Toshiba TV29C90 problem; Image fades to black...

[Bob Shuman]

Batteries Plus with many retail locations sell them for a fair price as
well.

Bob

"James Sweet" <jamessweet1@trashmail.net> wrote in message
news:fLtWj.1516$i51.747@trndny09...

Brian wrote:
Michael Kennedy wrote:

Note: Some SmartUPS units require 24 volts.. i.e. 2 12v batteries in
series to run.

Yes, this unit has two 12V batteries. New ones are on order! Shipping
is more than the batteries themselves ... they are heavy.

-Brian


Did you check locally? Many places carry a selection, Frys had a whole
shelf of them, I don't recall what the prices were like though.

 

In alt.engineering.electrical Tzortzakakis Dimitrios <noone@nospam.void> wrote:

| Professional washing machines. One of my very first days 'in the field' was
| to connect some of them. They have a large heating element, you can connect
| it single phase, or 3 phase, it just heats up faster (of course) when you
| connect it 3 phase. (they have a single phase motor, so it works also in
| pure 230 V).

If it has 3 elements rated for 230 volts, with 3 separate connections that
would be to three separate phase for a three phase feed, and all connected
to the one phase for a single phase feed, then it should heat up at the same
speed, while drawing three times the current (not accounting for the motor).

I don't know why it should heat up faster in three phase, or why you would
say "of course" about it. I would think it would heat up faster if you took
it over to London and hooked it up to a 240 volt supply.

--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
| by the abuse department, bellsouth.net is blocked. If you post to |
| Usenet from these places, find another Usenet provider ASAP. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |

 

In alt.engineering.electrical Tzortzakakis Dimitrios <noone@nospam.void> wrote:

| Professional washing machines. One of my very first days 'in the field' was
| to connect some of them. They have a large heating element, you can connect
| it single phase, or 3 phase, it just heats up faster (of course) when you
| connect it 3 phase. (they have a single phase motor, so it works also in
| pure 230 V).

If it has 3 elements rated for 230 volts, with 3 separate connections that
would be to three separate phase for a three phase feed, and all connected
to the one phase for a single phase feed, then it should heat up at the same
speed, while drawing three times the current (not accounting for the motor).

I don't know why it should heat up faster in three phase, or why you would
say "of course" about it. I would think it would heat up faster if you took
it over to London and hooked it up to a 240 volt supply.

--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
| by the abuse department, bellsouth.net is blocked. If you post to |
| Usenet from these places, find another Usenet provider ASAP. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |

 

In alt.engineering.electrical Benj <bjacoby@iwaynet.net> wrote:

| Since I'm posting from GoogleGroups I can't respond to Phil, but the
| rest of you can be enlightened.

Actually, I do see the ones the respond to my own posts. I think the reader
does that to keep the threading intact. New posts I won't see. And that is
what most of the spam is (I've seen some spammers that do followups to other
posts).


| In 120/240 or similar systems there is not the freedom to choose this
| ratio. The wiring of the source transformer determines it. As others
| have noted, in the "Edison" U.S. system the source is a center tapped
| transformer with the center tap grounded. This makes a two phase
| system with each 120v "leg" 180 degrees out of phase with the other
| one. The ratio of the high voltage (240v) and the low voltage (120v)
| is always therefore 2:1.
|
| In a three phase system there will be three transformers with
| secondaries (one for each phase) wired in a "star" or "Y"
| configuration. This is necessary because you need the center point of
| the "star" or "Y" to be ground for each low voltage phase. If you wire
| with a "delta" configuration there is no central grounding point
| available for the individual phases. IN three phase circuits the
| relationship between that individual phases to ground (say 120v) and
| the voltage measured between phases is not arbitrary. It is always
| determined by the square root of 3. Hence the between phase voltages
| being sqrt 3 x 120 = 208V. Just like the two phase system these
| ratios are determined by physics and can't be arbitrarily set.

There is no more or less option to choose once you have either system. The
choice you have is between the systems. If you have single phase, you only
get 2.0 as a ratio. If you have three phase, you only get 1.7320508 as a
ratio.


| Of course there is the issue that electric companies often will name a
| voltage one thing while actually supplying an other for small
| variations about the "standard" voltage.

They call it 208 volts, but it's closer to 207.8460969

Precise voltage is not really practical. The voltage standard is a target to
stay near.

--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
| by the abuse department, bellsouth.net is blocked. If you post to |
| Usenet from these places, find another Usenet provider ASAP. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |

 

In alt.engineering.electrical Benj <bjacoby@iwaynet.net> wrote:

| Since I'm posting from GoogleGroups I can't respond to Phil, but the
| rest of you can be enlightened.

Actually, I do see the ones the respond to my own posts. I think the reader
does that to keep the threading intact. New posts I won't see. And that is
what most of the spam is (I've seen some spammers that do followups to other
posts).


| In 120/240 or similar systems there is not the freedom to choose this
| ratio. The wiring of the source transformer determines it. As others
| have noted, in the "Edison" U.S. system the source is a center tapped
| transformer with the center tap grounded. This makes a two phase
| system with each 120v "leg" 180 degrees out of phase with the other
| one. The ratio of the high voltage (240v) and the low voltage (120v)
| is always therefore 2:1.
|
| In a three phase system there will be three transformers with
| secondaries (one for each phase) wired in a "star" or "Y"
| configuration. This is necessary because you need the center point of
| the "star" or "Y" to be ground for each low voltage phase. If you wire
| with a "delta" configuration there is no central grounding point
| available for the individual phases. IN three phase circuits the
| relationship between that individual phases to ground (say 120v) and
| the voltage measured between phases is not arbitrary. It is always
| determined by the square root of 3. Hence the between phase voltages
| being sqrt 3 x 120 = 208V. Just like the two phase system these
| ratios are determined by physics and can't be arbitrarily set.

There is no more or less option to choose once you have either system. The
choice you have is between the systems. If you have single phase, you only
get 2.0 as a ratio. If you have three phase, you only get 1.7320508 as a
ratio.


| Of course there is the issue that electric companies often will name a
| voltage one thing while actually supplying an other for small
| variations about the "standard" voltage.

They call it 208 volts, but it's closer to 207.8460969

Precise voltage is not really practical. The voltage standard is a target to
stay near.

--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
| by the abuse department, bellsouth.net is blocked. If you post to |
| Usenet from these places, find another Usenet provider ASAP. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |

 

In alt.engineering.electrical Thomas Tornblom <thomas@hax.se> wrote:
| phil-news-nospam@ipal.net writes:
|
|> In alt.engineering.electrical Thomas Tornblom <thomas@hax.se> wrote:
|>
|> | Residential power in Norway is normally 230V three phase btw, instead
|> | of 400V three phase. Their 230V outlets are two phase and ground
|> | instead of one phase, neutral and ground. Their three phase outlets
|> | therefore are blue instead of red and have four prongs instead of five.
|>
|> Is this the system where the voltage is 133 volts relative to ground and 230
|> volts between phases (and formerly 127 volts relative to ground and 220 volts
|> between phases)?
|
| Yes.
|
|>
|> If they still use that system, then I'm interested in buying a UPS designed
|> for that. But it is my understanding it is phased out in cities and hard to
|> find anymore in rural locations.
|
| It seems they are moving to 400V as well, but I know many Norwegians
| are paying a hefty premium on their three phase equipment, like
| heatpumps.
|
| My heatpump use an internally star configured 3x400V compressor, and
| it would have been easy to wire it for 3x230V if they had brought out
| all the leads.

If all 6 leads of the 3 windings are brought out separate, then it can be wired
in star for 400/230 volt systems, and in delta for 230/133 volt systems. But
for Europe in general there would be little reason to do that. There is also
no reason to do that in North America, as we don't have any 360/208 volt systems
at all.

If I were in Europe I'd rather than the 400/230 volt system. In North America
I'd rather have the 480/277 volt system.

--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
| by the abuse department, bellsouth.net is blocked. If you post to |
| Usenet from these places, find another Usenet provider ASAP. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |

 

In alt.engineering.electrical Thomas Tornblom <thomas@hax.se> wrote:
| phil-news-nospam@ipal.net writes:
|
|> In alt.engineering.electrical Thomas Tornblom <thomas@hax.se> wrote:
|>
|> | Residential power in Norway is normally 230V three phase btw, instead
|> | of 400V three phase. Their 230V outlets are two phase and ground
|> | instead of one phase, neutral and ground. Their three phase outlets
|> | therefore are blue instead of red and have four prongs instead of five.
|>
|> Is this the system where the voltage is 133 volts relative to ground and 230
|> volts between phases (and formerly 127 volts relative to ground and 220 volts
|> between phases)?
|
| Yes.
|
|>
|> If they still use that system, then I'm interested in buying a UPS designed
|> for that. But it is my understanding it is phased out in cities and hard to
|> find anymore in rural locations.
|
| It seems they are moving to 400V as well, but I know many Norwegians
| are paying a hefty premium on their three phase equipment, like
| heatpumps.
|
| My heatpump use an internally star configured 3x400V compressor, and
| it would have been easy to wire it for 3x230V if they had brought out
| all the leads.

If all 6 leads of the 3 windings are brought out separate, then it can be wired
in star for 400/230 volt systems, and in delta for 230/133 volt systems. But
for Europe in general there would be little reason to do that. There is also
no reason to do that in North America, as we don't have any 360/208 volt systems
at all.

If I were in Europe I'd rather than the 400/230 volt system. In North America
I'd rather have the 480/277 volt system.

--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
| by the abuse department, bellsouth.net is blocked. If you post to |
| Usenet from these places, find another Usenet provider ASAP. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |

 

[Gareth Magennis]

"Adrian C" <email@here.invalid> wrote in message
news:690dsrF2vapreU1@mid.individual.net...

Ross Herbert wrote:

When posters don't include their location it makes it very difficult to
give
information about where to obtain parts local to them. It is often
uneconomical
to buy a single part from organisations such as Mouser using their
shipping
service.

The OP's posting I.P. checks out as Pakistan....

--
Adrian C

And I thought it was only North Americans who thought they didn't have to
say where they live.


Gareth.

 

[Gareth Magennis]

"Adrian C" <email@here.invalid> wrote in message
news:690dsrF2vapreU1@mid.individual.net...

Ross Herbert wrote:

When posters don't include their location it makes it very difficult to
give
information about where to obtain parts local to them. It is often
uneconomical
to buy a single part from organisations such as Mouser using their
shipping
service.

The OP's posting I.P. checks out as Pakistan....

--
Adrian C

And I thought it was only North Americans who thought they didn't have to
say where they live.


Gareth.

 

[Dave Platt]

In article <PxwWj.104$oJ4.3499654@petpeeve.ziplink.net>,
dBc <not_necessary@thanks.com> wrote:

Greetings Jerry..

Interesting situation but not unlike what has been going on for years
in the south SF Bay Area (San Jose). Sutro Tower is towards SF for
about 50 miles while KNTV (Channel 11) is the opposite direction right
in San Jose - behind you. For several years (many years ago now), KNTV
sold a small 2 element antenna that you could mount on your TV mast
and point the opposite direction to your normal TV antenna.

My understanding is that KNTV 11 moved their transmitter site a couple
of years ago.

The old site on Mt. Loma Prieta was shut down in 2006. The new
transmitter site is on San Bruno Mountain, quite some distance to the
north: coordinates 37 deg, 41 min, 07 sec, West Longitude: 122 deg, 26
min, 01 sec.

Back when the NBC affiliation was moved to Channel 11, I had to add a
second antenna in order to pick it up properly (our primary antenna i
a standard log-periodic/reflector aimed north towards Sutro). I made
a single-channel Yagi for Channel 11, aimed it southwards, and merged
the signal to the main coax using a "Join-tenna" single-channel
combiner. Worked like a charm.

Doesn't work worth beans nowadays, since the Yagi towards Loma Prieta
rather than towards Mt. Bruno, and the Join-tenna is blocking the
Channel 11 signal coming in from the log-periodic. All we get on 11
is ghosts and snow. I need to go up on the roof, and either re-aim
the Yagi, or just jumper out the combiner and use the
northwards-pointing log-periodic for all channels - the beamwidth is
probably plenty sufficient.

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

[dBc]

Greetings Dave..

I did mention many years ago now.. To qualify that, how about back in
the 60's & 70's. I see that stations and licenses have moved all
around the place. Back in those days KNTV wasn't affiliated with
anyone since they were an independent station. Consider,
(http://en.wikipedia.org/wiki/KNTV). Heck, I remember when KLIV 1590
(as I recall) in San Jose was playing top 40 rock and roll music - NOT
exclusively news at all. In fact, I was one of those 15th callers
after hearing a certain song that won me a Coke jacket as I remember.
Too many years ago now but I AM curious how many San Jose folks would
ever remember KLIV playing top 40 - probably not many these days..

Those small two-element antennas mounted under the larger TV log are
still on MANY roofs in San Jose. Granted, probably not in the best of
shape but they're there! The twin lead would come from the larger log
down to the two-element Yagi, connect to it before going to the TV
inside the house. After all the complaints of bad video, KNTV did
something about it by offering these antennas - it DID work well!
Further, it was a inexpensive solution. They sold them like hotcakes
back in those days..

Regarding:
"I need to go up on the roof, and either re-aim the Yagi, or just
jumper out the combiner and use the northwards-pointing log-periodic
for all channels - the beamwidth is probably plenty sufficient."

You should try (at least initially) to re-aim it and see if that
resolves the issue. My bet, it will then work like a charm!! The
beam-width on a two-element array is broad as a barn! In fact, if you
were to only move it an inch or so right now, it would probably clear
up considerably. You're probably picking up multipath off of Loma.
Move away from that reflection point, and things will clear up
substantially if not totally. My bet will be totally clear video.

Ah, the things we do to avoid purchasing an inexpensive TV antenna
rotator..

Cheers,
Mr. Mentor




"Dave Platt" <dplatt@radagast.org> wrote in message
news:ronrf5-q35.ln1@radagast.org...
| In article <PxwWj.104$oJ4.3499654@petpeeve.ziplink.net>,
| dBc <not_necessary@thanks.com> wrote:
|
| >Greetings Jerry..
| >
| >Interesting situation but not unlike what has been going on for
years
| >in the south SF Bay Area (San Jose). Sutro Tower is towards SF for
| >about 50 miles while KNTV (Channel 11) is the opposite direction
right
| >in San Jose - behind you. For several years (many years ago now),
KNTV
| >sold a small 2 element antenna that you could mount on your TV mast
| >and point the opposite direction to your normal TV antenna.
|
| My understanding is that KNTV 11 moved their transmitter site a
couple
| of years ago.
|
| The old site on Mt. Loma Prieta was shut down in 2006. The new
| transmitter site is on San Bruno Mountain, quite some distance to
the
| north: coordinates 37 deg, 41 min, 07 sec, West Longitude: 122 deg,
26
| min, 01 sec.
|
| Back when the NBC affiliation was moved to Channel 11, I had to add
a
| second antenna in order to pick it up properly (our primary antenna
i
| a standard log-periodic/reflector aimed north towards Sutro). I
made
| a single-channel Yagi for Channel 11, aimed it southwards, and
merged
| the signal to the main coax using a "Join-tenna" single-channel
| combiner. Worked like a charm.
|
| Doesn't work worth beans nowadays, since the Yagi towards Loma
Prieta
| rather than towards Mt. Bruno, and the Join-tenna is blocking the
| Channel 11 signal coming in from the log-periodic. All we get on 11
| is ghosts and snow. I need to go up on the roof, and either re-aim
| the Yagi, or just jumper out the combiner and use the
| northwards-pointing log-periodic for all channels - the beamwidth is
| probably plenty sufficient.
|
| --
| Dave Platt <dplatt@radagast.org>
AE6EO
| Friends of Jade Warrior home page:
http://www.radagast.org/jade-warrior
| I do _not_ wish to receive unsolicited commercial email, and I will
| boycott any company which has the gall to send me such ads!

 

[dBc]

Greetings Dave..

I did mention many years ago now.. To qualify that, how about back in
the 60's & 70's. I see that stations and licenses have moved all
around the place. Back in those days KNTV wasn't affiliated with
anyone since they were an independent station. Consider,
(http://en.wikipedia.org/wiki/KNTV). Heck, I remember when KLIV 1590
(as I recall) in San Jose was playing top 40 rock and roll music - NOT
exclusively news at all. In fact, I was one of those 15th callers
after hearing a certain song that won me a Coke jacket as I remember.
Too many years ago now but I AM curious how many San Jose folks would
ever remember KLIV playing top 40 - probably not many these days..

Those small two-element antennas mounted under the larger TV log are
still on MANY roofs in San Jose. Granted, probably not in the best of
shape but they're there! The twin lead would come from the larger log
down to the two-element Yagi, connect to it before going to the TV
inside the house. After all the complaints of bad video, KNTV did
something about it by offering these antennas - it DID work well!
Further, it was a inexpensive solution. They sold them like hotcakes
back in those days..

Regarding:
"I need to go up on the roof, and either re-aim the Yagi, or just
jumper out the combiner and use the northwards-pointing log-periodic
for all channels - the beamwidth is probably plenty sufficient."

You should try (at least initially) to re-aim it and see if that
resolves the issue. My bet, it will then work like a charm!! The
beam-width on a two-element array is broad as a barn! In fact, if you
were to only move it an inch or so right now, it would probably clear
up considerably. You're probably picking up multipath off of Loma.
Move away from that reflection point, and things will clear up
substantially if not totally. My bet will be totally clear video.

Ah, the things we do to avoid purchasing an inexpensive TV antenna
rotator..

Cheers,
Mr. Mentor




"Dave Platt" <dplatt@radagast.org> wrote in message
news:ronrf5-q35.ln1@radagast.org...
| In article <PxwWj.104$oJ4.3499654@petpeeve.ziplink.net>,
| dBc <not_necessary@thanks.com> wrote:
|
| >Greetings Jerry..
| >
| >Interesting situation but not unlike what has been going on for
years
| >in the south SF Bay Area (San Jose). Sutro Tower is towards SF for
| >about 50 miles while KNTV (Channel 11) is the opposite direction
right
| >in San Jose - behind you. For several years (many years ago now),
KNTV
| >sold a small 2 element antenna that you could mount on your TV mast
| >and point the opposite direction to your normal TV antenna.
|
| My understanding is that KNTV 11 moved their transmitter site a
couple
| of years ago.
|
| The old site on Mt. Loma Prieta was shut down in 2006. The new
| transmitter site is on San Bruno Mountain, quite some distance to
the
| north: coordinates 37 deg, 41 min, 07 sec, West Longitude: 122 deg,
26
| min, 01 sec.
|
| Back when the NBC affiliation was moved to Channel 11, I had to add
a
| second antenna in order to pick it up properly (our primary antenna
i
| a standard log-periodic/reflector aimed north towards Sutro). I
made
| a single-channel Yagi for Channel 11, aimed it southwards, and
merged
| the signal to the main coax using a "Join-tenna" single-channel
| combiner. Worked like a charm.
|
| Doesn't work worth beans nowadays, since the Yagi towards Loma
Prieta
| rather than towards Mt. Bruno, and the Join-tenna is blocking the
| Channel 11 signal coming in from the log-periodic. All we get on 11
| is ghosts and snow. I need to go up on the roof, and either re-aim
| the Yagi, or just jumper out the combiner and use the
| northwards-pointing log-periodic for all channels - the beamwidth is
| probably plenty sufficient.
|
| --
| Dave Platt <dplatt@radagast.org>
AE6EO
| Friends of Jade Warrior home page:
http://www.radagast.org/jade-warrior
| I do _not_ wish to receive unsolicited commercial email, and I will
| boycott any company which has the gall to send me such ads!

 

[dBc]

Dave..

I should have mentioned that other than KSFO (560 kHz) in S.F. the
local south bay news station back in the earlier days was..

Do you remember what it was?

KXRX was the south bay news radio station. Yes, I realize that it's
not even in the state of Calif. these days. Nor does it have any
history on its Web site. To be able to rack up some free flight time,
my father flew the Peeper-in-the-Piper back in those days with the
late Bob Hallman of KNTV Channel 11 weather giving traffic reports as
my father flew. Later, Bob got his own license and started flying and
reporting on his own. After referencing KNTV history on Wikipedia, I'm
amazed to see no mention of Bob on KNTV alumni. I wonder if those
records are just lost or the company just doesn't keep historical
personnel files. With the transition of owners, I'll bet many a record
is either discarded or lost.

This was about the time my father was flying - perhaps a year or so
before:
http://www.historysanjose.org/exhibits_collections/object_details.php?object=178&exhibit=3&ps=48

Notice ALL the open space at then San Jose Airport - this was _before_
it became San Jose Municipal Airport.

Cheers,
Mr. Mentor



"dBc" <not_necessary@thanks.com> wrote in message
news:mcIWj.109$oJ4.3501235@petpeeve.ziplink.net...
| Greetings Dave..
|
| I did mention many years ago now.. To qualify that, how about back
in
| the 60's & 70's. I see that stations and licenses have moved all
| around the place. Back in those days KNTV wasn't affiliated with
| anyone since they were an independent station. Consider,
| (http://en.wikipedia.org/wiki/KNTV). Heck, I remember when KLIV 1590
| (as I recall) in San Jose was playing top 40 rock and roll music -
NOT
| exclusively news at all. In fact, I was one of those 15th callers
| after hearing a certain song that won me a Coke jacket as I
remember.
| Too many years ago now but I AM curious how many San Jose folks
would
| ever remember KLIV playing top 40 - probably not many these days..
|
| Those small two-element antennas mounted under the larger TV log are
| still on MANY roofs in San Jose. Granted, probably not in the best
of
| shape but they're there! The twin lead would come from the larger
log
| down to the two-element Yagi, connect to it before going to the TV
| inside the house. After all the complaints of bad video, KNTV did
| something about it by offering these antennas - it DID work well!
| Further, it was a inexpensive solution. They sold them like hotcakes
| back in those days..
|
| Regarding:
| "I need to go up on the roof, and either re-aim the Yagi, or just
| jumper out the combiner and use the northwards-pointing log-periodic
| for all channels - the beamwidth is probably plenty sufficient."
|
| You should try (at least initially) to re-aim it and see if that
| resolves the issue. My bet, it will then work like a charm!! The
| beam-width on a two-element array is broad as a barn! In fact, if
you
| were to only move it an inch or so right now, it would probably
clear
| up considerably. You're probably picking up multipath off of Loma.
| Move away from that reflection point, and things will clear up
| substantially if not totally. My bet will be totally clear video.
|
| Ah, the things we do to avoid purchasing an inexpensive TV antenna
| rotator..
|
| Cheers,
| Mr. Mentor
|
|
|
|
| "Dave Platt" <dplatt@radagast.org> wrote in message
| news:ronrf5-q35.ln1@radagast.org...
|| In article <PxwWj.104$oJ4.3499654@petpeeve.ziplink.net>,
|| dBc <not_necessary@thanks.com> wrote:
||
|| >Greetings Jerry..
|| >
|| >Interesting situation but not unlike what has been going on for
| years
|| >in the south SF Bay Area (San Jose). Sutro Tower is towards SF for
|| >about 50 miles while KNTV (Channel 11) is the opposite direction
| right
|| >in San Jose - behind you. For several years (many years ago now),
| KNTV
|| >sold a small 2 element antenna that you could mount on your TV
mast
|| >and point the opposite direction to your normal TV antenna.
||
|| My understanding is that KNTV 11 moved their transmitter site a
| couple
|| of years ago.
||
|| The old site on Mt. Loma Prieta was shut down in 2006. The new
|| transmitter site is on San Bruno Mountain, quite some distance to
| the
|| north: coordinates 37 deg, 41 min, 07 sec, West Longitude: 122 deg,
| 26
|| min, 01 sec.
||
|| Back when the NBC affiliation was moved to Channel 11, I had to add
| a
|| second antenna in order to pick it up properly (our primary antenna
| i
|| a standard log-periodic/reflector aimed north towards Sutro). I
| made
|| a single-channel Yagi for Channel 11, aimed it southwards, and
| merged
|| the signal to the main coax using a "Join-tenna" single-channel
|| combiner. Worked like a charm.
||
|| Doesn't work worth beans nowadays, since the Yagi towards Loma
| Prieta
|| rather than towards Mt. Bruno, and the Join-tenna is blocking the
|| Channel 11 signal coming in from the log-periodic. All we get on
11
|| is ghosts and snow. I need to go up on the roof, and either re-aim
|| the Yagi, or just jumper out the combiner and use the
|| northwards-pointing log-periodic for all channels - the beamwidth
is
|| probably plenty sufficient.
||
|| --
|| Dave Platt <dplatt@radagast.org>
| AE6EO
|| Friends of Jade Warrior home page:
| http://www.radagast.org/jade-warrior
|| I do _not_ wish to receive unsolicited commercial email, and I
will
|| boycott any company which has the gall to send me such ads!
|
|

 

[Dave Platt]

In article <mcIWj.109$oJ4.3501235@petpeeve.ziplink.net>,
dBc <not_necessary@thanks.com> wrote:

Regarding:
"I need to go up on the roof, and either re-aim the Yagi, or just
jumper out the combiner and use the northwards-pointing log-periodic
for all channels - the beamwidth is probably plenty sufficient."

You should try (at least initially) to re-aim it and see if that
resolves the issue. My bet, it will then work like a charm!!

That's certainly the easiest thing to do.

The
beam-width on a two-element array is broad as a barn!

The Yagi I built is somewhere in the neighborhood of 6 elements...
I decided I wanted some real gain and multipath immunity. I scaled
down one of the multi-element beam designs from the ARRL handbook by
around 10:1.

I was rather amazed when I tried it out. Even down at ground level,
with nearby buildings and trees in the way, I got a very clear picture
on 11 just by pointing it towards Loma. Up on the roof it works like
gangbusters.

In fact, if you
were to only move it an inch or so right now, it would probably clear
up considerably. You're probably picking up multipath off of Loma.
Move away from that reflection point, and things will clear up
substantially if not totally.

It has pretty good front-to-back rejection with deep side lobes, so
yeah, I'm just getting a confused mass of multipath backscatter from
Loma Prieta, nearby buildings, trees, and so forth.

Swinging it around towards SFO should certaily do the trick.

Ah, the things we do to avoid purchasing an inexpensive TV antenna
rotator..

Oh, I've got one, and we used to use it quite a lot... but they don't
play well in a household with two independent TiVo DVRs! We really
needed to have "all the signal, all of the time".

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

[Don Kelly]

----------------------------
<phil-news-nospam@ipal.net> wrote in message
news:g0diis02i7i@news1.newsguy.com...

In alt.engineering.electrical Don Kelly <dhky@shaw.ca> wrote:

| Yes -you are shorting a part of the winding but the switching is a bit
more
| complex than that so that short circuit currents are limited to
reasonable
| values. It is a multistep operation with reactor switching. On-load tap
| changers are expensive and are generally limited to applications where
this
| is absolutely needed (I have seen one where the tap changer was nearly
as
| large as the transformer).

I was thinking of what I might do to get some fine voltage control within
a
very limited range around 120 volts. The obvious option was a 0-140 volt
variable transformer. But I wanted to make sure I had a setup that could
be better limited, for example, to not allow an accidental too low
voltage.
I also didn't want to run all the power through the variable. So what I
was going to do was get a smaller variable transformer, and two buck-boost
transformers. One transformer would be wired 120->16 in buck mode to drop
the voltage down to 104. The other transformer would be wired 120->24 and
supplied via the 0-140 variable transformer, giving me a 0-28 variable
boost.
The end result is 104-132 over the full range of variable transformer
control
(assuming the boost transformer has no issues with being overfed at 140V).

So I might envision a transformer where the taps can be part of a boost
transformer added to the main transformer. The first buck transformer in
my above example would not be needed because the main transformer would be
designed with a 1st secondary at the lowest voltage of the adjustable
range.
A 2nd secondary on the same main transformer would have the adjustable
taps
and it would feed a separate boost transformer which has a secondary wired
in series with the 1st secondary of the main. So the taps would only be
dealing directly with a fraction of the power (assuming there is no back
feed issue involved) based on the needed adjustment range.

--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to
ignorance |
| by the abuse department, bellsouth.net is blocked. If you post
to |
| Usenet from these places, find another Usenet provider ASAP.
|
| Phil Howard KA9WGN (email for humans: first name in lower case at
ipal.net) |

--------------
If I read you correctly, you want to use a second secondary (lower power
rating) which is tapped and put in series with the main secondary. Now once
you do this, you have in effect a single secondary with taps just as in a
conventional tapped secondary. Sure the "tapped section" is lower power-
because it is a lower voltage but it still has to handle the same current.
Nothing is gained.
The problem in tap changing is not "power" but the current being switched.

In either case the voltage driving short circuit current on tap changing is
that between taps
Delta V =A(delta n) Delta Z =B(delta n)^2. where delta n is the change in
turns between taps. The short circuit current on such a change will be
proportional to 1/(delta n).

If you want fine control, then you could go to sliding carbon brush as in a
variac. The first idea of a separate transformer feeding a variac will not
solve the "too low" voltage problem of the variac because you are still
dealing with an autotransformer.


Don Kelly dhky@shawcross.ca
remove the X to answer

 

[Michael Moroney]

"daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> writes:

phil-news-nospam@ipal.net> wrote in message
news:g0dt3601543@news4.newsguy.com...

What about multiple parallel transformers, or at least multiple parallel
windings on the same core (on whichever side the tapping is to be done),
where the taps are stepped incrementally on each winding? Instead of a
shorted winding segment, you'd have windings of differing voltage in
parallel as each of the windings change their taps one at a time.

That's still essentially a shorted turn (or set of turns).

So when one is set for say 118V and the other is set for 120V, you have a
118V source connected in parallel with a 120V source and the only impedance
is the transformer windings??

OUCH!!! I think the magic smoke will be spewing in no time

Phil, did you see daestrom's excellent explanation how they use an
inductor to prevent a dead short but in a way such that the inductor is
virtually not there during normal operation (counterflowing currents)?

If these tap changers are rather expensive, I'm wondering what those
pole pig "voltage regulators" I mentioned are. I thought they were just
tapped autotransformers.

 

[William Sommerwerck]

Try BatteryPlex.com.

 

[Jim Yanik]

Sam Goldwasser <sam@plus.seas.upenn.edu> wrote in
news:6wr6c4xyru.fsf@plus.seas.upenn.edu:

Jerry <jerry_maple@hotmail.com> writes:

On May 13, 10:01 pm, Ablang <ron...@gmail.com> wrote:
The only reason Sharp isn't listed here is because they fail
so radically by computer failure, catching on fire, etc. etc.
that no-one has the piece of crap things fixed due to the cost
of getting "hopefully" one more year out of a dead dog.

They ALWAYS fail shortly after warranty.

Not true, mine failed WAY before the warranty was up! <G

Actually, mine was an assembly problem. The flex circuit contact pad
underneath the 4 little jellybean-sized exterior buttons was
misaligned, causing the pressing of the Start button to be a very
hit- or-miss proposition. Flex circuit pad replaced and correctly
aligned under warranty.

I'm still waiting for the infamous post-warranty-display-failure.

The problem with Sharp warranty service is that it's difficult to
find a repair shop that will fix them under warranty. Out of the 5 or
6 warranty service providers listed on the Sharp website for the
Phoenix area, I only found 1 that would do microwave warranty
service. Comments from the other shops indicated that they had big
problems getting paid by Sharp for warranty work.

I guess they've gone downhill....

I have a Sharp Carousel II (not built-in) from 1987 that's still fine,
hasn't needed repairs.

I have a 600W Sharp Carousel from 1979 that I replaced a shorted HV cap
after 20+ years of use,and it's STILL working fine.
It's got a larger cavity than the MWs of today.

--
Jim Yanik
jyanik
at
kua.net

 

[Don Kelly]

----------------------------
<phil-news-nospam@ipal.net> wrote in message
news:g0f7kg211lk@news3.newsguy.com...

In alt.engineering.electrical Benj <bjacoby@iwaynet.net> wrote:

| Since I'm posting from GoogleGroups I can't respond to Phil, but the
| rest of you can be enlightened.

Actually, I do see the ones the respond to my own posts. I think the
reader
does that to keep the threading intact. New posts I won't see. And that
is
what most of the spam is (I've seen some spammers that do followups to
other
posts).


| In 120/240 or similar systems there is not the freedom to choose this
| ratio. The wiring of the source transformer determines it. As others
| have noted, in the "Edison" U.S. system the source is a center tapped
| transformer with the center tap grounded. This makes a two phase
| system with each 120v "leg" 180 degrees out of phase with the other
| one. The ratio of the high voltage (240v) and the low voltage (120v)
| is always therefore 2:1.
|
| In a three phase system there will be three transformers with
| secondaries (one for each phase) wired in a "star" or "Y"
| configuration. This is necessary because you need the center point of
| the "star" or "Y" to be ground for each low voltage phase. If you wire
| with a "delta" configuration there is no central grounding point
| available for the individual phases. IN three phase circuits the
| relationship between that individual phases to ground (say 120v) and
| the voltage measured between phases is not arbitrary. It is always
| determined by the square root of 3. Hence the between phase voltages
| being sqrt 3 x 120 = 208V. Just like the two phase system these
| ratios are determined by physics and can't be arbitrarily set.

There is no more or less option to choose once you have either system.
The
choice you have is between the systems. If you have single phase, you
only
get 2.0 as a ratio. If you have three phase, you only get 1.7320508 as a
ratio.


| Of course there is the issue that electric companies often will name a
| voltage one thing while actually supplying an other for small
| variations about the "standard" voltage.

They call it 208 volts, but it's closer to 207.8460969

Precise voltage is not really practical. The voltage standard is a target
to
stay near.
-------------

Just a bitch that we have dealt with before:

Phil- please realize that 207.846096....... is meaningless except that it is
"about 208". 208V is correct to 3 significant figures which is actually
better than one can assume to be true in practice. If the voltage line to
neutral is actually 120.V (note the decimal) then we have 3 significant
digits implying something between 119.5 Vand 120.5.V
Then all you can truly claim is 208.V
If it is 120.0V then there is reason to assume 208.0 V but no more decimals
than that.
If you have a meter which gives you 120.000000V with less than 1 part in 120
million error then you can claim 207.846097V for line to line voltage Do
you have such a meter?

Engineering and physics students who ignore the principle of "significant
digits" lose marks for this "decimal inflation".

Sure- you can let the calculator carry the extra digits (as it will do
internally) but accepting these as gospel truth to the limit of the
calculator or computer display is simply not on as you can't get better
accuracy from a calculation than the accuracy of the original data (actually
you will lose a bit). All that you get rid of is round off errors in
calculations.

Since, as you say, precise voltage is not really practical, then
multi-decimal point numbers are meaningless. If we say 120V +/-10% then we
are talking about 108-132V which for line to line becomes 187-229V (average
208V) and any extra decimal points don't mean anything.

Don Kelly dhky@shawcross.ca
remove the X to answer

 

[Don Kelly]

----------------------------
<phil-news-nospam@ipal.net> wrote in message
news:g0f7kg211lk@news3.newsguy.com...

In alt.engineering.electrical Benj <bjacoby@iwaynet.net> wrote:

| Since I'm posting from GoogleGroups I can't respond to Phil, but the
| rest of you can be enlightened.

Actually, I do see the ones the respond to my own posts. I think the
reader
does that to keep the threading intact. New posts I won't see. And that
is
what most of the spam is (I've seen some spammers that do followups to
other
posts).


| In 120/240 or similar systems there is not the freedom to choose this
| ratio. The wiring of the source transformer determines it. As others
| have noted, in the "Edison" U.S. system the source is a center tapped
| transformer with the center tap grounded. This makes a two phase
| system with each 120v "leg" 180 degrees out of phase with the other
| one. The ratio of the high voltage (240v) and the low voltage (120v)
| is always therefore 2:1.
|
| In a three phase system there will be three transformers with
| secondaries (one for each phase) wired in a "star" or "Y"
| configuration. This is necessary because you need the center point of
| the "star" or "Y" to be ground for each low voltage phase. If you wire
| with a "delta" configuration there is no central grounding point
| available for the individual phases. IN three phase circuits the
| relationship between that individual phases to ground (say 120v) and
| the voltage measured between phases is not arbitrary. It is always
| determined by the square root of 3. Hence the between phase voltages
| being sqrt 3 x 120 = 208V. Just like the two phase system these
| ratios are determined by physics and can't be arbitrarily set.

There is no more or less option to choose once you have either system.
The
choice you have is between the systems. If you have single phase, you
only
get 2.0 as a ratio. If you have three phase, you only get 1.7320508 as a
ratio.


| Of course there is the issue that electric companies often will name a
| voltage one thing while actually supplying an other for small
| variations about the "standard" voltage.

They call it 208 volts, but it's closer to 207.8460969

Precise voltage is not really practical. The voltage standard is a target
to
stay near.
-------------

Just a bitch that we have dealt with before:

Phil- please realize that 207.846096....... is meaningless except that it is
"about 208". 208V is correct to 3 significant figures which is actually
better than one can assume to be true in practice. If the voltage line to
neutral is actually 120.V (note the decimal) then we have 3 significant
digits implying something between 119.5 Vand 120.5.V
Then all you can truly claim is 208.V
If it is 120.0V then there is reason to assume 208.0 V but no more decimals
than that.
If you have a meter which gives you 120.000000V with less than 1 part in 120
million error then you can claim 207.846097V for line to line voltage Do
you have such a meter?

Engineering and physics students who ignore the principle of "significant
digits" lose marks for this "decimal inflation".

Sure- you can let the calculator carry the extra digits (as it will do
internally) but accepting these as gospel truth to the limit of the
calculator or computer display is simply not on as you can't get better
accuracy from a calculation than the accuracy of the original data (actually
you will lose a bit). All that you get rid of is round off errors in
calculations.

Since, as you say, precise voltage is not really practical, then
multi-decimal point numbers are meaningless. If we say 120V +/-10% then we
are talking about 108-132V which for line to line becomes 187-229V (average
208V) and any extra decimal points don't mean anything.

Don Kelly dhky@shawcross.ca
remove the X to answer