Very cool that you are in Oregon. Excited to see this through to completion. It seems like you were maybe hinting it doing a 3 tube version of the same style amp in a step-by-step tutorial...?
Ok. I been thinking, if the drive voltage is 55 volts and the bias is set at -55 volts, if someone put a higher drive radio and it drives over the 55 volts would the grid be driven to positive volts
How does your key circuit behave when you are using ssb? Does it chatter or does the 220 mfd cap provide enough damping? I was also wondering if you had considered just running them as triodes in grounded grid. It sure lowers the part count and the complexity. At 27 mhz isn't it much more likely to become unstable and very likely to generate out of band RF for rookies?
For SSB there will be another 50uf 50V cap put across the 10uf with a switch. Tetrodes of the small end of the 4CX family will not work as triodes G1 only has a 1 watt dissipation and G2 has only 15 watts of dissipation and will draw far to much current without the normal voltages applied and another reason would be that you would have no control of the output power except for using an attenuator on the input to get rid of some of the drive power. As far as circuit complexity goes, if you are using 24 volts for the keying circuit all that is needed is a voltage doubler consisting of 2 diodes and 2 more caps to get your bias from the same source as the 24 volts and then if you use the two ANTEK transformers to get your high voltage you will already have your screen source except for the divider chain, so not really that many more parts. I choose not to build with triodes because I like the idea of having control of my power output without having to lower the drive power. With swamped grid input and careful attention to using a Pc choke on the plate and at least a 100 ohm resistor in series with the grid G1 if you do not use a Pc choke there, you will have a very well behaved amp that can give you almost 400 watts with only 4 watts of drive.
@@radiomedic111 I may not understand but if the grids are at dc ground not just rf ground then no current can flow ? And none of the grids are cathode connected so no issues there and a guy could add a zener to he cathode if need be to make it easier to drive. It may be that I should not be allowed near high voltage but this is what I have done. Still love your vids showing how it works and why it works. Great work sir.
@@DARKDUDE187 It has to do with the spacing of the grids, the drive power would blow through them like a blowtorch. Yes they are at RF ground but they are also in the electron stream flow an that makes them attract part of the drive power because it would require more drive from the cathode than the grids can handle. The tubes will put out full power with less than 1 watt of drive in normal operation. If you take a look at any of the BILL ORR "Radio Handbooks" from the 18th to the 24Th edition and look in the section that talks about the selection of tubes for use at grounded grid he gives an explanation on the subject.
@@DARKDUDE187 I have just found a source to Bill Orr's News Letters and there may be some info here that everyone can put to use or at least learn something from. www.bunkerofdoom.com/lit/Eimac_amateur_service_newsletters1979.pdf
There's a load of folks enjoying your videos on a homebrew linear amplifier Facebook group.
Very cool that you are in Oregon. Excited to see this through to completion. It seems like you were maybe hinting it doing a 3 tube version of the same style amp in a step-by-step tutorial...?
Hello and Thank You Yes if there is enough interest in this series I may go all the way to
the 3 tube 900 Watt a 4 tube 1.5KW Amp
Thanks
Ok. I been thinking, if the drive voltage is 55 volts and the bias is set at -55 volts, if someone put a higher drive radio and it drives over the 55 volts would the grid be driven to positive volts
Hi medic how you get 470 ohm greetz cor
How does your key circuit behave when you are using ssb? Does it chatter or does the 220 mfd cap provide enough damping? I was also wondering if you had considered just running them as triodes in grounded grid. It sure lowers the part count and the complexity. At 27 mhz isn't it much more likely to become unstable and very likely to generate out of band RF for rookies?
For SSB there will be another 50uf 50V cap put across the 10uf with a switch.
Tetrodes of the small end of the 4CX family will not
work as triodes G1 only has a 1 watt dissipation and G2 has only 15 watts of dissipation and will draw far to much current without the normal voltages applied and another reason would be
that you would have no control of the output power except for using an attenuator on the input
to get rid of some of the drive power.
As far as circuit complexity goes, if you are using 24 volts for the keying circuit all that is needed is a
voltage doubler consisting of 2 diodes and 2 more caps to get your bias from the same source as the 24 volts and then if you use the two ANTEK transformers to get your high voltage you will already have your screen source except for the divider chain, so not really that many more parts.
I choose not to build with triodes because I like the
idea of having control of my power output without
having to lower the drive power.
With swamped grid input and careful attention to using a Pc choke on the plate and at least a 100 ohm resistor in series with the grid G1 if you do not
use a Pc choke there, you will have a very well behaved amp that can give you almost 400 watts with only 4 watts of drive.
@@radiomedic111 I may not understand but if the grids are at dc ground not just rf ground then no current can flow ? And none of the grids are cathode connected so no issues there and a guy could add a zener to he cathode if need be to make it easier to drive. It may be that I should not be allowed near high voltage but this is what I have done. Still love your vids showing how it works and why it works. Great work sir.
@@DARKDUDE187 It has to do with the spacing of the grids, the drive power would blow through them like a blowtorch.
Yes they are at RF ground but they are also
in the electron stream flow an that makes them attract part of the drive power because it would require more drive from the cathode than the grids can handle.
The tubes will put out full power with less than 1 watt of drive in normal operation.
If you take a look at any of the BILL ORR "Radio Handbooks" from the 18th to the 24Th edition and look in the section that talks about the selection of tubes for use at grounded grid he gives an explanation on the subject.
@@DARKDUDE187 I have just found a source to Bill Orr's News Letters and there may be some info here that everyone can put to use or at least learn something from.
www.bunkerofdoom.com/lit/Eimac_amateur_service_newsletters1979.pdf