HDTenEightyP/NetNews huggingface dataset:
From: greg@coombs.anu.edu.au (Greg Price)
Subject: GPS questions
Keywords: GPS
Organization: Computer Services Centre, Australian National University
Date: 17 Aug 92 11:03:28 GMT

Hi, I have a couple of questions about how GPS works, but no-one know the
answer too around here. See if you can help me here....

1) How does the receiver separate out the different signals from a number
   of satellites if they are all transmitting on the same frequency (using
   180 degree phase modulation) and using one non-directional antenna?

2) The satellite has an accurate internal clock, and the receiver has
   another internal clock which it syncs with the satellites, and uses
   the propagation delay to determine this distance. How do you initially
   sync the receiver clock with the satellites from scratch?

Thanks,
Greg
(greg@coombs.anu.edu.au)
Newsgroups: sci.electronics
From: then@vipunen.hut.fi (Tomi  H Engdahl)
Subject: Re: AEA-FAX
Organization: Helsinki University of Technology, Finland
Date: 16 Aug 92 13:31:31

In article <6LRgPB4w165w@bluemoon.rn.com> gerry@bluemoon.rn.com (Gerard M. Foley) writes:

>   Since it seemed busted anyway, I just now pried it open.
>I have not finished tracing the schematic diagram of it,
>but believe it or not, it containes the following parts,
>and no more:  1 Dual Op-Amp  5 resistors  4 diodes 4
>capacitors! (Sorry for the spelling of "contains" up
>there).  There's magic in electronics!

The magic is mainly in software, because most decoding of the
fax signal is done in software. That's what I think.  I have seen 
a shareware program called Hamcomm, which can send and decode 
morse, rtty etc. signals. The circuit needed for decoding contains one
Op-amp and some passive components. The circuit filters the incoming
signal and converts it to square wave, which is send to one of the input pins
in the serial port. Every time the state in that input changes, UART
generates an interrupt. The software measeres time between interrupts
and so determines the signal frequency. When the program is used for sending,
the PC speaker ouput is connected (via passive low-pass filter) toi the
transmitter. Quite a hack.
I think that the fax device you mentioned works in the quite same way.

 
--

Tomi.Engdahl@hut.fi            "Don't force it; get a larger hammer"
then@vipunen.hut.fi                        
Newsgroups: sci.electronics
From: u009@csx.cciw.ca (G. Stewart Beal)
Subject: Re: Looking for a thermo-electric cooler....
Organization: Canada Centre for Inland Waters
Distribution: na
Date: Wed, 19 Aug 1992 20:35:59 GMT

In article <ALAVIGNE.92Aug17092513@bmerh930.bnr.ca> alavigne@bmerh930.bnr.ca (Andrew Lavigne) writes:
>
>I'm posting this for a friend who is trying to build a CCD camera for his
>scope.  He wants to know where he can obtain a thermo-electric cooler for
>his CCD chip.  Its also known as a 'peltier cooling module'.  Does anyone
>know where these can be obtained and about how much they are???
>
>Any replies or hints appreciated...
>
>Thanks,
>Andrew
>alavigne@bnr.ca

I saw a fairly cheap, small cooler (6 cans of pop) at the Price Club.
If the unit is too much, read the repair instructions and see where the
repair depot is. maybe they can get the module.
Newsgroups: sci.electronics,rec.video
From: douglas@apache.ctr.columbia.edu (Paul Douglas)
Subject: Any rf/video gurus out there??
Organization: Columbia University Center for Telecommunications Research
Date: Sat, 22 Aug 1992 06:14:28 GMT
X-Posted-From: apache.ctr.columbia.edu
X-Posted-Through: sol.ctr.columbia.edu

Hello, i'm trying to design a ckt which accepts a ch3 rf signal and
demodulates/separates the video and audio components.  I started with 
a ckt in RE which uses a MC1350 preamp and a MC1330 low level video 
detector.  In theory the output of the MC1330 should have a bandwidth of
> 8MHz which would allow me to (a) low pass filter it (cutoffT 4Mhz) for 
the video out and (b) band pass filter it at 4.5M then pass the audio carrier
on to a MC1358.  This unfortunately is only in theory.. it seems that the
bandwidth of the 1350/1330 combination is much less that 8Mhz, so depending
on how I tune the input ckt, I get either fairly noisy sound or video.
Moreover when I tune in the sound, I get the noise caused by the horizontal
sync pulses bleeding into the audio.

This leaves me with several questions.. 
(a) how can I improve the bandwidth and noise performance of the input 
    ckt?

(b) Would an active band pass filter perform better the the RC circuit that I
    have now? I checked out some active filter cookbooks, but all the
    active bandpass filters there seem be in the audio range.

(c) What type of low pass filter is best for filtering the output video?


I thought it would be relatively simple to modify the RE ckt, but as I have
learned rf electronics is challenging, especially if you want output
signal with good SNRs :-) :-).

Nevertheless, I'm enjoying the experience, but would really welcome any 
help/discussions/ckt diagrams from the gurus on the net.  Please send
mail to douglas@ctr.columbia.edu.  

Thanks, Paul

Newsgroups: sci.electronics
From: rich@pencil.cs.missouri.edu (Rich Winkel)
Subject: Looking for delayed stereo shutoff switch
Organization: University of Missouri
Date: 21 Aug 92 19:49:05 GMT

About 15 years ago I purchased a kit which would turn off my stereo after
a period of silence or after an adjustable delay.  It monitored the stereo
through a standard lineout connection.
I bought it from Southwest Technical Products, but they're no longer in
business.  Does anyone know of anything similar on the market?  This was
a very handy gadget.

Rich
From: rbs@aisb.ed.ac.uk (Robert Scott)
Newsgroups: sci.electronics
Subject: TV with black mountains
Date: 15 Aug 92 20:59:14 GMT
Reply-To: rbs@aisb.ed.ac.uk
Followup-To: sci.electronics
Organization: Department of AI, University of Edinburgh

I have a small portable colour TV which is fairly old.
After a few years, on start up a craggy black area was visible at the bottom
of the machine but after a time this would slowly recede and the picture
would again be visible over the entire screen.

Recently, this strange balck area has increased in size til it now
covers the bottom past of the screen. After a few minutes,
it may slowly disappear or it may not. I've found that if it goes into
a phase of black-mountains-not-disappearing then if I turn it off
and leave it for a few days then when I switch back on, although
the annoying black stuff is back at least it goes away.

Does anyone know what's happening?
Is it curable or is it going through the TV equivalent of
an agonising death?
I'd rather fix it for a few pounds rather than spend hundreds
on a new TV.

-- 
Rob Scott
Department of AI                Tel: 031-650-2713
University of Edinburgh         FAX: 031-226-2730
80 South Bridge               email: rbs@aisb.ed.ac.uk
EDINBURGH
EH1 1HN
Newsgroups: sci.electronics
From: andreas@dutedib.et.tudelft.nl (A.A.Buykx)
Subject: floating (?) pulse source -> info wanted
Summary: Info wanted for creating or buying a 50 Ohm terminated
		 floating pulse source, triggered once a second and generating
		 microsecond-pulsewidth pulses.
Organization: Delft University of Technology
Date: Wed, 19 Aug 1992 08:57:28 GMT


Hi there,

I need a 50 Ohm terminated floating pulse source, that can be triggered
and generates pulses with risetime < 10 micro s. and a 
pulsewidth < 10 ms. Has anyone information on commercially available
products, or on schemes for building some generator. A possibility would
be to use a pulse transformer, I believe, but that's all I know.

Thanks in advance.

Andreas
-- 
     =====================================================================
   === Andreas A. Buykx              === Electrical Materials Laboratory ===
   === andreas@dutentb.et.tudelft.nl ===  Delft University of Technology ===
     =====================================================================
Newsgroups: sci.electronics
From: dave@imax.imax.com (Dave Martindale)
Subject: Re: "Super-CD" ... soon ?
Organization: Imax Corporation, Mississauga Canada
Date: Tue, 18 Aug 1992 03:11:38 GMT

In article <2463@ulysse.enst.fr> krueger@cal.enst.fr (Martin Krueger) writes:
>
>Adding HISS ? I was always told the very big advantage of digital recordings is
>the absence of hiss. Just another way of restrecting the dynamic range on the
>lower end.

Yes, you add white noise (hiss) at a level equivalent to the amplitude of
the least significant bit in the 16-bit word.  This is at -96 dB, completely
inaudible under most music.

This is far below the level of hiss from analog magnetic tape - thus the
claim of "absence of hiss".  It isn't absolutely absent, but it's at a
far lower level.
Newsgroups: sci.electronics
From: Monty Solomon <monty%roscom@think.com>
Subject: Re: satellite
Reply-To: Monty Solomon <roscom!monty@think.com>
Organization: Proponent
Distribution: na
Date: Sun, 16 Aug 1992 20:58:35 GMT

In article <1992Aug10.864.20718@dosgate> commodore.chairman@canrem.com  
(commodore chairman) writes:
> 
> A friend has a satellite dish, and now he can't receive most of the
> channels he did a while back.  He says he gets the picture, but no
> sound.
> 
> Are the tv stations up to something?

It sounds like your friend has an illegally modified VC II.

Many of the encrypted channels are converting from VC II to VC II+.  

-- 
# Monty Solomon / PO Box 2486 / Framingham, MA  01701-0405
# monty%roscom@think.com
From: myers@hpfcso.FC.HP.COM (Bob Myers)
Date: Tue, 18 Aug 1992 19:13:53 GMT
Subject: Re: RGB Splitter for Mac?
Organization: Hewlett-Packard, Fort Collins, CO, USA
Newsgroups: sci.electronics


There are two possible solutions here; the clean one, the recommended one,
the one that will produce absolutely the ultimate in performance, build
strong bodies twelve ways, and make you the envy of your one-monitor friends,
is something called a "distribution amplifier," which takes a single input
but provides 2 (or more) outputs.  Several companies (Covid and Extron come
to mind - check your local AV distributor, or the Thomas Register) come to
mind.  These things are available for up to and beyond 1280x1024 workstation
display timing.  (You'll need something like 100 MHz bandwidth *minimum* for
an acceptable image at this resolution.)

The quick-and-dirty kludge of a solution is to open up one of the monitors
and remove the 75 ohm termination on all the video inputs (assuming that
your monitor doesn't simply have a switch that lets you go from "75" to
"HI Z" or something like that), and then connect to this monitor with BNC
"T" connectors to allow you to connect a cable to the second monitor, which
then goes at the end of the whole string.  It works almost as well, but now
you're stuck with either using two monitors all the time, or sticking an
external terminating resistor on the "T" if you're not using the second unit.


Bob Myers  KC0EW   Hewlett-Packard Co.      |Opinions expressed here are not
                   User Interface Tech. Div.|those of my employer or any other
myers@fc.hp.com    Fort Collins, Colorado   |sentient life-form on this planet.
Newsgroups: sci.electronics
From: wlsmith@valve.heart.rri.uwo.ca (Wayne Smith)
Subject: Re: What's a good price for a 4 channel 100 MHz analog scope?
Organization: The John P. Robarts Research Institute, London, Ontario
Distribution: na
Date: Fri, 21 Aug 1992 14:54:17 GMT

In article <1992Aug21.044556.26462@athena.cs.uga.edu> mcovingt@athena.cs.uga.edu (Michael A. Covington) writes:
>In article <1992Aug21.042535.5308@julian.uwo.ca> wlsmith@valve.heart.rri.uwo.ca (Wayne Smith) writes:
>>We're looking at a Tektronics (model 5045A?) 100 MHz 4 channel
>>analog scope that will cost us $2250 (can) or say $3085 (us).
>>What would fit our bill a little better would be a 4 channel 20
>>or 30 MHz job.  So...
>
>Who gives you an exchange rate of 1.37 on Canadian to US dollars?
>I was in Canada last week and the rate was 0.83...!

Oops.  I meant a US cost of $1860 ($2450 CAN.)
Newsgroups: sci.electronics
From: au240@cleveland.Freenet.Edu (Ari Pitkanen)
Subject: NiCa battery
Reply-To: au240@cleveland.Freenet.Edu (Ari Pitkanen)
Organization: Case Western Reserve University, Cleveland, OH (USA)
Date: Mon, 17 Aug 92 08:10:34 GMT


What happens when I discharge a NiCa battery (4 cells) completely empty.
Will one of the cells be charged in opposite direction or destroyed in
some other way ?

-- 
Ari Pitkanen
Snail: Kaitovayla 24 A7, 90570 Oulu. Tel. (358) 81 363 944
Email: au240@cleveland.freenet.edu
From: ae569981@longs.LANCE.ColoState.EDU (Alan Erickson)
Newsgroups: sci.electronics
Subject: ??optical mouse LED brightness
Date: 15 Aug 92 01:57:57 GMT
Reply-To: ae569981@longs.LANCE.ColoState.EDU (Alan Erickson)
Organization: Engineering College, Colorado State University


	Hi, all!

	A simple question(?): I'm sitting in front of a Sparc IPX;
	I can produce some heavy spots in the eyes by looking
	at the optical mouse LED. How in the world do they
	get an LED that bright? 

	Is it simply a "super-bright" LED?

	Is it a high-current, low duty cycle pulse? 
	If so, can this be done with any
	LED as long as you mind the average power dissipation rating?
	There are maximum forward current ratings; are these only
	applicable to continuous-duty operation?
	If operated in this way, is the expected device 
	lifetime affected?
	If operated in this way, how does power dissipated relate to 
	power output (does the device become less/more efficient)?

--------------------------------------------------
Alan Erickson, Perpetual Student

erickson@jupiter.nmt.edu
--------------------------------------------------
Newsgroups: sci.electronics
From: mpaul@unlinfo.unl.edu (marxhausen paul)
Subject: Re: A construction question about front panels for home-brew projects...
Organization: University of Nebraska - Lincoln
Date: Sat, 22 Aug 1992 13:08:05 GMT

If you find a source for  a reasonably priced one, please post it.  Our
shop could have used such a punch a zillion times over, but the only ones
I've found for sale (from Mouser Electronics, I think) were really quite
staggeringly expensive.

--
===============================================================================
paul marxhausen                              \/               grace 
university of nebraska - lincoln             /\              happens           
===============================================================================
Newsgroups: sci.electronics
From: rcheng@torag.guild.org (Raymond Cheng)
Subject: Resistor Colour Code Mnemonic
Date: Thu, 20 Aug 92 16:23:40 GMT
Organization: Torag Public Access Unix, Toronto
Distribution: ont

   I always forget the colour code used to code resistors. I recall
there was a mnemonic to remember this code... in fact, there was an
X-rated mnemonic and a G-rated mnemonic, if I recall correctly.

   I'd appreciate it if anyone could e-mail me their own favourite
mnemonic for remembering the code. I'll post a summary if enough
people ask for forwarded replies. I won't be reading this group for
about a week, so I won't be able to read any posted replies,
unfortunately... please e-mail!

   Thanks a bunch.

-- 
     ...Cheng

rcheng@torag.guild.org
rcheng@torag.uucp
Newsgroups: sci.electronics
Subject: re: Guided Vehicles
From: kwilli@elaine.ee.und.ac.za (KEVIN WILLIAMS : THIRD)
Date: 13 Aug 92 11:59:38 +0200
Organization: Electronic Eng., Univ. Natal, Durban, South Africa

I am currentry investigating circuitry to control a model car along a fixed 
track by means of a wire taped to the floor which carries some high 
frequency signal.

I would really appreciate hearing from anyone who has tried this before, and 
is willing to discuss some of the problems or successes you've had.

Thanks!

Kevin Williams

Department of Electronic Engineering
University of Natal, Durban
(KWILLI@ELAINE.EE.UND.AC.ZA)
Newsgroups: sci.electronics,comp.sys.mac.hardware
From: fredm@media.mit.edu (Fred Martin)
Subject: PowerBook 100 LCD screen replacement, the sad conclusion
Organization: MIT Media Laboratory
Date: Thu, 13 Aug 1992 22:58:44 GMT

My Sharp representative made a nice attempt to break the news gently,
but the conclusion was inescapable:

  Sharp LCD Model #LM64P791 is a custom Apple design, and cannot be
  sold to anyone other than Apple Computer, Inc.

Further, the rep believed, the design is significantly different from
other Sharp products, so the attempt to substitute a similar product
would be in vain.

On a related front, it turns out that the single-unit cost of laptop
LCD screens does in fact range from $500 to $600.  This confirms
information sent to me by a reader who works for Sony, who said both
this and that the OEM cost of the same products is in the $200 range.

It therefore can be safely concluded that Apple Computer is paying
$200 or so for a screen that it sells for $790.

In light of this, and the ease by which my PB100 screen was broken, I
have sent the following letter to Mr. John Sculley of Apple, Inc.  

It will be interesting to see if there is a response.


Yours, 

Fred Martin

enc: letter to Mr. John Sculley
----

Dear Mr. Sculley:

A recent incident occurred with my Apple PowerBook 100 computer that
has greatly shaken my faith in both the quality of design of Apple
products and the fairness of Apple Technical Support policy.

The computer slipped from my grasp and fell from a height of three
feet.  It landed, case closed, onto a carpeted surface.  The LCD
screen shattered.

A fall of this magnitude should not destroy a piece of equipment that
is built for portability.  The plastic case of the PowerBook 100 may
optimize some aesthetic of lightness, but it does so at the expense of
providing a degree of robustness that _any_ mobile equipment should
have.

After the screen broke, I called Apple Technical Support to get a
quote on the price of repair.  My shock at having my machine break
after this incident turned into horror when I learned the price of
repair: $790.  This price is perfectly outrageous; it is common
knowledge among the industry-aware that the OEM cost of similar LCD
screens is $200.  Apple Computer should not be trying to turn a large
profit on the cost of authorized repairs, especially if the design of
the product itself is in question.

I hope that future Apple products are not as poorly designed as is my
PowerBook 100.  Further, I hope Apple will reconsider its policy
toward the screen replacement of its existing computers, either
covering under warrantee damage due to minor circumstances, or pricing
authorized service in a manner that does not prohibit the repairs
themselves.


					Sincerely yours,

					Fred G. Martin
					M.S., Mechanical Engineering
-- 
Fred Martin | fredm@media.mit.edu | (617) 253-7143 | 20 Ames St. Rm. E15-301
Epistemology and Learning Group, MIT Media Lab     | Cambridge, MA 02139 USA
Newsgroups: sci.electronics
From: jory@athena.mit.edu (Jory Bell)
Subject: wanted: source for quick pcb manufacturing
Organization: Massachusetts Institute of Technology
Distribution: usa
Date: Fri, 21 Aug 1992 00:27:24 GMT

I am sure this is a FAQ, but...


I have to get two printed circuit boards made up pretty quickly
(ideally withing a couple of days, but I don't know if I can afford
that kind of rush surcharge). 

The two boards are two sided, with plated through holes, and covered
with surface mount chips... they are both about 2.75' diameter circles
(although we will probably just cut them out of squares ourselves). 

To get to the point, can anyone tell me of a good (cheap, fast) place 
to get these made up? My gratitude for this information would be
immense.

			thanks in advance,
			jory bell
			jory@athena.mit.edu
Organization: Queen's University at Kingston
Date: Saturday, 15 Aug 1992 10:22:45 EDT
From: <LEEK@QUCDN.QueensU.CA>
Newsgroups: sci.electronics
Subject: Re: GAL Programmer using 68HC705K1 - UPDATE
 <1992Aug15.043342.15538@ssc.wa.com>

In article <1992Aug15.043342.15538@ssc.wa.com>, markz@ssc.wa.com (Mark Zenier)
says:
>
>And read the posting again and ask, just given the information
>in the April Elektor article, 1) how the programmer knew the
>part was made by National, and 2) why the Elektor project
>differentiates between the original and A version parts.

Magic.  Any technology that's sufficiently advanced...
or in layman's term: stuff manufacturers won't tell you.

Because there are differences between how the two are implemented.
Simply put if you program a 16V8A as a 16V8, it won't do what you
intented to do.  Beyond that I am not supposed to say more.

>Not to mention more mundane things like what is the layout of
>the Jedec fuse map for the different parts.

The Jedec fuse map for the different parts are available in Data books.
In fact the Elektor article (April issue) is almost enough to get you
start programming 16V8 & 20V8 (not the A parts however).  Every single
sentence there is vital info.   Be sure to read it 4 or 5 times.

>Mark Zenier  markz@ssc.wa.com

K. C. Lee
Elec. Eng. Grad. Student
From: gkwan@balboa.eng.uci.edu (Greg Kwan)
Subject: Re: What is state-of-art in CD quality AD Converters?
Newsgroups: sci.electronics
Organization: University of California, Irvine
Date: 20 Aug 92 20:05:44 GMT

In article <l6!nwj#.cornhead@netcom.com> cornhead@netcom.com (Jeff Miller) writes:

>I am interested in CD quality, 18 bit studio quality, and DAT or variable 
>rate ADC's and DAC's. Evaluation units (like the Crystal board) would be 
>nice but not strictly necessary. Serial or parallel output is fine.
>If you know of any companies offering hot ADC or DAC products, zip 
>me a telephone number, maybe a part number, won't you? I'll 
>definitely summarize and post.

My knowledge is about a year old so I'd better post so that others can
correct me. Last I had heard, Crystal was working on 18+bit parts (I've
used the CS5328 18-bit ADC). They just introduced the complementary DAC
(CS4328?). It had a built-in digital filter but it was only spec'ed for
~97 dB dynamic range. The 5328 was ok, but didn't meet their published
noise spec. Note: they claim to only need a 51 ohm resistor and .01 uF
cap as an anti-aliasing filter (sample speed is in MHz range), but I've
seen others use more extensive filtering to achieve a slightly better
S/N Ratio. Pricing was ~$50 each in 1k quantities.

UltraAnalog had 20 bit converters out. They were expensive. (Maybe 3-5
times Crystal's prices in same quantities.) A product we tested that
used the ADC had unimpressive performance except for it's ~103 dB
dynamic range (when band limited and A-weighted).

The 'hot' ADC, however, was a new 20 bit offering from Analog Devices.
Designed by a group led by Bob Adams (who developed UltraAnalog's ADC),
it used differential inputs and was quite inexpensive. (Maybe $25 each
in 1k quantities? It was, however, single channel. Still it was $ com-
petitive with Crystal, which was the goal.) I never got the chance to
play with it but think they had a development board. [Sorry, I forgot
the part number :-(]

DAC's? Used Burr-Brown's PCM1700 with NPC5803 digital filter. Quite
decent performance (>105 dB dynamic range, A-weighted, close to 100
unweighted). [BTW, BB's PCM1750 [18 bit ADC] required an anti-alias
filter. We never got good results w/ the 1750.] As mentioned, Cry-
stal only spec'ed their 4328 to ~97 dB (A-weighted). Didn't get
pricing. UltraAnalog had 18 and 20 bit DAC's, but they were also
very expensive. Not sure what Analog Devices had.

Overall, the CS5328, NPC5803, and PCM1700 gave reasonable results.
< .02% distortion 20-20k (with transformer outputs!), linear phase*,
good crosstalk rejection, very linear distortion vs. input voltage.
Dynamic range was the only real problem.

*The phase was very linear except for a step at ~10kHz. Not sure
which part caused it. Still I think the group delay was < 5 usec,
20-20k.

expecting to be corrected,
greg

gkwan@balboa.eng.uci.edu