Four State QRP Group

Four State

4S-High Pass Filter
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4S High Pass Filter
Designed by
David Cripe NMØS

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and Information Group
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Kitted and Offered For Sale By The Four State QRP Group        


Featuring the famous NMØS Spiral coils, it is a None Simpler design, as seen in the Bayou Jumper and Cricket transceivers. This innovative and highly effective High Pass Filter (HPF) is a must have for experimenters. The kit includes all the components to finish the build, including a beautiful jet black PCB enclosure - another NM0S trademark. At 2"x2"x3" it will fit easily on your operating desk or workbench. See the specifications below for performance data.
Simple direct conversion transceivers frequently suffer from overload by nearby AM broadcast transmitters, causing their signals to leak through into the received audio. So if you live close to an AM station and have been frustrated by interference, this is the perfect filter project for you. NOTE: this isn't a QRP only design. Because of the high quality components, you can install behind your 100W QRO rig.

Notice: The 4SQRP High-Pass Filter should be used in conjunction with an antenna tuner between it and the rig. The HPF can introduce reactances that will create a non-unity VSWR that can affect the transmitter adversely.

Specifications and Design Features
    Beautiful jet black silk screened and easy building PCB enclosure.
    70 dB attenuation of frequencies below 1.6 MHz
    Cut off frequency <3.4 MHz.
    Maximum Power Throughput: Tested at 100W.
    Impedance: 50 ohms
    Extremely low insertion loss: 1 dB or less over pass band
    Enclosure Size: 2"x2"x3".
    NO TOROIDS to wind. Spiral coil inducors are etched on pcb's.
    Assembly Manual
    Response Curves
    Parts List
    Electronics 2000's Excellent Capacitor Identification Page  Posted with permission.
    Electronics 2000's Excellent Resistor Code Graphic Calculator  Posted with permission.
The 4S-HPF is carefully kitted and shipped by Johnny Matlock ACøBQ
Please direct shipment related questions to Johnny

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