Unknown Legends
With interest, I read the Microwave Legends article in the October issue of Microwaves & RF. I was interested in the history of radar development and I found the book by Louis Brown: History of Radar, the best source of historic information. From other books on radar development, I have foundto my surprisethat Boot and Randall were NOT the first who developed the cavity magnetron with high output power.

Japanese researchers at the Imperial Naval Laboratory succeeded in a similar development some six months before the British. They worked under Mr. Ito. Their magnetron operated by chance also at the 10-cm band. It delivered first ~400 W, later ~2 kW. The Japanese kept it very secret. Their Model 2 radars were sometimes successful but not very reliable.

The Germans used Philips magnetrons in their first radar developed by Kuhnold in 1934-1935. This was the first radar system in the world. Later, German radars mostly operated at 400 to 600 MHz. Microwave radars were copied after some Allied models were captured, but without much success. In my collection, I still keep a German Lorenz magnetron tube for 2 GHz. It delivered some ~200 W pulsed power and was used in an aircraft radar of which I failed to find any details.

Jiri Polivka
Santa Barbara, CA

Thank you so much for educating us on the Japanese radar development. History does have a way of crediting the wrong people sometimes. We will certainly check out the book by Louis Brown. We appreciate you sharing your impressive knowledge on this topic.

In our October FOCUS supplement, the wrong picture appeared with the product write-up titled, "Directional Couplers Span 1 To 18 GHz." The correct photo appears here. The photo that was originally printed showed 50- coaxial-towaveguide adapters from RLC Electronics, which are available in two options. Broadband adapters with option A flaunt superior electrical specifications over the entire adapter bandwidth, depending upon model. Over 7.05 to 10.00 GHz, for example, a WR112-to-N/SMA adapter offers a voltage standing wave ratio of 1.2:1 and insertion loss of 0.07 dB. Adapters with option B deliver enhanced performance over a specific portion of an adapter's bandwidth. For example, for a selected 1.47-GHz portion of a full 7.05-to-10.00- GHz bandwidth, a WR112-to-N/SMA adapter delivers VSWR of 1.1:1 and 0.07 dB insertion loss.

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