input image rejection filter for 20m band

[Marek128b]

try nr. 1

tested 8 turns for 0.28uH tested 24 turns for 2.8uH

C1/C3 = 470pF C2 = 47pF

ins. Loss = 22.3dB F_low = 4.19MHz F_middle = 6.45MHz F_max = 9.70MHz

BW = 5.51MHz

[Marek128b]

NanoVNA

Start: 1MHz Stop: 20MHz

CH1 LOGMAG 10dB

config in # 3

[Marek128b]

using new design from qrp labs. File

[Marek128b]

may only use one toroid and else aircoils.

Filter Tool

Air Coil Tool

[Marek128b]

Wrapping wire

[Marek128b]

calculated whindings

82nH

note: 5mm Diameter

4.7uH

note: 12mm Diameter

[Marek128b]

Ideal Simulation of 20m BP Filter

[Marek128b]

Big 2.2uH

small 130nH

Simulation

[Marek128b]

limited components

used 1nF instead of 820pF

[Marek128b]

real world test with nano VNA

software: NanoVNA Saver v0.6.4

settings:

S21 trough:

Markers:

marker 1 and 2: -6,5dB to -14dB = delta 7,5dB

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Soldering header for switchable capacitors:

[Marek128b]

tested countless values

C1/C3 = 1nF C2 = 22pF

L1/L3 = 5turn 5mm L2 = 15turn 12mm

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results

Band: 20m only BW: 2,82 MHz ins. Loss: 6,2dB

S21 curve:

markers:

VNA Settings on NanoVNA saver v0.6.4:

[Marek128b]

40m Filter idea

[Marek128b]

tested with 47pF and fixed design

config in NanoVNA Saver v0.6.4:

markers:

S21 graph: