Re: Persistence seems lacking...

Bob Macklin <macklinbob@...>
 

To me QRP means SMALL.

The receivers for small low power operation are generally very simple,
primitive receivers like regens, direct conversion, and possibly crystal
detectors.

Not mutt band, multi mode, RICEBOXES!

I've got the ARRL QRP book. and it is full of simple primitive stuff.

Bob Macklin
K5MYJ
Seattle, Wa.
"Real Radios Glow In The Dark"

----- Original Message -----
From: "Bill Cromwell" <wrcromwell@...>
To: <QRPLabs@groups.io>
Sent: Monday, September 09, 2019 11:02 AM
Subject: Re: [QRPLabs] Persistence seems lacking...


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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