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
With 12.5 ohms, Elsie output looks great. I had forgotten about low FET output impedance.
Curt KB5JO
|
|
|