HDTenEightyP/NetNews huggingface dataset:
From: smckinty@sunicnc.France.Sun.COM (Steve McKinty - Sun ICNC)
Newsgroups: sci.electronics
Subject: Re: Coax Question
Date: 21 Jul 1992 07:57:40 GMT
Organization: SunConnect
Distribution: world
NNTP-Posting-Host: hardy.france.sun.com

In article <1992Jul20.140143.19341@yang.earlham.edu>, jeremiah@yang.earlham.edu (Jeremiah Wilton) writes:
	> I am wondering what kind of coax is used in Ethernet thin and thick wire 
	> connections.  I am unconvinced that some really expensive special stuff 
	> is necessary.  Might not RG-58 or 59 work for thinwire?  How about 
	> composite video cable (the thin cheap stuff)?  The real question is: What 
	> are the limiting factors in coax for Ethernet?  Capacitance, inductance, 
	> impedance, resistance?  Sheilding?  Wire gauge?
Well, all of them in a way. Ethernet is designed for 50 ohm, so you have to use
that. For very short runs, thats about it. Longer runs you need to worry about
cable losses, and the shielding matters if you want to avoid causing
interference to radio/TV, or picking up interference from heavy machinery,
motors etc.

	> 
	> Why is RG-58 used in low-power FM applications (like receiving) while 
	> RG-59 is used for TV?  I know about 50 ohms vs. 75 ohms, but what does 	        > that mean, and why are they different sizes?

If you have a signal source, like a transmitter and you want to get
maximum energy from it into something else, like an antenna, then you need to
make sure that the impedance of the source matches the impedance of the
target. If it doesn't, not all the energy will be transferred, some will
'bounce' off the connection. At best this wastes the signal, at worst enough
power can be reflected to damage the transmitter. I have accidentally wired
a 5metre length of 93 ohm cable into a 50ohm thinwire ethernet network. The
whole network went to pieces, 10-second file transfers took 15 minutes!
All cause by packets 'bouncing' off the cable mismatch & corrupting other
data on the wire.

The actual choice of impedance (50ohm, 75ohm, 93ohm etc) doesn't matter as long
is the whole system (transmitter/cable/antenna or antenna/cable/reciever) is
the same. It just so happens that some simple antennae have an impedance of
about 50ohms at their tuned frequency, so 50ohms is an obvious choice for the whole system. When you start adding extra elements to an antenna, the impedance
drops but folding the a dipole into a loop increases it again. Somewhere along
the way, 75ohms came out as the impedance of a 'standard' TV antenna, and
hence of TV cable. If I remember correctly a folded dipole has 300ohm
impedance, and led to the use of 300ohm balanced feeder in some places.

As to the sizes, the impedance of a co-ax cable depends on the ratio of the
diameters of the inner & outer conductors, so different impedances will have
different sizes. Larger diameter cables also have less loss, so they can
carry more power from a transmitter, or keep a weak signal 'alive'
between an aerial and a reciever.


Steve
From: parker@gdls.UUCP (The Dougster)
Newsgroups: sci.electronics
Subject: Re: PC masks from a laser printer??
Date: 27 Jul 92 19:09:21 GMT
Organization: General Dynamics Land Systems, Sterling Heights, MI

In article <1992Jul27.065039.5734@lugb.latrobe.edu.au>, MATGBB@LURE.LATROBE.EDU.AU (BYRNES,Graham) writes:
> Dear Knowledgeable ones,
> Up until now I have made my PCB's using donut and tape transfers on
> overhead proj film, exposing Electrolube +ve resist on the copper.

[other stuff deleted]

I found this out for my silkscreening doings...

Vellum (some say onion skin) works better at
taking the toner from the laser printer, and still allows
the visible or IR or UV to pass through and expose any
photosensitive coatings below.


Douglas                       Reply to:  gdls!parker@ilium.troy.msen.com
DoD #1961                     BMW #55821                  Renting N56136
From: martin@yvax.byu.edu
Newsgroups: sci.electronics
Subject: Re: Radar detectors
Date: 28 Jul 92 16:40:32 -0700
Organization: Brigham Young University


I heard about a device that would 'confuse' radars making them think
that the car is going at lower speed; does anyone know anything about
this?.        


 Martin


Newsgroups: sci.electronics
From: sysrick@starbase.spd.louisville.edu (Rick McTeague)
Subject: Probably a FAQ: CATV channel frequencies
Organization: University of Louisville
Date: Wed, 22 Jul 1992 03:33:40 GMT

I'd like to know the frequencies used by each of the TV channels on
cable television. Yes, I know about 2-13 being the same as broadcast
TV... what about the rest, though?

Rick
-- 

Rick McTeague
Electrical Engineering Department, Speed Scientific School
University of Louisville, Louisville, KY 40292
(502) 588-7020

Internet: sysrick@starbase.spd.louisville.edu

Disclaimer: I'm a stand-up comedian; if anyone takes me seriously, I'm
            doing something wrong!
Newsgroups: sci.electronics,rec.video
From: rubin@chocktaw.cis.ohio-state.edu (Daniel Rubin)
Subject: Re: Blue Lasers
Organization: The Ohio State University, Department of Computer and Information Science
Date: Tue, 28 Jul 1992 01:08:35 GMT

>Hmm...I doubt it.  A couple of friends and I built a laser-sourced
>projection TV in college (red only) and had tremendous problems in
>controlling flicker.  We could get rid of it, but only at the
>expense of a jittery picture and almost NO brightness, or lotsa
>brightness, stable picture, and LOTS of flicker.
>I doubt lasers will be a viable alternative until there is some method
>of building very fast scanning apparatus and make them fail-safe as

Why not just use more than one laser here?  Scan the picture in 2 blocks
with 2 lasers or 6 lasers for color.  Why stop there keep adding lasers
until you have got a sharp flicker free image.  Sounds like a great look
what I built project...

								- Dan
-- 
  Daniel Joseph Rubin    |  "...A good football team for the alumni, parking
rubin@cis.ohio-state.edu |  for the faculty and sex for the students."
      GO        GO       |  - President E. Gordon Gee on the three things that
    BENGALS  BUCKEYES    |  a great university president must provide.....
Newsgroups: sci.electronics
From: rbruce@robocomp.corp.mot.com (Rob Bruce)
Subject: Re: CATV channel frequencies USA (long)
Organization: MOTOROLA 
Date: Wed, 29 Jul 1992 01:17:57 GMT

Thanks very much Andy. This serves as a very handy reference!

-- 


Rob Bruce

+----------------------------------+------------------------------------+
| Don't even *think* of flaming me | e-mail: ATCM56@waccvm.corp.mot.com |
+----------------------------------+------------------------------------+
From: stlucas@gdwest.gd.com (GSS 087272 St. Lucas)
Newsgroups: sci.electronics
Subject: Crown electronics help
Date: 24 Jul 92 19:52:33 GMT
Distribution: usa
Organization: General Dynamics Corp.

My daughters stereo was made by Crown, model CD-2000.  The cassette
motor in it has died again, and needs replacement.  The 800 number my
phone book has, 800-669-5055, gets received with a 'no. cannot be
completed as dialed', and the straight phone no., 213-639-5055, changed
area code to 310-639-5055, gets a 'no. no longer in service' message.
Anyone out there have a working phone number for these guys?  Are they
still in business?
The cassette motor is marked
Mitsumi, m34w-6c-2LD, R14 6536 DC 12V, 2000/3600 rpm ccw, 0879aa.
Anyone know of Mitsumi replacement parts?  My local electronics shops won't
touch the thing.
BTW, interchanging the 669 and 639 in the numbers above gets the same
responses.

-- 
Joe St.Lucas    stlucas@gdwest.gd.com        Standard Disclaimers Apply
General Dynamics Space Systems: our last launch (DSCS III) assuring the
security of our great country for years to come.
From: damian+@pitt.edu (Liquid Cooled Spherical Imaging)
Newsgroups: sci.electronics
Subject: Re: Two-sided CD's *DO* exist! (was Re: Life after CDs)
Date: 29 Jul 92 12:35:51 GMT
Organization: RaveReaction CandyLoop Clothing

Andrew Smith (asmith@physics.adelaide.edu.au) remembers :

>I vaguely recall once seeing advertisements on television for a horse
>racing game of some sort.  It used the same idea as above to record a
>number of different race calls; the idea was that each time you played
>the record, you got a different outcome.  I don't remember any details
>of the game; this must have been around 1975 give or take a couple of
>years.
>
>- Andrew.


I have this game at my house right now.  It is called AT THE POSTS.  The
game is made up of a few 12" records with about 6 different outcomes per race
(ie different horses win).  I was really excited about it as a kid, but haven't
touched it since.  I was *really* surprised to see it mentioned *anywhere*.
Oh, well, I'll put it back on the shelf in my mind to gather dust once again.


-- 
                               Pure DIESEL Power
        GUARANTEED          ------------------------         WON'T SLIP
            TO              damian@unix.cis.pitt.edu           ON THE
    SUSPEND DISBELIEF!      ------------------------      ICIEST SURFACES!
From: spcecdt@deeptht.armory.com (John DuBois)
Newsgroups: sci.electronics
Subject: Re: Zapper (IR remote control from computer)
Date: 31 Jul 92 03:06:41 GMT
Organization: The Armory

In article <92206.104206HARVEY@SLACVM.SLAC.STANFORD.EDU> HARVEY@SLACVM.SLAC.STANFORD.EDU writes:
+There was a file posted some time ago for a circuit which would allow
+you to control your remote controls from your PC. It was called the
+Xanadu Zapper. Any help locating the file would be appreciated.

     I have a version for control of IR remote equipment through a serial
port, including command line & curses interface software for UNIX (and
mouse selection, under SCO UNIX), along with an extensive writeup.  Mail
me if you're interested.

	John
-- 
John DuBois	spcecdt@deeptht.armory.com	KC6QKZ
Newsgroups: sci.electronics
From: david@cs.uow.edu.au (David E A Wilson)
Subject: Re: A telephone question
Keywords: telephone
Organization: Dept of Computer Science, Wollongong University, Australia
Date: Tue, 28 Jul 1992 06:50:19 GMT

dcheenne@unlinfo.unl.edu (Dominique J. Cheenne) writes:
>Why are the letters "Q" and "Z" not on the telephone keypad?

Well, here in Australia Telecom has just started putting letters above
the digits and have put Q & Z on the 1 button.

>And why do the letters start on the number 2 key? Starting on the
>number 1 key would have allowed for the entire alphabet with even
>one letter to spare...

In the very early days it was found that picking up the phone to dial it
would generate spurious 1 pulses so the exchange was modified to eat leading
1s. Thus no number started with 1 (or 0 as that got you the operator). When
exhanges were named they just used 2-9. This is my understanding of the reason
but I may well be wrong.

For more information read the comp.dcom.telecom newsgroup or better still
look in the telecom archives on lcs.mit.edu.
-- 
David Wilson				(042) 21 3802 voice, (042) 21 3262 fax
Dept Comp Sci, Uni of Wollongong	david@cs.uow.edu.au
Newsgroups: sci.electronics
From: johnh@macadam.mq.edu.au (John Haddy)
Subject: Re: Are there any large PALs/GALs?
Organization: Macquarie University, School of Mathematics, Physics, Computing and Electronics
Date: Fri, 24 Jul 1992 00:02:05 GMT

In article <jeremym.711852401@sfu.ca>, jeremym@fraser.sfu.ca (Jeremy Thomas McDonald) writes:
|> I was wondering if there are any PALs/GALs that have a large number of D flipflops.  I need to implement two 12-bit counters and a 15-state FSM and and 8-bit
|> register.  I also need three 8-bit I/O ports.  I want to design a controller
|> to act as a pseudo-Dual port RAM controller, with a high speed 20ns RAM chip
|> (single ported) attached to one of the ports on the PAL/GAL, and the PAL/GAL
|> acting as a time slicer for the RAM.  One port on the PAL is read-only, the
|> other is write-only.
|> Any help in this area would be much appreciated, as going with external
|> MSI logic eats up tons of board space.  Thanks.
|> e-mail to: jeremym@fraser.sfu.ca
|> 

First, have you considered dual-port ram chips? IDT and Cypress both make parts
with reasonable speed. Assuming that you've discarded this option:

Sounds like you need to head toward an FPGA. Look at parts from Xilinx (3000
series - the new 4000's are _very_ pricey). These parts download their
configuration from a little 8 pin serial prom on power up. Alternatively, if
you have a uP, you can load them with a word-wide dump. These things will run
with a 50MHz clock too!

Actel and Lattice also make FPGA's - the Lattice parts are known as pLSI.

However, you don't really need to go this far. A dual port Ram controller can
be made much more simply if a simple time-slice (50% access each) is required and
you can live with some latency of response. If you really need ultra-speed, then
you will indeed need to look at the more complex solution. Otherwise:

Treat the whole dual port unit as a synchronous solution that alternates between
a write cycle and a read one. Consider using a RAM such as IDT71982 (16kx4 -
other depths are available - you don't mention how big you need the bank) that
has separate inputs and outputs. Then you won't need data bus buffering. You will
still need address bus tristate buffers though. A single PLD should be able to
handle the state machine - it has four major states: write cycle but no write
request; write cycle with a write request; read cycle but no read request; read
cycle with a pending read request.

Depending on the address bus width, you should be able to get away with five
chips, 2xRAM, 2xBuffers and 1xPLD.

----------------------------------------------------------------------------

      |  _  |_   _   |_|  _   _|  _|              Electronics Department
    |_| (_) | | | |  | | (_| (_| (_| \/           School of MPCE
    ---------------------------------/-           Macquarie University
                                                  Sydney, AUSTRALIA 2109

    Email: johnh@mpce.mq.edu.au, Ph: +61 2 805 8959, Fax: +61 2 805 8983

----------------------------------------------------------------------------
From: sldf3@pluto.ee.usu.edu (beal weston r)
Newsgroups: sci.electronics
Subject: Re: Energy transfer effiency of microwave oven
Date: 27 Jul 92 16:51:04 GMT
Organization: Utah State University

In article <1992Jul23.221140.8403@eecs.nwu.edu>, yeap@eecs.nwu.edu (Kok-Hoo Yeap) writes:
|> A question about energy transfer in microwave oven:
|> 
|> A microwave oven with a glass of water, volumn V. 
|> Let Pa be the power draws from the AC outlet,
|> Pb be the power actually received to heat up the water.
|> Ef = (Pb / Pa) * 100.0 is the efficiency of energy transfer.    

I think that the bottleneck would be the magnetron that converts current to
microwaves.  I have no idea what the efficiency of that is.

|>    
|> If we plot Ef vs V, what does the curve look like ?
|> Does Ef depends on the volumn of water V, or is it always a constant ?

the energy transfer would depend on the surface area to volume ratio and the
skin depth of the material.  The skin depth is dependant on the resistivity of
the material and the frequency.  Of course the frequency is constant, so the real
important variables are the resistivity and the surface area.

|> 
|> If Ef depends on what you put in the oven chamber, which
|> material/food has higher energy transfer efficiency and why ?

salt ( ions ) is quite conductive so the skin depth is shallow.  The heat developes
in the crystals instead of speading throughout.

Anyone feel free to correct me ( be gentle ), but that`s what I remember off hand.



%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%          							    %%
%%  Weston Beal			:  I have a piece of hard rock      %%
%%  sldf3@sol.ee.usu.edu	:  candy, but it's not for eating.  %%
%%  sldf3@cc.usu.edu		:  It's for looking through.        %%
%%                                                                  %%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Newsgroups: sci.electronics
From: nsus_ss@uhura.cc.rochester.edu (Nick Susch)
Newsgroups: sci.electronics
Subject: Spice Docs?
Date: 31 Jul 92 12:30:14 GMT
Organization: University of Rochester - Rochester, New York

I was just wondering if there was a nice documentation package to spice
anywhere on the net that I could FTP. Does any one know of one? Thanks.

--
They say there is strangeness too dangerous | /\/ick Susch - U. of Rochester
In our theatres and bookstore shelves,      | nick@blaise.cif.rochester.edu
That those who know what's best for us      |    or
Must rise and save us from ourselves.       | nsus_ss@uhura.cc.rochester.edu
				   -RUSH
Organization: Penn State University
Date: Fri, 31 Jul 1992 15:29:32 EDT
From: <GNR100@psuvm.psu.edu>
Newsgroups: sci.electronics
Subject: Re: Spice Docs?

        How about Pspice?  I could really use documents on that.
             gnr100@psuvm.psu.edu
Newsgroups: sci.electronics
From: strauss@Aero.org (Daryll Strauss)
Subject: Video from a Mac
Organization: The Aerospace Corporation
Date: Tue, 28 Jul 1992 17:58:45 GMT

We'd like to be able to display our Mac screen on a video monitor and be
able to record the Mac screen. I think we've got the appropriate set
hardware, but we are running into problems. I'm hoping that you might
have some advice. The setup is a Mac IIfx with a SuperMac video 8*24
card. That card supports a number of monitors modes including NTSC
underscan and NTSC overscan. We also have an
encoder/decoder/sync-generator combination box. Finally we have an SVHS
monitor.

So I figured that we needed to send the RGB output from the Mac, while
the card is on one of the NTSC settings, through the encoder to get SVHS
output into the monitor. The picture starts out looking fine, but slowly
drifts to the left. Within about 20 seconds the right edge of the image
drifts off and the picture completely scrambles. If I wait a little
longer the cycle repeats. It is almost as if I need a horizontal hold,
but our SVHS monitor doesn't include one.

Do you have any clues or suggestions? I suspect I'm missing something
obvious, but I've only got the basic knowledge of video so I can't be
sure. (Be gentle, I'm really a software guy ;-) I can send further
details to anyone if that would help. Please respond via email.

						Thanks in advance,
							- |Daryll

-- 
Daryll Strauss          			     f	The Aerospace Corp.
strauss@aero.org		      		     n	Mail Stop: M1-102
...!uunet!aero.org!strauss			     o	P.O. Box 92957
NeXTMail: daryll@harlot.rb.ca.us                     r  Los Angeles, Ca. 90009
"It's my reality and I'll warp it if I want to!"     d	(213) 336-9358
Newsgroups: sci.electronics
From: medin@catbyte.b30.ingr.com (Dave Medin)
Subject: Re: good op amps for audio
Reply-To: medin@catbyte.b30.ingr.com
Organization: Intergraph Corporation, Huntsville AL
Date: Fri, 24 Jul 1992 23:36:01 GMT

In article <amigo.711917764@milton>, amigo@milton.u.washington.edu (The Friend) writes:
|> 
|> 	Interested in the best op amps for work in active crossovers, 
|> and maybe replacement in CD players (which are known to not have the best
|> op amps installed).

Although this subject should generate quite a few different
opinions, I still favor the NE5532 (dual) or NE5534 (single) for
general purpose audio use. The chip has about the best noise
(combination of current and voltage noise) figure for general
purpose audio, and has excellent output drive and full-swing
bandwidth. It is also readily available and cheap. It will drive
low impedance or complex loads fairly well, compared to most other
op-amps, as well. Often times, active crossovers can present some
difficult loads to their op-amps. It is in driving reactive
and low impedance loads that the 5532 excels.

Many of the high-end esoteric ultra-low voltage noise op-amps are
only in their prime when working with input impedances less
than 200 ohms. Considering contributions to OVERALL noise
is important in selection. Low current noise is the prime parameter
if your source impedance is high, while voltage noise is most important
if the source is of low impedance. Usually, an amp with outstanding
performance in one area will be poor in the other area. For example,
to lower voltage noise in a bipolar op amp, the current density in
the input transistors is increased. However, the increased current
density increases the current noise referred to the inputs...

The J-FET amps usually have poorer voltage noise performance but
are the best choice when input impedances are above 5 - 10K because
of their low current noise. The old TL074 is still a good choice
for a J-FET amp, although it will not drive the same loads the 5532
will. The TL074 is also readily available and cheap.

-- 
--------------------------------------------------------------------
       Dave Medin			Phone:	(205) 730-3169 (w)
    Intergraph Corp.				(205) 837-1174 (h)
       M/S GD3004
  Huntsville, AL 35894 		Internet: medin@catbyte.b30.ingr.com
				UUCP:  ...uunet!ingr!b30!catbyte!medin

   ******* Everywhere You Look (at least around my office) *******

 * The opinions expressed here are mine (or those of my machine)
From: grant.ranson@outlan.ersys.edmonton.ab.ca (Grant Ranson) 
Newsgroups: sci.electronics
Subject: Re: hex display 
Date: 28 Jul 92 19:11:00 GMT
Reply-To: grant.ranson@outlan.ersys.edmonton.ab.ca (Grant Ranson) 
Distribution: world
Organization: Outland BBS-UUCP

TO:ALL 
FROM:grant.ranson@outlan.ersys.edmonton.ab.ca 
 
A further suggestion, regarding the hex display question mentioned
below: 
JS> 
JS> In article <55066@mentor.cc.purdue.edu>
JS> > falatic@mentor.cc.purdue.edu (MacGyver) writes:  Hi! I am looking
JS> > for a chip to convert BCD (actually, straight 4 bit  binary) to
JS> Hexadecimal (A-F). I need something LIKE a 7447 driver, but that
JS> > one does not   treat 10d-15d the way I need. Anyone who can help,
JS> > please reply thru E-Mail if possible, or post here.
JS> 
JS> 
JS> How's your budget? :-)    The IDEAL part is the HTIL311 display
JS> from Texas Instruments. Inside the packeage are: a four bit latch
JS> (tristate), BCD to display converter, LED drivers, and a 5 X 7
JS> matrix of LEDs. Apply BCD data to the input pins, pulse the DV (
JS> data valid ) pin, and presto,  hex code shows up on the display.
JS> 
JS> I'm using these in a DTMF project I'm working on. Unfortunatly the
JS> last time I dared to ask they cost about $13 each, but still a cool
JS> part. 
JS> John
JS> 
JS> 
JS> ------------------------------------------------------------------------
JS> John Schuch              hbg6@phx.mcd.mot.com             
 
You might want to try programming a small EPROM (2708-style) with a
table containing segment pattern info for each of the 16 possible
inputs.  Connect the incoming data to a0..a3 of the 2708, and feed its

---
 ~ MMST 2.09 UnRegisteredered 
Newsgroups: sci.electronics
From: rainer@spot.Colorado.EDU (Rainer Malzbender)
Subject: Re: software for the 8051
Organization: University of Colorado, Boulder
Date: Wed, 29 Jul 1992 03:36:53 GMT

In article <1992Jul27.214623.4511@Princeton.EDU> jsm@phoenix.Princeton.EDU (John Scott McCauley Jr.) writes:
>I'm looking for software to program a DS5000 (8051 + 32k ram on a chip).
>I thought I could use eforth51, but doesn't look too promising....

I've used TASM, by Speech Technology, on some projects. It's your basic
assembler, with a hitch: it uses tables which define the instruction set,
and the assembler can produce code for a bunch of 8-bit micros (Z80, 6502,
8048, 8051, and a bunch more). You could even write your own table for
some unsupported micro.

It's on simtel and the various mirrors (wuarchive, oak, ?) under 
ms-dos/crossasm.

Not to be confused with Borland's assembler of the same name!

-- 
Rainer Malzbender                               This sig has no slack since I'm
Post-doc, Physics                               using it all.
U. of Colorado, Boulder (303)492-1366           rainer@shelley.colorado.edu