GMD

The L band 1.6 Ghz auto tracking meterological telemetery receiver I maintained at age 17. It used a “pencil tube” for a local oscellator, had a rotating offset reflector over the dipole at the antenna focus, and could thus automatically track our balloon packages out to several hundred miles at 100,000 ft altitude. Perhaps the reason I ended up maintaining this equipment was that nobody else was foolish enough to go out in -10 degree weather, replace thyratron tubes, and rebalance the servo electronics… but I enjoyed it… 🙂

Here is a GMD-1 I used at Cape Kennedy during Apollo 13

Here is one of their GMD-2s with the fancy parametric preamp and 400MHz ranging transmitter in its radome at Cape Kennedy needed mostly for Arcas sounding rockets that could reach some 200,000ft