[BC] Assistance With A PI Network Calculation

[Dana Puopolo]

A Y network looks like the letter T with a series coil, shunt cap and another
series coil.

A pi network looks like the pi symbol (actually more like an unside down U).
It has a coil to ground, a series cap and a second coil to ground.

-D

------ Original Message ------
Received: 
From: "Harold Hallikainen" <harold at hallikainen.com>
To: "Broadcasters' Mailing List" <broadcast at radiolists.net>
Subject: Re: [BC] Assistance With A PI Network Calculation

Though I haven't worked it out, I THINK a pi network is similar to a 90
degree T network. For the T network, each component has the same reactance
as the "characteristic impedance" of the network. And when using a 90
degree network to transform impedance, the characteristic impedance of the
network should be the geometric mean of the source and load impedances
(square root of the product of the two impedances). See
http://sujan.hallikainen.org/rw/theory/theory13.html .

Again, just thinking about it, I THINK a pi would behave similarly to an
L. The math is left as an exercise for the student.

Harold


> I was going through my junk box trying to determine what kind
> of AM transmitter I might be able to build with available
> parts.  I came up with enough parts for a final power
> amplifier using three 1625s (12 volt version of the 807) in
> parallel.  Wonder if someone could give me the approximate
> values of the input and output capacitors for the PI network
> at 3.8 MHz?
>
> The 1625s will have about 700 volts on the plates with 300 MA
> which is a plate load of 2333 ohms.  The output of the PI
> network will of course feed 50 ohms.
>
> Thanks,
>
> Tom
>
>
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