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Questions tagged [vacuum-tubes]

This tag is for questions relevant to vacuum tubes, also known as thermionic valves or simply valves.

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2 votes
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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 ...
Zeiss Ikon's user avatar
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0 votes
1 answer
79 views

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 ...
Zeiss Ikon's user avatar
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2 votes
1 answer
347 views

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 ...
mort win's user avatar
4 votes
1 answer
373 views

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 ...
Zeiss Ikon's user avatar
  • 4,147
2 votes
3 answers
834 views

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 ...
HolgerFiedler's user avatar
0 votes
0 answers
54 views

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 ...
jjdobrikin's user avatar
4 votes
1 answer
282 views

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 ...
Andrew's user avatar
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1 vote
1 answer
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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 ...
Zeiss Ikon's user avatar
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2 votes
3 answers
459 views

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, ...
Zeiss Ikon's user avatar
  • 4,147
1 vote
1 answer
86 views

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 ...
Zeiss Ikon's user avatar
  • 4,147
2 votes
0 answers
147 views

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 ...
Zeiss Ikon's user avatar
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3 votes
4 answers
306 views

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 ...
Mike Waters's user avatar
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5 votes
3 answers
536 views

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 ...
Zeiss Ikon's user avatar
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4 votes
1 answer
2k views

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 ...
Zeiss Ikon's user avatar
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4 votes
1 answer
373 views

Is it practical to use a magnetic amplifier as an AM modulator in a transmitter?

If I'm building a vacuum tube HF transmitter (say, 40 m band), obviously the simplest mode to build is CW; it's common to key the oscillator input to the final (in order to keep the oscillator running ...
Zeiss Ikon's user avatar
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8 votes
2 answers
607 views

help identifying a vacuum tube

I recently bought this tube for use in an art project and would like to know what it is and what it was originally used for. Unfortunately, the silkscreen labelling on the glass envelope was worn off ...
niels nielsen's user avatar
4 votes
2 answers
417 views

Pi Matching circut for tube PA - what values?

I am working on my 80m and 40m CW transmitter and ran into a problem: I need to match the high impedance of PL504 to 50ohm coax, a Pi match seems to be the best, but I don't know how to calculate ...
thegamebusterpl's user avatar
14 votes
6 answers
6k views

Why are vacuum tubes still used in amateur radios?

I wonder, even in this modern generation why the outdated vacuum tubes are used. In other electronic circuits they have been replaced by more efficient (and small) transistors years ago. Why they are ...
Sumithran's user avatar
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6 votes
1 answer
488 views

Pentode vs. Triode in Tuned RF Reflex Receiver

I'm planning on building a multi-band vacuum tube receiver. I've got a circuit diagram in hand for a two triode twin reflex with optional regeneration (P.E. Edelman, Reflex Radio Receivers, 1924, Fig....
Zeiss Ikon's user avatar
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