Hi,

I am looking for some help in understanding amplifier concepts (solid
state only) and product specifications. I have searched for
definitions and essays on the topic, but , having no electronics
exposure, I find it hard to understand the concepts clearly. So if
someone can please help:

1. What actually is amplification of a RF signal: is it the
scaling up
of the amplitude?

I want to amplify a signal where the output has very low distortion
and noise. It should be as close to the input signal as possible:

2. Does push-pull setup mean that it's a class AB amplifier in
which
two amplifiers amplify the same signal, but the opposite two halves
of
the input signal?

If this is true, in an amplifier like this:
http://www.communication-concepts.com/ar347.htm

If two solid state amplifiers are rated at 600W each, and it's a
push-
pull arrangement, how come the output of this amplifier is 1000 watts
(or 1.2 kw theoretically)
If one Motorola amplifier is amplifying half the signal, the other
amplifying the other half, wouldn't the total output be 600W for the
whole signal?

3. In class AB amplifiers, is the output signal an exact replica
(but
amplified) version of the input signal?

4. What is an octave when dealing with amplifiers?

5. Is this communication concepts HF 1000 watt amplifier a class
A,
class AB, or class C amplifier?
http://www.communication-concepts.com/ar347.htm

6. Does anyone know the detailed specs for this same
communication-
concepts 1000 watt HF amplifier?
Specs like:
a. Duty cycle
b. Phase stability
c. Phase change with power
d. Gain flatness
e. Pulse droop
f. Harmonics
g. Spurious
h. Rise/fall times
i. VSWR or load SWR
j. Gate delay

7 Can this amplifier be "controlled" to give graded amplification
less
than 1000 watts specified, or will it work only at this maximum
level?

Any help is appreciated.

Thanks

Vijay

wrote:


I am looking for some help in understanding amplifier concepts...


Tell us what you're trying to amplify. What type of signal? AM? FM?
SSB? Other?

What frequency?

Since you mention 600 watts, this is obviously for a transmitted
signal.

AM and SSB signals require a "linear" amplifier (usually Class AB) so
that the amplitude variations aren't distorted.

FM signals can use a more efficient Class C amplifier since amplitude
variations are of no concern.

4. What is an octave when dealing with amplifiers?

An octave is a 2:1 frequency ratio (just like in music). 20 MHz is an
octave above 10 MHz.


5. Is this communication concepts HF 1000 watt amplifier a class
A, class AB, or class C amplifier?http://www.communication
concepts.com/ar347.htm

Probably Class AB. Definitely not Class C, as they mention linearity
to 800 watts.



7 Can this amplifier be "controlled" to give graded amplification less
than 1000 watts specified, or will it work only at this maximum
level?

You can vary the output by controlling how much signal you feed into
the amp. You could put a variable attenuator between whatever RF
driver you're using and the amplifier. According to the specs, 10
watts input will give 1000 watts output. Therefore, 5 watts input
would give about 500 watts output.

Art N2AH

On Wed, 24 Oct 2007 06:39:52 -0700, Art Harris
wrote:

wrote:


I am looking for some help in understanding amplifier concepts...


Tell us what you're trying to amplify. What type of signal? AM? FM?
SSB? Other?

What frequency?

Since you mention 600 watts, this is obviously for a transmitted
signal.

AM and SSB signals require a "linear" amplifier (usually Class AB) so
that the amplitude variations aren't distorted.

FM signals can use a more efficient Class C amplifier since amplitude
variations are of no concern.

4. What is an octave when dealing with amplifiers?

An octave is a 2:1 frequency ratio (just like in music). 20 MHz is an
octave above 10 MHz.


5. Is this communication concepts HF 1000 watt amplifier a class
A, class AB, or class C amplifier?http://www.communication
concepts.com/ar347.htm

Probably Class AB. Definitely not Class C, as they mention linearity
to 800 watts.



7 Can this amplifier be "controlled" to give graded amplification less
than 1000 watts specified, or will it work only at this maximum
level?

You can vary the output by controlling how much signal you feed into
the amp. You could put a variable attenuator between whatever RF
driver you're using and the amplifier. According to the specs, 10
watts input will give 1000 watts output. Therefore, 5 watts input
would give about 500 watts output.

Art N2AH
Class A amplifiers are linear, AB are fairly linear but have
relatively high intermod distortion.

Thanks Art