100 Watts or 500 Watts

[george fritkin]

Just  some simple questions.  Why use an 813 for an amp.   125 watt plate
dissipation,  50 watts of heater power, and a large physical size.  The "modern"
572b uses 25 watts for heater power has 225 watts dissipation and is cheap. I
have two SB200s they put out 800 watts PEP and they can be bought real
inexpensive. Every couple of years I stick new tubes in them for kicks and use
the pulls as spares or "presents".

I love building, but I am practical too.  But have fun guys and please be
careful.

George, W6GF






________________________________
From: Ron D'Eau Claire <[hidden email]>
To:
Sent: Wed, December 22, 2010 9:20:47 AM
Subject: Re: [Elecraft] 100 Watts or 500 Watts

Time to dig out some old ARRL Handbooks from the 60's. My '62 Handbook has a
nice 813 grid driven amp that runs Class C for CW and AB2 for SSB, the
famous "one band kilowatt" amplifiers using a pair of 813's (each band had
its own RF 'deck' with a common power and metering circuit so each amp could
be pre-tuned and ready to go at the snap of a relay or switch) and a
Kilowatt grid-driven 4-400A amp, in addition to the usual assortment of
ground grid amps.

A builder today may need to 'beef up' the pi-network output filter to meet
modern spurious emission standards (typically for the second harmonic) or
use an outboard half-wave filter for each band for that purpose.

Ron (radios should glow in the dark) AC7AC

-----Original Message-----
On 12/22/2010 11:30 AM, a lister wrote:

Grounded-grid is not the only way to design a tube amplifier. Although a
traditional grid-driven circuit is a little more complicated, it's one way
to get more gain.

Amen to that. When I was little, "grounded grid" was vaunted as the way to
use triodes without needing neutralization, even though one took a real hit
on gain. Unfortunately, the old-time big amps that use/used several triodes
in parallel in grounded grid still have a tendency to "take off."

The 813 and the various Eimac ceramic tetrodes are wonderful tubes, and if
one can go high voltage low current, they are excellent performers. Again,
when I was young, solid state devices wouldn't function in the VHF/UHF
region, and the 4CXnnn series were practically a necessity. Need I refer to
the beautiful amps vended by one of the early moonbounce guys?

I for one would like to see designs using these tubes. Not all of us need
linear/linearized amps.

John Ragle -- W1ZI

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html



     
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[Cookie]

I will throw out another opinion about amplifier gain that has nothing to do
with CB or IMD. 


If an operator is currently running QRP at 10, 5 or less watts, adding the KPA-3
to boost power to 100 watts will give you a very large power boost and will be
enough power for a lot of QSOs, both domestic and DX.  You can still turn the
K-3 down to 100 mw if you want to give your antennas and patience the acid
test.  If you add a 500 watt or bigger amplifier you have another nice boost
in power and you have a combination that will give you smooth power increases
from 100 mw to 500 watts or with a bigger amp the legal limit.  To my way of
thinking, this is a better combination than trying to solve the problems of home
brewing or modifing a commercial amp.

Food for thought?
Willis 'Cookie' Cooke
K5EWJ


     
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[AC7AC]

CONTENTS DELETED

The author has deleted this message.

[Vic K2VCO]

I have worked as a BC engineer and I'm very, very careful. In addition to following work
procedures like the use of a 'shorting stick', there are various design principles
important for safety. There should never be a way for someone to come into contact with
HV, no matter what component or combination thereof fails (within reason, of course).

Just for example: you often see a 'safety' RF choke across the output of a pi-network.
Supposedly this will cause a fuse to blow if the plate blocking capacitor breaks down and
puts HV on the antenna. But most such chokes are too puny -- they will blow before the
fuse! Interconnections between remote power supplies and RF decks are another risky area.
I prefer to put it all in one box, or at least an enclosed rack.

I only work on such projects when I am feeling 1) alert and 2) patient. 'Patient' is
really important. If you are operating in the 'every time I try to fix something I break
something else' mode, then STOP. I like to spend a lot of time thinking about what I'm
about to do before doing it.

This is getting off-topic for the reflector, so this will be my last post on the subject!

On 12/22/2010 11:36 AM, Ron D'Eau Claire wrote:

> Good point George. The question was specifically about the 813 and it's a
> "nostalgia bottle" for many of us. It was popular after WWII because you
> could get them for as little as 50 cents each in the USA. Even in the 60's
> they were still available 'surplus' for a few dollars. Typically the socket
> cost far more than the tube.
>
> The biggest cost in a tube amp is in the power supply (including high
> voltage hardware) and in the input/output network components that can handle
> the voltages involved.
>
> You can avoid those costs by buying a used amp, even if it's not functional
> (but hopefully has a good power transformer).
>
> Other than learning to work around thousands of volts (only one mistake
> allowed per lifetime) tube amps are extremely simple things compared to most
> high power solid state amps. And tubes tend to be much more tolerant of
> abuse than solid state.
>
> But that comment about only one mistake allowed per lifetime around the
> typical tube amp power supply was serious. I'm always very cautious about
> encouraging today's typical ham to mess around with even moderate or low
> power tube gear if he/she has "grown up" around solid state running from a
> few tens of volts at the most. One needs a wholly different set of
> procedures, concerns and attitudes to work around even a few hundred volts
> safely.
>
> Over the years we've lost a number of wonderful, bright, prolific designers
> and builders in the Ham community to one momentary mis-step around a high
> voltage power supply.
>
> Ron AC7AC
>
>
> -----Original Message-----
>
> Just  some simple questions.  Why use an 813 for an amp.   125 watt plate
> dissipation,  50 watts of heater power, and a large physical size.  The
> "modern"
> 572b uses 25 watts for heater power has 225 watts dissipation and is cheap.
> I
> have two SB200s they put out 800 watts PEP and they can be bought real
> inexpensive. Every couple of years I stick new tubes in them for kicks and
> use
> the pulls as spares or "presents".
>
> I love building, but I am practical too.  But have fun guys and please be
> careful.
>
> George, W6GF
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[W7CS]

As a recent K3/P3 kit assemblier(4910) and an old timer (licenced in
'47). I'm still trying to understand all the nuiances of the K3
operation.  Thank you, the Elecraft Reflector, for all the good ideas and help.

But as I understand it, the quote of the HF DX'rs is " Life is too
short for QRP", 500 Watts.

So my New Years and B'Day (79) present next month will be a 2nd hand
but good working AL 1500.   I really like 8877s.  I worked WAS, WAC,
VUCC, and 95 DXCCs on 2M with one, using CW.

So maybe I'll try a bit of HF for a change with my K3/100.

BTW, it should also make and excelent EME transceiver, especially
with the purposed extenal 10MHz driven REF Lock module.

GL es 73,

Chuck,  W7CS

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html