Nuts and Volts - August 2015

I am thrilled to see that there were four very informative and very well written articles on radio.

For J.W. Koebel's article, "Fix Up That Old Radio," I saw the mention of the fact that pre-WW II radios had DC power provided by the radio to the speaker to energize the electromagnet in the speaker.

A bit of a warning here. About

20 years ago from the "School of Hard Shocks," I learned these radios have a lot of dangerous voltage on the speaker field wire (90 to 250 volts).

I found out the hard way while checking out the innards (a lot larger and more component-laden than the De Wald 618) of a cabinet radio for a coworker who was finishing the cabinet.

I didn't measure the voltage with a regular meter, but my "skin meter"

said REALLY HIGH and biting.

Tim Brown N&V Q&A

Good point, Tim. I had one of these old speakers and know exactly what you mean. Also, a good way to learn XL = 2piFL is if you disconnect the speaker while energized (my skin meter registered that, as well)

Bryan Bergeron

Radio and Rockets

I found Bryan Bergeron’s editorial on amateur radio interesting. I agree with him on the points he made.

I would like to take the time to call attention to an increasing use of amateur radio: model rocketry.

It has been done in the past, but I’d like to call specific attention to the efforts of Bdale Garbee and Keith Packard in producing Arduino-based open source flight computers for model rockets. I have no financial connection to the Altus Metrum company but have had the privilege of attending launches where Altus Metrum products were in use, and sometimes Bdale and Keith were there developing stuff.

GPS coordinates of the rocket’s location and throughout the flight are relayed to ground via telemetry using one of the ham bands. This link — altusmetrum.org —should take you to more information that could/should be part of a future application/article of amateur radio.