TV Boxes

VHF signal boosters and UHF converters


Television got its start in the U.S. in the Big Cities. In the late '40s and early '50s, unless you lived in or near New York City, Philadelphia, Chicago, Los Angeles, or one of the other major population centers, TV reception was likely to be an iffy thing. There were only about 100 TV stations in the entire US. People put up big rotatable antennas to capture the weak signals from 50 or 100 miles away, and augmented the tuners in their TV sets with signal boosters. These were tunable amplifiers for channels 2 through 13 (channel 1 was dropped in mid-1948) installed between the antenna and the TV set. Almost all had continuous tuning (rather than click-stop channel selectors), so you could peak up the signal just right. After 1952, the number of TV stations rose dramatically, so that by the mid to late 1950s, the vast majority of the US population was within easy reception range of at least one TV station, and boosters fell from popularity.

All the boosters in my collection are tube-type units. The common circuit configurations were either one or two 6J6 dual triodes in either a push-pull or cascode circuit, or a 6AK5 low-noise tetrode. A selenium rectifier almost universally provided the DC supply voltage. The challenge for the engineers was to come up with a circuit that increased the desired signal without adding noise of its own, and do it for a reasonable price. It seems that styling of the cabinets was at best a secondary consideration -- most of these little boxes are pretty plain.

Most of my Booster collection in one photo! Now in their new, dedicated home!

Click Here to go to my Booster collection page.
Alphabetical, with thumbnail photos.

See my WANTED page too! 

 

The first commercial UHF TV station in the US, Portland Oregon's KPTV, received its license and went on the air in late 1952. The FCC had authorized the new TV channels 14 through 83 earlier that year, to relieve the crowding that was occurring as commercial television boomed in the post-war period. To receive the new channels, if any were assigned in your area, you would need a converter for your existing TV set (which of course tuned only 2 through 13). Though the TV set manufacturers were pretty quick to make built-in UHF tuners an (extra-cost) option for their sets, it wasn't until 1964 that the FCC required UHF capability in all new TVs, and 1975 before they had to be as easy to use as the VHF tuners. Add-on converter boxes were therefore the common way to get the additional channels for many years.

Here are some pictures of a few of the 50+ UHF converters I have in my collection. Most are tube-type, with a 6AF4 oscillator and a 1N82 (or similar) germanium diode mixer being the usual active components, plus a selenium rectifier for power. Fancier models included an output "IF" amplifier tube. By the 1960s, solid-state (transistor and tunnel-diode) models were available. All are continuous tuning (no click stops for each channel), and convert the UHF channels to VHF channel 5 or 6. RF preamplifier stages are unknown to these UHF converters; the only tubes initially available that would amplify the 400-900 MHz signals were either too noisy to improve the picture, or too expensive.

UHF converter manufacturers, coming along when TV technology had pretty firmly established itself, had more time and resources to spend on styling. While none of the converters I've seen are anywhere near as stylish as radios of the 1930s, they hold their own in the diminished design environment of '50s and '60s television.

Much of my UHF Converter collection in one photo! (120K file) (It's in attic storage now.)

My UHF Converter Collection
Alphabetical, with basic information, and an increasing number of picture links. 		  UHF Converter Clones
The same models but with several different nameplates.

If you have any old Boosters or UHF converters, or information about them, that you would be willing to donate or sell, please contact me -- perhaps we can do business! See my WANTED page.

In addition, I occasionally have a few units that are excess to my needs, that I offer for sale.

My email address is k8zhd@yahoo.com.

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Updated March 16, 2009 1