The W2AZL Converter

The construction of a W2AZL 2 meter receiving converter was one of my earliest projects and one of a very few early projects to survive until now. The output of the converter fed a 20 meter receiver. I made no changes in the design and the construction information was supplied by W2AZL.

The construction information appeared in the December 1959 QST and I believe later in the ARRL Handbook.

This converter with schematic and layout provided for home construction was "State of the Art" at the time in terms of overall performance and was considered "the standard" for serious weak signal work on 2 meters. It used a couple of somewhat rare (at the time) 417A low noise triode tubes for the RF stages. This tube is still available but at a fairly high cost and is used by audiophiles. The mixer tube is a 404 and the oscillator a 396. When properly constructed the converter noise figure could be adjusted to less that 2 dB.

This particular converter when originally built had a measured noise figure of 1.8 dB (149° K) and it still works great. If I can recall correctly the 417 tube was used in the first stage of the IF amplifier (70 MHz) in the Western Electric/Northern Electric (NorTel) TD2 long haul microwave radio. The tube at the time appeared to be used mainly in the telephone industry.

With today’s modern components a noise figure much lower that 1.8 dB can easily be obtained on 2 meters. This performance increase may not be all that apparent due to the typically high band noise on 2 meters especially in urban and suburban areas.

Here is another W2AZL converter. This one was built by VE6JF who did a great job putting it together. It also had a measured noise figure of 1.8 dB.

While we are on the subject of 417 converters here is a 6 meter converter that I have using these tubes.

This one was built by Don Watters (SK) and his call sign at the time was VE2HW. It may be the only one of this design made. It uses two 417A tubes as RF amplifiers and a 6U8 mixer/oscillator.

Revised August 21, 2011

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