Commercial TV and Radio transmitters 1

[WoodrowJWeen]

I was just curious. Does anyone know if commercial television and radio stations still use vacuum tubes in the final amplifier stages of the transmitter or are they now solid state?

 

[GOTWW]

Hello WoodrowJWeen, Well I am no broadcast engineer, but the last time I looked into it it was a no hands down winner of the Vacuum tube. There is yet no viable competition in the Power-Linearity-Bandwidth-Efficiency regime. Sure the solid-state promoters sell "gracefull degredation, high reliability, etc." but in the commercial broadcast world that mean "gracefull customer loss", or "gracefull customer loss for the sponsors". Better to have a second tube, with a hot cathode ready to go with a switch of the hand. Sure for some mission critical FAA approach radars and thier 6-foot diameter radial power combiners the solid state may be more appropiate, as the final few seconds of a 747 landing in fog. Sorry fact is that I do not know what triode or klystron tube they are now using. And there is surely a few nickle and dime broadcasters that utilize solid-state transmitter for their limited audiance. But then again I might be wrong.

 

[DanEE]

Both.. depends on what's the best suited for a specific application.

Harris Communications is one of the major suppliers of commercial television site transmitter systems and produces both solid state and tube based transmitters as shown in the links below.

I've installed and maintain some equipment installed at a local television station.. Their analog TV transmitter is similar technology as the Harris DTV solid state below and their new digital HDTV transmitter is "tube", an IOT as discussed in the second link below..

http://www.broadcast.harris.com/product_portfolio/prod_media/platcdbro.pdf

http://www.broadcast.harris.com/product_portfolio/product_details.asp?sku=

http://WWWPOWERCD

 

[SolderingGunslinger]

At the University of Arizona, we have transmitters with solid and hollow state finals. Usually, you will find that low power transmitters use solid state finals and high power transmitters use tubes.

I'll parenthetically decode the acronyms for the non EE types who may lurk.

Harris and others do indeed make high power solid state transmitters, however the additional up front cost usually exceeds the savings (if any) of the solid state devices over the projected life of the transmitter.

High power UHF systems still means tubes. KUAT-DT uses E2V MSDC IOT s (Multi Source Depressed Collector Inductive Output Tubes. A type of klystron.) While the 60+ KW TPO (Transmitter Power Output) could be achieved with FETs (Field Effect Transistors), the efficiency is lower and the initial cost higher than the tubes.

We do have low power TV and DT transmitters which are all solid state. They have the advantage of being less time consuming to tune up when replacing active components, but they also do not appreciate the Summer temperatures which we have in Tucson and require an air conditioned building. The IOTs are liquid cooled and don’t mind the heat of the Sonoran Desert. Aside from being at 8,550-Ft in the Santa Catalina mountains 6,000-Ft above and 20º cooler than the city of Tucson.

I remain,

The Old Soldering Gunslinger