Topics

HT20 LPF performance

Curt
 

Has anyone simulated the HT20 LPF?   Using ELSIE to simulate, must be doing something wrong, seeing 3 dB loss at 14 MHz.  Of course a deep 60 dB suppression at 25 MHz.  I am using 50 ohm input and 50 ohm output impedance.   What does the actual output spectrum look like on a scope?  ( I don't own one ).

Curt KB5JO

Curt
 

Found ARRL Lab test results Dec 2018 QST.  Actual suppression greater than 55 dB

Curt KB5JO

K7AHR
 

I would not expect the input impedance to be 50 ohms, for one thing. This could affect your results substantially, especially where the impedance at the fundamental frequency is concerned.

Dave Benson
 

Curt-

I have. <g>

The source impedance is 12.5 ohms. That's how the HT is able to put out 5W - there's an impedance transformation in the LPF.

73- Dave


On Mon, Aug 26, 2019 at 9:45 AM Curt via Groups.Io <rhulett1=consolidated.net@groups.io> wrote:
Has anyone simulated the HT20 LPF?   Using ELSIE to simulate, must be doing something wrong, seeing 3 dB loss at 14 MHz.  Of course a deep 60 dB suppression at 25 MHz.  I am using 50 ohm input and 50 ohm output impedance.   What does the actual output spectrum look like on a scope?  ( I don't own one ).

Curt KB5JO

Curt
 

With 12.5 ohms, Elsie output looks great.  I had forgotten about low FET output impedance.

Curt KB5JO