Radio model information

Heathkit DX-100 Transmitter


Date of Manufacture:1956 (DX-100B from 1959)

Manuals and schematics :

Download Here

Tube and Semiconductor Complement:

6AL5, 5V4, 2x5R4GY, OA2, 12AX7, 12BY7, 2x1625, 6AU6, 12BY7, 5763, 2x6146, 6AQ5

Model Notes

  • Phone or CW on 160, 80, 40, 20, 15, 11 and 10 meters.
  • Built-in VFO, modulator, and power supplies. 5-point TVI suppression.
  • Kit contains all parts—tunes—hardware—cabinet, etc.—Easy-to-build.
  • Coils are pre-wound and cable is pre-harnessed.
  • High quality components are used throughout for reliable performance.

For mods, see

This transmitter is a completely proven piece of ham gear. Amateur radio operators in the field are enthusiastic in praising its performance under actual operating conditions. It provides the latest and most desirable design features, and combines high quality with real economy.

The model DX-100 is a completely bandswitching rig for phone or CW operation on 160, 80, 40, 20, 15, 11 and 10 meters. It has a built-in VFO, or may be excited from crystals. Crystal sockets are built in. The easy-to-build kit contains all parts necessary for construction, including tubes, cabinet, hardware, etc. The detailed step-by-step instruction manual features plenty of pictorial diagrams for easy assembly. Pi network output coupling allows matching non-conductive loads from 50 to 600 ohms, and is only one of the design features of this outstanding performer.

This transmitter employs push-pull 1625 tubes modulating parallel 6146 tubes. RF output is in excess of 100 watts on phone, and 120 watts on CW.

The VFO credit consists of a 6AU6 tube operating as a clapp oscillator in the frequency ranges of 1750 to 2000 kc, 7000 to 7425 and 6740 to 6807.5 kc. An OA2 regulator tube stabilizes the B supply to the oscillator screen grid.

A 12BY7 tube is used either as a modified Pierce crystal oscillator, or as a buffer, depending on whether the function switch is on crystal or VFO. The plate circuit of this stage is untuned when operating 160 or 80 meters, slug-tuned to 40 meters for operation at 40, 20, or 15 meters, and slug-tuned to 20 meters when operating on the 10-11 meter band.

A 5763 tube drives the parallel 6146 final. Pi network interstage coupling is employed between this stage and the final grid.

The 6AQ5 clamp tube serves to protect the 6146 tubes by reducing screen voltage automatically if grid drive to the final tubes is removed.

A single 12AX7 tube provides two stages of resistance—coupled triode speech amplification in the audio section. A 12BY7 driver provides input voltage to the 1625 modulator tubes. The speech amplifier and the modulator stages have been designed to restrict the audio speech range. This provides a "hard hitting" audio modulation with plenty of punch.

Separate power supplies are used for low-level and high-level functions. The low voltage transformer contains all the filament windings, including the filament for the high voltage rectifiers. It has a tapped secondary to supply voltage for the bias rectifier. A 12-volt center tapped winding supplies audio and RF stage filaments. The low voltage supply delivers 360 volts at 160 ma to the low power audio and RF stages. The bias rectifier voltage is 75 volts. The high voltage supply provides plate and screen potential for the final RF and modulator stages. The entire power section of the transmitter is fused (both sides of the line) at the line plug. All power supply components, including transformers and chokes are well rated for their service.

The DX-100 has been "amateur designed" to incorporate all of the most desirable features for convenient and effective amateur communications.

Specifications:RF Power Output... 100-125 watts phone, 120-140 watts CW. Output Impedance... 50-600 Ω (non reactive). Output Coupling... Pi network (coaxial). Operation... Crystal-VFO, CW-Phone, Local-Remote. Band Coverage... 160, 80, 40, 20, 15, 11, 10. Audio Output... 85 watts at 300-3000 cycles. Tube Complement: Power Section... 6AL5 bias rectifier, 5V4 low voltage rectifier 2—5R4GY high voltage rectifier, OA2 regulator. Audio Section. 12AX7 speech amplifier, 12BY7 audio driver, 2—1625 modulator. RF Section... 6AU6 VFO, 12BY7 crystal oscillator-buffer, 5763 driver, 2—6146 parallel power amplifier, 6AQ5 clamp. Power Requirements... 115 volts AC, 50 to 60 cycles. Standby... 150 watts. CW... 400 watts (intermittent). Phone... 450-600 watts. Cabinet Size... 20-7/8" wide x 13¾" high x 16" deep. Net Weight... 100 lbs. Shipping Weight... 107 lbs.