EEVblog #569 - Tour of an Analog TV Transmission Facility

[vk6zgo]

It always was Composite video in the old days,as it is a more rugged format than the others,needs only one cable/link channel,& everything is designed for it.

Wasn't it all Betacam in those days? They stored video as separate luma/chroma.

Only inside the machines/tapes-----the workhorse signal format was always Composite in TV Broadcasting.
Domestic & Quasi-Pro stuff played around with different formats a bit,but Broadcasting requires precise timing,& using multiple cables everywhere has the inherent risk of different time delays between the two component signals,unless each one of a cable pair is exactly the same length.

Multiply this by the thousands of Coax runs in a TV Studio!

The other formats could be derived from Composite if you needed them.

At TVW7, the AVA-Graphics suite used RGB for the Pix Monitors,& probably internally ,but the suite output was Composite.

The  Studio Cameras did use various versions of Component Video internally,but what appeared as "Camera Output" to the Vision Switcher input was also always Composite.

Note on Betacams, etc:-

Where I worked,Betacam was used by the News Dept mainly--The large VTRs were mainly reel to reel Sony Helical scan,with some similar Bosch units,& an old Quad scan cartridge unit for Commercials.
Later,Panasonic Digital Videocassette machines (Large Broadcast format) were used.

[SeanB]

Composite works well, you just need a bandwidth of about 15-20MHz and good DC response. I used a potted module made by Opamp Labs for both audio and video distribution. Was a pain to depot the one to fix it when the output stage died. Simple inside, a 709 opamp and a discrete output stage with 2 small signal diodes to provide bias. One of the 2N3904/5 transistors had died, so they were replaced with a 2N2905/2N2222 combo with a new set of diodes. Had to add a small pair of heat flags to the devices as they ran warm, probably what had cooked the originals. It was driving 20 75R terminated video inputs. Might be considered a little high load wise but it did drive it for a decade or so before failure.

[rolandpenplotter]

Well Dave, looks like it's Tuesday again...



*AHEM!*

[warp_foo]

David Kilpatrick did a great tour, easy to listen to and informative. Two thumbs up as they say.

An overall excellent excellent video in so many ways.

He was a good guide, but I can't help feeling he was holding back a bit; he didn't exactly seem enthused and very driven about it (mind you, it's his daily job - he's seen it a thousand times); it may just be the bloke's character though. I loved the video, but I'm more looking forward to being back in the lab, with Dave's infectious excitement and passionate enthusiasm - I'm one for details - EXCESSIVE details, and David seemed to only skim over the basics, although I can appreciate HOW much there is to talk about for a limited amount of time in a place like this... maybe I'm wrong, who knows

I got the exact opposite reaction. Dave¹ asked a question, and Dave² answered quickly and comprehensively. I quite like the interchange between the two.

m

[vk6zgo]

David Kilpatrick did a great tour, easy to listen to and informative. Two thumbs up as they say.

An overall excellent excellent video in so many ways.

He was a good guide, but I can't help feeling he was holding back a bit; he didn't exactly seem enthused and very driven about it (mind you, it's his daily job - he's seen it a thousand times); it may just be the bloke's character though. I loved the video, but I'm more looking forward to being back in the lab, with Dave's infectious excitement and passionate enthusiasm - I'm one for details - EXCESSIVE details, and David seemed to only skim over the basics, although I can appreciate HOW much there is to talk about for a limited amount of time in a place like this... maybe I'm wrong, who knows

I got the exact opposite reaction. Dave¹ asked a question, and Dave² answered quickly and comprehensively. I quite like the interchange between the two.

m

I've done more of these tours than I care to remember,& it is hard to get the balance just right!
Some groups are more technical than others,so you tend to drop some of the more basic stuff.
In this case,there is a wide spread of technical levels.

[Co6aka]

Some may have seen these videos by following YouTube suggestions, but I am watching with my jaw resting on the floor

Not jaw-dropping, but on a related note...

http://englishrussia.com/2014/01/19/the-main-russian-tv-tower/
http://englishrussia.com/2011/08/02/a-visit-to-the-almaty-television-tower/
http://englishrussia.com/2013/08/01/date-with-lena-m/

And, an unrelated teardown: http://englishrussia.com/2013/11/17/disposal-of-old-stuff-in-russia/

[Rasz]

ok then

http://en.wikipedia.org/wiki/Warsaw_radio_mast

highest manmade object until 2008, or 1991 if you count the day it collapsed due to retarded service crew error
 2MW at 225 kHz

YT clips (in Siema language/Polish) show transmitter, glowing tube (50 second mark in first clip), tube teardown, mast itself, collapsed mast (third clip)
http://altao.pl/artykuly/najwyzszy-maszt-na-swiecie-zbudowany-w-polsce–-646-metrow-.htm

[dave_k]

Some may have seen these videos by following YouTube suggestions, but I am watching with my jaw resting on the floor

Not jaw-dropping, but on a related note...

http://englishrussia.com/2014/01/19/the-main-russian-tv-tower/
http://englishrussia.com/2011/08/02/a-visit-to-the-almaty-television-tower/
http://englishrussia.com/2013/08/01/date-with-lena-m/

And, an unrelated teardown: http://englishrussia.com/2013/11/17/disposal-of-old-stuff-in-russia/

Wow! Would love to have seen that Lena M radar operating back in it's day. That installation makes the Ch 7 transmitter look rather pissy.

[GiskardReventlov]

I really enjoyed this EEVBlog episode: particularly David K's contributions. My understanding is that the signal combiner is, in essence, a cavity tuned to the amplified signals. It would be interesting to learn more about cavities and particularly how the input signals are introduced to the cavity, and the output signals derived: are they electromagentically / capacitively coupled with the cavity acting as a form of low loss faraday cage?

I agree here David K. was great (okay he got the acronym wrong for the CIND no big deal) he knew his way around and answered every question.
I also would like to have seen the inside of that combiner. The first time I saw rf equipment I thought all the parts were missing from the inside.

Great video, I've never seen any equipment like that.  I'm not even sure what I was looking at in some cases. I'm still pondering what that was that required the "widow stick"?

[IanB]

I'm still pondering what that was that required the "widow stick"?

If something is charged up to thousands of volts and you touch it you are dead, leaving your wife a widow. So you short it to earth using said stick to make sure it cannot be charged up to thousands of volts before you work on it.

[IanB]

I'm still pondering what that was that required the "widow stick"?

Watch this, if you haven't already:



(Note the comments at 1m55s...)

[GiskardReventlov]

If something is charged up to thousands of volts and you touch it you are dead, leaving your wife a widow. So you short it to earth using said stick to make sure it cannot be charged up to thousands of volts before you work on it.

I know, I know, but what was that part that he pulled out? It was a tube, it had rf shielding, it was heated, they could have told me it was a warp core.
The prop makers could not have made cooler looking stuff than what's there.

They should have dismantled all of it, trucked it to another location and started a geek museum.  My god those UHF waveguides are so amazing. It's heartbreaking to think it'll all be discarded. It really is a work of art and it was the state of the art, no doubt, at the time. Sydney has 4million folks, that could support 1 geek museum. Sydney Steampunk Geek Museum.

[vikpc]

So clean in the facility.. i want to see their air conditioners
And cooper RF tubes looks amazing!

[Moshly]

Here's a few pics of one of the Melbourne Mt.Dandenong towers.

Have a look at the 'rats-nest' of wiring inside the tower 
You can see the 2 coaxes running up the inside left back tower leg

[hikariuk]

If something is charged up to thousands of volts and you touch it you are dead, leaving your wife a widow. So you short it to earth using said stick to make sure it cannot be charged up to thousands of volts before you work on it.

I know, I know, but what was that part that he pulled out? It was a tube, it had rf shielding, it was heated, they could have told me it was a warp core.
The prop makers could not have made cooler looking stuff than what's there.

It was a valve (or vacuum tube, if you prefer).  A very big expensive one.

[GiskardReventlov]

It was a valve (or vacuum tube, if you prefer).  A very big expensive one.

I found out after watching another vid that they cost $30-40 thousand each. They had extras stored in a plain old metal cabinet.
This was the video that Dave said "had stuff they weren't supposed to show" . But I guess it'd take a trained eye to know what stuff that was.

FWIW widow's stick is a.k.a earth grounding stick and probably a lot of others.

[Globe Collector]

  You know the travesty of all this is that all that beautiful gear was probably bound for some scrap metal yard where a "ham-Fisted" yargon was waiting with a ten pound hammer in his hairy paw.
   Dave K. should be "spewing" as you can see those cabinets were his "babies". The only bit which will survive is the exciter that Dave J. walked out with.
    I still can't believe that at least some of this beautifully crafted gear is not diverted to our musea for future generations to marvel at and learn from. Even our electrical engineering schools could benefit handsomely from a bequiethment of such gear, give the next generation a sample of how it should be done.
    Here in Hobart, when Pay TV went digital and to Ku band satellite, the old E-PAL 2.5GHz band transmitter ended up in a scrap yard. I remember seeing the klystron after the Yargon had "adjusted" it, just silver plated rings and cavities all dented and bits of beryllium oxide everywhere.

[GiskardReventlov]

I still can't believe that at least some of this beautifully crafted gear is not diverted to our musea for future generations to marvel at and learn from.

I suggested a museum too. Maybe it's a matter of someone local initiating it, but maybe there's some secret knowledge they want to keep close. It definitely won't happen if nothing's done. Locals clubs should get together and make it happen.  Start a kickstarter campaign?

[dave_k]

Sad to report that the transmitter has mostly been torn apart and scrapped now .. however I have managed to save a few sub-assemblies. Have been scrapping a lot of old analogue TV transmitters, including some German made ones featuring gold-plated tube cavities .. might have to get Dave around to shoot some more videos?

[StjepanV]

Hi there guys/gals!

I have a question what is "filament supply" mentioned at https://youtu.be/mR_wJkxKSXU?t=34m57s . I don't understand what that filament is used for, and how?

@Mods: apologies if I'm posting it in wrong location since there was warning that: this topic has not been posted in for at least 120 days.
Unless you're sure you want to reply, please consider starting a new topic.

[f4eru]

Vacuum tube electronics usually use heated cathodes to have a better electron emission :
https://en.wikipedia.org/wiki/Triode
This heater filaments, like in a light bulb, need a separate supply.