EEVblog #569 - Tour of an Analog TV Transmission Facility

[EEVblog]

How long do those big-ass transmitter valves last?

A long time I believe. I think Dave mentioned they are circa $30K each too.

[Icarus]

That's great blog episode man.

[Derick Freese]

Thanks for taking to time to drive up and make this video.  I've been inside a few transmitter bunkers, but never an active one.  This helps me put together what used to be inside, so I can understand what those musty buildings used to look like inside.

[Rasz]

Big thanks to David Kilpatrick for making this tour possible, donating his time and knowledge.

[dave_k]

How long do those big-ass transmitter valves last?

A long time I believe. I think Dave mentioned they are circa $30K each too.

I can check the log book when I am in the office next, and will tell you exactly how long they last! 

Yes, they are not cheap but when you consider the hundreds of staff and thousands of hours worth of effort and millions of dollars in revenue these valves were responsible for putting to air, $30k to $40k is not much by comparison.

[Http 418]

Was hoping to see some more dumpster diving, allthough this wasnt at the EEVblog corporate tower

Great video, sooo much shiny copper Love to see stuff not build down to a price

Thanks to David and TXAustralia to allow us to see the inner sanctums

-Http 418

[JackOfVA]

Many ceramic high power tubes can be rebuilt - in the absence of a major disaster, the normal failure mode is related to cathode emission and there are (or at least used to be) services that would disassemble the tube and replace the cathode, evacuate and reseal and it's good for another 20 or 30K hours. A rebuild would cost 20 or 25% of the price of a new tube, so the cost savings was worth it.

We used to see 20-30K hours in the large AM transmitter tubes.

Perhaps Dave can arrange for an AM broadcast facility tour as well. Parts are much larger there - we had a walk-in phasing network, for example, the size of a large walk-in closet.

Also, it would be interesting to see the other half of the chain - the TV studio where programming is originated. Lots of goodness there as well, but not as high power impressive as the transmitter plant.

[Ketturi]

One of the most pornographic and interesting EEVblogs so far, you don't see that everyday and most of us would never have access to transmission facilities. The EEVblog -Dave should have taken all abandoned hardware that are going to be disposed. Teardowns for next decade   

[atw60444]

Many thanks Dave & Dave_K great stuff I wonder why the reluctance to show the Digital Kit? I can't really think of a reason other than paranoid management 
Mind you, having conducted tours of Telephone Exchanges, the old equipment rattling and moving about is much more interesting to watch than the blank sole-less digital kit with just the whine of cooling fans. Why are the feeders so shiny? Copper usually goes dull brown left open to the air. It's it the atmosphere in the station, does Dave_K spent his spare time with a can of Brasso and a rag? LOL

[hikariuk]

That was awesome.  And well worth the hour of work I didn't do so I could watch it

Also Houston Fearless appear to still exist but they've branched out into other areas.

[wilheldp]

How long do those big-ass transmitter valves last?

A long time I believe. I think Dave mentioned they are circa $30K each too.

Did you snag one of the spent ones?

[vindoline]

Thanks Dave and Dave.  This is one of my favorites. I was surprised at how clean and dust free everything was. Did you guys dust the cabinets before filming, or is the equipment always kept  like that?!

[dave_k]

It is always like that.

[Co6aka]

if they're combining 5 ~10kW transmitters toward the antenna, why is the total output power so low (looked like under 10kW)?

I think Dave said they meter and reference by average power; the HDTV transmitters are QAM. (Think "SSB" -- PEP vs. average power.) Also, combining is lossy, with loss dependent upon the type of combiner, channel/frequency separation, and channel bandwidth. Separation and bandwidth also typically dictate the type of combiner.

(A milliwatt is a terrible thing to waste... )

[VK3DRB]

Thanks Dave and Dave for a great blog. Beautiful engineering throughout. I noticed the SWR meters for the upper half and lower half.

A small goof...

The transmitters hour meter = 100000 + 80275.9 hours. Assuming 167 hours use per week (one hour off per week). That equates to 20.75 years of "continuous" operation. From when the transmitter closed, that would mean the transmitter began its working life in 1982, not 1981 as was stated.

That sort of engineering is what we would find in IBM mainframes of the day. Someone should check out the Thermal Conduction Modules used in the IBM 3090 mainframes. Almost orgasmic in design.

Thanks for the excellent presentation Daves.

cheers,
Yet another Dave

[rolandpenplotter]

Many thanks Dave & Dave_K great stuff I wonder why the reluctance to show the Digital Kit? I can't really think of a reason other than paranoid management 
Mind you, having conducted tours of Telephone Exchanges, the old equipment rattling and moving about is much more interesting to watch than the blank sole-less digital kit with just the whine of cooling fans. Why are the feeders so shiny? Copper usually goes dull brown left open to the air. It's it the atmosphere in the station, does Dave_K spent his spare time with a can of Brasso and a rag? LOL

I agree with your thoughts on moving mechanisms; I've been on a tour of three BT exchanges (one was a UAX13 [or UAX10?] - in my little village where I still live; it's now AXE10, then on a tour of a large TXE4 locally and also a System X about 5 miles away). Of all the exchanges, the Strowger was the most mesmerising and entertaining - I even used to walk up to it at night sometimes, and stand next to the air vent outside, so I could hear the "Clu-clu-clu-clu-clu-clu-clu-clu-CLONK" of the selectors!

I remember, back in the 1990s, our village was upgraded to System Y (Ericcson), and there was a skip outside the exchange FULL of Strowger switches, cable harnesses, power supplies... and a ringing generator which I was given (why did I throw it away... nuts!).

If you've never heard a Strowger exchange, it's high time you did:



The little blue compresser underneath the wall-mounted black telephone, is using the same principle as on the Radio Tx; they blow compressed air into the cable trunks to prevent water ingress & corrosion. The whine you can hear in the background is the ringing generator, which generates all the tones (engaged, equipment engaged, NU tone... etc)

Attached: Ringing generator (cream), cable compressor (blue)

Yes, this was a superb tour, but moving things entertain much more, and that is noone's "fault"

As for the copper being shiny, it's probably lacquered or coated, to prevent corrosion.

[atw60444]

@Roland. Yeah, I guess the feeders are lacquered, but it seems a bit like unnecessary effort.
At risk of getting into trouble for being off topic. I used to maintain Strowger and TXE4 exchanges. And I have a selection of UAX13 racks in the shed, the same as the video.
I'm not weird, honest! 

[rolandpenplotter]

@Roland. Yeah, I guess the feeders are lacquered, but it seems a bit like unnecessary effort.
At risk of getting into trouble for being off topic. I used to maintain Strowger and TXE4 exchanges. And I have a selection of UAX13 racks in the shed, the same as the video.
I'm not weird, honest! 

Ahhh, so you're the guy who used to walk around sweeping up all the metal dust from the switches, hmm?

Oooh! Wanna sell some? (unlikely)

[GreyWoolfe]

Talk about RV valve porn   And who says size doesn't matter!

[Frantone]

David Kilpatrick from TXAustralia takes us on a detailed tour of the old decommissioned 10kW analog TV transmission system at the Artarmon facility in Sydney. How it all works from the broadcaster video input to final transmission output up the 180m broadcast antenna. Plus some teardowns of the old equipment that's been used to transmit the Channel 7 TV signal in Sydney since 1981.
Copper rigid coaxial lines, waveguides, filters, splitters, combiners, converters, transmission valve, power supplies and all the equipment necessary to transmit a 10kW analog TV signal in a major city like Sydney.

Beautiful one Dave!  I spent some time in my younger days at high power valve AM broadcast radio transmitter sites, and they are (well, WERE) true marvels.  Thanks for the great vid....   

[electronics man]

Great one dave and dave I'm now looking fowerd to the teardowns

[bxs]

@dave_k & @Dave,

Thank you very much  loved it 

[calzap]

Many ceramic high power tubes can be rebuilt - in the absence of a major disaster, the normal failure mode is related to cathode emission and there are (or at least used to be) services that would disassemble the tube and replace the cathode, evacuate and reseal and it's good for another 20 or 30K hours. A rebuild would cost 20 or 25% of the price of a new tube, so the cost savings was worth it.

We used to see 20-30K hours in the large AM transmitter tubes.

Perhaps Dave can arrange for an AM broadcast facility tour as well. Parts are much larger there - we had a walk-in phasing network, for example, the size of a large walk-in closet.

Also, it would be interesting to see the other half of the chain - the TV studio where programming is originated. Lots of goodness there as well, but not as high power impressive as the transmitter plant.

Tube rebuilding services still exist and are doing a good business.   The Econco division of CPI (www.cpii.com) is located near in Woodland, Calif, near me and is going strong.  It's unlikely TX Australia will hand over the old tubes to Dave unless they can't be rebuilt.

Mike in California

[ZeroAviation]

@dave_k & @Dave

Epic video guys! Love the old analog stuff!

[ve7xen]

if they're combining 5 ~10kW transmitters toward the antenna, why is the total output power so low (looked like under 10kW)?

I think Dave said they meter and reference by average power; the HDTV transmitters are QAM. (Think "SSB" -- PEP vs. average power.) Also, combining is lossy, with loss dependent upon the type of combiner, channel/frequency separation, and channel bandwidth. Separation and bandwidth also typically dictate the type of combiner.

(A milliwatt is a terrible thing to waste... )

Hmm yeah, that just seems like a heck of a lot of loss. As far as measuring the power for digital, most digital modulation I'm aware of (no experience with digital TV of course) is designed to have a flat power envelope, so I'd expect the power output stays fairly constant, thus not needing differentiation between 'peak' and 'average' power output. Average or peak, I was still expecting to see at least a couple 10s of kW heading to the antenna with 50kW of transmitters.

However because of the whole flat power envelope thing, it wouldn't surprise me at all if the average power of the digital broadcasts is much, much lower than the 10kW peak of the old AM stuff, which would explain the 'low' output.