[Amps] Load Pulling

[Tom Rauch]

> Thanks Tom for your reply. To my reconing the output
> is a carrier of 2MHz pulses (500nS period) with a very
> low duty cycle (20nS). The pulse, at least
> theoretically, carries a lot of harmonics extending up
> to 30MHz.

> Perhaps an antenna tuner, a 50 OHM dummy load, a
> current metter for the amp suply, and an osciloscope
> to watch the magnitude of the output pulse could
> provide a clue where the output impedance lies, but I
> am not sure about the acuracy of such a measurement


If the signal is broadband you cannot use a tuner. By 
definition all matching circuits and the load must have 
negligible impedance change over the signal bandwidth. Since 
the carrier is at 2MHz and the pulse duration is only 20nS 
the narrowest BW would be 100kHz (50kHz up and down) with a 
raised sine waveshape. This alone rules out use of a "tuner" 
since the BW is almost certainly hundreds of kHz  with a 
20nS pulse of any decent waveshape.

I doubt the application requires passing significant 
harmonic levels up to 30MHz. Nearly all systems have limits 
on harmonics of the carrier frequency. So the question is 
....  does the system need harmonics? It might have them and 
not need them, but it would probably require wide modulation 
bandwidth.

What is the envelope rise time? What is the envelope fall 
time?

73 Tom