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BP-1A 3-30MHz variable BandPass Filter

Written By EA3GCY

BP-1A 3 to 30Mhz continuous variable Band-Pass Filter Kit

The BP-1A kit is a 3 to 30MHz continuous bandpass filter. It is intended to improve the front stage in analog receivers or SDR (software defined receivers), experiments in radio laboratories, measuring instruments etc. where a filter is required to select any frequency segment within of 3 to 30 MHz range. In particular, medium and low cost SDR receivers need bandpass filters when receiving HF (OC) radio signals.

The BP-1A allows you to tune and select the frequencies of any amateur radio or HF broadcasting band. The tuning is done manually with a potentiometer that allows to be located at any point in the coverage range. The BP-1A incorporates three relay-switched bandpass filters covering from 3 to 6MHz, 6 to 12MHz and 12 to 30MHz.
Each filter is composed of two varicaps tuned RF toroidal transformers with an input and output impedance of 50ohms. A single potentiometer controls the three filters and the switching of the filters is done with a simple three-position switch.


  • Band Pass filter from 3 to 30Mhz continuos with manual tune.
  • Three tuning ranges: from 3 to 6MHz, 6 to 12MHz and 12 to 30MHz.
  • Manual control via potentiometer.
  • Dual LC filter for each margin composed of toroids and varactors.
  • Suitable for analog or software-defined receivers (SDR), HF instrumentation, RF experiments in laboratories, etc.
  • Input and Output impedance: 50 ohms.
  • Power supply: 10 -14V
  • PCB dimensions: 70 x 70 mm
  • All parts KIT

40 meter band
20 meters band
15 meters band

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