Radio Receptor C1709-P UHF Television Converter (1950s)

     

Have you ever bought a TV or radio that was truly "new in the box" (NIB)? I was delighted to find this Radio Receptor UHF television converter complete in its original box.

It clearly had never been used. There wasn't a single fingerprint anywhere, not to mention any marks of day-to-day wear. The original power cord was still pliable, whereas many of that vintage would be brittle and cracked. All the controls worked smoothly, and when I carefully powered it up, it worked exactly like a brand-new unit.

Who Needs a UHF Converter?

Soon after World War II, the United States settled on a set of VHF (very high frequency) television channels, numbered 2-13. These channels are still used all over the United States. The earlier channel 1 was discarded, although some early TVs, such as my 1946 RCA 630TS and 1948 Hallicrafters 505, were designed to receive this now-defunct channel.

By the late 1940s, however, those channels became insufficient for crowded population areas. In 1949, the Federal Communications Commission proposed to add dozens of new UHF (ultra high frequency) channels, which would supplement the existing VHF frequencies and permit additional TV channels within a given broadcast area.

The new UHF scheme was finalized in 1952, and on September 18, 1952, station KPTV in Portland, Oregon became the first commercial TV station to broadcast in the new UHF band.

Other stations slowly followed suit, but UHF broadcasting remained spotty until 1964, when the FCC mandated that all US televisions must receive UHF as well as VHF broadcasts.

This chronology defines the 12-year window (1952-1964) during which UHF converters such as the Radio Receptor found a market niche. For a fraction of the price of a new television, you could hook one of these up to your old VHF-only TV and receive the new UHF broadcasts.

How Does it Work?

On the front of the converter are two knobs, as the first photo shows. The left knob lets you turn on the converter and switch between VHF and UHF reception. The right knob tunes in UHF channels.

Connecting the converter is very simple. On the back of the converter, you connect separate VHF and UHF antennas. Using ordinary antenna wire, you connect the converter's output to the antenna terminals of your VHF TV.

When you choose VHF, the converter simply passes the signal through to the TV, so you tune the TV normally, choosing VHF channels 2-13. To receive UHF broadcasts, you switch your TV's VHF tuner to channel 5 or channel 6 (whichever one is unused in your area) and use the right knob of the converter to tune in UHF channels 14-83.

The model number on my converter is C1709-P. The Radio Receptor company, which was based in Brooklyn, New York, supplied the same unit to several different retailers, including Silvertone, DeWald, Co-Ax, and Truetone, who relabeled the cabinet but changed nothing inside.

The next photo shows the chassis removed from its cabinet. As you can see, the internals are shielded inside metal cages.

This converter uses three miniature glass tubes: a 6X4 rectifier, a 6AF4 oscillator, and a 6BK7 IF amplifier.

After purchasing this converter, I hooked it up between an antenna and my Philco Predicta television, then slowly powered it up using a variac. It worked nicely, tuning in clear signals over the entire UHF band. I subsequently tried it out on my restored RCA 630TS and it performed just as well. Here is a snapshot of the Radio Receptor in action.

(Note that in real life, the TV screen is not as washed out as it appears in this photo. My digital camera automatically adjusts for the background lighting, making the picture appear much too bright.)

Following those initial flight tests, I retired the Radio Receptor to a shelf in my office, where it will remain unused until I decide whether to replace its original capacitors or simply leave it untouched. There's something appealing about leaving an unsullied original completely as found.

If you're curious about early television converters and boosters, don't miss Mark Nelson's TV Boxes website. It's the best, and as far as I know, the only, Internet resource for these interesting little devices.

2011 Update: Now that the United States has switched from analog to digital TV broadcasts, the utility of analog UHF converters has almost vanished. However, there are a handful of low-power UHF stations still broadcasting analog signals in North America. You can use the AntennaWeb website to find TV stations (both digital and analog) in your area.

©1995-2014 Philip I. Nelson, all rights reserved