Sunday, October 26, 2008

All-Tube DX-100 AM Transmitter

Thousands of these Heathkit transmitters were built by radio hams on a budget back in the 60s, and many are still around in various stages of operation or decomposition. Here is a typical example: Its homely appearance, inept grey on grey paint styling attempts, and general boatanchor aspect make this both a perennial favorite among those who wish to transmit a powerful signal, and a burden.

It weighs about 100 pounds, and getting it up the stairs is a struggle indeed. Opening and servicing are too. There are many faults, aside from the lackluster styling. The VFO is hard to control, the audio quality is so so, the overall construction is crude and the heat it produces is prodigious. This example also has a lot of scuffs and dirt. It only puts out CW or AM. It is ugly. On the front panel, where the mic is connected, it says "mike".

Like many other analog technologies, Amplitude Modulation had its day, went into decline, and now is enjoying a bit of a comeback.

Yet hundreds of these, if not thousands, are still on the air today. Despite the limitations and shortcomings, hams have kept them going and putting out healthy signals. Over time, many modifications have been developed to improve the efficiency and audio quality to the point where they can sound quite good. One of these can cover the entire New England, New York, Quebec and Pennsylvania area, on a good night. A typical microphone for this rig is the ubiquitous D-104.

Is this a gem in the rough, or a permanent boatanchor to be dealt with at an estate sale? Can such as relic be rejuvenated, or is it too late? Zoom in to see the crud and the filth that might be cleaned up with some elbow grease and effort, and creative use of a spray can.

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