High voltage arc gap design

Ouch! That close, did that person live through that/et seq.?

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.

| 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.

| Feh. Examine the remains of three 20 kV lightning arrests mistakenly | connected across a 66 kV transmission line. | | The fireball looked pretty cool too. But not to the lineman who was | standing practically underneath them closing the switch.

Wish you had videos/pictures.

Which kind of mistake was make? Wrong type of protectors? Wired the wrong way?

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

They have that, it's called QVC. And it's still not enough. ;-)

Tim

-- Deep Fryer: A very philosophical monk. Website @

It was a portable substation, mounted on a semi trailer, used when it was necessary to de-energize a fixed station for maintenance.

The portable unit has a high side switch, lightning arresters, high side fuses, a transformer and low side breakers. The transformer has primary and secondary windings with taps so that it can be reconfigured for multiple uses. The substation maintenance group's responsibility is to reconfigure it as we specified and then our crews connect and energize it.

The substation group took a unit that had previously been used for a 12 kV to 4 kV step-down and rewired it for 66 kV to 12 kV. They did a turns ratio test to verify the work and then shipped it.

Unfortunately, the lightning arresters consist of three 20 kV units per phase, stacked in series. When this station had been used with a 12 kV input, the bottom two sections of each phase were jumpered to ground. Nobody noticed this (there's a whole story behind the problems at this utility that lead up to this f*k-up worthy of another post.

When the unit was delivered, due to its construction, nobody could see the jumpers. Our crew hooked it up and, Blam!

To answer Joseph's question, nobody was hurt. The handle of the high side switch was accessible by swinging a panel up. Our (tall) lineman bitched about this, having to bend over to operate the switch. But the end result was that he was standing underneath a steel roof.

The portable substation was well grounded, so nobody got shocked.

It was quite an event. I was standing about 100 feet away. After the initial fault, the system breaker (about 20 miles away) de-energized the entire line. We stood there for a few seconds and, just as a few people were thinking about walking up to it, someone shouted, "Wait for the reclose!" Sure enough, the system operators had neglected to disable the reclose operation. About 15 seconds later, another fireball.

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.

There's always the 'Jesus channels'. When they are able to keep their transmitters on the air, that is.

700 Mhz to 800 Mhz. In other words, everything above Ch 52.

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.

Wow. Only one reclose? Or was some system monitor person really on the ball?

You mean they resurrect it (the transmitter) every 33 year?

On Jun 1, 7:58 pm, "Michael A. Terrell" wrote: ...

You're quite sure about that, are you?

Cheers, Tom

I don't think it was lost, They just didn't use it because it falls on the IF freq of the receiver or close to it.

But then again, I could be incorrect there.

"

I meant VHF low band, 30 to 50 Mhz. What do you expect when I can't sleep more than a few hours a day? :(

There's a nice, though I don't know how accurate, history of USA's Channel 1 at

Back that early, I don't know if there were any TVs using a 45MHz IF; early ones used 21MHz, or thereabouts, much to the consternation of amateur operators wanting to transmit on the 15 meter band.

Now how did we get to this from "high voltage arc gap design"??

Cheers, Tom

In alt.engineering.electrical 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? | | 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.

In alt.engineering.electrical Michael A. Terrell 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.

| Unfortunately, the lightning arresters consist of three 20 kV units per | phase, stacked in series. When this station had been used with a 12 kV | input, the bottom two sections of each phase were jumpered to ground. | Nobody noticed this (there's a whole story behind the problems at this | utility that lead up to this f*k-up worthy of another post.

Technically, configured wrong. That and inadequate checklist/testing.

I'll look forward to the "another post" some day.

| It was quite an event. I was standing about 100 feet away. After the | initial fault, the system breaker (about 20 miles away) de-energized the | entire line. We stood there for a few seconds and, just as a few people | were thinking about walking up to it, someone shouted, "Wait for the | reclose!" Sure enough, the system operators had neglected to disable the | reclose operation. About 15 seconds later, another fireball.

How long did it take to make the repairs and reschedule the substation maintenance?