[Elecraft] Tube radios and such

[Don Brown]

Hi

Keep in mind I was speaking mostly tongue in cheek. I know there is still=
 a place for tubes and the high power transmitter tubes are very reliable=
. I was mostly speaking of the small receiving tubes that are notoriously=
 unreliable. I made a fair living back in the late 60's replacing tubes i=
n TV sets when most people expected some tube replacement every 6 months =
to 1 year. I have 3 Sony TV's one of which is over 16 years old and none =
of them have ever required service. The only tube is the CRT.

It was common for many 8 to 10 tube communication receivers to draw 200 t=
o 300 watts (many TV's of that era 500+ watts) most of which was filament=
 current. When I worked for Tektronix I worked on some of the old 500 ser=
ies O-scopes that had over 35 tubes in them. In cold weather they made fa=
irly good room heaters. In the summer you only turned it on when you need=
ed to make a measurement.

Yes you can buy a tube for $5 to $10 but You could most likely do the sam=
e job with a transistor or FET for $0.10 to $0.20
at 1/1000 the power.

I learned electronics with tubes and I wouldn't take anything for that ex=
perience. A lot of it still applies to FET's. When transistors and FET's =
came out I adapted. When IC's came out I adapted again. The same with Mic=
roprocessors. Now I make a fairly good living fooling around with micropr=
ocessors.

There is nothing wrong with nostalgia and the warm orange glow of a tube =
has a certain appeal to some. If you want to restore old radios or home b=
rew something with tubes there is nothing wrong with that and it may be a=
 lot of fun. I just see no reason for a commercial manufacturer to go the=
re (BTW I know Eric was joking about building a tube kit).

I don't think we are to the point of cost effectively replacing tubes in =
power amps over say, about 200 watts with transistors but it may not be l=
ong. Who knows what may be around the corner in this business. What ever =
it is, I for one will learn and adapt.

Don Brown
KD5NDB

  =20
----- Original Message -----
From: k6se@juno.com
Sent: Saturday, September 28, 2002 10:38 AM
To: DolfinDon@msn.com; elecraft@mailman.qth.net
Subject: Re: [Elecraft] Any AM detecting go'en on?

Don, KD5NDB wrote:

"Its nice to have a radio that can deliver 100 watts out using less power
than it takes to heat the filaments in the old tube radios and probably
10 times more  reliable."
----------
I'd sure like to find a radio that efficient!  5 volt filaments at even
25 amps uses 125 watts.  My power-efficient K2 uses 13.8 volts at 15
amps, or 207 watts, when running 100 watts RF out.
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

"With the exception of high power amps I think we should let the glow
bottles die. If you can even find them you have to mortgage the house to
buy them. I'm not sure how much longer power amps will use tubes as it's
getting more cost effective to build them solid state as well.  (From
someone who spent 10 years swapping tubes."
----------
I recently bought a new 12BY7 for my old TS-830S for $5.00.  I had no
trouble finding it and not a bad price, considering the increased cost of
living since the '80s.

Mortgage the house?  When you consider even the price of high-power
vacuum tubes, they're not as expensive as they were years ago.  For
example, in 1970, a pair of 3-500Zs cost $90.  Today, when the cost of
living is certainly more than three times what it was then, you can buy a
pair of 3-500Zs for $250.  The relatively low-powered and common-used
6146A which cost about $5 in 1970 can still be bought new for about $15
for the ruggedized military version (6146W).

Unlike Don, I have never had to swap tubes out in any of my kilowatt
amplifiers (in over 47 years).  My Alpha 76CA has thousands of tough
hours on it in contests and chasing DX, and still is going strong with
the original tubes.  IMHO, short PA tube life is due to either:

1) The tube was factory-defective (one-year warranty), or

2) Care was not exercised in driving the tube (watch that grid current
religiously!)

Until solid state high power RF amplifiers are as cost-effective as
vacuum tube amps, I'll stick with that "archaic" technology.

73, de Earl, K6SE


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