Heathkit Virtual Museum

DX-40 Phone & CW Transmitter

DX-40 Phone & CW Transmitter


  • 6146 final amplifier for full 75-watt plate power input.
  • Phone and CW operation on 80, 40, 20, 15, 11 and 10 meters. Pi network output coupling.
  • Switch selection of three crystals—provision for external VFO excitation.
  • D'Arsonval movement panel meter indicates final grid or plate current.

The DX-40 is an entirely new transmitter, featuring increased power, clean keying characteristics and stability made possible by the efficient circuit design. An ideal rig for the novice who intends to operate on phone as soon as he gets his general-class ticket, yet needs a CW rig in the meantime. Experienced hams also will find the DX-40 appealing since it provides the phone and CW facilities desired in a low-power rig.

The plate power input of the model DX-40 is 75 watts on CW, and peaks to 60 watts with controlled-carrier phone modulation. It covers the 80, 40, 20, 15, 11 and 10 meters with single-knob bandswitching. PIP network coupling is also featured between the buffer circuit and the final amplifier thus improving stability and attenuating the higher order harmonics, reducing the possibility of television interference. A line filter is incorporated to prevent RF radiation through the power line. The efficient oscillator and buffer circuit provides adequate drive to the 6146 amplifier from 80 to 10 meters even with an 80 meter crystal. A drive control adjustment provides excellent maximum to minimum drive requirements. A five-position function switch provides an extra "tune" position, allowing you to switch on the oscillator without the final amplifier being on, so the operator can locate his own signal on the band. TUning the buffer stage to proper drive level before the final is on also prevents the possibility of damage to the final amplifier tube.

The tube lineup features a 6CL6 Colpitts oscillator, a 6CL6 buffer, 6146 amplifier, 12AX7 dual-triode speech amplifier, 6DE7 dual-triode modulator, and a heavy-duty 5U4GB rectifier. The modulator circuitry features an audio frequency shaping network allowing a higher average output level on voice frequencies where it is required. Provision is made for three crystals. A four-position switch selects any of the three crystals or a jack for external VFO. The crystal sockets are easily accessible through a "trap door" in the back of the cabinet. An external VFO (variable frequency oscillator) can also be used to excite the transmitter for the general or advanced-class ham. Power for the VFO is available at a socket on the rear apron of the chassis.

Top-quality components are used throughout. The transformers are potted types, ceramic switches are used in the final RF circuits, all coils are pre-wound, etc. The circuit features liberal shielding and careful physical placement of components and leads for stable operation. The circuit design has been extensively tested "on the air" with excellent reports, assuring you of the best possible performance. Besides being carefully designed both electrically and physically, the styling of the DX-40 is outstanding. Two large knobs on the front panel provide smooth antenna and final tuning. Between them is a switch for the easy-to-read front-panel meter with a D'Arsonval movement that indicates final grid or plate current. The function switch is at the lower left, providing selection of off, tune, standby, phone and CW. The drive control is in the center. The key jack is at the extreme left, and a pilot light is at the extreme right. Its attractive and professional appearance is in keeping with the fine operation it can provide for you in your ham shack. You can build this rig yourself and be proud to show it off to your fellow hams. Assembly instructions are complete in every respect. The manual contains complete step-by-step instructions that are tied-in closely with large pictorial diagrams, to prevent costly mistakes. Assembly proceeds smoothly from start to finish even for an individual who has never built electronic equipment before. Whether you are a newcomer or an old-timer, you will find the DX-40 a very worthwhile addition to your ham shack. Shpg. Wt. 26 lbs.

Specifications—Power Input... 75 watt CW, 60 watt peak controlled carrier phone. Output Impedance... 50-1000 Ω. Output Coupling... Pi network (coaxial). Operation... Crystal-VFO, CW, Phone. Band Coverage... 80, 40, 20, 15, 11, 10 meters. Tube Complement... 5U4GB Rectifier, 12AX7 Speech Amplifier, 6DE7 Controlled Carrier/Modulator, 6CL6 Crystal Oscillator, 6CL6 Buffer, 6146 Final Amplifier. Power Requirements... 117 volts AC, 60 cycles, 175 watts. Cabinet Size... 13" wide x 8½" high x 9" deep. Net Weight... 21 lbs. Shipping Weight... 26 lbs.

Back to Ham Radio Kits

Copyright ©2023 by Cyberventures Unlimited.Terms of Use