: From: "Tom Rauch" <w8ji@contesting.com>
:The 4CX250 amp looks like a CB amplifier Skipp. It certainly can't
:be a very good amp for ham radio.
If you refer to one of the diagrams on the sonic server, it is a partial
circuit of
the Pride DX-300 Amateur Amplifier with 80-10 meter coverage. It's well
built but could always use improvements as most any amplifier could. The
circuits are posted to provide ideas and information. The input circuit
of this
amplifier is a circuit worth using in low drive applications. I've never
had it
on the CB Band, nor am I interested in using it there.
:It takes 1-5 watts of drive, and worse yet has no screen regulation,
:current limiting, or metering.
I wouldn't consider 1 to 5 watts drive a bad thing at all. Many qrp hf
rigs are
sold and used by Amateurs. Screen regulation to a tetrode amplifier
should
be included along with many other "upgrades" to the current level of
Amplifier work. It does have metering. In the 15 plus years I've owned
an
amplifier of this model, it's never gone qrt. Not every amplifier built
has to be
driven with 100 watt exciters.
I've done many improvements to this amplifier circuit which I'm happy to
talk
about. This model amplifiers main sin is 6.3 volts on the heater.
Actually, I've
found about 4 watts is the max drive I'd apply to the circuit. There's a
laundry list of amplifier improvements which I've done to this amplifier.
: I certainly hope not many are used on amateur bands!
Properly worked through, there's no reason it's operation should
be avoided. It's a nice amplifier and my test equipment verifies it. A
lot
more stable than some 3-500z and 8877 amateur amps sold in the
past.
: It looks like a copy of a CB amplifier marketed under the guise of a
: "amateur linear" by a company that sold out-of-band crystals for
: CB radio's in the 70's and early 80's.
As built from the factory, this amplifier operates the 80 through 10
meter amateur bands with modification.
My misc Dentron and Amp Supply amplifier Collection looks like a
batch of amplifiers sold to the amateur market under the guise of a well
engineered circuit. A lot of Hams were sure taken in... for many
years...
Used amplifiers make cost effective rebuild projects and a real bargain
barn parts source. It's a smart way to get started with home brew.
Heck, I see SB-220's moved up to six meters. A lot more practical
way to get there vs buying a commercially made box. We see them
here on amps all the time.
:73, Tom W8JI
:w8ji@contesting.com
Fact is, a 4CX250 is an excellent tube for linear operation, cathode or
grid driven. The circuit shown on sonic preforms well, 4 watts input
on 28.5MHz gives me 310 watts out the door. I'm impressed with this
much gain for a single valve.
I've use a similar circuit on 52MHz with much success.
I provide complete and partial amplifier circuit diagrams on sonic for
information and ideas only. Some are good circuits, others are just
worth looking at. The daf circuit is also over there waiting a rehash.
If that gets boring, there's some great mp3 software and south park
episodes you can watch.
cheers
skipp
nospam4me@juno.com
http://sonic.ucdavis.edu amateur radio pages.
[sidebar]
The other replies/posts you've received have been from other sources. I
know that "toll free" has an Amateur Call sign. I think he just likes to
get a rise out of some you with his CB jargon. Not my bag, sorry.
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