magnetic field

On Mon, 01 Sep 2003 05:18:59 +0100, Watson A.Name - Watt Sun wrote:

www.ee.nmt.edu/~langmuir/E100/E100.htm

I got Not Found error.
Click to expand...
So did I, until I realized that it's:

www.ee.nmt.edu/~langmuir/E100/E100.html

The upper & lower case should have told me it was wrong. Nobody running a
unix box would use ".htm"

--
Then there's duct tape ...
(Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx
 
Just your run-of-the-mill SPAM!!!!!

--
Tweetldee
Tweetldee at att dot net (Just subsitute the appropriate characters in the
address)

Time is what keeps everything from happening all at once.
<gavrett@sbcglobal.net_> wrote in message
news:ERT4b.17924$Ih1.6803684@newssrv26.news.prodigy.com...
Not much of a deal as far as I could see!

"Troy Lane" <t_lane@bellsouth.net> wrote in message
news:S7L4b.2255$mG4.1312@bignews5.bellsouth.net...
Everything you need in consumer electronics...for LESS!
http://www.fastlanedistributors.com
Click to expand...
 
White noise source, level comparator, pulse generator.
White noise is generated with a reverse biased transistor junction and
amplified. A comparator produces a pulse whenever a threshold is crossed. The
time period of the pulse is random in length.
That is only one idea. Others involve inductors and diodes, capacitors,
etc. You can build a circuit that simulates the action of "strange attractors"
and produces a very nice distribution of random values.
Or use the white noise circuit about with a sample and hold, and a fixed
rate clock. At fixed intervals, a reading is taken and spit out. Now you have
random voltage levels at a known interval.

Cheers!

Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip
 
First, if what kind of area are you living?
Is the mains voltage there 110(/120) or 220(/230)V?
If it is 220V, then a voltage of approx. 60++V at the antenna connector of a
TV is not a rarity, but rather too small. It may indeed cause problems, but
some that can be dealt with. If the mains voltage is at most 110V, then the
64V appear a little too much as there should be losses making it a little
less then half of the mains voltage. But because 64 * 2 is only little more
than half of the assumed mains voltage (which is never exact), and 2
would-be identical capacitors are sometimes not really identical, I do not
think that it will mean real insulation problems. In any case, as the
antenna shielding and most likely the TV's non-HV part is obviosly not
grounded (not a failure, this is meant to be so), a little improvised
patchwork will easily solve this problem. Consider using a decoupling
antenna transformer (Ver 1) or a set of 2 capacitors if an appropriate
transformer is unavailable (Ver 2).

The following schematic shows the connection of an average TV's power supply
to explain how the antenna voltage comes into existance.

-> Fixed Width Font Needed


<----{ LC }--x-------{ rectifier }--------- different
To Mains { Filter } | { switch PS }--------- PS output
<----{ Fuse }--|----x--{ LV rect. }--- voltages
| | |
--- --- |
--- --- | common LV ground +
To Ground NOT | | | chassis + shielding
<----! CONN !--x----x-----------------x------ (antenna, AV, Scart)
ECTED Resulting V: Mains / 2

The 2 capacitors between line and chassis form a voltage divider which
divides the mains voltage approximately by 2. However the maximal current
is still very limited due to the low capacitance values.

There are 2 approaches to solve this problem:

1) To ground the antenna shielding separtely (just a wire between it and
some grounded object). This is the easiest solution, but far not the most
reliable one if there exists another ground connection within the antenna
circuitry (may then cause a current not to be underestimated).

2) To insulate the antenna AND its shielding by an inductive or capacitive
decoupling device. This is usually reliable in most circumstances.

Ver1: (indictive)

This schematics uses 2 HF transformers, the RC stuff is against ESD+Static.
It is best used when both ends are improperly grounded and both connected
devices are sensitive to external voltage.

To Ground <---------
|
ANTENNA <---->|<-|->|<---- ANTENNA
To Outlet <|> | <|> To TV
SHIELD <--x->|<-x->|<-x-- SHIELD
| | |
x-||--x--||-x C = 33 pF, 1kV
| | |
|_---_|_---_| R = 10 MOhm
--- ---

A simpler solution would consist of only one HF transformer and one resistor
(10M) between the shieldings, it is best used if one side is grounded and
the other one is not and either is sensitive (may not apply to your setup).

Ver2: (capacitive)

! Less reliable, may cause interference, may also not solve your problem !

Just connect 2 capacitors of either 470 pF, 1kV in series with the antenna
cable and its shielding: TV -- C -- ANT, SH -- C -- SH. That's all.

Please be aware that all 3 devices require a grounded shielding themselves
in order to minimize static and interferences.

P.S. The HF trafos are sometimes hard to find, in this case a few turns of
wire around a pencil may help things.

Jim Y wrote:
I am not an electrician or electrical engineer, but have questions for
those of you who are.

I have been having problems with my telephone. My telephone and TV cable
are connected (in some
manner) from Comcast. Comcast sent a technician out and he discovered my
television sets were
feeding voltage into the system. He said the device is not designed to
take voltage from the
output side of the box. Their connecting box (I have no idea what it is
called) converts one type of signal to another for both telephone and
television reception.

One TV (kitchen counter) had approximately 64 volts AC between the cable
antenna sheathing and
the wall circuit ground. (All of my wall outlets are properly grounded
and were recently
checked by an electrician.) After the technician left, I dug out my
multimeter and tested it
myself. I disconnected the cable from the kitchen TV and placed one test
lead on the threaded
portion of the TV connector and one test lead in the ground opening of the
wall outlet. The TV
was still plugged in to the wall outlet naturally. The voltage fluctuated
between 62 and 68
volts. Unplugging the TV loses the voltage as expected.

The technician checked the other TV sets in my home and found they all had
a voltage across the
same ground connections but in the 8 to 20 volt range. He made some
wiring changes to the outside connection box and said the cable feed now
bypassed the phone connection so I should no longer have the problem on
the my phone.

My questions are:
Why is there a potential across the grounded antenna shielding and the
outlet ground? Is this normal?
Why so high on one TV?
Should I consider replacing the TV with the high voltage?
Is this a dangerous situation? I am concerned.

Thank you,
Jim Y
Click to expand...
 
Using my multitester, the voltage from the wall outlet read 122.5 volts AC. With the TV plugged
into an outlet, coaxial antenna cable connected to the TV and one test lead on the ground of
the cable (the outer sheath) and one test lead to the *hot* (small opening) opening of the
outlet, I read 122.5 volts. Moving the second lead from the small opening of the outlet to the
large one (white or ground), there is NO potential as it should be. This tells me that the
outer sheathing of the coaxial cable is connected to ground when the TV is plugged in and the
coaxial cable connected to the TV.

It is only when the coaxial cable is disconnected from the TV and I place one lead to the
*grounded* cable connection (threaded portion of TV cable connection) and the other lead to the
outlet ground opening that I read 64 volts. As long as the coaxial antenna cable is connected
to the TV that voltage is going into the ground.

Jim Y

Jim Y <j.s.yablonsky@NOSPAMatt.net> wrote in message
news:AaK4b.122049$0v4.8811086@bgtnsc04-news.ops.worldnet.att.net...
I appreciate the comments, but some of it is going over my head. My electronic knowledge is
limited. My multitester is an LCD Digital with a 20 megohm input impedance. I have an outlet
tester - all duplex outlets in the house are properly grounded for three prong plugs. Several
months ago, an electrician replaced my *old* fuse box replaced with circuit breakers. He
checked all wiring at that time for proper grounding.

Unplugging the TV, I checked for resistance between the coax outer shield and the ground/earth
pin in the wall outlet. It is open.


Jim Y <j.s.yablonsky@NOSPAMatt.net> wrote in message
news:UOy4b.123142$3o3.8656931@bgtnsc05-news.ops.worldnet.att.net...
I am not an electrician or electrical engineer, but have questions for those of you who are.

I have been having problems with my telephone. My telephone and TV cable are connected (in
some
manner) from Comcast. Comcast sent a technician out and he discovered my television sets
were
feeding voltage into the system. He said the device is not designed to take voltage from
the
output side of the box. Their connecting box (I have no idea what it is called) converts
one
type of signal to another for both telephone and television reception.

One TV (kitchen counter) had approximately 64 volts AC between the cable antenna sheathing
and
the wall circuit ground. (All of my wall outlets are properly grounded and were recently
checked by an electrician.) After the technician left, I dug out my multimeter and tested
it
myself. I disconnected the cable from the kitchen TV and placed one test lead on the
threaded
portion of the TV connector and one test lead in the ground opening of the wall outlet. The
TV
was still plugged in to the wall outlet naturally. The voltage fluctuated between 62 and 68
volts. Unplugging the TV loses the voltage as expected.

The technician checked the other TV sets in my home and found they all had a voltage across
the
same ground connections but in the 8 to 20 volt range. He made some wiring changes to the
outside connection box and said the cable feed now bypassed the phone connection so I should
no
longer have the problem on the my phone.

My questions are:
Why is there a potential across the grounded antenna shielding and the outlet ground?
Is this normal?
Why so high on one TV?
Should I consider replacing the TV with the high voltage?
Is this a dangerous situation? I am concerned.

Thank you,
Jim Y
Click to expand...
 
Lou wrote:
Hello,
I am trying to locate either a manual, schematic or personality module
pinouts for a Heathkit ID-4801 Eprom Programmer. Any help would be greatly
appreciated.

Thanx,
Lou Davidson
Click to expand...

Schema for 2716 EPROM personality module posted to
alt.binaries.schematics.electronics
Hope it's of use to you. The 27128 and 27128A are the largest and
latest devices for which wirings are supplied. What device are you
interested in?

The printed examples of wiring for old EPROMS are too small to scan
clearly. The programmer schematic itself is also pretty small.
 
Most of the service manuals I have show something
like this section at the front...

----

"After correcting the original service problem, perform
the following safety checks before releasing the set
to the customer:

"Check the metal trim, "metallized" knobs, screws,
and all other exposed metal parts for AC leakage.
Check leakage as described below.

"LEAKAGE TEST

"The AC leakage from any exposed metal part to earth
ground and from all exposed metal parts to any ex-
powered metal part having a return to chassis, must not
exceed 0.05 mA (50 microamperes). Leakage current
can be measured by any one of three methods.

"1. A commercial leakage tester, such as the
Simpson 229 or RCA WT-540A. Follow the
manufacturers' instructions to use these instru-
ments

"2. A battery-operated AC milliammeter. The Data
Precision 245 digital multimeter is suitable for
this job.

"3. Measuring the voltage drop across a resistor by
means of a VOM or battery-operated AC volt-
meter. The "limit" indication is 50mV, so
analog meters must have an accurate low-voltage
scale. The Simpson 250 and Sanwa SH-63Trd
are examples of a passive VOM that is suitable."

----

Then they show a diagram of a "probe circuit"
used to measure leakage with a 50mV voltmeter.

One side of a 1.0K resistor is connected to earth
ground. The other side is the "probe" that is used
to contact various exposed metal parts of the
equipment under test.

In parallel with this 1K resistor is a series combination
of a 10.2 ohm resistor and a 0.15 microfarad capacitor.
The 50mV meter is also in parallel with the 1K resistor.

This seems to apply to the US models of international
equipment. Other countries likely have similar limits
and measurement standards.

-----

The OP could at least try using a 1K resistor as a
"probe" and see how much leakage current is coming
out of his TV receiver. If it is more than 100 mV (1/10
of one volt), I'd be concerned enough to discontinue
using the equipment until/unless repaired.

----

!!! WARNING AND DISCLAIMER !!!

NOTE THAT THIS IS A POTENTIALLY
LIFE-THREATENING SITUATION.

USE ALL DUE CAUTION AND DILIGENCE.

NOBODY SHOULD ATTEMPT TO MAKE
THIS SORT OF MEASUREMENT OR TO
DECLARE ANY EQUIPMENT "SAFE" OR
"FAULTY" WITHOUT ADEQUATE TRAINING
AND/OR EXPERIENCE.
 
Sam Acme <sam@sam.com> wrote in message
news:3f56ad7d_1@news.iprimus.com.au...
How much RF power required for more than 600Km line of sight (say from a
satellite to earth) data communication?

Is there any off the shelf solution (or home made) for such a system?
(Transceiver on the satellite must be small, light weight, low power-high
efficient, while we do not have such restrictions on the other transceiver
to be used on earth)

Do we need special license to use transceivers at these frequencies?





If you've got a 1mtr^2 aerial/dish picking up the signal and generating 1uV
Click to expand...
in a 50ohm load and the satellite is illuminating a spot on the Earths
surface about 800km across then ohms law and the area of a circle suggest
you only need an 11mW transmitter on the satellite (assuming absolutely no
losses).
I've honestly no idea if this is true. It was just a passing thought :)
regards
john
 
If you've got a 1mtr^2 aerial/dish picking up the signal and generating
1uV
in a 50ohm load and the satellite is illuminating a spot on the Earths
surface about 800km across then ohms law and the area of a circle
suggest
you only need an 11mW transmitter on the satellite (assuming absolutely
no
losses).
I've honestly no idea if this is true. It was just a passing thought :)
regards
john
Click to expand...
one of the first lunar probe transmitters was 0.1w at 108 mhz.
 
"Dave VanHorn" wrote -
one of the first lunar probe transmitters was 0.1w at 108 mhz.
Click to expand...
Yeah, and to receive it, they used steerable dishes that were
as big (and likely cost as much) as your whole neighborhood!
 
"pillip" <pillip@pillip.com> writes:

Thanks

I took the whole thing apart and soldered it again. It's working flawlessly,
although I hope there is no electrical risk involved as I only covered the
wires with electrical tape.
Click to expand...

There should not bee any electrical risk with only electricla tape
cover on SVGA cable. All the signals going in that cable are very
low voltage (5V or less) and limited power signals.


"DarkMatter" <DarkMatter@thebarattheendoftheuniverse.org> wrote in message
news:u97elvc75ioq4uidok0a9p8bg7901b6t7n@4ax.com...
On Wed, 03 Sep 2003 23:09:22 GMT, "pillip" <pillip@pillip.com> Gave
us:

My kids severed the signal cable from the monitor to the video card, so I
bought a SVGA Monitor cable and tried soldering the wires together. I
have
managed to get the proper display, but the picture has a blue tinge to
it.
Here is what I did:

From Monitor Cable (9 wires) To SVGA Cable
(13
wires)
Red Video
Red Video
Green Video
Green Video
Blue Video
Blue Video
Yellow (Pin 14 V Sync) Black
(Pin
14 V Sync)
White (Pin 13 H Sync) Yellow
(Pin
13 H Sync)
Green (Pin 10 Sync Gnd) Black Yellow (Pin
10
Sync Gnd)
Brown (Pin 5 Gnd) Orange (Pin 5 Gnd) + White
Orange (Pin 5 Gnd)
Red (Pin 15 SCI)
White Red (Pin 15 SCI)
Orange (Pin 12 SDA)
Red
(Pin 12 SDA)
White Video Gnd
White Brown (Pin 11)
Red Video Gnd
Red Video Gnd
Green Video Gnd
Green Video Gnd
Blue Video Gnd
Blue Video Gnd

The only wire left in the SVGA cable bundle is the brown wire (pin 4
Frame
Gnd). I would be grateful if you could help me out here. Taking the
Monitor
to a service company is not an option.



Make sure each wire that has its own return has a good integral
return (the three coaxes) Check your wiring over one more time, and
include actual continuity tests. It sounds like two colors are "down"
or at least the red gun. The connector can also be at fault. Also,
make sure you have the shields on any coaxes trimmed back properly ,
and no tiny frays causing a short. If the connector has a metal "can"
of shell, make sure no shorts occur upon assembly of the shell head.

I have seen everything from the cheapest over-ses connectors to full
mil spec, solid pin, gold plated versions. Cheaper, hollow pin
connectors can provide poor, resistive contact with the socket. It
really sounds as if you have no more than a simple continuity problem
with one or more of the lines. Make sure that if you made a splice
that you cut away all of the damaged cable.

I know a lot of this is obvious, but sometimes simple things get
overlooked...

Fix a flat tire, and get "completely finished", only to find that
there were two damage sites, and you have to start over. :]
Click to expand...
--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/
 
"Richard Crowley" <rcrowley7@xprt.net> wrote in message
news:vlgb4g99clps7e@corp.supernews.com...
"Dave VanHorn" wrote -
one of the first lunar probe transmitters was 0.1w at 108 mhz.

Yeah, and to receive it, they used steerable dishes that were
as big (and likely cost as much) as your whole neighborhood!
Click to expand...
i don't know that to be true, but i have the schematics for the transmitter.

moonbounce is done by hams all the time, on the 2 meter band.
given that the moon is a really lousy reflector, and also the wrong shape,
it seems entirely reasonable to me that a low noise receiver, with a
reasonable antenna, could pick up a tenth of a watt from that distance.
 
Dave VanHorn wrote:

i don't know that to be true, but i have the schematics for the transmitter.
Click to expand...
Are those available for download somewhere?

Cheers,

Andi

--
If Mr. Edison had thought smarter he wouldn't sweat as much.
- Nikola Tesla
 
Tomi Holger Engdahl <then@solarflare.cs.hut.fi> wrote in message news:<laj1xuvcrn4.fsf@solarflare.cs.hut.fi>...
"pillip" <pillip@pillip.com> writes:

Thanks

I took the whole thing apart and soldered it again. It's working flawlessly,
although I hope there is no electrical risk involved as I only covered the
wires with electrical tape.


There should not bee any electrical risk with only electricla tape
cover on SVGA cable. All the signals going in that cable are very
low voltage (5V or less) and limited power signals.
Click to expand...
I did this to a monitor ; I used epoxy to protect the wiring inside
the repaired plug (it was one of those awkward ones with all 24 pins)

-A

"DarkMatter" <DarkMatter@thebarattheendoftheuniverse.org> wrote in message
news:u97elvc75ioq4uidok0a9p8bg7901b6t7n@4ax.com...
On Wed, 03 Sep 2003 23:09:22 GMT, "pillip" <pillip@pillip.com> Gave
us:

My kids severed the signal cable from the monitor to the video card, so I
bought a SVGA Monitor cable and tried soldering the wires together. I
have
managed to get the proper display, but the picture has a blue tinge to
it.
Here is what I did:

From Monitor Cable (9 wires) To SVGA Cable
(13
wires)
Red Video
Red Video
Green Video
Green Video
Blue Video
Blue Video
Yellow (Pin 14 V Sync) Black
(Pin
14 V Sync)
White (Pin 13 H Sync) Yellow
(Pin
13 H Sync)
Green (Pin 10 Sync Gnd) Black Yellow (Pin
10
Sync Gnd)
Brown (Pin 5 Gnd) Orange (Pin 5 Gnd) + White
Orange (Pin 5 Gnd)
Red (Pin 15 SCI)
White Red (Pin 15 SCI)
Orange (Pin 12 SDA)
Red
(Pin 12 SDA)
White Video Gnd
White Brown (Pin 11)
Red Video Gnd
Red Video Gnd
Green Video Gnd
Green Video Gnd
Blue Video Gnd
Blue Video Gnd

The only wire left in the SVGA cable bundle is the brown wire (pin 4
Frame
Gnd). I would be grateful if you could help me out here. Taking the
Monitor
to a service company is not an option.



Make sure each wire that has its own return has a good integral
return (the three coaxes) Check your wiring over one more time, and
include actual continuity tests. It sounds like two colors are "down"
or at least the red gun. The connector can also be at fault. Also,
make sure you have the shields on any coaxes trimmed back properly ,
and no tiny frays causing a short. If the connector has a metal "can"
of shell, make sure no shorts occur upon assembly of the shell head.

I have seen everything from the cheapest over-ses connectors to full
mil spec, solid pin, gold plated versions. Cheaper, hollow pin
connectors can provide poor, resistive contact with the socket. It
really sounds as if you have no more than a simple continuity problem
with one or more of the lines. Make sure that if you made a splice
that you cut away all of the damaged cable.

I know a lot of this is obvious, but sometimes simple things get
overlooked...

Fix a flat tire, and get "completely finished", only to find that
there were two damage sites, and you have to start over. :]
Click to expand...
 
\
The photo of one guy's receiving antenna on the front of the magazine
("QST"?) shows the dish as big as his house. And "steered" with
two junker car chassis running on a circular track. I'm sure most
hams use more modest receiving antennas, but only by means of
blasting the moon with hundreds (thousands?) of watts.
Click to expand...
here's the seti league's antenna. this is probably about 8' across and about
3' high.
http://www.setileague.org/eme/emeant2.jpg
four antennas transmit, and the other four receive. notice that the antennas
are wound in different directions. when the signal reflects, it is changed
to the other rotation direction.

here, they describe the system.
http://www.setileague.org/eme/emepix1.htm
power up the pipe is 150 watts.

given the large path loss, the signal coming off the moon will certainly be
much less than 100mw
 
"Dave VanHorn" wrote ...
antenna. this is
probably about 8' across and about 3' high.
http://www.setileague.org/eme/emeant2.jpg
Click to expand...
Thanks for the reference, Dave.
I couldn't figure out what interest SETI had in the
moon (which most of us believe to be uninhabited!)
Until I read further that it is a "reference standard"
for radio-astronomy calibration. Ingenious!
 
"Richard Crowley" <rcrowley7@xprt.net> wrote in message
news:vlka4qq40ig3b3@corp.supernews.com...
"Dave VanHorn" wrote ...
here's the seti league's [EME] antenna. this is
probably about 8' across and about 3' high.
http://www.setileague.org/eme/emeant2.jpg

Thanks for the reference, Dave.
I couldn't figure out what interest SETI had in the
moon (which most of us believe to be uninhabited!)
Until I read further that it is a "reference standard"
for radio-astronomy calibration. Ingenious!
Click to expand...
big kind of awful reflector in the sky.
 
"Richard Crowley" (rcrowley7@xprt.net) writes:
"Dave VanHorn" wrote -
one of the first lunar probe transmitters was 0.1w at 108 mhz.

"Richard Crowley" wrote...
Yeah, and to receive it, they used steerable dishes that were
as big (and likely cost as much) as your whole neighborhood!

"Dave VanHorn" wrote ...
i don't know that to be true, but i have the schematics for the
transmitter.

moonbounce is done by hams all the time, on the 2 meter band.
given that the moon is a really lousy reflector, and also the wrong shape,
it seems entirely reasonable to me that a low noise receiver, with a
reasonable antenna, could pick up a tenth of a watt from that distance.

The photo of one guy's receiving antenna on the front of the magazine
("QST"?) shows the dish as big as his house. And "steered" with
two junker car chassis running on a circular track. I'm sure most
hams use more modest receiving antennas, but only by means of
blasting the moon with hundreds (thousands?) of watts.



The date of the photo might be crucial.
Click to expand...

The first amateur moonbounce took place in 1953 (the first moonbounce
ever, by the US Signal Corp, was in 1946), though they never tried
to contact anyone (obviously); they just hear their own signal back
from the moon.

That was before parametric amplifiers (Sam Harris is credited with
making the first practical paramp, he was a ham and did moonbounce),
and transistors. They had to use either fairly noisy diode mixers
(I forget what frequency they used) or fairly noisy tubes in the front
end. I suspect the transmitters were fairly effective, but still
they likely needed every bit of ERP they could get.

And large antennas had to be the norm in the old days. Not many doing
moonbounce, and still not so great receivers. I'm not sure how many put
their equipment right at the antenna, rather than facing the losses
of the feedline.

But once enough got on with those big antennas, and other factors improved,
it became easier for others to do it. A guy in Australia did it
in the sixties from Australia, and they had something like a 150watt power
limit. But, he had a lot of space on the farm, and he had big rhombics.
I thought he had a section to allow some directing, but basically he
could only do moonbounce when the moon was in the right place for
the antenna.

When Sam Harris started working at Arecibo, he worked it so they
used the antenna for moonbounce one or two times in 1964 or so.
That thing had so much gain that it made moonbounce feasible for
a lot of people during the brief time it was tried.

So there's a balance. The guys with the big arrays enable people
with much smaller systems to do moonbounce.

Along the way, the receivers got better. First, they used
paramps, and then solid state devices started getting better.
I remember one review of a fairly early FET converter, and
the writer said it compared well with his 416 (or was it a 417?)
converter, and the 416 was considered basically the best front
end tube for VHF/UHF at the time. He admitted that it meant
his tube converter needed adjusting, but considering there was
no finicky adjustment of the FET converter, it bode well for
the future.

So if someone wants to hear their own echo at this point, they may
find they still need a fairly good system. But because there
people with good systems, others can get by with less.

Michael
 
"db" <javaguy11111@yahoo.com> wrote in message
news:903bda3b.0309051847.1839e21@posting.google.com...
After doing a google search of the newsgroups, this has hardly been
mentioned so I will give a little background from what I have learned.

An anisotropic conductor is one that will conduct in say the z
direction, but not in the x and y directions. It is has been most
commonly used in the manufacture of lcd displays to attach the wires
to the lines. It is now being considered for use in mounting BGA's and
flip chip components.

Basically it works by having small metallic particles embedded in a
film/tape or a paste. When the component is pressed against the pad,
the particles get trapped between the two pads and complete the
connection. The whole component is heated to cure the tape or paste so
the component stays in place.

The nice part is that the process is relatively low temperature
(~200C) and removeable with solvent or low heat.. Easier than
umounting and reballing a BGA that did not solder right.

Has anyone experimented with these materials for hobbyist use for
mounting BGA chips. Anyone know where a roll of this anisotropic
conducting film could be bought. It seems like this would be a method
to allow the hobbyst to experiment with BGA and other high pin density
components that are so common now.
Click to expand...

You've got my attention, I'll be waiting for an answer too.
 
"Richard Crowley" writes:
The photo of one guy's receiving antenna on the front of the magazine
("QST"?) shows the dish as big as his house. And "steered" with
two junker car chassis running on a circular track. I'm sure most
hams use more modest receiving antennas, but only by means of
blasting the moon with hundreds (thousands?) of watts.
Click to expand...

"Michael Black" wrote ...
The date of the photo might be crucial.
Click to expand...
This one was on the cover of QST just 2-3 years ago at the most.
 
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