EEVblog #569 – Tour of an Analog TV Transmission Facility


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.
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25 comments

  1. From 10 mil tracks to 100mm coaxes… Amazing!

  2. Well, this was worth waiting for.

    Thanks Dave.

    -Cecil AA5CE

  3. I guess the combination of high power and RF techniques makes it very impressive even for someone who’s not into power or RF.

  4. Rigid wave guide in this manor has fallen from grace.

    I install Uw systens and the size of those pipes make my head spin. But know consider the price of just those pipes.

    Money.

    -C

    AA5CE

  5. Thanks Dave! Very cool tour of a usually mysterious place for most people.

    Mike

  6. Thanks Dave, what a great video! It is amazing how all this 33 years old gear is kept in such a pristine condition. No dust, no oxidation, no scratches, not even yellowed paint or plastic. No wonder it still worked well until it was turned off.

    BTW what’s the service life of that 5KW valve? I guess this is one of the very few parts that needed a periodic replacement.

    Hint for the next video: a sneak peak into one of those little houses standing next to the large cell towers 🙂

  7. I am still impressed and speechless that you could just walk into your TX facility, get their transmitter, get a guided walkaround, an even take the TX modulator home. All that even without advance notice. “Brilliant”, “OMG” or “WOW” does not even come close to express my feeling about that.

    I would assume that I would get into prison if I tried that in here …

  8. Love it! thanks Dave / David 😛

  9. Loved seeing all the plumbing!
    Well done Dave, thoroughly enjoyed looking into the bowels of the now extinct analogue television transmitter. It’s great to see the fine engineering that has gone into these things as opposed to the built in obsolescence that is seen everywhere these days…

    Cheers!

  10. Absolutely fantastic, David seemed to be a good host showing you around ,I really enjoyed the video .
    Paul de M0BSW

  11. Great stuff, Dave!

    I was kind of surprised how your host just reached into that PA cavity without using the shorting stick first. Yeah, the thing had been powered down for a few weeks, and the interlocks/bleeders SHOULD remove the plate voltage, but like most passive safety devices you should never rely on them. Complacency can kill around equipment like that.

    Did you grab one of the PA valves along with the rest of the stuff? They make a nice desk ornament or doorstop if nothing else. I have a 6166 in my valve collection, which is a similar tetrode used in RCA TV xmtrs. About 20 lbs of silver plated copper in the anode radiator…

  12. Beautiful.

    Just goes to show that past a certain point you can’t avoid needing a plumber rather than an electrician.

  13. A. Ma. Zing. Arm thick copper “pipes”. Serious business going on here. Precision modulated signals at currents big enough to melt metal. Thank you for this!

  14. OUTSTANDING!!

    As an RF enthuasiast, it was fantastic to see all that high power stuff in an installation normally well out of reach to most people.
    I am surprised that you were allowed to film in there at all!

    Thanks Dave for going up to the site and making that very interesting vid! An excellent effort.
    And you got a nice piece of rack gear to keep.
    I can only hope that some of that gear shows up on a Hamfest table somewhere!

    A Big Thankyou from BigAdam!

  15. Great video, thanks Dave and David for providing a unique view into the world of high power RF. This was the most enjoyable programme I’ve seen in while, two thumbs up!

  16. Great video, love this kind of stuff.

    Sort of reminds me of the WLW 500kW AM transmitter tour video (from Dayton Hamvention 2013): https://www.youtube.com/watch?v=CbHjcwIoTiY

    • Hello EEV Bloggers!

      Sorry a long one….

      Just scroll down to the other comments to save time with mine!

      But if not ..then read on…

      First of all just let me say that this is the first time I’ve had (or seen by video) any guided tour around any transmitter site.

      I am a UK amateur (G4GVV) but preferred to keep my identity as “Simon” on the “sign in” (but you can look me up on QRZ if you really want to and there won’t be much to see!)

      Both Dave’s video and the Dayton one (from Craig) have certainly opened my eyes to particular things and have prompted me to ask more questions!

      Here goes..

      First the copper/brass Ag plated coax transmission lines etc, perhaps someone can answer this.

      Dave Kilkpatrick talks about pressurising the final feeder for a medium power VHF installation with “dry air” mainly for purposes of moisture rain exclusion, and that makes sense.

      BUT in the BIG AM/LF transmitters (50kW/500kW up) were these coax tubular coax lines ever water cooled?

      I know the valve/tube anodes were, but the very nature of those coax feeder tubes, looking like central heating pipes suggested they could be water cooled as well lowering conductive ohmic/skin losses, especially at LF where the lower dielectric losses could be tolerated.

      Perhaps the dielectric loss as the result of using water was too much to reclaim, I don’t know.

      (As long as they took the trouble to purify the water with all of those including all of those necessary pyrex pipes! As seen in the WLR video, again something that needed to be considered!)

      BUT the main thing I need to ask relates to the following.

      The circa 1920/30 AM transmitter for WLR in Ohio used a massive modulation transformer (180kVA?)but was a.c coupled(?) to a reactance modulation choke(?) in the anode/plate of the valve/tube (if I’ve understood Craig’s video correctly).

      Now this is my question, at some point in history, “they” realised (I think) that using such huge elements to perform the amplitude modulation of the carrier was wasteful and f…ing inconvenient. (35,000 Lb for a transformer introduces huge logistic problems)

      I learned from a friend of mine back in university some 40yr ago (also a UK ham) that they went away from this modulation method and went on to use TWO quite BIG AM transmitters that were combined together and carrier PHASE MODULATED one against the other so that the two signals would add or subtract by the control of the AF modulation signal to produce the composite AM RF signal for a VERY BIG transmitter.

      Is that why the Sydney analogue TV transmitter used two final class A transmitters (not to be confused with exciters)?

      You would always need to ensure that one of the transmitters was always going to produce a bigger carrier than its “twin” so that there was never going to be greater than 100% modulation.

      (and that’s not even involving the stuff about the quaintly named vestigial sideband modulation used for old style analogue TV!)

      It almost seems (to me) that Edwin Armstrong’s FM system/idea was used by the AM broadcasters (or at least the transmitter engineers) to improve the efficiency of AM TXs.

      Here is my last question (and a boring one at that) when (or if) did phase carrier modulation for implementing AM transmission become the “de facto” means of doing it?

      If I’m wrong and I’m talking garbage, I apologise for wasting your time having to read this but I have a pretty vivid recollection that phase modulation of two AM transmitters WAS used for broadcast AM sites.

      It certainly does away with huge wound components so it must I’m sure it must have been economy driven.

      Just curious.

      Simon (G4GVV)

      • RCA developed their “Ampliphase” phase-to-amplitude modulation scheme for use in AM broadcast transmitters, eliminating the high level audio stages, modulator tubes, and the modulation transformer/reactor. RCA first used this scheme in their BTA-50G 50kW AM rig in 1956. It quickly took over because it greatly reduced the cost of the transmitter, and somewhat reduced the power consumption.

        2 separate RF carrier signals were generated, and the audio input was used to vary the phase relationship between them. Both signals were amplified to ~50% of desired output power, and the signals were combined in the output stage, where the phase variations would cause the 2 signals to add or cancel, producing the final AM output signal.

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

      • No,Simon,both TV Transmitters are complete in themselves,& have equal output power.

        Not all TV sites used two Tx in parallel,some like TVW7 used two Tx which could each supply the needed output
        .
        These were switched day about,with the idle Tx in standby.
        If the active unit failed,the other one would be automatically put to air.

        With the MF AM Transmitters,there were several methods used to replace the old type modulation transformer/choke circuits.

        One is the method you described,but normally it would be done at low level,followed by Linear Amplifiers.

        Another way is to use a balanced modulator to get DSB,then reintroduce the carrier.
        Again Linear Amps were used.

        Thirdly,various versions of transformerless High Level modulation.

  17. Many kudos for David Kilpatrick for excellent explanation!

    I’ve been watching this video open mouth from amazement. Thanks Dave for arranging the video tour!

  18. Awesome! I really enjoyed this video, many thanks.

    I don’t suppose I can ‘suggest’ the transmitter go to the kurrajong radio museum after you have finished with it ? There’s a lot of interesting kit out there. I have no association with the museum beyond being an interested HAM.

    I’m looking forward to the teardown.

    Cheers

  19. Awesome video, Dave. Loved it.

    Reminded me of a few years in my youth when I was an airborne radar technician aboard the E-3 AWACS in the US Air Force. Our radar transmitter was a 4 stage affair, with exciters in a cabinet in the cabin —> flex coax to the aft lower compartment, to a solid state primary amp of ~200 watts —> flex coax to a traveling wave tube secondary of ~2,000 watts —> waveguide to a massive tertiary klystron power amp of [classified] watts —> waveguide up the pedestal to the rotating phased array antenna on top.

    The klystron was in a containment vessel about the size of a VW Beetle and was cooled by an ethelyne glycol and water (EGW) mixture. We had to achieve a specific outside air temp at altitude before I could radiate in order to guarantee adequate cooling from the heat exchangers. Also had to monitor the conductivity of the EGW to ensure no chance of arcing inside the containment vessel.

    The waveguide went through the sidewall adjacent to my control station, and there was a big manual shunt switch in the line that redirected the output to a dummy load for testing and to ensure we didn’t sterilize everyone aboard the tanker during refueling! I’ll never forget the sound of that dummy load absorbing the massive power from the transmitter. It was like a monstrous nest of angry metal hornets buzzing around inside a copper can. I always imagined myself bursting into flames if that waveguide failed!

    Anyway, enough reminiscence. Thanks for bringing back the fond memories, Dave. I still miss that job; one of the best times of my life…

  20. Awesome subject and video, thanx a million David ( a friendly man 😉 ) and Dave.

  21. That was an excellent video. Thanks for sharing!

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