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The grounded-grid amplifier that I am looking at requires 1100 volts Max.

  • How do I safely deliver this rated voltage without getting hurt?
  • Should I consider a alternative amplifier?

By request here are the specs of the amp.

  • It is dual tube ground grid amp.
  • Wattage is expected up in the hundreds.
  • Square tuned cavity.
  • Amp will be coupled to a wave guide system.
  • Operates in the MHZ region.
  • Details in the 1976 amateur radio handbook pages 228 - 231.
  • Power supply will be designed into the overall unit and will not be home brewed.

My intent with the amp is that it plays a central part in this design that i am working on. Power will be delivered via separate power source. The applications will be bountiful, currently, I am in the design phase, I cannot yet be able to operate.

For the sake of it, I want to add this. My intent with the amp was to be used as part of a unit that will be designed for Data transmission via a wave guide system.

The reason why I came here for help was that the amp came from an radio handbook the overall unit will be built as part of a radio unit.

If this is intended to be in the electrical engineering, then put it their.

If anyone can propose a alternative amp I will be fine with that. The only thing that I am worried about is the amount of voltage that I have to generate is mind blowing.

Is their something missing that is needed to put up that people need so this question can be answered?

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  • $\begingroup$ why do you wish to use it? power output, low cost, or what? $\endgroup$ – niels nielsen Oct 30 '18 at 0:19
  • $\begingroup$ Are you planning to build (aka home-brew) a power supply or something else? It might be useful to describe the amplifier, give it's specifications, and so forth. $\endgroup$ – K7PEH Nov 3 '18 at 15:25
  • $\begingroup$ You say "...applications will be bountiful" -- I was assuming the application was amplifying an RF signal from a transmitter of sorts given this is an amateur radio forum. But, maybe you should list some of these applications. Also, for a power amplifier delivering power in the 100s of watts, an HV of 1100 volts might be considered modest by many home-brewers. My home-brew power amp I built in high-school (~1964) used an HV of 3000 volts. $\endgroup$ – K7PEH Nov 3 '18 at 23:07
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Those are good questions you asked. I can share what I've done in the past when building amps. But first, I'd like to caution you about your plans. By the nature of your questions, I strongly suggest you not build equipment that utilizes this level of voltage. Too many unforgiving mistakes lie in wait that can result in lethal shock. But if you choose to proceed, please read about electrical safety first, and have someone experienced with high voltage assist with the project.

Safety message aside, now on to suggested implementations. I infer from your question that you are asking how to convey the voltage from an external power supply to the amplifier in a safe manner. Very good question. Because of the voltages involved, the component choices are few. My first amplifier I built used a Millen high voltage connector and high voltage wire used in CRT TVs at the time. These connectors are still available surplus at places like Fair Radio Sales. The connector worked but I was never satisfied with the wire to connector junction because the conductor was too easily exposed.

When I built my second amplifier, I used RG11 coax mated with an HN coaxial connector. This arrangement is well within the 1100V you mentioned in your question. The RG11 is rated to 5kV I believe, and the HN connector working voltage is 1500; the connector dielectric withstand voltage is also 5kV.

Although I haven't used them, another option is the Alden line from Amphenol. I recently saw two different ones on a surplus parts web site, one rated 15kV and the other 30kV.

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  • $\begingroup$ I know a guy on 75m that almost lost his hand using those dangerous Millen HV connectors. He reached back behind his Drake L4-B amplifier and his hand became a path between the exposed conductor and ground. $\endgroup$ – Mike Waters Nov 27 '18 at 2:30
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The only safe method of doing this is to have the power supply safely inside --or directly attached to-- the same enclosure as the amplifier.

I did that here with my own homebrew legal-limit HF linear amplifier. It's in a 6' rack; the 4kV power supply is on the bottom, and the amplifier is above it. No wires exposed at all.

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  • $\begingroup$ Certainly not the only safe method. The AC supply from the wall is at least if not more dangerous, but we don't give those wires any thought. $\endgroup$ – Phil Frost - W8II Nov 27 '18 at 15:17
  • $\begingroup$ @PhilFrost-W8II Who do you mean by "we"? :-) And how is 240V "at least if not more dangerous" than 4 kV? $\endgroup$ – Mike Waters Nov 27 '18 at 18:35
  • $\begingroup$ By "we" I mean anyone in the modern world that's used any electrical device that plugs into the wall. And by "more dangerous" I mean the lethal thresholds for current and duration of AC shock are less than DC. Point being, 240 VAC is plenty enough to be lethal, but people seem to feel safe enough plugging in a hair dryer. $\endgroup$ – Phil Frost - W8II Nov 27 '18 at 20:05
  • $\begingroup$ Current through one's skin= voltage ÷ resistance of that skin. Respectfully, you know that, @PhilFrost-W8II . Think of the energy stored in a 35 uF filter capacitor in a 4 kV PS! $\endgroup$ – Mike Waters Nov 27 '18 at 21:40

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