Author Topic: Analog TV Transmitter Teardown Teaser  (Read 28354 times)

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Offline free_electron

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Re: Analog TV Transmitter Teardown Teaser
« Reply #50 on: January 05, 2014, 11:16:30 pm »
Here ya go

plus : fold the rear seats down, combine it with the 'frunk' and you can drag in massive hauls of equipment (in style)
« Last Edit: January 05, 2014, 11:22:33 pm by free_electron »
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Offline calexanian

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Re: Analog TV Transmitter Teardown Teaser
« Reply #51 on: January 05, 2014, 11:40:23 pm »
What year is it?

1985

no.. it cant be that old! Interior looks too good.
Charles Alexanian
Alex-Tronix Control Systems
 

Offline (In)Sanity

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Re: Analog TV Transmitter Teardown Teaser
« Reply #52 on: January 05, 2014, 11:41:03 pm »
Here ya go

plus : fold the rear seats down, combine it with the 'frunk' and you can drag in massive hauls of equipment (in style)

LOL,  same color as the one that blew past me in my former SLK.   Ok,  I miss the power.  But love the MPG.    Better off with MPG.   I actually thought about buying a Model S until I realized I would just be trying to compensate for something.   Better off spending the extra money on more solar power and/or solar hot water. 

Jeff
 

Offline dr.diesel

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Re: Analog TV Transmitter Teardown Teaser
« Reply #53 on: January 05, 2014, 11:41:44 pm »
Here ya go

You mailing your new ride to Dave?  :-//

Offline Driver

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Re: Analog TV Transmitter Teardown Teaser
« Reply #54 on: January 06, 2014, 08:14:16 am »
Long time viewer, first time poster... Good to see ch7 give away the gear like this!

Any ETA's for broadcast? :D
 

Offline williefleete

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Re: Analog TV Transmitter Teardown Teaser
« Reply #55 on: January 06, 2014, 03:53:46 pm »
Can't wait to see all the high power RF porn, dave was practically creaming his jeans at the rails on the rack mount stuff
im a picaxe fan particularly the 08M's
 

Offline echen1024

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Re: Analog TV Transmitter Teardown Teaser
« Reply #56 on: January 06, 2014, 04:40:31 pm »
What Dave REALLY wants is the Model X SUV. That way, he can haul all types of gear, and, with the top battery, he won't have the embarrassment of saying "This oscilloscope is more expensive than my car."
I'm not saying we should kill all stupid people. I'm just saying that we should remove all product safety labels and let natural selection do its work.

https://www.youtube.com/user/echen1024
 

Offline DeepThought

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Re: Analog TV Transmitter Teardown Teaser
« Reply #57 on: January 06, 2014, 04:47:01 pm »
EEVBlog pirate radio FTW
 

Offline singera

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Re: Analog TV Transmitter Teardown Teaser
« Reply #58 on: January 06, 2014, 10:10:03 pm »
climbing to the top of the antenna
 

Offline calexanian

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Re: Analog TV Transmitter Teardown Teaser
« Reply #59 on: January 07, 2014, 02:02:40 am »
No thank you! I am so glad we have mountains here in California to put our antennas on!
Charles Alexanian
Alex-Tronix Control Systems
 

Offline vk6zgo

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Re: Analog TV Transmitter Teardown Teaser
« Reply #60 on: January 07, 2014, 03:34:27 am »

It's more than 14 years since I've delved into these beasts,so I might have forgotten some points,but here goes:-

I am most familiar with the NEC Transmitters at TVW7,which have Sync Tip Output Powers of 13kW to allow for various losses in the feed system.

In this generation of NEC's high power Transmitters,the Sound (“Aural” in “NEC- speak”) & the Vision  RF signals do not pass through the same amplifier chain,but are passively combined at the output of the Transmitter.


Valve/Tube PA:-(Vision)


Big tetrodes like the NEC 8F76R can easily provide around 13dB of power gain in Television service,with a Sync Tip Output power of around 13kW.

13dB is a convenient figure,as it translates to a power gain of 20times.,so 13kW output requires 650W of drive to the valve PA.

TRPAs:-

Normally,there is one TRPA driving the Vision (Valve) PA,having in this case an output of 650W,& two,(in TVW7's case) or more TRPAs operating in parallel to provide the Aural Output .

The total output power of the sound carriers combined is approx-10dB w.r.t. Vision Sync Tip power.
The TRPAs are also designed to deliver around 13dB of gain,so in each case require around 32.5W of drive from the exciter.

NEC had extensive experience with  BJT RF PAs in their lower power Transmitters,so these TRPAs are extremely reliable in service.

Modular Construction:-


NEC used modular construction extensively in this series of Transmitters.

An example is  the TRPAs &.their power supplies..
These are situated “back to back”,so that if the power supply fails,it may be removed & replaced with a spare without  delving deeply into the “innards: of the Transmitter.

If a TRPA fails,it can simply have the RF connections removed,& be pulled out of the mounting slot.

Note on Sync Tip Power:-

Analog TV systems,except for very early ones,notably the British 405 line system use so called “Negative Modulation”,where the most negative part of the Video signal,the Sync Tips,corresponds to maximum RF Output Power.

This is very convenient when measuring Transmitter Output Power,as a “peak hold” voltmeter may be used .
It is simple to produce such a device which is hardly affected by the 64uS time between Line Syncs.

The reading is really PEP,but it is much easier to perform in this case,than with SSB.
The relationship between Vision & Aural power can also be determined easily using the same meter,as PEP & Average power of an FM signal is the same.(It does get a little bit messier with the 2 carrier Stereo Sound system used in Australia,but is still pretty close!)

Average power can be determined with greater accuracy using a water cooled Load,with the Transmitter modulated  with Blanking & Syncs.
To obtain an accurate figure for Sync Tip Power using this method,however,it is necessary to very precisely set the modulation,so correction factors may be applied.

I have used "around" & " approx" a fair bit,as no components are perfect,or perfectly stable in their characteristics over time,especially large Power tubes.
A tube may have more than 13 dB Power gain when brand new,& require less drive than it will 20000 hours later!



 

Offline dmm

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Re: Analog TV Transmitter Teardown Teaser
« Reply #61 on: January 07, 2014, 10:29:49 am »
Radio Frequency Systems. I used to personally build and wire those antenna switching frames, in their now no longer existing Broadcast division/factory that was located in Lonsdale, SA.

I was at RFS at Lonsdale as well between 1995 and '98. I designed the wiring for the interlock system on the RF power switch panels, amongst other things. Worked for RFS again in 2003 in their Kilsyth facility.

dmm   :-DMM
 

Offline Ed.Kloonk

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Re: Analog TV Transmitter Teardown Teaser
« Reply #62 on: January 07, 2014, 11:33:19 am »
Tease Me...Tease Me...
 

Offline SeanB

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Re: Analog TV Transmitter Teardown Teaser
« Reply #63 on: January 07, 2014, 03:51:24 pm »
Camel toe song? Don't worry, I do not really want to link to it. GIY if you want.
 

Offline Nickk2057

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Re: Analog TV Transmitter Teardown Teaser
« Reply #64 on: January 12, 2014, 04:23:55 pm »
question.... when you went into the place what did the guy ask you and such? made me think that you are not allowed to be inside that place and he may cite you on a trespass warning or something..... sure fooled the hell out of me... lol
just keep believing in yourself.. you can do some remarkable things in your life when you break through the ice and make things happen with the stuff you make
 

Offline rolandpenplotter

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Re: Analog TV Transmitter Teardown Teaser
« Reply #65 on: January 12, 2014, 04:42:47 pm »
Sooooo... Dave.... when are we to expect this amazing video?


:)
 

Offline station240

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Re: Analog TV Transmitter Teardown Teaser
« Reply #66 on: January 12, 2014, 11:34:18 pm »
5 ton truck you say, you mean like the types you can hire for a hundred something bucks a day that come with a tailgate ?

Fair point about the beryllium warning, same stuff in microwave magnetrons.
 

Offline rolandpenplotter

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Re: Analog TV Transmitter Teardown Teaser
« Reply #67 on: January 13, 2014, 11:46:16 pm »
Considering that "Teardown Tuesday" is normally released on a Tuesday, and that tomorrow is Tuesday, I think (and I hope) that this episode will be released tomorrow.

The suspense is too much!
 

Offline electronics man

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Re: Analog TV Transmitter Teardown Teaser
« Reply #68 on: January 15, 2014, 08:01:48 pm »
So when's it coming dave it was Tuesday yesterday we are still waiting
follow me on twitter @get_your_byte
 

Offline rolandpenplotter

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Re: Analog TV Transmitter Teardown Teaser
« Reply #69 on: January 15, 2014, 09:01:10 pm »
So when's it coming dave it was Tuesday yesterday we are still waiting

Dave is a busy chap - patience is an amazing virtue. He has said, on YouTube comments:



(The comment was under video #568)
« Last Edit: January 15, 2014, 09:02:43 pm by rolandpenplotter »
 

Offline electronics man

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Re: Analog TV Transmitter Teardown Teaser
« Reply #70 on: January 15, 2014, 09:49:49 pm »
Well it's nice to have lots of brilliant vidios over a long time to look forward too
follow me on twitter @get_your_byte
 

Offline rolandpenplotter

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Re: Analog TV Transmitter Teardown Teaser
« Reply #71 on: January 15, 2014, 10:01:36 pm »
Well it's nice to have lots of brilliant vidios over a long time to look forward too

Yup :)

If my desire for electronics is high, but my concentration for practical work is dying off (midnight to 5am), I'll type "EEVblog teardown" or "EEVblog repair" into YouTube, and re-watch some of the many hundreds of videos our Dave has shot over the years; they NEVER get boring. Dave is a man with a family and a young child, and he also manufactures things, and does many other "real life" things which we have no right to know about, since it's his personal business. We all want "more more more!" from him because he is SUCH an amazing teacher... but patience is a REAL virtue, and it's SO easy to forget that what we see of Dave on YouTube is about 1% of his whole life (if that?) - I have to constantly remind myself :)
« Last Edit: January 15, 2014, 10:03:12 pm by rolandpenplotter »
 

Offline CRCasey

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Re: Analog TV Transmitter Teardown Teaser
« Reply #72 on: January 16, 2014, 11:53:55 pm »
I have to say that teaser photo at the end of the video is total wave-guide porn!

Thanks Dave.
 

Offline vk6zgo

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Re: Analog TV Transmitter Teardown Teaser
« Reply #73 on: January 21, 2014, 06:57:48 am »
5 ton truck you say, you mean like the types you can hire for a hundred something bucks a day that come with a tailgate ?

Fair point about the beryllium warning, same stuff in microwave magnetrons.

I may have led you astray with the beryllium.

Eimac/Varian & others do refer to beryllium as an internal component of their tubes,but It may be a blanket "protect your butt" thing,as I seem to remember the older documentation specifically referred to its use in water cooled tubes.

There does not appear to be any necessity for its use in external anode air cooled tubes,as there is no requirement to have an insulating material of high thermal conductivity.
The Anode is what gets hot & the fins are directly connected to it,so no thermal link is required.

There is also no requirement for such material in the external insulation,as transfer of heat from the anode to the other elements is not desirable.
 


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