[AMPS] Re: Input Impedance.

[Rich Measures]

>At KE9NA wrote:
>
>Snip....
>>At 10:30 PM 3/23/98 -0600, you wrote:
>>>>>Everybody claims this, but I haven't seen it.  The input impedance does 
>>>>>NOT vary with input power.  I have the exact same match applying 100 
>>>>>watts as I do 5.  My SWR does not change. 
>
>Your SWR does not change enough to see it because as you lower the input
>power, you also lower the cathode current, maintaining about the same
>input impedance. Try this...tune up your amp and apply 100 watts drive.
>Note the cathode current. Reduce the drive to 50 watts. The cathode current
>should be close to 1/2 what it was at 100 watts input. Since input impedance
>equals drive power divided by peak cathode current squared, you can see how
>the input impedance stays fairly close throughout the operating range. The
>low Q of the tuned input L/C allows compensation for any variations in the
>drive/cathode current ratio.
>
€  well said, Phil.  .  Murphy was right.  Things are usually more complicated than they look.  
>
>
>
>
>
>Phil, K5PC
>
>"To do is to be".....Sartre
>"To be is to do".....Aristotle
>"To be or not to be".Shakespere
>"Do be do be do".....Sinatra
>
>
>--
>FAQ on WWW:               http://www.contesting.com/ampfaq.html
>Submissions:              amps@contesting.com
>Administrative requests:  amps-REQUEST@contesting.com
>Problems:                 owner-amps@contesting.com
>Search:                   http://www.contesting.com/km9p/search.htm


cheers
Rich...

R. L. Measures, 805-386-3734, AG6K   


--
FAQ on WWW:               http://www.contesting.com/ampfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm