Questions tagged [vacuum-tubes]
This tag is for questions relevant to vacuum tubes, also known as thermionic valves or simply valves.
20
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Question about low voltage from mains for tube amplifier 811h
Edit: So I guess what i really want to know is more technical question regarding 572b tubes. What plate voltage is minimum to safely drive 572b tubes? what is lowest filament voltage to optimally ...
2
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How can I key low voltage and still keep a tube VFO running constantly?
I'm interested in building a VFO based single tube CW transmitter.
These devices are known to have issues with frequency drift and chirp; frequency drift can apparently be mitigated by ensuring ...
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Given that transmit "chirp" is mainly thermal related, what parts would need to be temperature regulated to limit chirp?
I'd like to build a Colpitts (or Hartley) oscillator based one-tube CW transmitter, and I'd like to use a VFO circuit rather than crystal control (in part because of the expense and limited ...
- 4,147
2
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answer
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How to identify this vacuum tube?
I have a vacuum tube and need help working out what it is. The numbers on the tube are APW 8047 it 4 pin and fits in a B4 socket. I wasn't able to find it with a Google search of the number. Are there ...
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Can a regen receiver be used as a CW transceiver?
I've looked for a while, but I've never found a design like what I imagine: a single-tube (valve) regen CW transceiver (no cheating with a tube/valve that has two or more triodes/tetrodes/pentodes in ...
- 4,147
2
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3
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What are the properties of the radiation of a magnetron?
It is commonly known that electromagnetic radiation from an antenna is polarized; the electric field is parallel to the rod and the magnetic component is perpendicular to it.
What does the radiation ...
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Simple minimum component RF Amplifier Design
Looking for advice/assistance in Retrofitting sans Cabinet Antique 2 and 3 Dialer 1920's TRF tube radios to operate with low safe Plate voltages.Both Hollow State and Solid State. The plan is to ...
4
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Identification of valve
My favorite receiver used for 40 m AM broadcasts has a cracked valve, but the valve type normally printed on the glass has rubbed away. Can anyone tell me what the numbers for this valve are ?
The ...
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How to identify the mic connection pins in Heathkit SB-102?
One of the things I need to do to put my Heathkit SB-102 into service is connect a microphone. I've got a suitable crystal mic, with four conductors in the cable -- two for the mic element, and two ...
- 4,147
2
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3
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Will a "crystal set" work with an untuned RF amp stage?
In my ongoing process of building up to a homebrewed general coverage receiver/transceiver, a first step might reasonably be a crystal set, where a tuned circuit and simple, or even improvised, ...
- 4,147
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Can the transmit and receive functions of a boat anchor transceiver share the tank circuit?
I'm starting design work on a two-tube (two-valve, for those who prefer that term) reflex-regen receiver that I hope will cover AM broadcast through 160m-10m -- both amateur bands and those "in ...
- 4,147
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Has this regeneration control been done?
I'm planning to build a two-tube reflexed RF regen receiver soon. I'm examining methods of controlling the regeneration — it needs to be possible to both initiate and halt oscillation in all bands (I ...
- 4,147
3
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4
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How is working on DC high voltages as in a tube radio different from 120VAC?
Suppose that I am familiar with the safety procedures for working on 20 A 120 VAC 60 Hz household lines.
What should I be prepared for before working on high voltage DC circuits (say, 800 volts) as ...
- 8,081
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Heathkit SB-102 Plate Current out of control
I bought a "technician special" Heathkit SB-102 transceiver. Everything seems to work well until I attach a dummy load and try to go through the "initial tune up" procedure in the manual.
At the ...
- 4,147
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Frequency Display for Old Tube Radio
I have a Hallicrafters S-120 1960s vintage vacuum tube receiver (an "All American Five" superhet with solid state rectifier replacing one of the "five" tubes). It works well, doesn't have excessive ...
- 4,147