short wave receiver preselector circuit schematic

SW Receiver Preselector Circuit

This is a Preselector for SW receivers (diy hf preselector) circuit. The entry low capacitance of MOSFET modern, with two gates, will create negative inverse reaction through a uncoupled source resistor. Applied right this technique allows the creation of a entrance RF stage field with a relatively high dynamic range.

Radio amateur working on short wave: there is no need to tell, in the days of our times, the ability to face the signals of high level is a necessity – for preventing overload of the receiver and intermodulations caused by very strong signals.

Unlike of entry sections in many SW high quality receivers, this schematic has no difficulty in handling RF input signals up to 2.5 Vvv. In this case we have 3Vvv on an impedance of 50 Ω.

short wave receiver preselector circuit schematic

Adjustment capacitor C1 determines the global amplification, which is mainly because because LC network resonance at the circuit input. The 6 entrance coils are coiled on ceramic dcores of very high quality with diameters of at least 10 mm. Ferrite pearl is located right on the terminal gate 1 of T1, for a preventing parasites oscillations in the VHF and UHF bands. Output coil L7 is 20 turns (A) and 4 respectively turns (B) coiled on a ferrite core ring type G.2-3/FT16.

Frequencies domains of the selector with active input are:

  • 1: 30-100kHz
  • 2: 100-300kHz
  • 3: 300-900kHz
  • 4: 900-2700kHz
  • 5: 2700-9000kHz
  • 6: 9000-30000kHz

Coils values

  • L1 = 56mH
  • L2 = 5.6mH
  • L3 = 560µH
  • L4 = 56µH
  • L5 = 5.6µH
  • L6 = 560nH
  • L7 = see text above


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  • jjdobrikingmail-com

    I am looking for Circuits, Modules, PC board RF Amplifiers to use in converting Antique/Vintage TRF Tube (Triodes) to lower safer voltage semiconductors. I plan to use Radio on a Chip ZN 714-MK484/LM386 PC Boards as Detector/1st Audio, (headphones) and a PC Board Power Amplifier for Loudspeakers.
    Also for building STEAMPUNK TRF Radios using Antique/Vintage Components, Variocouplers, Variometers, Variable Condenser/Coil Assemblies as well as Individual Variable Condensers and Coils.
    It Looks like the SW Preselector Circuit can be adapted.
    A Variocoupler to replace the C1 L1 thru 6 and a Variometer to replace the L7A & B Coils.
    73 de Jordan ve7jjd

  • smilli contro

    This circuit has clearly been scanned from another source. Typically for this website, crucial construction information has ben left out. Shameful.

  • Siddhalingesh

    It would be great if you can provide the winding details of the 6 entrance coils.

  • AKMANSOY Fazli Cemil

    schematics looks fine . Yet it will be more easy to find it , and buy it , ready to use.

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