Could that be a signal booster?

[Captain Video]

Seller says he thinks it is. I am interested on buying it, but would like to know for sure. What do you guys think?

http://produto.mercadolivre.com.br/M...r-de-sinal-_JM

[wa2ise]

Might be, hard to tell as it's in some foreign language. But looking at the chassis picture, the power transformer looks larger than what'd I'd expect for the amount of power one tube would consume. It may be missing some parts of it.

Here in the USA we used to have UHF to VHF converter boxes so you could watch a UHF station on an older VHF only TV set. Don't know if other countries had situations like that or not. Maybe this box was one of those.

[Captain Video]

It looks really beat up, I think that maybe there are some parts missing. It is not a UHF converter, we had UHF converters here as well, in the late 1950's and during the 1960's. Those were used only in small towns far away from the big cities; we had no UHF stations back them, but the VHF stations used the UHF band to re-broadcast their signals to the rural areas.

I bought one of those old tube types UHF converters very recently. The tubes do light up, but I don't know if it works or not because I don't have an UHF antenna to hook to it.

My UHF converter is on the pictures below:

[ChrisW6ATV]

Yes, it does look like a TV signal amplifier with one 300-ohm input and two 300-ohm outputs. It looks home-made rather than commercially-manufactured, but I am only guessing.

[Captain Video]

That was one of the first things I thought - that it was home made.

[Sandy G]

I'd vote for home-brew, too.

[kx250rider]

I think it might also be a 1-channel UHF converter. No way to tell without knowing what the tube is.

Charles

[merrylander]

It says right in the first sentence "Amplifier for antenna", what more do you need?

[Captain Video]

Yeah, but look at the rest of his text:

"Amplificador para antena, acho eu. Não tenho certeza o que seja. Quando ligado na tomada uma luz e a válvula acende. Não sei o que é, não testei, não sei se funciona."

Which translated to English means:

"Amplifier for antenna, I guess. I am not sure what it is. When plugged in, a light and a tube lights up. I don't know what it is, I didn't tested it, I don't know if it works."

[wa2ise]

Originally Posted by Sandy G

I'd vote for home-brew, too.

Building a wide band VHF RF amplifier with tubes or other discrete parts requires a lot of skill to pull off and have it be low noise, decent gain, and not oscillate. Whoever may have made it channel specific (which is easier, using tuned circuits), to get some weak station of interest. Strong stations on other channels may get thru with decent enough signal to noise ratio to make it usable to him.

IOW, don't expect a lot of performance if it does work.

[Captain Video]

"IOW, don't expect a lot of performance if it does work."

I know, but that doesn't even concern me. I will bid on it, but I want to have it more for the curiosity aspect of it than for any other reason. I collect not just the vintage TV sets, but also almost everything related to the early days of television.

[hifi_nut]

Por um punhado de Reais vale a pena arriscar, você nunca perderá muito, mesmo que não funcione.



For all of you non-portuguese speaking folks, I just said that for the amount involved Captain Video isn´t risking much, even if that contraption doesn´t work.

[Captain Video]

Haha!!! É verdade!!!

That's true!!!

[merrylander]

Hey, it's my wife who speaks Portugese, not me but the first sentence was a no brainer.

[Old1625]

Originally Posted by wa2ise

Building a wide band VHF RF amplifier with tubes or other discrete parts requires a lot of skill to pull off and have it be low noise, decent gain, and not oscillate...

You aren't kidding! It took me quite a few tries to make a VHF signal booster out of tubes. I finally came upon a push-pull design using a 6AQ8 (IIRC) that worked OK on the VHF high band.

UHF boosting is the zenith of RF amp building art.

The big thing I learned is that if the TV set involved is halfway decent then the only real gain in adding a booster is if it can be placed nearest the antenna to push the signal down the line.