magnetic field

[Fred Abse]

On Fri, 01 Aug 2003 18:40:45 +0100, Bob Myers wrote:

In such an environment, technical competence starts to move to having
more to do with operating skills and know-how (e.g., you still need to
know how to interpret what you see on a scope if you want to make sure
you've got a clean, legal signal coming OUT of the box) than the more
traditional "design and build" sorts of skills.

More importantly, you need to know what to do about it if you _haven't_
got a clean, legal signal. To most, these days, I suspect, that means a
trip to the shop.

--
Then there's duct tape ...
(Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx

 

[Cliff]

Robert:



Thanks for your response, I would like to ask for a little more help if you
dont mind, would you happen to know some of the links for the various
circuits published on the web. I tried looking for them but I was not able
to find any.



Thanks.



"Robert Monsen" <postmaster@BulkingPro.com> wrote in message
news:haHWa.45183$Ho3.7272@sccrnsc03...

How far is the plate from the sensor? Another option would be to use a
Sharp
IR sensor, which you can get for about $10 US. They are quite accurate to
about 3m, and can output distance either as a voltage or as a bit stream.

As far as ultrasonic sensors go, take a look at http://www.digikey.com for
parts. They all seem out of your price range, though.

I managed to obtain some ultrasonic transducers from
http://www.allcorp.com
They were cheap, but you'll have to build up a circuit around them to do
the
distance measurement. There are various circuits for this published on the
web.

Regards

"Cliff" <nospam@nospam.com> wrote in message
news:%fAWa.43571$o%2.21604@sccrnsc02...
I would like to measure the movement of a 4x4 inch steel plate as it
moves
towards and away from an ultrasonic sensor.

The basic idea is to have the ultrasonic sensor pointing directly to the
flat 4x4 inch steel plate. The plate would be moving around 2 feet
towards
and away from the sensor.

I don't care about the accuracy of the device; all I care is about the
repeatability of the reading.

I would appreciate if someone could give me a link to such device, I
would
be needing around 60 of them so a cheap sensor would be best (under $25
US
dollars if possible)

I appreciate your help.

 

[Robert Monsen]

The search is 'ultrasonic ranger circuit':

http://www.google.com/search?q=ultrasonic+ranger+circuit

By the way, I was wrong in the original post, the cheap ultrasonic
transducer was from http://www.goldmine-elec.com/.

Regards
Bob Monsen

"Cliff" <nospam@nospam.com> wrote in message
news:2TUWa.50275$uu5.5067@sccrnsc04...

Robert:



Thanks for your response, I would like to ask for a little more help if
you
dont mind, would you happen to know some of the links for the various
circuits published on the web. I tried looking for them but I was not able
to find any.



Thanks.



"Robert Monsen" <postmaster@BulkingPro.com> wrote in message
news:haHWa.45183$Ho3.7272@sccrnsc03...
How far is the plate from the sensor? Another option would be to use a
Sharp
IR sensor, which you can get for about $10 US. They are quite accurate
to
about 3m, and can output distance either as a voltage or as a bit
stream.

As far as ultrasonic sensors go, take a look at http://www.digikey.com
for
parts. They all seem out of your price range, though.

I managed to obtain some ultrasonic transducers from
http://www.allcorp.com
They were cheap, but you'll have to build up a circuit around them to do
the
distance measurement. There are various circuits for this published on
the
web.

Regards

"Cliff" <nospam@nospam.com> wrote in message
news:%fAWa.43571$o%2.21604@sccrnsc02...
I would like to measure the movement of a 4x4 inch steel plate as it
moves
towards and away from an ultrasonic sensor.

The basic idea is to have the ultrasonic sensor pointing directly to
the
flat 4x4 inch steel plate. The plate would be moving around 2 feet
towards
and away from the sensor.

I don't care about the accuracy of the device; all I care is about the
repeatability of the reading.

I would appreciate if someone could give me a link to such device, I
would
be needing around 60 of them so a cheap sensor would be best (under
$25
US
dollars if possible)

I appreciate your help.

 

[Cliff]

Thanks, I appreciate your help.

 

[Patrick Leonard]

Yes yes, I know. Have you seen my post regarding antennas and plasma balls?

The whole idea though is that I want to do it using (already available)
radio signals.

"Wayne Shanks" <wshanks@charm.net> wrote in message
news:4aiXa.253$8C2.32884@news.abs.net...

Patrick Leonard wrote:
So I didn't really get a definitive answer...just a few experiments
which I
tried and didn't work. I gather I'd have to have a giant antenna (or be
really close to the transmitter) for anything to happen.


I guess my post did not get through

Yes you can light a led from an antenna, the antenna must be resonant,
you must be transmitting appreciable power at the resonant frequency of
your antenna, and the feed impedance of your antenna must be matched to
the LED load.


look at
http://literature.agilent.com/litweb/pdf/5966-0785E.pdf

wayne shanks




Anyway, I got to thinking about something. At all times the electrons
in
the antenna are moving back and forth. This motion obviously isn't
enough
to light an LED....but its still motion. Constant motion. And, it would
seem
to me, that if we introduce a *time* element, we could get any amount of
work we want. Sure, at any given moment the amount of energy is
minimal,
but over some arbitrary length of time, we could get any arbitrary
amount of
energy. So what if instead of lighting the LED we just tried to make it
flash?

The question then becomes how can we build up the energy over time?
That's
what I'm now asking: What mechanism could be implemented so as to allow
the
small amount of energy availble at the antenna to build up for however
long
amount of time, in order to flash an LED?

Perhaps a capacitor with several Farad capacitance?

 

[Wayne Shanks]

Patrick Leonard wrote:

So I didn't really get a definitive answer...just a few experiments which I
tried and didn't work. I gather I'd have to have a giant antenna (or be
really close to the transmitter) for anything to happen.

I guess my post did not get through

Yes you can light a led from an antenna, the antenna must be resonant,
you must be transmitting appreciable power at the resonant frequency of
your antenna, and the feed impedance of your antenna must be matched to
the LED load.


look at
http://literature.agilent.com/litweb/pdf/5966-0785E.pdf

wayne shanks

Anyway, I got to thinking about something. At all times the electrons in
the antenna are moving back and forth. This motion obviously isn't enough
to light an LED....but its still motion. Constant motion. And, it would seem
to me, that if we introduce a *time* element, we could get any amount of
work we want. Sure, at any given moment the amount of energy is minimal,
but over some arbitrary length of time, we could get any arbitrary amount of
energy. So what if instead of lighting the LED we just tried to make it
flash?

The question then becomes how can we build up the energy over time? That's
what I'm now asking: What mechanism could be implemented so as to allow the
small amount of energy availble at the antenna to build up for however long
amount of time, in order to flash an LED?

Perhaps a capacitor with several Farad capacitance?

 

[Watson A.Name - 'Watt Sun]

In article
<a8eXa.66722$hOa.22075@news02.bloor.is.net.cable.rogers.com>,
transactoid@rogers.com mentioned...

So I didn't really get a definitive answer...just a few experiments which I
tried and didn't work. I gather I'd have to have a giant antenna (or be
really close to the transmitter) for anything to happen.

Anyway, I got to thinking about something. At all times the electrons in
the antenna are moving back and forth. This motion obviously isn't enough
to light an LED....but its still motion. Constant motion. And, it would seem
to me, that if we introduce a *time* element, we could get any amount of
work we want. Sure, at any given moment the amount of energy is minimal,
but over some arbitrary length of time, we could get any arbitrary amount of
energy. So what if instead of lighting the LED we just tried to make it
flash?

The question then becomes how can we build up the energy over time? That's
what I'm now asking: What mechanism could be implemented so as to allow the
small amount of energy availble at the antenna to build up for however long
amount of time, in order to flash an LED?

Perhaps a capacitor with several Farad capacitance?

If you read my other post about my forever flasher, you will find that
the average current is only 100 microamps at 3V. That's a tiny 300
microwatts, less than a third of a milliwatt. So, yes, you can get
the antenna power to flash a LED, but you don't need a big capacitor,
all you need is a very low duty cycle flasher. Mine draws 17 mA peak,
but becaause the duty cycle is low, the average is only 100 microamps.
So the trick is to get the voltage up to 3V, and have a bit more than
100 microamps so that the small 100 uF cap can charge up.


--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@

 

[Watson A.Name - 'Watt Sun]

In article <4aiXa.253$8C2.32884@news.abs.net>, wshanks@charm.net
mentioned...

Patrick Leonard wrote:
So I didn't really get a definitive answer...just a few experiments which I
tried and didn't work. I gather I'd have to have a giant antenna (or be
really close to the transmitter) for anything to happen.


I guess my post did not get through

Yes you can light a led from an antenna, the antenna must be resonant,
you must be transmitting appreciable power at the resonant frequency of
your antenna, and the feed impedance of your antenna must be matched to
the LED load.

It's awful difficult to make a resonant antenna for the AM BCB,
especially the low end. So it really isn't a must, all you have to do
is put up a long wire antenna and do as best as you can with the total
RF energy that comes in. Making the antenna resonant would tune out
other stations that might contribute to the total antenna power.

look at
http://literature.agilent.com/litweb/pdf/5966-0785E.pdf

wayne shanks




Anyway, I got to thinking about something. At all times the electrons in
the antenna are moving back and forth. This motion obviously isn't enough
to light an LED....but its still motion. Constant motion. And, it would seem
to me, that if we introduce a *time* element, we could get any amount of
work we want. Sure, at any given moment the amount of energy is minimal,
but over some arbitrary length of time, we could get any arbitrary amount of
energy. So what if instead of lighting the LED we just tried to make it
flash?

The question then becomes how can we build up the energy over time? That's
what I'm now asking: What mechanism could be implemented so as to allow the
small amount of energy availble at the antenna to build up for however long
amount of time, in order to flash an LED?

Perhaps a capacitor with several Farad capacitance?

--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@

 

[Bob Myers]

"Fred Abse" <excretatauris@cerebrumconfus.it> wrote in message
newsan.2003.08.01.21.04.56.815469.759@cerebrumconfus.it...

On Fri, 01 Aug 2003 18:40:45 +0100, Bob Myers wrote:

In such an environment, technical competence starts to move to having
more to do with operating skills and know-how (e.g., you still need to
know how to interpret what you see on a scope if you want to make sure
you've got a clean, legal signal coming OUT of the box) than the more
traditional "design and build" sorts of skills.

More importantly, you need to know what to do about it if you _haven't_
got a clean, legal signal. To most, these days, I suspect, that means a
trip to the shop.

By necessity, in many cases. The "clean, legal signal"
example may not be the best, as final amplifiers and such may still
be generally serviceable by the knowledgeable amateur. But
if pretty much anything else in the transceiver goes bad,
what are you going to do? It's not like the local Radio
Shack is going to have the custom DSP chip or whatever
you need in stock, even assuming that you had the equipment
and skill needed to get fine-pitch surface-mount parts in and
out of the thing...

Bob M.

 

[Bill Bowden]

"Bob Myers" <nospamplease@addressinvalid.com> wrote in message news:<3f2aabd5$1@usenet01.boi.hp.com>...

I think
it's a safe bet that something like the latest Kenwood, ICOM,
or Yaesu transceiver is FAR beyond the ability of almost
any amateur to duplicate. They offer many, many more
features than we ever thought of just 20 or 30 years ago,
and they're far more reliably - but they might as well be
boxes filled with magical elves, for all the chance an amateur
has of building something similar or even really doing much
repair or modification of the "storebought" rig.

Yes, the "boxes" are probably designed by a team of engineers
where one guy designs the front end, another the output end,
and some other guy does the digital stuff, and someone else
the power supply, etc. There's probably one guy in charge
who knows how everything fits together, but not too many details
of individual sections. Makes it sort of hard for any one person
to fully understand the magic box.

-Bill

 

[Eric Immel]

Patrick Leonard wrote:

So I didn't really get a definitive answer...just a few experiments which I
tried and didn't work. I gather I'd have to have a giant antenna (or be
really close to the transmitter) for anything to happen.

I knew a guy, some time ago, who did experiments with long wire
antennas and earthquake prediction. A Google search turned up evidence
of his continuing existence:

http://www.rexresearch.com/tate/tate.htm

His circuit is essentially two voltage doublers pointing in opposite
directions. The antenna is the power source, the doublers are referred
to earth ground and output is taken from the hot ends of the doublers.

Urban areas, of course, work better for "stealing power" from the air.
The longer the (untuned) wire, the more power is available for the
charging the caps.

Figure 3 on Joe's page shows the voltage & power versus load resistance
as being just about the minimum to illuminate a low voltage LED
continuously. This was in a high radio energy area with lots of AM radio
stations.

So what if instead of lighting the LED we just tried to make it
flash?

This is a good idea. Allow energy to accumulate to an amount sufficient
to illuminate the LED briefly. The trick is to accumulate the energy
quickly enough that you don't have to wait an hour for a 100ms flash.
You've gotta blink sometime. That rate is set by antenna efficiency and
transmitter proximity.

The question then becomes how can we build up the energy over time?

The circuit above does this automatically.

Perhaps a capacitor with several Farad capacitance?

Only if you wanted to wait a reaallly long time for the flash. The time
required to reach the trigger voltage depends on the value of the
capacitor and the charging current. The larger the capacitor, the longer
the charging time. The smaller the charging current the longer the
charging time.

The amount of energy required to make a flash depends on how bright you
want it to be and how long you want it to last. This energy, combined
with flash rate will tell you the size of capacitor to use.

Assume the each flash of the LED will draw 10 mA at 2V. That gives a
power for of 20mW (2V*10mA=20mW) this is an indirect measure of the
brightness of the flash. If each flash lasts for 100ms, that gives an
energy of 2mJ (20mW*100ms=2mJ).

The graph shows that antenna/voltage multiplier setup seems to reach a
peak power of about 2mW. At that rate, the cap will reach a stored
energy level of 2mJ in 1s, or so. The voltage looks like it can reach at
least 4V. To get 2mJ out of 4V the storage capacitor would have a total
value of .25 uf (.25uf=2(2uJ)/(4V^2). Since the caps in Joe's circuit
are in series, they each need to be twice that value. .25 uf would give
the highest flash rate capable of delivering 2mJ per flash. In reality,
many factors will affect the flash rate and brightness of the LED.

The triggering circuit will absorb some of the energy and dissipate it
as heat. The caps won't completely discharge. The caps may leak. The
triggering circuit may load the caps in its off state. The discharge
rate won't be constant. The charging current (therefore the charging
time) will vary with RF field strength (which may depend on time of day)
and antenna efficiency. A lightning strike might destroy the antenna,
circuitry and operator. My math could be wrong. My reasoning could be
wrong. In practice the thing to do is build one and test it with a range
of capacitors (in clear weather, away from power lines (duh)).

Any number of flasher techniques would probably work. A relaxation
oscillator with the LED in the discharge path comes to mind as a logical
choice.

As I recall, the early antennas were 100 feet or so of 20 AWG stranded
wire lifted by weather balloons. Seems like a kite or even a tall tree
might work.

EI

 

[Chuck Norisez]

Sometimes those WWVB clocks in close proximity will interfere with one
another.

Chuck

 

[Jim Thompson]

On Tue, 05 Aug 2003 14:09:16 -0400, Jeff Wisnia
<jwisnia@conversent.net> wrote:

Our home was wired for cable TV when we built it18 years ago using RG59
cable installed before the sheetrock went up. I installed a current
state of the art cable TV distributution amplifier to make sure we had
sufficient signal to drive the 6 cable outlets, and it worked fine.

When we upgraded to digital TV this year, I had to buy a new 900 Mhz
distribution amplifier, but now the higher numbered channels are
noticably snowy on the two longest cable runs, when viewed on "cable
ready" sets without a digital set top box.

I could replace those runs with wider bandwith cables, but the only
reasonable way to do that will be to punch through to the outside of our
home's walls and run the cables around that way, dammit.

Are there reasonably priced cable TV booster amplifiers with adjustable
bandwith slopes on the market? I think that could provide a way to live
with the existing RG59 for a while longer, without overloading the lower
channels. I don't have access to an RF lab anymore, so I can't easily
DIY this project.

Thanks guys,

Jeff

Try ChannelPlus. I seem to vaguely remember mention of "tilt" in
their literature.

Is your existing cable routed through an attic? If so use the
existing RG59 to "pull" good dual(or quad)-braid RG6. The loss
difference is substantial.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| Jim-T@analog_innovations.com Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

For proper E-mail replies SWAP "-" and "_"

Why is it that Democrats can't debate politely?
And are only rude and interruptive.
Lack of mental capacity?

 

[Fred Abse]

On Tue, 05 Aug 2003 02:12:44 +0100, Bill Bowden wrote:

Makes it sort of hard for any one
person to fully understand the magic box.

Why?

Anything that one or several human brains have devised, another can
understand, given sufficient application.

--
Then there's duct tape ...
(Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx

 

[Watson A.Name - 'Watt Sun]

In article <Xns93CE72D0B80BCou812@216.168.3.44>,
inorbit@outerspace.org mentioned...

Try this one:

http://tripoint.org/kevtris/Projects/led/flasher.html

A well working forever flasher, I think.

Yeah! That's the one! I remember seeing that quite a while ago, but
I didn't have the URL bookmarked.

This is what I'm trying to make. I didn't realize that he used only a
..1 F capacitor. I was going to use a whole farad, maybe more. The 1F
5V supercaps are $2.79 at Mouser, which is more than a dollar cheaper
than Digi-Key. I could use a couple in parallel.

I'm not sure why the guy used and inductror in his Infini-Flasher. I
didn't, and my flasher works just fine, and only draws 100 uA average.

My guesstimate is that it will run for a couple hours per charge. But
that assumes no leakage in the 1F capacitor. But I don't know if
that's true. From what I find about regular electrolytics, large ones
in the 100,000 uF range have several milliamps leakage, so that would
be much greater than the flasher current, and so, might reduce the
running time greatly. Knowing this leakage would help me plan on how
many caps to order and use. Saves my time, too, since I wouldn't have
to cut and try over a period of days to find out.


--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
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My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@

 

[Watson A.Name - 'Watt Sun]

In article <d2tvivog43mfn8lilpmd4vt31mn6n3ibd1@4ax.com>, Jim-
T@analog_innovations.com mentioned...

On Tue, 05 Aug 2003 14:09:16 -0400, Jeff Wisnia
jwisnia@conversent.net> wrote:

Our home was wired for cable TV when we built it18 years ago using RG59
cable installed before the sheetrock went up. I installed a current
state of the art cable TV distributution amplifier to make sure we had
sufficient signal to drive the 6 cable outlets, and it worked fine.

When we upgraded to digital TV this year, I had to buy a new 900 Mhz
distribution amplifier, but now the higher numbered channels are
noticably snowy on the two longest cable runs, when viewed on "cable
ready" sets without a digital set top box.

I could replace those runs with wider bandwith cables, but the only
reasonable way to do that will be to punch through to the outside of our
home's walls and run the cables around that way, dammit.

Are there reasonably priced cable TV booster amplifiers with adjustable
bandwith slopes on the market? I think that could provide a way to live
with the existing RG59 for a while longer, without overloading the lower
channels. I don't have access to an RF lab anymore, so I can't easily
DIY this project.

Thanks guys,

Jeff

Try ChannelPlus. I seem to vaguely remember mention of "tilt" in
their literature.

Is your existing cable routed through an attic? If so use the
existing RG59 to "pull" good dual(or quad)-braid RG6. The loss
difference is substantial.

...Jim Thompson

I'm not sure if you mean replace the whole cable or just the
accessible part. Replacing the part that is accessible would help,
even tho it's only a fraction of the total run. Or else a 6dB per
octave high pass filter that cuts down the level of the lower
channels.


--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@

 

[Andrew VK3BFA]

Jeff Wisnia <jwisnia@conversent.net> wrote in message news:<3F2FF2CC.82D971F4@conversent.net>...

Our home was wired for cable TV when we built it18 years ago using RG59
cable installed before the sheetrock went up. I installed a current
state of the art cable TV distributution amplifier to make sure we had
sufficient signal to drive the 6 cable outlets, and it worked fine.

When we upgraded to digital TV this year, I had to buy a new 900 Mhz
distribution amplifier, but now the higher numbered channels are
noticably snowy on the two longest cable runs, when viewed on "cable
ready" sets without a digital set top box.

I could replace those runs with wider bandwith cables, but the only
reasonable way to do that will be to punch through to the outside of our
home's walls and run the cables around that way, dammit.

Are there reasonably priced cable TV booster amplifiers with adjustable
bandwith slopes on the market? I think that could provide a way to live
with the existing RG59 for a while longer, without overloading the lower
channels. I don't have access to an RF lab anymore, so I can't easily
DIY this project.

Thanks guys,

Jeff

If you can, crank up the gain on the 900Mhz head amp, then fit
attenuators on the wall plates of the short runs to compensate for
overloading (or even at the head amp end) - these attenuators are
only a buck or two so this inelegant solution might work....
Andrew Vk3BFA

 

[Harry Conover]

Jeff Wisnia <jwisnia@conversent.net> wrote in message news:<3F2FF2CC.82D971F4@conversent.net>...

Our home was wired for cable TV when we built it18 years ago using RG59
cable installed before the sheetrock went up. I installed a current
state of the art cable TV distributution amplifier to make sure we had
sufficient signal to drive the 6 cable outlets, and it worked fine.

When we upgraded to digital TV this year, I had to buy a new 900 Mhz
distribution amplifier, but now the higher numbered channels are
noticably snowy on the two longest cable runs, when viewed on "cable
ready" sets without a digital set top box.

I could replace those runs with wider bandwith cables, but the only
reasonable way to do that will be to punch through to the outside of our
home's walls and run the cables around that way, dammit.

Are there reasonably priced cable TV booster amplifiers with adjustable
bandwith slopes on the market? I think that could provide a way to live
with the existing RG59 for a while longer, without overloading the lower
channels. I don't have access to an RF lab anymore, so I can't easily
DIY this project.

Thanks guys,

Jeff

Jeff, I had the same problem about a year back, and none of the
suggested solution worked for me. Long run of the old RG59 are simply
too lossy at high frequencies to be readily compensated.

My eventual solution was to run the new cable by whatever means was
available. Fortunately my home has air conditioning ductwork, so most
of the cable ended up running though the A/C ducts to the attic, then
were fished down the walls. Sometimes I did have to cut though the
sheetrock, but with a little effort sheetrock is trivially easy to
repair, spackle, and paint. Wall-paper is equally easy to deal with.

Harry C.

 

[A E]

Andreas Trenkwalder wrote:

Hi!

I'm working on an autonomous mobile robot using a atmel mega128 mcu. This
device has 2 usarts but i have 3 serial devices i want connect to. So my
question is has anyone an idea or a shematic on how to multiplex the usart
lines to connect two devices to one usart?

tnx,
Andreas

On a PIC, I used its own comparators as a crude multiplexer, but it needs a few
more PIC pins to do this, but few external parts are needed.
How fast do you want to go? And do you need three full duplex ports? And what,
exactly, do you mean by serial devices? A device like a PC or RS-232 type
peripheral?
Because I2C is a serial interface that you can use to connect many devices to
one serial port.

 

[Andreas Trenkwalder]

On a PIC, I used its own comparators as a crude multiplexer, but it needs
a few
more PIC pins to do this, but few external parts are needed.
How fast do you want to go?
And do you need three full duplex ports?

115200 full duplex (bluetooth module)
19200 half duplex (gps module)
9800 half duplex (compass module)

And what,
exactly, do you mean by serial devices? A device like a PC or RS-232 type
peripheral?
all of the devices are rs-232 type with ttl voltage levels

Because I2C is a serial interface that you can use to connect many devices
to
one serial port.
yes i will connect other devices trought i2c. do you know a i2c to ttl rs232

converter ic?

tnx,
Andreas