572Bs? Also, the mods shown at the begining are still valid is using 4 811s? Thanks
The problem with four tubes like the 811 or 572B is they really should be neutralized for stable operation above 20 MHz. Four tubes have too much feed through capacitance to be stable above ~20 Mhz at 1500Vdc, and this problem is proportionally worse as the anode voltage is increased.
Almost everyone, such as the Heathkit Warrior, the Gonset four-tube 811 amplifier, and the Ameritron four-811 tube, neutralize.
Yaesu in the FL2100 eventually had to add a rather poor implementation of neutralization with just two tubes, but this is because of the voltage. Ameritron, in the AL572 amplifier, has to neutralize the four 572.
If proper stability tests are run on the 30L-1 as-manufactured, it will fail miserably. The Dentron Clipperton will fail also. If the neutralization is removed from the AL811H, Heathkit Warrior, or Gonset, they will miserably fail proper stability tests.
I likely have some videos of this.
With that in mind, and because the 30L-1 amplifier components can never make use of the full power of four 572's, it makes absolutely no sense to run tube cost up and amplifier stability down by adding two extra tubes that will not increase useful output significantly but will significantly decrease stability. Maybe three tubes, not four. Three tubes are on the edge of needing neutralization but are more stable than using four.
I personally would never use four.
@@Jerrythenerdful Tom, very thorough reply. Highly appreciated. I'll start by adding the bracket on the back of the variable cap. It makes a lot of sense and can't see any problems. Thanks.
@@CH_Pechiar I have not documented the electrical advantage by actual measurements because they would be so involved. But if the amplifier is shipped, not having the air variable weight hanging on the front sub-panel, and also having that capacitor supporting some of the tank coils, is reason enough. This is the third 30L-1 we have received with a loose tuning capacitor (out of maybe ten or eleven).
I have documented in other amplifiers that wider and shorter grounding paths result in improved upper-frequency performance. It is almost always the sum of many small things that makes the difference in performance, and not just one single major thing.
@@Jerrythenerdful I have here 2 of mine and the club's one. I'll check in the three of them. I agree that, unless a big design flaw stands out, improvement is the sum of small issues, sometimes related to cost of production at the time.
I have this amplifier with the same modification, but I get the same power output as you are getting with the four valves and you said that your only using two, can you please explain?
The 572 and the 811 both have a good bit of reserve emission, the 572 which has always been oxide coated (by Cetron and from China) and the modern 811 even more than the early 811 tubes.
The real limit in 811 tubes is the anode dissipation of 65 watts, not the emission current or peak power. You need four tubes to get around 260W of dissipation so the anodes do not melt down, not because of emission or peak power limits.
Collins beats the death out of 811 tubes by high voltage. They are up near the 2000-volt area. The Collins is also not neutralized and that makes it unstable on 10M and 15M with four tubes.
Everything gets better by dropping back to two 572B. The amp is more stable, and the dissipation becomes 320 watts with two 572 tubes instead of 260W with four 811s, plus 572s like the nearly 2kV anode a whole lot better than 811 tubes do. Plus everything can be converted back to make it a museum amp instead of a workhorse.
@@Jerrythenerdfulthank you
Great video, but need help finding 100 ohm non-inductive resistors, as none available from stackpole?
I have thousands of new RF components. Either email me at my ctrengineeringinc.com email or I think I have them listed on eBay if that listing is still up.
@@Jerrythenerdful hi jerry good day. can i have ebay link of 100ohm resistors and the 16guage wire for parasitic?
My question is do you perhaps have a written upgrade procedure for this mod and a parts list? or better yet can you provide the needed parts.
Thanks
73 de K2AES
There are some papers here
www.ctrengineeringinc.com/download-files-page/
Bogus. Two 572B tubes does not equal the same power output as four 811A's. The Mu of a 811a is 150, the 572b is only 160, and the last 10 points is above the 1500 volts that the 811a is rated two.
Your comment doesn't make sense. The mu makes very little difference in output power in a cathode driven amp. The output and input are out-of-phase and in series in a cathode driven amp. This gives it a high level of negative feedback. Because of that, the major determinant of gain in a cathode driven is the ratio of driving impedance at the cathode and load line at the anode. So much for mu and gain, if that was what you were trying to say.
As for power limits, Collins uses much higher anode voltage than 811 tubes should be operated at. Because the voltage is so high the gain is up from normal voltages of 1500 volts. The 811 tubes would make a great deal of power at that voltage, but they are grossly dissipation limited. The anodes are so frail the 811s cannot be used anywhere near full emission without melting the anodes down.
The 572s cure that.
@Jerrythenerdful Sorry. Two 572's are not going to produce 1000 watts of RF. If that were true, every Linear manufacturer would have done it. Ameritron had their AL-811 HD with four 572's and stated a maximum output of 1000 watts. No one has a two tube 572 with that much gain, unless you are driving it with over 100 watts in and exceeding plate voltage.
IF Collins had higher plate voltage than the 811A's would allow, wouldn't that shorten their life? Yet, many are still in service with near original sets.
Try presenting your entire test setup so everyone can see what you are doing. I have seen too many people make claims with black boxes.
@@Ferret488 The gain of a cathode driven amplifier is largely set by the ratio of anode operating loading impedance to the cathode drive impedance. You seem to either not understand that, or be unwilling to accept a common well-known engineering fact.
I designed the 811 amplifier series in 1991. The AL811 uses 1500Vdc on the anode. The voltage and power determine the impedance of the loadline, the cathode drive impedance hovers around 220 ohms per tube regardless of high voltage. Thus gain is set by the high voltage and desired power level. This is why we have to re-tune an non-class A RF amplifier at increased drive, the increased power and fixed voltage moves the loadline lower. That also decreases gain.
There were no tricks involved. The typical 30L1 I see is about 2000 volts or so operating voltage on a normal 120V or 240V main. That is 25% higher than an AL811 and far higher than the fragile 811 tube should be run. It makes the gain of the 30L1 too high for the anode dissipation in the 811 tubes. But one 572 is almost the dissipation of THREE 811 tubes. The 572 solves the severe anode dissipation problem and gives good safety at the Collins 2kV or so.
The filament emission is more than enough in any of those tubes to not saturate. Emission limits are not a factor at these cathode current levels. Instead of wasting time and making up conspiracy theories in your head, run the test yourself and get some data.
Hello Jerry - there is always a keyboard warrior, UA-cam seems to attract them.
I carried out the upgrades recommended by you on my AL-811HXCE and fitted 4x572B's, delighted with the results. As a matter of interest which of the 572B valves do you recommend, i.e.' from which manufacturer.
73 & Happy New Year.
@EI6DPToo bad you didn't listen to what he said before you also made a comment. He specifically said that TWO 572's would output over 1000 watts, not four.
It is hilarious that the person credited with helping to design the AL-811 amp is also criticizing the design.