sci.electronics.repair - 25 new messages in 9 topics - digest

sci.electronics.repair
http://groups.google.com/group/sci.electronics.repair?hl=en

sci.electronics.repair@googlegroups.com

Today's topics:

==============================================================================
TOPIC: OT: Big boys power cable jointing - or not?
http://groups.google.com/group/sci.electronics.repair/t/53e189613358ab92?hl=en
==============================================================================

== 1 of 1 ==
Date: Sun, Jan 16 2011 10:56 am
From: Baron

N_Cook Inscribed thus:

>
> Local power cut last week , the errant joint was laid by the trench so
> I had to nose.
> http://diverse.4mg.com/power_cable1.jpg
> I laid a foot ruler laid over for scale. A few hundred houses affected
> but I assume this cable only supplied a few dozen, then the linesmen
> isolated the area transformer to fix the break , or do they work live?
> . Two cable ends marked by "O" . Tar infill not obviously burnt, just
> what seems to be an inadequate crimp had partly melted off the left
> hand end. I somehow expected something like a phosphorous cauldron
> like they use for welding railway line - not a crimp.
> And certainly not an open crimp as showing the flute betwen the "o"s
> in this closeup
> http://diverse.4mg.com/power_cable2.jpg
> Orange is probably clay pipe surround, along with lead sheet inside
> that and then tar. Remaining cables showed no damage so no shorts.
> The end of the cable is cut clean across the wire strands and no sign
> of any
> brazing or the like. Wire strops and marine hawsers use a closed ring
> crimp hydraulically compressed on. How much of a bang would such 1
> inch diameter cable failure make a couple of feet underground?

About 20 years ago I was working on a factory site, when there was a
muffled pop and the lights went out, the factory grinding to a halt.

Out in the yard was a transformer and switch gear inside a brick
enclosure. No obvious signs of damage. The electricity board
engineers showed up and started to inspect the area.

Suddenly without any warning one of the engineers had one leg disappear
up to his knee through the tarmac. The surface had collapsed under his
weight into a cavity right where the cable had blown out. It took
several days to fix.

They put in a new transformer and feed cable. They used a hydraulic
crimping machine to make the joints in the cables, then potted the
whole lot in epoxy resin. I still have a new unused resin pack that I
was given from that repair. Must be well out of date by now... ;-)

--
Best Regards:
Baron.

==============================================================================
TOPIC: AA-sized conductor (fake battery) wanted
http://groups.google.com/group/sci.electronics.repair/t/33083a4b1e46ccc0?hl=en
==============================================================================

== 1 of 6 ==
Date: Sun, Jan 16 2011 10:59 am
From: Baron

Michael A. Terrell Inscribed thus:

>
> Baron wrote:
>>
>> D Yuniskis Inscribed thus:
>> >
>> > Yeah, when I hear complaints about all of my crap ^H^H^H er,
>> > *toys*,
>> > I think about *these* sorts of things! :> The first friend
>> > (above)
>> > gave me a 3KW FERRUPS (UPS) one day. I was trying to figure out
>> > how to get it *into* the truck (weighed a couple hundred pounds...
>> > the
>> > batteries alone weighed more than 100 pounds). He "disappeared".
>> > And came back a few minutes later with a front-end loader, scooped
>> > the UPS into the bucket and dropped it onto the truck.
>> >
>> > Sheesh!
>>
>> Indeed. :-) In my case it would still be in the truck.
>
>
> You need one of these!
>
>
<http://www.harborfreight.com/1000-lb-capacity-hydraulic-scissor-table-cart-93116.html>
>

Hey that looks nice ! Don't know what I would do with it ! But it
looks nice.

--
Best Regards:
Baron.

== 2 of 6 ==
Date: Sun, Jan 16 2011 11:06 am
From: Baron

Michael A. Terrell Inscribed thus:

>
> David Nebenzahl wrote:
>>
>> On 1/15/2011 9:28 PM Michael A. Terrell spake thus:
>>
>> > Baron wrote:
>> >>
>> >> Very true ! A trick I've used to clean up the end of damaged
>> >> bolts.
>> >
>> > How rebolting! ;-)
>>
>> Aaaaaah, the guy's nuts I say. Cross-threaded between the ears.
>> Tapped out, ready to die.
>
>
> Left hand thread in a right handed world!
>

That reminds me of a little tale. Many many years ago, an apprentice
was given the task of drilling some holes in a piece of metal. He was
given a drill of the right size and told to get on with it.

He came back quite some time later with a very badly burnt and blunted
drill, a piece of metal with a burned depression in it.

The foreman had sneakily given the lad a left hand drill... :-)

--
Best Regards:
Baron.

== 3 of 6 ==
Date: Sun, Jan 16 2011 11:56 am
From: D Yuniskis

On 1/16/2011 11:59 AM, Baron wrote:
> <http://www.harborfreight.com/1000-lb-capacity-hydraulic-scissor-table-cart-93116.html>
>
> Hey that looks nice ! Don't know what I would do with it ! But it
> looks nice.

Great for moving (light) pool (billiard) tables, pinball machines, etc.

Of course, the latter can be moved by a person with a suitably strong
*back*

== 4 of 6 ==
Date: Sun, Jan 16 2011 12:17 pm
From: Baron

D Yuniskis Inscribed thus:

> On 1/16/2011 11:59 AM, Baron wrote:
>>
<http://www.harborfreight.com/1000-lb-capacity-hydraulic-scissor-table-cart-93116.html>
>>
>> Hey that looks nice ! Don't know what I would do with it ! But it
>> looks nice.
>
> Great for moving (light) pool (billiard) tables, pinball machines,
> etc.
>
> Of course, the latter can be moved by a person with a suitably strong
> *back*

Well that rules me out then ! ;-)

--
Best Regards:
Baron.

== 5 of 6 ==
Date: Sun, Jan 16 2011 1:35 pm
From: "Michael A. Terrell"

Baron wrote:
>
> Michael A. Terrell Inscribed thus:
>
> >
> > Baron wrote:
> >>
> >> D Yuniskis Inscribed thus:
> >> >
> >> > Yeah, when I hear complaints about all of my crap ^H^H^H er,
> >> > *toys*,
> >> > I think about *these* sorts of things! :> The first friend
> >> > (above)
> >> > gave me a 3KW FERRUPS (UPS) one day. I was trying to figure out
> >> > how to get it *into* the truck (weighed a couple hundred pounds...
> >> > the
> >> > batteries alone weighed more than 100 pounds). He "disappeared".
> >> > And came back a few minutes later with a front-end loader, scooped
> >> > the UPS into the bucket and dropped it onto the truck.
> >> >
> >> > Sheesh!
> >>
> >> Indeed. :-) In my case it would still be in the truck.
> >
> >
> > You need one of these!
> >
> >
> <http://www.harborfreight.com/1000-lb-capacity-hydraulic-scissor-table-cart-93116.html>
> >
>
> Hey that looks nice ! Don't know what I would do with it ! But it
> looks nice.

Get heavy things from the bed of a pickup truck to your workbench.
You should have seen the fun Ihad unloading a 60 Gallon air comressor
from my truck last year. Two guys with a forklift loaded it, and slid
it all the way forward. I had to use a chain hoist to inch it back to
the tailgate, then lift it an inch above the bed before I pulled the
truck out. Then I lowered it to the ground and 'walked' it into my
shop.

--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.

== 6 of 6 ==
Date: Sun, Jan 16 2011 1:36 pm
From: "Michael A. Terrell"

Baron wrote:
>
> Michael A. Terrell Inscribed thus:
>
> >
> > David Nebenzahl wrote:
> >>
> >> On 1/15/2011 9:28 PM Michael A. Terrell spake thus:
> >>
> >> > Baron wrote:
> >> >>
> >> >> Very true ! A trick I've used to clean up the end of damaged
> >> >> bolts.
> >> >
> >> > How rebolting! ;-)
> >>
> >> Aaaaaah, the guy's nuts I say. Cross-threaded between the ears.
> >> Tapped out, ready to die.
> >
> >
> > Left hand thread in a right handed world!
> >
>
> That reminds me of a little tale. Many many years ago, an apprentice
> was given the task of drilling some holes in a piece of metal. He was
> given a drill of the right size and told to get on with it.
>
> He came back quite some time later with a very badly burnt and blunted
> drill, a piece of metal with a burned depression in it.
>
> The foreman had sneakily given the lad a left hand drill... :-)

The boy's not too sharp, I say! He tried to back up his hard drive
on the Xerox machine! ;-)

--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.

==============================================================================
TOPIC: Electronic curiosities
http://groups.google.com/group/sci.electronics.repair/t/92fb1a53d8547e80?hl=en
==============================================================================

== 1 of 9 ==
Date: Sun, Jan 16 2011 11:07 am
From: Jeff Liebermann

On Sun, 16 Jan 2011 00:38:07 -0800, David Nebenzahl
<nobody@but.us.chickens> wrote:

>On 1/15/2011 10:14 PM Jeff Liebermann spake thus:
>> <http://en.wikipedia.org/wiki/Direct-conversion_receiver>

Before I blunder onward, permit me to say that I've locked horns with
the censors on Wikipedia (actually Wikibooks) and got a first hand
taste of why some of the articles are rather marginal. However, it's
still the best reference around for obtaining general information
about almost any topic and tends to be more understandable than
someone peer reviewed research paper or marginally reviewed book
extract. In topics that I am familiar, I can usually find something
in the article that could use improvement. I usually include a
Wikipedia reference primarily so that those unfamiliar with the topic
can get a general understanding.

>OK, so this is why I absolutely *hate* Wikipedia.

Nothing is perfect. Finding errors is not sufficient grounds for
hatred. A lawyer friend has a similar problem with the various laws
and legal decisions. All of them could use improvement and almost any
written law can be misread and misinterpreted. Unlike Wikipedia,
readers are unable to repair the written legal system. Despite
chronic deficiencies, the legal system is still functional, and there
are few attorneys that *hate* the written law simply because there are
mistakes. Some tolerance would be helpful here.

>Here's the lead
>paragraph in the article:
>
> In telecommunication, a direct-conversion receiver (DCR), also known as
> homodyne, synchrodyne, or zero-IF receiver, is a radio receiver design
> that demodulates the incoming signal by mixing it with a local
> oscillator signal synchronized in frequency to the carrier of the wanted
> signal. The wanted modulation signal is obtained immediately by low-pass
> filtering the mixer output, without requiring further detection. Thus a
> direct-conversion receiver requires only a single stage of detection and
> filtering, as opposed to the more common superheterodyne receiver
> design, which converts the carrier frequency to an intermediate
> frequency first before extracting the modulation, and thus requires two
> stages of detection and filtering.
>
>Now, class, how many things are wrong here? (And please correct *me* if
>I'm incorrect):
>
>o First of all, superhet receivers have only one stage of detection and
>filtering, not two, after the last IF stage, right? (I suppose there may
>be some filtering in or around the mixer stage, but I don't think that's
>what they're claiming, which I assume is filtering out the carrier.) So
>where do they get "two stages of detection and filtering"?

The original paragraph is poorly written and you managed to
misinterpret it. I'll try to do better.

A direct conversion receiver usually uses only a single stage for both
detection and filtering. In any receiver, there is only one stage of
detection. The articles reference to
"...and thus requires two stages of detection and filtering"
should read
"...and thus requires separate stages of detection and filtering". Is
that better?

>o Is their explanation of how DCR works even correct?

Yes, it's correct. Mixing with a local oscillator (or reference
signal) on the operating frequency, as in a homodyne receiver, is
considered direct conversion. That includes extracting the carrier
from the receive signal, and subsequently mixing the carrier with the
receive signal to extract the modulation (such as in an I-Q
demodulator). Mixing with a signal that is NOT on the operating
frequency, is heterodyne conversion. Note that it doesn't matter
where the signal is mixed in a (super)heterodyne receiver. One active
stage can do everything as in an autodyne receiver.
<http://en.wikipedia.org/wiki/Autodyne>

>I don't understand
>the business of mixing the signal with a LO signal: why would you do
>that?

The mixing is to extract the modulation. It's called a product
detector for AM and SSB.
<http://en.wikipedia.org/wiki/Product_detector>
<http://www.google.com/images?q=product+detector>
If you extract the carrier signal from the receive signal, mix these
together, and low pass the result, you get demodulated AM or SSB. With
slope detection, you can also demodulate FM. Extracting the carrier
is simply lots of amplification so that the amplitude modulation is
clipped (limited) and thus removed. For SSB, a PLL is often helpful
for weak signals, but not really necessary as just IF noise will
usually suffice to produce a usable carrier component.

>They're a little vague: does "synchronized in frequency to the
>carrier" mean *exactly* the same frequency as the carrier (???),

Yes. Exactly the same frequency. In order for a product detector or
direct conversion receiver to work, it needs to multiply (mix) the
carrier (with no modulation components present) with the receive
signal. What's left is the modulation.

>or some
>other frequency to produce a sum or difference frequency? (In which
>case, we're back to IF, aren't we, so what's "direct conversion" about this?

No. The distinction is that direct conversion uses a mixing signal
that is exactly the same as the receive signal. If the signal was
offset, it would be consider (super)heterodyne conversion.

>If I were in front of a firing squad and had to try to describe DCR
>without actually knowing what it is, I'd guess(tm)(R) that it's a bunch
>of tuned RF stages followed by a detector.

Sure. The detector is allowed to use the received signal to perform
the demodulation, it's still direct conversion. Think of TRF (tuned
RF) type of receiver as a special case of direct conversion, where the
demodulator is rather simplistic.

>Anyhow, I think I've shown that even if I'm way off base, Wikipedia
>articles tend to be extremely badly written,

There's plenty of room for improvement. There may be mistakes but
they are NOT badly written.

>if not outright full of
>doubtful information.

They make an effort to reduce errors. Where it become difficult is
that there are so many areas of technology where there are multiple
points of view with large areas of overlap and controversy. As long
as the source of such "doubtful" information is specified, multiple
points of view are presented, and the author is fairly neutral, I
don't have any problem with presenting controversial information.

>What else would one expect of the "encyclopedia"
>that any PlayStation-playing, junk-food wolfing pimple-faced
>junior-high-school student can edit?

The next time you research a topic, instead of using Google or
Wikipedia, try using Google Scholar instead.
<http://scholar.google.com>
This should give you a wide selection of papers and articles written
by qualified experts who probably don't own a Playstation. Some of
the papers have been peer reviewed and are thus deemed correct and
often even authoritative.

If that is insufficiently accurate, try searching for terms using
Google patent search.
<http://www.google.com/patents>
If you think Wikipedia is full of inaccurate information, wait until
you read some of the hogwash found in some patents. Try searching for
"perpetual motion" for a good start.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

== 2 of 9 ==
Date: Sun, Jan 16 2011 11:41 am
From: "William Sommerwerck"

"Geoffrey S. Mendelson" <gsm@mendelson.com> wrote in message
news:slrnij6e69.p2d.gsm@cable.mendelson.com...
> William Sommerwerck wrote:

>>>> What does this have to do with the perceived need
>>>> for an RF stage at the receiver?

>>> Read the rest of the posting, it explains why.

>> I did. It was even more confusing.

> Ok, maybe this will make more sense.

> Hams either use resonant antennas or antenna tuners.
> Resonant antennas by virtue of the fact they are resonant in-band, are not
> resonant out of band and therefore reduce out of band signals.
> Antenna tuners (for reception) act as preselectors which reduce out of
band
> signals. In practice and design, they are TRF stages.
> So if you buy a ham radio with an antenna tuner, it may not have a tuned
> front end as specfied, but in reality it does.

I'm not sure that's correct. My Yaesu ("joy of ham's desiring") has a
switchable antenna tuner and switchable RF stage, and they're not
interlocked in any way. No engineer would design a ham transceiver that
depended on an antenna to provide adequate selectivity.

Besides, the RF stage is also there to improve sensitivity (when needed). As
for selectivity... image rejection is more-important than selectivity, and
this is a triple-conversion receiver.

== 3 of 9 ==
Date: Sun, Jan 16 2011 11:47 am
From: "William Sommerwerck"

> No engineer would design a ham transceiver that
> depended on an antenna to provide adequate selectivity.

Whoops.

> No engineer would design a ham transceiver that
> depended on an antenna tuner to provide adequate
> selectivity.

== 4 of 9 ==
Date: Sun, Jan 16 2011 12:23 pm
From: Baron

Jeff Liebermann Inscribed thus:

> On Sun, 16 Jan 2011 00:38:07 -0800, David Nebenzahl
> <nobody@but.us.chickens> wrote:
>
>>On 1/15/2011 10:14 PM Jeff Liebermann spake thus:
>>> <http://en.wikipedia.org/wiki/Direct-conversion_receiver>
>
> Before I blunder onward, permit me to say that I've locked horns with
> the censors on Wikipedia (actually Wikibooks) and got a first hand
> taste of why some of the articles are rather marginal. However, it's
> still the best reference around for obtaining general information
> about almost any topic and tends to be more understandable than
> someone peer reviewed research paper or marginally reviewed book
> extract. In topics that I am familiar, I can usually find something
> in the article that could use improvement. I usually include a
> Wikipedia reference primarily so that those unfamiliar with the topic
> can get a general understanding.
>
>>OK, so this is why I absolutely *hate* Wikipedia.
>
> Nothing is perfect. Finding errors is not sufficient grounds for
> hatred. A lawyer friend has a similar problem with the various laws
> and legal decisions. All of them could use improvement and almost any
> written law can be misread and misinterpreted. Unlike Wikipedia,
> readers are unable to repair the written legal system. Despite
> chronic deficiencies, the legal system is still functional, and there
> are few attorneys that *hate* the written law simply because there are
> mistakes. Some tolerance would be helpful here.
>
>>Here's the lead
>>paragraph in the article:
>>
>> In telecommunication, a direct-conversion receiver (DCR), also
>> known as homodyne, synchrodyne, or zero-IF receiver, is a radio
>> receiver design that demodulates the incoming signal by mixing it
>> with a local oscillator signal synchronized in frequency to the
>> carrier of the wanted signal. The wanted modulation signal is
>> obtained immediately by low-pass filtering the mixer output,
>> without requiring further detection. Thus a direct-conversion
>> receiver requires only a single stage of detection and filtering,
>> as opposed to the more common superheterodyne receiver design,
>> which converts the carrier frequency to an intermediate frequency
>> first before extracting the modulation, and thus requires two
>> stages of detection and filtering.
>>
>>Now, class, how many things are wrong here? (And please correct *me*
>>if I'm incorrect):
>>
>>o First of all, superhet receivers have only one stage of detection
>>and filtering, not two, after the last IF stage, right? (I suppose
>>there may be some filtering in or around the mixer stage, but I don't
>>think that's what they're claiming, which I assume is filtering out
>>the carrier.) So where do they get "two stages of detection and
>>filtering"?
>
> The original paragraph is poorly written and you managed to
> misinterpret it. I'll try to do better.
>
> A direct conversion receiver usually uses only a single stage for both
> detection and filtering. In any receiver, there is only one stage of
> detection. The articles reference to
> "...and thus requires two stages of detection and filtering"
> should read
> "...and thus requires separate stages of detection and filtering". Is
> that better?
>
>>o Is their explanation of how DCR works even correct?
>
> Yes, it's correct. Mixing with a local oscillator (or reference
> signal) on the operating frequency, as in a homodyne receiver, is
> considered direct conversion. That includes extracting the carrier
> from the receive signal, and subsequently mixing the carrier with the
> receive signal to extract the modulation (such as in an I-Q
> demodulator). Mixing with a signal that is NOT on the operating
> frequency, is heterodyne conversion. Note that it doesn't matter
> where the signal is mixed in a (super)heterodyne receiver. One active
> stage can do everything as in an autodyne receiver.
> <http://en.wikipedia.org/wiki/Autodyne>
>
>>I don't understand
>>the business of mixing the signal with a LO signal: why would you do
>>that?
>
> The mixing is to extract the modulation. It's called a product
> detector for AM and SSB.
> <http://en.wikipedia.org/wiki/Product_detector>
> <http://www.google.com/images?q=product+detector>
> If you extract the carrier signal from the receive signal, mix these
> together, and low pass the result, you get demodulated AM or SSB. With
> slope detection, you can also demodulate FM. Extracting the carrier
> is simply lots of amplification so that the amplitude modulation is
> clipped (limited) and thus removed. For SSB, a PLL is often helpful
> for weak signals, but not really necessary as just IF noise will
> usually suffice to produce a usable carrier component.
>
>>They're a little vague: does "synchronized in frequency to the
>>carrier" mean *exactly* the same frequency as the carrier (???),
>
> Yes. Exactly the same frequency. In order for a product detector or
> direct conversion receiver to work, it needs to multiply (mix) the
> carrier (with no modulation components present) with the receive
> signal. What's left is the modulation.
>
>>or some
>>other frequency to produce a sum or difference frequency? (In which
>>case, we're back to IF, aren't we, so what's "direct conversion" about
>>this?
>
> No. The distinction is that direct conversion uses a mixing signal
> that is exactly the same as the receive signal. If the signal was
> offset, it would be consider (super)heterodyne conversion.
>
>>If I were in front of a firing squad and had to try to describe DCR
>>without actually knowing what it is, I'd guess(tm)(R) that it's a
>>bunch of tuned RF stages followed by a detector.
>
> Sure. The detector is allowed to use the received signal to perform
> the demodulation, it's still direct conversion. Think of TRF (tuned
> RF) type of receiver as a special case of direct conversion, where the
> demodulator is rather simplistic.
>
>>Anyhow, I think I've shown that even if I'm way off base, Wikipedia
>>articles tend to be extremely badly written,
>
> There's plenty of room for improvement. There may be mistakes but
> they are NOT badly written.
>
>>if not outright full of
>>doubtful information.
>
> They make an effort to reduce errors. Where it become difficult is
> that there are so many areas of technology where there are multiple
> points of view with large areas of overlap and controversy. As long
> as the source of such "doubtful" information is specified, multiple
> points of view are presented, and the author is fairly neutral, I
> don't have any problem with presenting controversial information.
>
>>What else would one expect of the "encyclopedia"
>>that any PlayStation-playing, junk-food wolfing pimple-faced
>>junior-high-school student can edit?
>
> The next time you research a topic, instead of using Google or
> Wikipedia, try using Google Scholar instead.
> <http://scholar.google.com>
> This should give you a wide selection of papers and articles written
> by qualified experts who probably don't own a Playstation. Some of
> the papers have been peer reviewed and are thus deemed correct and
> often even authoritative.
>
> If that is insufficiently accurate, try searching for terms using
> Google patent search.
> <http://www.google.com/patents>
> If you think Wikipedia is full of inaccurate information, wait until
> you read some of the hogwash found in some patents. Try searching for
> "perpetual motion" for a good start.
>
Good Grief ! If William started a search for "perpetual motion" he'd
dissappear under a mountain of hits.

--
Best Regards:
Baron.

== 5 of 9 ==
Date: Sun, Jan 16 2011 1:58 pm
From: David Nebenzahl

On 1/16/2011 3:38 AM William Sommerwerck spake thus:

[me said:]

>> Another book (which I frankly don't like as much since
>> it's so math-heavy: wouldn't electronics be so easy to
>> learn if all that goddamn math didn't get in the way?)...
>
> I hope you're joking, because without that math, you can't begin to truly
> /understand/ electronics. Mathematics is used to model the physical world.
> When you understand the math, you have a much better comprehension of the
> physics involved.

Hint: I don't use smiley faces.

Of course math is essential to understanding electronics. I'm OK with
algebra and trig, but have problems with calculus, even though I have a
basic understanding of it (differentiation, integration, etc.).

Maybe in the next lifetime ...

--
Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.

== 6 of 9 ==
Date: Sun, Jan 16 2011 2:16 pm
From: "Phil Allison"

"David Nebenzahl"

>> <http://en.wikipedia.org/wiki/Direct-conversion_receiver>
>
> OK, so this is why I absolutely *hate* Wikipedia. Here's the lead
> paragraph in the article:
>
> In telecommunication, a direct-conversion receiver (DCR), also known as
> homodyne, synchrodyne, or zero-IF receiver, is a radio receiver design
> that demodulates the incoming signal by mixing it with a local
> oscillator signal synchronized in frequency to the carrier of the wanted
> signal. The wanted modulation signal is obtained immediately by low-pass
> filtering the mixer output, without requiring further detection. Thus a
> direct-conversion receiver requires only a single stage of detection and
> filtering, as opposed to the more common superheterodyne receiver
> design, which converts the carrier frequency to an intermediate
> frequency first before extracting the modulation, and thus requires two
> stages of detection and filtering.
>
> Now, class, how many things are wrong here? (And please correct *me* if
> I'm incorrect):

** Only one error.

A basic superhet has two stages of filtering ( RF and IF) followed by one
stage of detection.

> o Is their explanation of how DCR works even correct? I don't understand
> the business of mixing the signal with a LO signal: why would you do that?

** To shift the modulation down to base band - silly.

> They're a little vague: does "synchronized in frequency to the carrier"
> mean *exactly* the same frequency as the carrier (???),

** Yep - that is exactly how it works.

In the case of an AM receiver, the original carrier can be extracted and
then mixed with the original AM signal to recover the modulation. Some
hi-fi AM tuners worked this way.

> If I were in front of a firing squad and had to try to describe DCR
> without actually knowing what it is, I'd guess(tm)(R) that it's a bunch of
> tuned RF stages followed by a detector.

** The you would be justifiably shot.

Cos that describes a TRF receiver.

> Anyhow, I think I've shown that even if I'm way off base, Wikipedia
> articles tend to be extremely badly written, if not outright full of
> doubtful information.

** Bob Dylan wrote a song about people like you.

..... Phil

== 7 of 9 ==
Date: Sun, Jan 16 2011 2:18 pm
From: "Phil Allison"

"David Nebenzahl"
>
> It occurred to me that maybe they (the Wikipedia article) are referring to
> FM, not AM, DCR (it doesn't say)?
>

** Don't think DCR works with FM.

..... Phil

== 8 of 9 ==
Date: Sun, Jan 16 2011 3:14 pm
From: "William Sommerwerck"

>>> Another book (which I frankly don't like as much since
>>> it's so math-heavy: wouldn't electronics be so easy to
>>> learn if all that goddamn math didn't get in the way?)...

>> I hope you're joking, because without that math, you can't
>> begin to truly /understand/ electronics. Mathematics is used
>> to model the physical world. When you understand the math,
>> you have a much better comprehension of the physics involved.

> Hint: I don't use smiley faces.

Hint: I don't generally assume they're there, unless I see them. As an
extremely sarcastic person, I rarely fail to see sarcasm when it's present.
Don't complain that I missed something that wasn't there.

> Of course math is essential to understanding electronics.
> I'm OK with algebra and trig, but have problems with calculus,
> even though I have a basic understanding of it (differentiation,
> integration, etc).

Calculus is pretty simple -- if you have a good book. I can't recommend any,
because I don't know any off the top of my head. (Recommendations, anyone?)

I took calculus in high school 45 years ago, at a time when very, very few
high schools in the US offered it. We were given a book to study over the
summer, which carefully walked the reader through the basics of the
differential calculus. When we got to class in the fall, we a preliminary
understanding under our belts.

You also need to learn about Laplace transforms. They make it possible to
analyze circuits with simple algebra, rather than differential equations.
Very, very handy.

== 9 of 9 ==
Date: Sun, Jan 16 2011 3:51 pm
From: Adrian C

On 16/01/2011 21:58, David Nebenzahl wrote:

> Of course math is essential to understanding electronics. I'm OK with
> algebra and trig, but have problems with calculus, even though I have a
> basic understanding of it (differentiation, integration, etc.).
>
> Maybe in the next lifetime ...
>

Nah, plenty to read in this one :)

I wonder if you are aware of this collection of US Navy training
manuals. Looks pretty well written, and only written 13 years ago so
relatively recent.

http://www.rarmy.com/coleman/neets/index.html

--
Adrian C

==============================================================================
TOPIC: Ping Arfa
http://groups.google.com/group/sci.electronics.repair/t/143edaa6a4176223?hl=en
==============================================================================

== 1 of 1 ==
Date: Sun, Jan 16 2011 11:13 am
From: Baron

Hi Arfa,
Re: Samsung TV. New processor board. £120. Exchange.
I don't know what the actual cause was. :-(

--
Best Regards:
Baron.

==============================================================================
TOPIC: Walkman Speakers
http://groups.google.com/group/sci.electronics.repair/t/6948823fdf40b407?hl=en
==============================================================================

== 1 of 4 ==
Date: Sun, Jan 16 2011 11:25 am
From: vjp2.at@at.BioStrategist.dot.dot.com

20yrs ago I got walkman speakers that didn't use batteries. THirty years ago
I ran several 8ohm speakers off my pocket sized cassette recorder without
additional power. Now I can't buy ready made walkman speakers without
batteries. I'm prepared to make my own (housing will stink) but why?

- = -
Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus, BioStrategist
http://www.panix.com/~vjp2/vasos.htm http://www.facebook.com/vasjpan2
---{Nothing herein constitutes advice. Everything fully disclaimed.}---
[Homeland Security means private firearms not lazy obstructive guards]
[Urb sprawl confounds terror] [Phooey on GUI: Windows for subprime Bimbos]

== 2 of 4 ==
Date: Sun, Jan 16 2011 11:36 am
From: "William Sommerwerck"

> 20 years ago I got Walkman speakers that didn't use batteries.

You mean they don't have their own amplification.

> Thirty years ago I ran several 8-ohm speakers off my pocket-
> sized cassette recorder without additional power. Now I can't
> buy ready-made Walkman speakers without batteries. I'm
> prepared to make my own (housing will stink) but why?

I have several pairs of these I got during promotions at office-supply
stores. They use highly-efficient drivers that can produce reasonable volume
from the minuscule output of a pocket Walkman or Discman (20mW to 50mW).

Such speakers can't play very loud or produce a lot of bass. This is almost
certainly the reason they're no longer made, and have been replaced by
amplified systems for iPods. I have no idea where you would find the
necessary drivers.

== 3 of 4 ==
Date: Sun, Jan 16 2011 12:00 pm
From: D Yuniskis

On 1/16/2011 12:25 PM, vjp2.at@at.BioStrategist.dot.dot.com wrote:
> 20yrs ago I got walkman speakers that didn't use batteries. THirty years ago
> I ran several 8ohm speakers off my pocket sized cassette recorder without
> additional power. Now I can't buy ready made walkman speakers without
> batteries. I'm prepared to make my own (housing will stink) but why?

Some "powered (amplified) speakers" can also be used passively.
But, sound level is markedly lower.

The market has shifted to "iPod speakers" which expect higher
efficiency "earbud" reproducers *or* "amplified docks".

You can similarly complain that you can't buy blank Beta video tape or,
better yet, blank *8 track* media!

== 4 of 4 ==
Date: Sun, Jan 16 2011 1:05 pm
From: vjp2.at@at.BioStrategist.dot.dot.com

*+-Some "powered (amplified) speakers" can also be used passively.
*+-But, sound level is markedly lower.

I thought of that, Phillips SBA 1602, No luck.

==============================================================================
TOPIC: WTB ICL7149CM44
http://groups.google.com/group/sci.electronics.repair/t/86e85510deca02fc?hl=en
==============================================================================

== 1 of 1 ==
Date: Sun, Jan 16 2011 11:56 am
From: Bo-Lennart

On Jan 16, 10:38 am, Bo-Lennart <bo-lennart.karls...@telia.com> wrote:
> Hi...I wonder if someone have an IC, for sale, in their junk-box.
> The IC is labeled ICL7149CM44.
> It's a 3 3/4 digit auto-range DVM circuit.
>
> Best regards from SWEDEN
> Bo-Lennart Karlsson

My e-mail is:
Bo-Lennart.Karlsson@Telia.com

==============================================================================
TOPIC: Magnifying glass for smd components
http://groups.google.com/group/sci.electronics.repair/t/152fab9f5593225c?hl=en
==============================================================================

== 1 of 1 ==
Date: Sun, Jan 16 2011 12:13 pm
From: Baron

Hi Arfa,
Arfa Daily Inscribed thus:

>
>
> "Baron" <baron.nospam@linuxmaniac.nospam.net> wrote in message
> news:igt358$gkj$2@news.eternal-september.org...
>> D Yuniskis Inscribed thus:
>>
>>> On 1/15/2011 10:52 AM, Baron wrote:
>>>> D Yuniskis Inscribed thus:
>>>>> I have found that adequate *light* is more important than
>>>>> magnification (but that may just be the age of my eyes)
>>>>
>>>> I can certainly empathise with that last paragraph. Good lighting
>>>> is very important. Particularly where identifying colors is
>>>> required.
>>>
>>> I find that I need more than "good" :-/
>>>
>>> I used to be able to read the markings on DIPs at arm's length
>>> "with a glance". Now, I need to rock them back and forth to get
>>> the light to reflect off them at the right angle before things
>>> are visible (at times, I swear they have changed to BLACK INK!! :<
>>> )
>>>
>>> Ditto for color codes. Seems like the colors have crept closer
>>> together in the spectrum :-/
>>
>> Yes colours have definitely become harder to read. I've used the
>> "PTFE" tape trick on IC's and SMD parts a number of times to read the
>> markings.
>>
>> --
>> Best Regards:
>> Baron.
>
> But bear in mind what I said on here a few weeks ago about how hard it
> is to distinguish similar coloured bands under CFL light, due to the
> hugely discontinuous spectrum that the stupid things put out ...
>
> Arfa

Yes I do remember !

--
Best Regards:
Baron.

==============================================================================
TOPIC: Philips PM5131 Manual
http://groups.google.com/group/sci.electronics.repair/t/0408aa402bb47498?hl=en
==============================================================================

== 1 of 1 ==
Date: Sun, Jan 16 2011 12:20 pm
From: Archon

Hi, Anyone out there got a good copy of page 41 of this manual
(Calibration table)

The PM5131 Function Gen manual is available from hundreds of download
sites free and pay, all have the same copy with page 41 doubled over.

All I need is page 41....anyone? Will pay!!

Remove _SpamNO to email me direct

TIA JC

==============================================================================
TOPIC: OT--Actual electronics repair question
http://groups.google.com/group/sci.electronics.repair/t/1c7563aead5e20a6?hl=en
==============================================================================

== 1 of 1 ==
Date: Sun, Jan 16 2011 1:38 pm
From: "Michael A. Terrell"

Meat Plow wrote:
>
> On Sun, 16 Jan 2011 00:25:40 -0500, Michael A. Terrell wrote:
>
> > Meat Plow wrote:
> >>
> >> On Sat, 15 Jan 2011 13:25:29 -0800, Jeff Liebermann wrote:
> >>
> >> > On Sat, 15 Jan 2011 20:54:48 +0000 (UTC), Meat Plow
> >> > <mhywatt@yahoo.com> wrote:
> >> >
> >> >>I think it stores in erasable prom but can't be sure. I had it open
> >> >>once and don't recall seeing anything big enough to be a supercap or
> >> >>battery. It's really miniaturized.
> >> >
> >> > I'm too lazy to dig out the schematic, but I guess(tm) it's NVRAM of
> >> > some sort. I don't see a coin cell inside. Some inside photos:
> >> > <http://www.mods.dk/picture.php?brandid=7&model=vx-5r> Registration
> >> > required to see them full size.
> >>
> >> Yeah I got the schematic around somewhere, to lazy to dig it up.
> >>
> >> > Note the big white circle that is silk screen to the PCB. That's
> >> > where the speaker magnet is positioned. I suspect that if you place
> >> > some foam tape to put some pressure on the PCB, it might reduce the
> >> > microphonics.
> >>
> >> I think i read that suggestion a long time ago too.
> >>
> >> > Also, two reasons it's only on 440Mhz. It might be a seperate VCO
> >> > oscillator for each band, and the LO multiplier ratio is higher for
> >> > 440 than for the other bands.
> >>
> >> Understood.
> >>
> >> > Incidentally, I sorta blundered across this BNC to SMA adapter made
> >> > specifically for various Yaesu handhelds. Looks better than the
> >> > easily broken adapters I've been using.
> >> > <http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=350298285336>
> >> > There a bunch of others with similar design available.
> >>
> >> Yeah I have a couple SMA - BNC adapters. Bought them at a ham fest a
> >> good while back. If you are going to use the SMA with an external
> >> antenna in your home or vehicle they make an adaptor with coax
> >> inbetween connectors. I have one that has an SMA on one end, a couple
> >> feet of very thing 50 ohm coax (not sure the number but it's half as
> >> thin or more as RG58/U) and a SO239 on the other. Beats using a BNC -
> >> SO239 adapter.
> >
> >
> > RG-174?
>
> Could have been. About the right diameter.

I have a 1000 foot spool under my main workbench to make custom
probes with.

--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.

==============================================================================

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