15 votes
Accepted

Why are vacuum tubes still used in amateur radios?

The last mass-produced vacuum tube was the Cathode Ray Tube, Thankfully those are now going the way of the dodo, replaced with much more practical LCD or OLED displays. (Edit: it turns out the ...
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  • 4,329
10 votes

Why are vacuum tubes still used in amateur radios?

As far as I know, vacuum tubes are used in newly-manufactured radio equipment (as opposed to still-in-use old equipment) for one purpose: high-power amplifiers. The advantages of vacuum tubes in this ...
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  • 23.1k
9 votes

Why are vacuum tubes still used in amateur radios?

Vacuum tubes are neither outdated nor less efficient. See https://spectrum.ieee.org/semiconductors/devices/the-quest-for-the-ultimate-vacuum-tube The above IEEE Spectrum article talks about a vacuum ...
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  • 4,258
7 votes

What are the properties of the radiation of a magnetron?

I'm sorry if this answer doesn't answer your literal questions – it's just that these questions aren't strictly answerable. it is commonly known that electromagnetic radiation from an antenna is ...
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6 votes
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help identifying a vacuum tube

This looks like a JAN-CTL-5948A, found via images within the search results for "huge vacuum tube". According to the linked site (from which the picture is also taken): The primary application of ...
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6 votes

Why are vacuum tubes still used in amateur radios?

There's one more reason vacuum tubes are still used in amateur radios: personal preference of the amateur building the radio. Speaking for myself, I understand what's going on inside a vacuum tube ...
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  • 3,881
3 votes

How is working on DC high voltages as in a tube radio different from 120VAC?

800 volts is far more likely to burn you. Just doubling the voltage from 120 to 240 will quadruple the power heating your flesh. This is just basic Ohm's Law: [P=E*I] DC is one nasty customer: It ...
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3 votes
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Identification of valve

Are you sure that you are correct in the comments about your pin 2 and pin 7? (The conventional numbering for these tubes is as in your drawing, so conventionally pins 8 and 5). If you look very ...
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  • 311
3 votes

Pentode vs. Triode in Tuned RF Reflex Receiver

It is a pleasure to follow your adventures with vacuum tubes. A number of references indicate that "triode-strapped pentodes" can be directly substituted in regenerative receiver circuits. In Sound ...
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  • 7,683
3 votes

Pi Matching circut for tube PA - what values?

DISCLAIMER: I offer these results only as a possible solution. Completing this design may depend on many other factors, thermal and electrical, steady state and transient, component- and layout-...
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3 votes
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Pi Matching circut for tube PA - what values?

Inspection of figures 17.17 through 17.19 in the ARRL Handbook suggest that the components in your Pi network might need to be adjusted: Jim Tonne, W4ENE, wrote a utility called PIEL to calculate ...
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  • 7,683
3 votes
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Is it practical to use a magnetic amplifier as an AM modulator in a transmitter?

An interesting question. Not sure I can properly answer it but I'll contribute what I know. AM modulation methods Changing the RF output tube plate voltage was a very common way of producing AM when ...
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  • 311
2 votes

help identifying a vacuum tube

If the diameter of the glass base (just above the metal mounting bracket) is approx 5 ", its a type 5948 or 5948A, If the diameter o the glass base( just above the metal mounting ring) is apprx 7&...
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2 votes

How to identify the mic connection pins in Heathkit SB-102?

Referring to the circuit diagram for this set www.nostalgickitscentral.com/heath/schematics/heathkit_schema_sb102.pdf The mic connector has 2 pins and the grounded body as the 3 connections. As you ...
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  • 311
2 votes

Will a "crystal set" work with an untuned RF amp stage?

A 1N3409 is a 39 volt Zener, completely unusable in a crystal radio (unless you are sitting at the base of the broadcast tower. ;-) Historically, 1N34 germanium diodes have been used because of the ...
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  • 7,515
2 votes
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What are the properties of the radiation of a magnetron?

Paraphrasing the Wikipedia entry for the magnetron, we learn that, ... a stream of electrons passes by the openings to metal cavity resonators and causes microwaves to oscillate within, similar to ...
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  • 7,683
2 votes

What are the properties of the radiation of a magnetron?

I once wondered if a microwave oven magnetron might make a good transmitter, for CW for EME. I took a spectrum analyser and antenna to the kitchen and microwaved a glass of water, and I saw... The ...
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  • 8,171
1 vote

Can a regen receiver be used as a CW transceiver?

Is this even possible, in terms of meeting FCC standards for spectral purity, etc., or in terms of staying on the same frequency for transmit that it's tuned to receive? The biggest problem is almost ...
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  • 7,515
1 vote

Will a "crystal set" work with an untuned RF amp stage?

Many radios do include a preamp that amplifiers the RF signal coming from the antenna. However there are many issues to consider. A truly broad amplifier will not only amplifier the radio signal you ...
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  • 1,208
1 vote

Can the transmit and receive functions of a boat anchor transceiver share the tank circuit?

You can use the tuning circut of the regen and, to be exact, the regen stage as a VFO for your transciever! Couple it to the separator amp with a 100pF cap between separator grid and the to of VFO ...
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1 vote

How is working on DC high voltages as in a tube radio different from 120VAC?

First of all, a voltage of 800VDC can be very dangerous if you happen to be touching anything at ground potential. An 800V potential is REALLY eager to pass some current down to ground, compared to a ...
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  • 4,329
1 vote

Heathkit SB-102 Plate Current out of control

In response to tuning the finals and grid dip: I’ve tuned a lot of IF strips as a Navaids Tech. VORs and Tacans mostly. Ham later. The procedure was always to start at the first IF and work to the ...
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1 vote

Heathkit SB-102 Plate Current out of control

The creap could be a bad capacitor or the circuit is over loaded due to excessive voltage on the plate. This sounds systematic of a component failure and requiring component isolation and L-C meters. ...
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