4S-High Pass Filter
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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.
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
All proceeds are applied toward funding OzarkCon.   Thank you for supporting The Four State QRP Group.