On Tuners and UHF Mods/Adapters
 

Perhaps this is a fuitless pursuit, but I'm curious to know whether there is any surviving information on UHF tuner add-ons. By this I don't mean standalone UHF converter boxes, but rather the type that would have been sold as an optional "feature" of one's television set.

There's some interesting information in http://www.antiqueradio.org/art/RCAC...nerArticle.pdf which describes a combination VHF/UHF tuner and how they are two separate parts combined.

The service data for my set even makes reference to an attachment point for a UHF signal in the tuner (http://vintagepc.site50.net/site/fle...ice/TV_004.png).

Presumably if you went for the option when purchasing the set, your dealer could then install the additional tuning mechanism (for sets with separate knobs for each) and special UHF mixer strip in place of one of the VHF channels, and it would feed the output of the UHF tuner to your IF strip.

My curiosity in how this works has me wondering if one could cobble together a functional UHF adapter in this same fashion with the correct reference literature. A schematic of an external converter could be of significant value since it would essentially be doing the same thing.

Was the crude principle behind it (excluding tuning mechanics and such) simply to frequency-shift the UHF station down to VHF frequencies with a simple superheterodyne receiver, or is there more to it than that?

Looking on a certain auction site the standalone ones seem deceptively simple with only one or two tubes. If shipping from the US wasn't often 2-3x the price of these I'd be tempted to pick one up just to see what the insides are like.

Edit: I see a few BTC-99s floating around for a reasonable price. Are those any good? Is there service literature available?

The only sets with strips I know of were Zeniths but never seen
any with them installed.

If a tuner has a UHF IF jack just about any tuner will work.
Just add B+ usually 12 V & antenna, ground the AFT if it has it.
When you go to UHF the VHF RF amp & mixer are just turned into
2 more IF stages. All UHF tuners are cap tuned as far as I know.

The RCA tuner is an odd ball, never seen anything like it.

Some probably had add on kits but with the added costs I
doubt many were sold. The set-top box is the easy way out.

73 Zeno:smoke:

Philco sets had a center mounted (between the two chassis) UHF tuner that was available as a dealer add-on or factory installed. Early 1953 model shown here: http://www.videokarma.org/attachment...4&d=1291836085
I have seen some of the "kits" for this installation on eBay.

jr

That looks nice... and could almost look a match for my own copper plated chassis... Mighty tempted to get one and make it blend in to my own set in a reversible way.

Do they appear for sale often/cheap or are they much sought after by enthusiasts? I only see one at the moment.

I think that is the same listing that I saw a year or so ago on eBay... I suspect that they are not in great demand, although some people *do collect* the cute little set top box UHF tuners. Seems as if somebody here had one for sale.

jr

The eBay seller churrolady from Wisconsin had some original add-on UHF tuner kits (meant for dealer installation, not consumer) in both the RCA and Philco brands over the last year.

.

Standard Coil made UHF strips, for almost every tuner they built. The strips worked a little better in the cascode tuners, but they were available for the penthode tuners as well. They didn't work as well, plus the UHF transmitting power was rather weak. Once they upped the power, they worked fairly well.
I remember, Zenith used strips, more than other firms. In the Neutrode tuners there was a separate set of contacts, just for the UHF antenna.
I could go on and on about UHF tuners, as Milwaukee was a UHF town, from early 1953.

Yes, I bought one of those NOS Philco convertors from churrolady and did a video on it. http://youtu.be/ucJym4IYmpk?t=10m42s

https://farm9.staticflickr.com/8183/...15c1b89313.jpg

WOW! that's a really nice looking pair of Philcos! Interesting that they both have the slide-rule dial rather than the rotary style that both of mine have. I think that mine were both dealer installed... perhaps these are factory? I have also seen another style that is a slide-rule type, but the scale is tilted (prism perhaps), for better viewing from above.
jr

I have this brown metal box set-top converter RCA made. Connects like the Blonder Tongue units but is much older, like the Mallory units with the slide rule tuner and glass dial
Its got two channels, selected by a large gold plastic knob. 3 positions; VHF, UHF1 and UHF2. It definetly uses strips, not a variable CAP tuner.

Most of the towns (beyond fringe of 60 miles from Philly and Baltimore) here had exactly 2 channels, so this set up worked well. You likely could not get UHF more than 35 miles away, with the lower effective radiated power of these UHF's, which always shared call letters with the town's AM stations, in the early 50's.

When power increased and antennas got better:thmbsp:, the markets got larger, so some in-between smaller stations went away.:sigh:

Interesting! Likely a model U2 (Ch KCS79), which can be pre-set to two different UHF channels and outputs on channel 5 or 6. These were also installed (sans cabinet) *inside* various RCA TVs, perhaps a dealer option.
I have a 17" metal cabinet table model RCA 17T200 that has one installed on the right side, just behind and below the speaker.

jr

Interesting. I gather this relied on your tuner being able to oscillate at the correct frequency - so you had to have an oscillator tube that could handle it? Or was it so that nearly all VHF oscillators could work at UHF frequencies?

Also... does anyone have comments on single-tube vs 2-tube UHF converter boxes? I heard folks say the 2 tube ones were better/less finicky, but does that still make a difference for signal quality if you feed it cable?

It seems that the 6J6 was usable at UHF frequencies. Some sets used a 6J6 as a UHF oscillator and they lasted a whole lot longer, than the 6AF4.
Regarding: the set top convertors, the Blonder-Tongue and the Granco one tubers worked fairly well, the Regency's, not very well, if at all.
The hottest two tube units seemed the Turner's and the Radio Receptors.
I don't know how many different brand names that the Mallory's were sold as. :scratch2:

I have my eyes peeled for a BT 99 which seems to be common and cheap.

Alternately... there's probably no reason one couldn't fabricate a UHF channel strip with a 3d printer, a few small brads for the contacts, and some calculations to figure out what the coil inductance should be....

UHF television in the 1950s was crude compared to the '60s to now, as the stations operated with low power on very high UHF channels, 70-83. Youngstown, Ohio's first UHF channel, WFMJ-TV, now on channel 21, for example, began its operations on channel 73. It is safe to say that these early UHF stations didn't have much range, due to their very low ERP outputs.

I did not realize that, in the early days of commercial television, most cities only had, at most, two television channels. However, I do remember seeing early editions of TV Guide and other television listings which, in many cases, showed one station being affiliated with two or more (!) networks. Some stations, located in smaller cities, were affiliated with all four commercial television networks of the time--NBC, ABC, CBS and the now-defunct DuMont network. This was often found in cities which only had one TV station; the programming from each network was carefully selected and was probably rotated from time to time, to fit into the station's broadcast schedule which wasn't that long to begin with; the stations didn't sign on until late in the day, and probably signed off as soon as prime time ended, as there were no local newscasts (as we know them today, anyway) in the very early days of commercial TV.

BTW, I did not realize, either, that Milwaukee has always had mainly UHF TV stations. The city's NBC affiliate, WTMJ-TV, for example, began and is to this day on channel 4. (One station in the city did switch to a UHF channel a couple years ago, when FOX purchased several stations in various cities and switched them to that network.) If there were any UHF stations on in Milwaukee in the early fifties, they may well have been on channels 70-83, which today is no longer used for telecasting, but for land-mobile and probably other non-video radio services.