1. QRPLabs@groups.io

Re: Persistence seems lacking...

Bill Cromwell
 

Hi,

When we are telling what something is and explaining how it works it can be useful to compare it to what is is NOT. So vacuum tubes can be useful in that regard even when we are talking about solid state and QRP (not necessarily the same thing). That requires the audience to know how tubes work. Some tube transmitters are QRP 5 watts or less of RF output. "QRP receiver" is about the same as division by zero. Receivers don't really have RF output beyond local 'leakage'. A tube receiver the size of a refrigerator is still just a receiver with no RF output.

Some of us still use vacuum tubes beyond nostalgia because they still do what they have always done (good, bad, and indifferent) AND we already have them. If I was starting out today I would probably not gives tubes a second glance. The heater power alone for two or three tubes exceeds the input DC power to the RF circuits.

73,

Bill KU8H

On 9/9/19 1:38 PM, Shirley Dulcey KE1L wrote:
Distortion, in particular the kind of distortion that tubes produce, is part of what we think of as the characteristic sound of an electric guitar. Guitar amplifiers are not designed for minimum distortion, and they are often pushed to and beyond their limits to get that tube distortion to happen. A common way of handling guitars for a large venue is to use a small tube amplifier, put a microphone in front of it to capture the result, and then put that through a clean stack of solid state amplifiers to fill the space.
In addition to distortion from the amplifier, guitar players use a variety of effects boxes to distort their sound in other ways. Those effects happen before the amplifier, so whatever the amp does to the signal is stacked on top of the distortion from the boxes.
Tubes are still a cost-effective way to get a kilowatt or more of RF output, especially if you buy one of the many used linear amplifiers that are available. (I know - off-topic for QRP!) Other than that, their primary appeal in ham radio is nostalgia. They have the appeal of being technology that you can almost understand and imagine making at home. It would take a fair amount of specialized gear but you COULD make your own rudimentary vacuum tubes. Making your own transistors would be far more challenging, and making sophisticated integrated circuits is far beyond what any individual could do.
On Mon, Sep 9, 2019 at 9:19 AM Braden Glett <@kd8zm <mailto:@kd8zm>> wrote:
"PS is anything still driven by valves?"
Yes - plumbing. Other than that, you should probably have the hobby
of working on guitar amplifiers rather than radio! :) Amps still use
tubes for that nice, warm sound, real or imagined.
--
bark less - wag more
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