SkyWave 2879AB Amplifier
 

"I AmnotGeorgeBush" wrote in message
...
From: (Dr.Death)
"Telstar Electronics" wrote in message
ups.com...
I'm surprised dogie hasn't ratted him out,


Are you really? Dogie and Griffy are buds!


That makes sense.

SkyWave 2879AB Amplifier
 

"I AmnotGeorgeBush" wrote in message
...
From: (Dr.Death)
"Telstar Electronics" wrote in message
ups.com...
I would think that a regular in the group would

have better sense then to spam the group with
his product. You can now join Lou Franklin

and AAA Rf Products.plonk


Lou has good stuff.


I agree, but am tired of the monthly spamming of the group. If he wants to
post and have it as his sig file, that would be cool.

SkyWave 2879AB Amplifier
 

JSF... you're right about those "big amps". They are nothing but
hay-wired prototypes, mostly designed and constructed by persons having
no electronic background. I have looked at many of them over the years
and have found that they have major flaws such as inadequate cooling,
improper tuning, and instabilities/oscillations caused by improper
layout and long wires running around all over inside. Because of these
issues, their owners must keep a steady stream of expensive output
transistors flowing through them... if you know what I mean... LOL

www.telstar-electronics.com

SkyWave 2879AB Amplifier
 

On a sunny day (22 May 2006 04:45:06 -0700) it happened "Telstar Electronics"
wrote in
.com:

JSF... you're right about those "big amps". They are nothing but
hay-wired prototypes, mostly designed and constructed by persons having
no electronic background. I have looked at many of them over the years
and have found that they have major flaws such as inadequate cooling,
improper tuning, and instabilities/oscillations caused by improper
layout and long wires running around all over inside. Because of these
issues, their owners must keep a steady stream of expensive output
transistors flowing through them... if you know what I mean... LOL

www.telstar-electronics.com

Hi, I am reading on your website
http://www.telstar-electronics.com/S...Amplifiers.htm
about efficiency and conductingangle.
My question, has anyone ever attemped a class D (pulse width) modulated amp
with MOSFETS for 27Mc?

The limit would be the switching time, say if we have 1nS switching FETS,
and 37 nS period time, we use a bridge, so per 37 nS we switch 4x = 4nS

We dissipate any power (not counting Rds-on losses), could we achieve 80%
efficiency?
There are also losses from transformer and Pi filter of course.
And perhaps you would need a switchmode to get a higher operating voltage,
mmm that would bring it down to .8 x .8 = 64 % + filter and other losses....
But it COULD take you into the kW range with cheap FETS?

Whatdoyouthink? ;-)

SkyWave 2879AB Amplifier
 

Telstar Electronics wrote:

JSF... you're right about those "big amps". They are nothing but
hay-wired prototypes, mostly designed and constructed by persons having
no electronic background. I have looked at many of them over the years
and have found that they have major flaws such as inadequate cooling,
improper tuning, and instabilities/oscillations caused by improper
layout and long wires running around all over inside. Because of these
issues, their owners must keep a steady stream of expensive output
transistors flowing through them... if you know what I mean... LOL

www.telstar-electronics.com

Kind of like building an amp and running it with class C bias?

You know what that means?

SkyWave 2879AB Amplifier
 

Jan,

Sure you can run class D at 27MHz... the problem is distortion. Class D
is very efficient but is really only meant for digital signals.

www.telstar-electronics.com


Jan Panteltje wrote:
On a sunny day (22 May 2006 04:45:06 -0700) it happened "Telstar Electronics"
wrote in
.com:

JSF... you're right about those "big amps". They are nothing but
hay-wired prototypes, mostly designed and constructed by persons having
no electronic background. I have looked at many of them over the years
and have found that they have major flaws such as inadequate cooling,
improper tuning, and instabilities/oscillations caused by improper
layout and long wires running around all over inside. Because of these
issues, their owners must keep a steady stream of expensive output
transistors flowing through them... if you know what I mean... LOL

www.telstar-electronics.com

Hi, I am reading on your website
http://www.telstar-electronics.com/S...Amplifiers.htm
about efficiency and conductingangle.
My question, has anyone ever attemped a class D (pulse width) modulated amp
with MOSFETS for 27Mc?

The limit would be the switching time, say if we have 1nS switching FETS,
and 37 nS period time, we use a bridge, so per 37 nS we switch 4x = 4nS

We dissipate any power (not counting Rds-on losses), could we achieve 80%
efficiency?
There are also losses from transformer and Pi filter of course.
And perhaps you would need a switchmode to get a higher operating voltage,
mmm that would bring it down to .8 x .8 = 64 % + filter and other losses....
But it COULD take you into the kW range with cheap FETS?

Whatdoyouthink? ;-)

SkyWave 2879AB Amplifier
 

On a sunny day (22 May 2006 07:47:53 -0700) it happened "Telstar Electronics"
wrote in
.com:

Jan,

Sure you can run class D at 27MHz... the problem is distortion. Class D
is very efficient but is really only meant for digital signals.

www.telstar-electronics.com

Hi, you know class D audio amps exist I suppose?
There are even class D power amp chips for audio.
These use PWM (pulse width modulation).
You can make any output waveform with PWM (as long as the switching frequency
is much higher then the output frequency).

This links shows some basics for a modulator (driving class D for example):
http://www.netway.com/~stevec/ham/pd...lid_state.html

I can also think of a 'digital' solution, say you have 8 RF amps,
1W, 2W, 4W, 8W, 16W, 32W, 64W, and 128W,
now simply switching these on with an 8 bit digital audio signal (one on each
bit) and summing the RF output together, will give you a 255W AM modulated
transmitter with less then 1/255 (0.4 percent) distortion (have not tried)?
Since these RF amps can be class C (no need for A, AB, B, any linear!!) you
should get good efficiency.
The stages are only 'on' or 'off'.

So, maybe someone could combine some :-)
Nice for experiments....
hehe

SkyWave 2879AB Amplifier
 

On a sunny day (Mon, 22 May 2006 15:32:12 GMT) it happened Jan Panteltje
wrote in :

On a sunny day (22 May 2006 07:47:53 -0700) it happened "Telstar Electronics"
wrote in
s.com:

Jan,

Sure you can run class D at 27MHz... the problem is distortion. Class D
is very efficient but is really only meant for digital signals.

www.telstar-electronics.com

Hi, you know class D audio amps exist I suppose?
There are even class D power amp chips for audio.
These use PWM (pulse width modulation).
You can make any output waveform with PWM (as long as the switching frequency
is much higher then the output frequency).

This links shows some basics for a modulator (driving class D for example):
http://www.netway.com/~stevec/ham/pd...lid_state.html

I can also think of a 'digital' solution, say you have 8 RF amps,
1W, 2W, 4W, 8W, 16W, 32W, 64W, and 128W,

Actually I think I have this wrong, should be Volts (RF output) ratio or
powers of 2.
So 1 W in 50 Ohm: U^2 / 50 = 1, so U = sqrt(50) = 7V eff, the next higher
higher one would be 14V eff or 3.92 W,
better start at the high side...

So for your 300W in the highest bit: U^2 / 50 = 300, U^2 = 15000,
so U = sqrt(15000)= 122V eff.
The next lower one (bit 7) would be 122 / 2 = 61V eff, so 61^2 / 50 = 74.42W,
bit 6 would be 61 / 2 = 30.05 V, makes 18.06W
bit 5 would be about 15 *15 / 50 = 4.5W
bit 4 would be 7.5 x 7.5 / 50 = 1.125 W
etc etc.
I have also been thinking about doing SSB this way.
For SSB we need half the bits, and one bit to change the phase of the driving
carrier 180 degrees.
Hope I got that right.

You'd be selling lots of amps!!!

SkyWave 2879AB Amplifier
 

On a sunny day (Mon, 22 May 2006 16:41:03 GMT) it happened Jan Panteltje
wrote in :


I have also been thinking about doing SSB this way.
For SSB we need half the bits,

No, same bits, but bit 8 as sign bit changing carrier phase 180 degrees....

We'll get there....

SkyWave 2879AB Amplifier
 

Your statement about having the switching freq much greater then the
output freq I agree with. But if you wanted to make an amp for 27MHz...
what switching freq would you have? 2X, 5X, 10X ? Also, with a high
switching rate... with square-waves... you have tremendous harmonic
content. You also would require much higher frequency amplifers...
along with the quantum leap in complexity of combining all those
amplifiers, A/D conversion, etc... I think your idea would work... it's
just not practical in my mind.

www.telstar-electronics.com