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The Red Hot 40 is a high performance QRP CW transceiver kit for the 40m band. It has been designed to operate well in the presence of large out-of-band (shortwave broadcast) and in-band (contest station just down the road) unwanted signals. It should easily meet the requirements of most QRP'ers, from the most competitive contester to the casual operator.

The kit contains all the parts needed to build a complete working radio. The only things the user will have to supply are a power source, loudspeaker or headphones, a set of paddles or straight key (suitably wired) and a matched 40m antenna system.

The kit is designed so that no wiring-up is required - all the components are mounted on a single double-sided with plated through holes, solder masked and silk screened printed circuit board that measures 4.5" by 5". Pre-drilled front and rear panels with U shaped top and bottom panels are provided that form a clamshell type case that is smart, strong and functional. The case is red anodized aluminum with an engraved legend.

The Red Hot 40 is a single band QRP CW transceiver optimized for good RF performance rather than for low current drain. As such, it is suited mainly for operation from home-based stations or portable operations with fairly large battery capability (e.g. field day). On receive the current drain can be as much as 150mA. It can produce any output power from 0 to over 5 Watts. The output power is set with a small trimpot inside the rig.

The Red Hot 40 uses fully electronic RX/TX switching (no relays) that gives very smooth, thump-free, semi-break-in operation. The transmit output waveform is edge rate controlled to minimize bandwidth usage. As a bonus, this makes for very nice sounding Morse code on the air. The Red Hot 40 offers many advanced features that make it easy to use.

The Red Hot 40 has a single conversion superheterodyne receiver and an equivalent single stage down-conversion transmitter. The I.F. is 9MHz with the VFO at 2MHz. The Red Hot 40 was originally designed to utilize either a 1 turn or a 10 turn TUNE pot. The Red Hot 40 kit is supplied with a 10 turn pot as standard. The Red Hot 40 also has an RIT pot with center detent.

No frequency calibration or scale is needed because the rig has a built in frequency counter, known as the Audible Frequency Annunciator (AFA). This plays the KHz digits of the frequency to you in Morse code over the speaker/headphones. The AFA has two modes of operation. Manual mode, where the frequency is announced only when you press the front panel pushbutton, and automatic mode, where the AFA "pips" at every KHz as you tune up or down the band, then, recognizes when you stop tuning, and announces the frequency automatically.

The Red Hot 40 has a built in Morse code keyer chip from the Embedded Research TiCK line. This keyer allows you to swap the paddles over, set the speed, tune-up, run straight key mode and run in either iambic A or B modes.


  • Case 5" x 5" x 2" nominal, red anodized and engraved aluminum clamshell design.
  • Weight 1 lb. 2 oz. (515 g) +/- your soldering style!
  • Mode CW
  • Keying Semi-break-in, all electronic, TiCK (Rev. 1.02) keyer built in. 1/8" stereo jack connection -
  • DIT = tip of the jack plug (can be modified)
  • Frequency control VFO, varicap diode tuned, main tuning control and RIT control
  • Stability Approx. +300Hz drift first 30mins, +50Hz drift per hour thereafter
  • Frequency counter AFA, accurate to within 1KHz, manual and automatic modes - user selectable
  • Frequency range A (nominal) 70KHz segment of the CW end of 40m (7MHz) - user selectable
  • Antenna 50? BNC connector
  • Output power 0 to 5 Watts nominal (7 Watts typical) - user adjustable. Some variation in output power is to be expected if the power supply voltage is changed after the power control has been adjusted - this is normal.
  • Output protection 2SC1969 output device is SWR protected - will run into open or short circuit loads
  • Output match Better than 1.5:1 into 50? nominal
  • Output spectrum Relative to main carrier at 5W output, all harmonics -70dB or better, all spurii -50dB or better
  • Receiver Single conversion superheterodyne, JFET pre-amp, high level double balanced mixer
  • Receive sensitivity MDS -135dBm nominal
  • Receive IP2 Figure not yet available - check website for updates
  • Receive IP3 Figure not yet available - check website for updates
  • RX Blocking Range Figure not yet available - check website for updates
  • Intermediate frequency 9MHz
  • Receive filter 4 crystal main filter, 1 crystal unwanted sideband noise filter
  • Receive bandwidth 300Hz nominal
  • Stopband attenuation -70dB typical
  • AGC Audio derived, 2 PIN diodes plus N6KR's NE602 method
  • AGC range 100dB nominal
  • Audio output 1W into 8? nominal (13.8V power supply, loudspeaker or headphones).
  • The output will directly drive mid/high impedance earphones.
  • Speaker/headphone connection is by 1/8" stereo jack.

Supporting Files and Documents

 Red Hot 40m Assembly Manual

 Red Hot 40 Schematic part 1

 Red Hot 40 Schematic part 2

 Red Hot 40 Schematic part 3

 Red Hot 40 Schematic part 4

 Red Hot 40 Schematic part 5

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