I have been asked if any of the Explorer I recordings were still available in WAV, etc format. There is one posted at http://www.amsat.org/amsat-new/index.php. Select the "Select a Topic" drop down menu and scroll down to "Sounds from the first satellites." There are a few recordings there with the info about the recordings. One of them is the Explorer I telemetry. You will hear several constant audio tones with one of them shifting between two tones. There was a geiger counter on board that counted cosmic ray particles according to the info I have read. After a certain number had been counted the tone shifted and after another quantity had been counted it shifted back again.
The 108 mHz antenna was a six element colinear arrangement consisting of six half waves (wire elements) suspended over a 13x13 ft wooden frame covered with chicken wire laying on the roof of my house. This oriented it up about 75-80 degrees above the southern horizon. No tracking. The satellites had to fly through the main lobe of the antenna pattern.
The receiving arrangement was a modified TeCraft (I think) converter with a 6BQ7 TV RF amplifier front end feeding an National NC-300 Amateur band receiver. Not very good as noise figures go today but pretty good for 1958.
I still have all of the original reel to reel tapes, some of their contents transferred to cassette tape.