Eico model 711 "Space Ranger" Receiver

The Eico 711 "Space Ranger" communications receiver is a transformer-operated, single-conversion 455 KHz IF general coverage receiver using 4 tubes and covering 550 KHz through 30 MHz in 4 bands. The receiver also uses silicon diodes in a voltage doubler power supply, has a BFO, bandspread, and an S-meter as well as connections for an external Q-multiplier. Tubes are 12 volt versions of those typically found in a minimalist superhet with no RF stage; 12BE6 as converter, 12BA6 as IF amplifier, 12AV6 as audio preamp/ detector/ noise limiter, and 12AQ5 as audio output. With the exception of the doubler power supply, the circuit, tube choices, and Q-multiplier connection remind me of an updated version of the Heathkit AR-3.

The Eico 711 "Space Ranger" is relatively rare. I purchased this one a a hamfest (amateur radio swap meet). It is the first one I had ever seen. In fact I did not know that Eico had ever introduced a shortwave radio. It is more known for test equipment, ham radio transmitter and transceiver kits, and some excellent Hi-Fi gear. For some examples, see the Eico list category on my home page.

Osterman's book Shortwave Receivers Past & Present lists the Eico 711 in his "Briefly Mentioned" section likely because of its rarity. He notes that it was available for $50 as a kit and $70 built. Its late introduction date in 1967 and the established competition of the Knight-kit Star Roamer and the Heathkit GR-64 kits probably were the reasons for its rarity. It was also priced at about $10 more than the competition. Here is a short column in the July 1967 Popular Science that describes the 711.

The Eico 711 cabinet is more substantial than that of its competitors. In fact, I am almost certain that the front face is made of heavy glass. If not glass, it is certainly one of the toughest plastics I have come across. I tried to scratch the very edge of the front with a screwdriver blade in an attempt to determine if it was glass or plastic. The screwdriver would not leave a scratch leading me to the conclusion of glass. (Update 5-2023, It is tough but not shatter prooof glass as confirmed by a ham who revieved an Eico 711 in a damaged package that had resulted in broken glass.)

Repair notes:
Probably because of its rarity, I could not find a schematic or manual on the web. After some inquiries on net forums, Tyler, KC0YUA, came through with a copy of the schematic and manual pages. Thank you Tyler. The schematic and chassis pictorial are here as a PDF. Send me an e-mail if you need other manual pages.

A former owner had worked on this set and replaced the power cord with a good three wire grounded cable. The set's large electrolytic had been disconnected and several smaller caps had been mounted on a terminal strip under the chassis. I was not pleased with the result and replaced those caps with matching electrolytics for the doubler. Deoxit was sparingly applied to the switches and controls. Most of the other caps in the set are ceramic and did not need replacement. As with any set that started life as a kit, I checked all solder joints and ground connections. Oscillator tracking was checked with a frequency counter.

I found that the rather long wire that connects the main tuning cap with the bandspread cap (visible in the picture above) had been neatly dressed very close to chassis metal adding significant unwanted capacitance when the tuning and bandspread caps were at minimum. I re-dressed that wire up away from the chassis to correct the problem.

Alignment
The IF alignment was close to the specified 455 Khz, but alignment for two of the shortwave bands was off considerably.

Performance
After completing alignment, the results were as expected for a single conversion superhet with one stage of IF and no RF amp. The receiver met expectations as a decent-performing minimalist short wave listener's radio, on a par with its competitors. The variable BFO allowed for relatively easy tuning for SSB on 80 meters. I consider the set to be very good-looking example of 1960s shortwave sets with its front panel which, if not made of heavy glass, certainly looks like it.

Date 3-16-11