High voltage arc gap design

Michael A. Terrell wrote:


In 1945, the FCC decided to move the 42-50 Mcs Original FM Radio Band to 88-106 Mcs (later 88-108 MHz).
Because FM broadcasting would be vacating 42-50 Mcs, TV Channel 1 was moved down to 44-50 Mcs in the old FM band. The TV & FM Radio Allocations which went into effect on February 25, 1946 (mybd), were as follows: .
New FM radio band: 88-106 Mcs
Channel 1 44 - 50 Mcs Channel 2 54-60 Mcs Channel 3 60-66 Mcs Channel 4 66-72 Mcs Channel 5 76-82 Mcs Channel 6 82-88 Mcs Channels 7-13 as presently assigned
Although several television stations were scheduled to move to to the new Channel 1, no TV stations ever broadcast on 44 - 50 Mcs.
It could not be used immediately because it was necessary for all existing FM stations to move out of the 42-50 Mcs spectrum to the 88-106 Mcs FM Band.
When all the FM stations finally did move, the FCC decided to re-allocate 44 - 50 Mcs to other services. Thus, Channel 1 disappeared.
There was no renumbering of the remaining channels.
--
Virg Wall, P.E.

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VWWall wrote:

...that is a rather HIGH voltage arc gap...
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wrote: | | "Paul Hovnanian P.E." wrote: |> |> "Michael A. Terrell" wrote: |> > |> > Robert Baer wrote: |> > > |> > > From reliable soft failure analog to crappy on/off digital. |> > > TV is the first frontier... |> > |> > That spectrum had value for other uses. A 1 Mhz slice at the bottom |> > end is fairly useless for anything other than local radio service. It |> > also has very different propagation, and is reserved for radio by |> > international agreement, because it can easily cross multiple borders. |> > With the high background noise in most areas you need a kilowatt or more |> > to cover a small town. The only time I've had clear reception in years |> > was when the whole region was without electricity for 30 miles or more, |> > right after the hurricanes a few years ago. |> |> What spectrum is that? | | | 700 Mhz to 800 Mhz. In other words, everything above Ch 52. | | |> I read a thread some time ago on an hdtv group about what TV stations |> would be doing after the date for dropping analog. Some stations will |> keep their secondary UHF frequencies as their new primary broadcast |> frequencies. But many plan to switch their digital broadcasts to the |> frequency they now use for analog. In other words, it appears that TV |> stations will be spread across the VHF/UHF bands more or less as they |> are today. | | | Not likely. They already lost channels 70 to 83, and Ch 14 in some | areas ( Chicago?) for UHF land mobile service. The DTV conversion is | shaving 17 more channels for the original UHF TV spectrum. Ch 1 was lost | over 50 years ago to land mobile fire and police radio VHF High band | service. | | In less that a year there will only be 51 of the 83 channels assigned | over the years.
Except not channel 37.
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snipped-for-privacy@ipal.net wrote:

Channel 37 is reserved for the alien invasion forces communications network.
They learned their lesson after the Independence Day fiasco. That's when they tried to piggyback their signals on our satellite system. Jeff Goldblum managed to intercept and hack their command and control infrastructure.
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"Paul Hovnanian P.E." wrote:

Sorry guys, but that is just more misinformation being spread by the alien's pre-invasion force. They control almost all the Sci-Fi publishers, and 95% of Hollywood. The real channel is 42, and NTSC. It's the aliens who are behind the forced conversion to DTV, so no useable TV set will see their signals. :)
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On Wed, 04 Jun 2008 18:18:24 -0700, Paul Hovnanian P.E. wrote:

I wonder why, when they had that captured alien in the cage, and the guy asks, "What do you want us to do", and the alien says, "We want you to die!", the guy didn't ask, "Why?"
Maybe they were emulating CheneyBush and the Ayrabs: "They want us all to die!"
Has anybody asked them "Why?" Could it be because they think we want them all dead, because of the CheneyBush actions?
Thanks, Rich
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Richard The Dreaded Libertarian wrote:

Muslims have stated over and over that there are 3 choices: convert, pay infidel tax, or die. There is a really good chance they actually mean it.. Eric
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| "Michael A. Terrell" wrote: |> |> Robert Baer wrote: |> > |> > From reliable soft failure analog to crappy on/off digital. |> > TV is the first frontier... |> |> That spectrum had value for other uses. A 1 Mhz slice at the bottom |> end is fairly useless for anything other than local radio service. It |> also has very different propagation, and is reserved for radio by |> international agreement, because it can easily cross multiple borders. |> With the high background noise in most areas you need a kilowatt or more |> to cover a small town. The only time I've had clear reception in years |> was when the whole region was without electricity for 30 miles or more, |> right after the hurricanes a few years ago. | | What spectrum is that? | | I read a thread some time ago on an hdtv group about what TV stations | would be doing after the date for dropping analog. Some stations will | keep their secondary UHF frequencies as their new primary broadcast | frequencies. But many plan to switch their digital broadcasts to the | frequency they now use for analog. In other words, it appears that TV | stations will be spread across the VHF/UHF bands more or less as they | are today.
More UHF and less VHF. But the big point is they are juggling around. Some people will need UHF antennas where VHF sufficed (viewers of only the major networks in most big cities). Others will need VHF antennas where UHF was once all they needed. The government needs to set up an antenna coupon program, too.
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| From reliable soft failure analog to crappy on/off digital. | TV is the first frontier...
It is the tradeoff we get for more efficient use of the spectrum.
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snipped-for-privacy@ipal.net wrote:

But how efficient is it to have several hundred megahertz of on-air spectrum used for selling soap, anyway? Couldn't there just be one station in each district running all the commercials and we could get by with much less spectrum, power consumption and overall cost. I'm surprised TV has lasted this long - every time I visit someone with cable, a random flip through the available channels lands on a commercial more than half the time, it seems. Maybe people like watching commercials?
Bill
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They have that, it's called QVC. And it's still not enough. ;-)
Tim
-- Deep Fryer: A very philosophical monk. Website @ http://webpages.charter.net/dawill/tmoranwms
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Tim Williams wrote:

There's always the 'Jesus channels'. When they are able to keep their transmitters on the air, that is.
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Paul Hovnanian P.E. a crit :

You mean they resurrect it (the transmitter) every 33 year?
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List make and model of transmitter. List operating power out. Is this a very old unit or a modern one? what year made? Is it stock or has it been modified?
Step 1: clean transmitter. Blow out dust with compressed air, use dry rag and paintbrush then wipe with distilled water and/or rubbing alcohol. clean all insulators and capacitors. clean transformers and bushings. replace air filters. inspect door interlocks.
Step 2: operate onto dummy load, if no trip then start investigating the antenna system. If fails while on DL start troubleshooting the fault sense circuit.
Observe all safety procedures. If you don't know what these are make will out prior to step 1.
Read manual and contact tech service
Step 3: get power company to monitor the AC for a few days. Inspect TVSS surge suppressor. Inspect main circuit breaker and replace as needed.
Step 4: buy and install new tube
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All else failing, you could just measure the arc-over voltage: ramp up high voltage through a resistor and see when and where she snaps.
That'll give you an answer that covers both questions of gap-setting, and of gap & surface conditions.
Why wonder when you can measure?
Cheers, James Arthur
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Oh, another question: any fried bugs piled up beneath this thing?
Cheers, James Arthur
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;-) At that power level, they tend to vaporize rather than just fall down dead. Used to have a problem with flies getting into the air- variable neutralizing capacitor in a 1kW AM broadcast transmitter, and vaporizing themselves while drawing a pulse of current large enough to engage the over-current relay. Things got more exciting one day when the protection circuits didn't. One of the results was a track melted in the ceramic core of a 200W wire-wound resistor, molten ceramic dripped down on the deck below. Didn't find the fly carcass, though.
Cheers, Tom
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Tom Bruhns wrote:

That's because the fly made an ash out of itself. ;-)
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<snip>
Molten ceramic? That's good stuff! (But don't show this to Tim Williams ;-)
Grins, James Arthur
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James Arthur wrote:

Yeah, Tim will demand a royalty payment from him. ;-)
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