-----Original Message-----
From: Rich Measures <measures@vcnet.com>
To: amps@contesting.com <amps@contesting.com>
To: <amps@contesting.com>
Date: 11 August 1999 01:25
Subject: Re: [AMPS] Pi-Net math
Dick
>Rich...
>
> ........
>........... Time to do your homework.
>
? I did the homework, Dick. I built the Pi-network test
model. I used
Ian's calculated values for: 2000-ohms RL / Ro=50-ohms /
7.00MHz / Q=10
or so.
- Ian's results:
"The accurate formula - in ARRL Handbooks since 1995 -
gives
C1=102.1pF, L=5.57uH, C2=463.9pF. When analysed with the
load present,
this checks out with Q=9.98. "
- My results . Without RL and Ro, the resonant freq. was
7.37MHz, which
checks out mathematically. When I connected the 2000 ohm
and 50 ohm
resistors, the resonant frequency did not appear to drop to
7.00MHz as
had been predicted.
Is there perhaps something that I am doing wrong, Dick? .
Ian? . Tom?
. Peter? Any suggestions would be greatly appreciated.
In normal use, you don't have resistors loading the circuit
at both ends - you put a load on one end and use the circuit
to transform the impedance so that looking into the network
you see the desired impedance. If you remove one of the
resistors, I think the resonant frequency will decrease.
Without doing any maths, I think I agree that the resonant
frequency doesn't change if you load the circuit with the
designed resistor values at both ends.
Steve
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