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Homebrew Forty Oner 40M band transceiver | Radioaficion Ham Radio

Homebrew Forty Oner 40M band transceiver


This name and part of schematic are taken from 49′er where 40 represents the band, and 9 is 9V battery to supply the rig.

“Forty – Oner” means that one watt is produced on 40M band. The idea to build simplest and smallest working rig came to my mind after hours of surfing the Internet QRP resources.

But the simplest not necessary means comfortable to operate.

Homebrew Forty Oner 40M band

Technical data and assembly

  • Supply voltage: Typically 13,8V. Less voltage – less output power. Should work down to 7,5V.
  • Frequency range: 7000,8 kHz – 7037,4 kHz ( QRP calling frequency in Europe is 7030 kHz )
  • TX output power: Theoretically up to 1W, in practice 0,7 W or less. Use small heatsink on 3866.
  • Frequency stability : Very good even on the edge of span, but FET follower is a must. Crystal’s cases shall be soldered and grounded. Use 10k helipot instead of ordinary potentiometer if you don’t need fast tuning.
  • QSK&Sidetone : Very useful but you must be aware of “knocking” into a speaker due to RF detection in AF amplifier stage during transmission. Grounding pin 3 of LM386 helps but this require additional transmit/receive SPST switch (couldn’t find the room for this ). Sidetone needs adjustment of signal level.
  • RX sensitivity: Improved by adding serial R&C on pin 1 of LM386.
  • RX audio: Excellent if you spend some time tuning AF filter. Small speaker is enough.
  • Antenna output: Calculated for 50 ohms. For wire antennas use ” Mini ATU “
  • Workload: Two full week-ends If you have all components, case and your wife’s agreement. Use universal board for digital applications.
  • Efficiency report: Using Inverted Vee antenna I ‘ve made several European’s QSOs with RST 559 or better.

Homebrew Forty Oner 40M band

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