3-500z tube Triode. Grounded Grid, Floating grid, Tetrodes and Pentodes скачать в хорошем качестве

3-500z tube Triode. Grounded Grid, Floating grid, Tetrodes and Pentodes

I'm all over the place on this one. I started out wanting to do a vid just on grounded grid vs grid driven triode and floating grid vs grounded grid. I think I went left a little and was rambling and touching on a lot of other stuff along the way. Anyway, let me try to clean up my thoughts here: There are basically 3 major types of rf amplifier tube categories. Triode (grid driven), Tetrode (grid driven with Turbo aka screen) and Grounded Grid. Yes, there are more like Pentode and others, but we are trying to keep it simple here. Triode, a 3 element tube with the Plate (Output), Control Grid (drive), and Cathode (ground). The heater heats the Cathode, electrons are boiled off the Cathode due to the heat, and the Plate which has the HV on it pulls the electrons to the plate. The Control Grid is in the middle, and it is like a valve which controls the amount of the electron flow. A little voltage on the control grid makes a big difference on how many electrons can now make it to the plate. Tetrode adds a 4th element, the screen grid. The Screen grid is a 'helper' grid after the control grid and before the Plate that helps pull those electrons to the plate. I call it Turbo-Charging. However, in the case of amps, turbocharging will not get you more output, what it does is lower the amount of drive needed.....usually by a Lot. IMHO one of the reasons you don't see very many Tetrode amps is because of the low drive needed. FCC didn't want amp makers making amps needing 5 watts drive, so most HF amp makers went with Triodes need 100 watts drive. Also Tetrode amps are more complicated and fragile than Triode amps. IMHO tetrode amps if setup and ran right, have more gain and will have more audio than a Triode amp....at least on AM. On SSB, its all audio anyway, so that doesn't apply. Also, though it's true that Tetrode amps in general are not quite as clean as a Triode amp, it you take into consideration that to use a high drive Triode amp with a low output radio (CB), you would need a driver amp in-between. The combination of the low power radio, driver amp, then final amp in total would be much dirtier than the so called 'dirty' tetrode amp, if everything was equal. The grounded grid amplifier or tube. Some tubes are made to be grounded grid, aka the 3-500z, 572B, and many others. However, most other tubes, but not quite all, even though were not specifically made for grounded grid, can be ran grounded grid. This includes Triodes, Tetrodes, and even Pentodes. Most sweep tubes are Pentodes with 5 grids and they are often used and ran in the grounded grid configuration. 6lf6, 6lq6 and the many subs are the most common sweep tubes, and they are all Pentodes. and are usually ran grounded grid. Palomar, D+A and except for the modulating type Maco's (Duster, 75, Super 75) they use the tubes grounded grid. Some tubes like the 4cx250B for one is not recommended for grounded grid. For grounded grid, the control grid is grounded. If it is a Tetrode or Pentode, the other grids are grounded too. The plate is the same, but the drive comes in thru the cathode. Yes, the cathode is what is heated up by the filament and burns off the electrons, but now you are adding the drive to it too. Yes, it all works together just fine. Whats good about a grounded grid tube is that it is sturdy, dependable, forgiving and has a low parts count. I guess the only negative is that it needs a much higher drive level and grounded grid don't normally swing much. In CB slang, they don't have that swing. You overdrive a grounded grid amp, the 'over' drive power goes straight thru the tube and out to the plate. Some CB'ers use this and call it 'Over the Top'. I don't, nor do I recommend this. 2 reasons, that 'Over the Top' watts is going to be dirty watts, 2nd, I never run my stuff that hard. If the max drive for one of my amps is 100 watts, I probably won't hit it with more than 90. I don't like my stuff blowing up, I like it to last a long time. Want Mo Watts, get a bigger amp. Back to why I originally started this video. Back in the day, amp makers floated the cathode grounds. The thinking was this help stabilize the amp. Modern thinking is No, directly ground the grids. Only issue with direct grounding is that if there is a flash or short, the choke on the grid would act like a fuse. With the grid being grounded, no flash protections., Hence, if you ground the grids, make sure you use a glitch resistor in the HV in case of a short or flash. Pretty much all amp makers and builders now ground the grids directly.