sci.electronics.repair@googlegroups.com

Today's topics:

* Recommendation for electronics forums? - 21 messages, 8 authors
http://groups.google.com/group/sci.electronics.repair/t/a2a97ca7806d8277?hl=en
* USB device interfering AM radio - 3 messages, 3 authors
http://groups.google.com/group/sci.electronics.repair/t/3ab7201fcff1b0c6?hl=en
* BAD SEXY SEEMS - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/58152be38535fb6f?hl=en

==============================================================================
TOPIC: Recommendation for electronics forums?
http://groups.google.com/group/sci.electronics.repair/t/a2a97ca7806d8277?hl=en
==============================================================================

== 1 of 21 ==
Date: Sun, Mar 20 2011 12:51 am
From: D Yuniskis

Hi David,

On 3/19/2011 6:39 PM, David Nebenzahl wrote:
> I'm looking for an online electronics forum (web-based) where I can post
> some questions.
>
> Don't get me wrong: I love, and usually prefer, Usenet. But I'm trying
> to educate myself here, am working on a project, and a web forum that
> allows one to post pictures would be better for my purposes. At least
> I'd like to try it. (The subject of my current research is the ins and
> outs of op amps.)
>
> Ideally, I'd like a forum where rank amateurs like me can post questions
> that may be answered by "respected regulars" with lotsa knowledge on the
> subject.

I think you have to refine your overall goals/interests.
There are many places you can find out "how to use an op amp"
(or, "how an op amp works", etc.).

But, what you *want* to use that op amp for is probably where
you will get far more pertinent information/advice if you can
refine your needs better.

E.g., using an op amp to design a battery charger is different
than using an op amp to buffer the pickup from an electric
guitar or to implement a feedback loop in a robotic servo
controller.

A place that will give you "textbook" advice on how an op amp
works (or can be applied) will leave you wondering, "OK, now how
do I use that to ____________?" OTOH, a more targeted "forum"
can tell you, "Why bother with an op amp? You can use a pair of
transistors configured like ___________ to give you the results
you need... with the following advantages: " Or, "If you use
an op amp in that sort of application, you will need to add an
external output stage to give you increased ___________. You
can do that by _____________."

> Now, if the answer turns out to be "What, are you nuts? There ain't no
> such thing!", then I guess I can live with that ...

== 2 of 21 ==
Date: Sun, Mar 20 2011 2:06 am
From: "Michael A. Terrell"

"Geoffrey S. Mendelson" wrote:
>
> David Nebenzahl wrote:
> > I'm looking for an online electronics forum (web-based) where I can post
> > some questions.
>
> Get a ham license. Then you can find people who actively design and build
> things, like to talk about them and would gladly help you.

You've got to be kidding. I know a lot of hams who don't even own a
soldering iron. They ship their radios off for factory service, unlike
40 years ago.

--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.

== 3 of 21 ==
Date: Sun, Mar 20 2011 2:10 am
From: "Michael A. Terrell"

David Nebenzahl wrote:
>
> I'm looking for an online electronics forum (web-based) where I can post
> some questions.
>
> Don't get me wrong: I love, and usually prefer, Usenet. But I'm trying
> to educate myself here, am working on a project, and a web forum that
> allows one to post pictures would be better for my purposes. At least
> I'd like to try it. (The subject of my current research is the ins and
> outs of op amps.)
>
> Ideally, I'd like a forum where rank amateurs like me can post questions
> that may be answered by "respected regulars" with lotsa knowledge on the
> subject.
>
> Now, if the answer turns out to be "What, are you nuts? There ain't no
> such thing!", then I guess I can live with that ...

news:sci.electronics.basics or news:sci.electronics.design are both
good. You get more hand holding in the .basic group, but you see the
same people from the .design group. They have more patience on the
.basic group which is intended to teach electronics, while the .design
group is to trade ideas between professional designers.

--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.

== 4 of 21 ==
Date: Sun, Mar 20 2011 4:12 am
From: "Phil Allison"

"Geoffrey S. Mendelson"
>
> Get a ham license. Then you can find people who actively design and build
> things, like to talk about them and would gladly help you.

** Only the " silent majority " ever did that ..........

And none of them or the current few would have a clue about the use of
op-amps in relation to audio.

Wot a fuckwit idea.

Musta come from a radio ham.

.... Phil

== 5 of 21 ==
Date: Sun, Mar 20 2011 4:22 am
From: "Phil Allison"

"Geoffrey S. Mendelson"

> Why not get your education from people who actually use the things

** Errr - since when do current radio hams use op-amps for anything ??

Most have no soldering irons or design knowledge at all.

> and follow
> an almost 100 year tradition of educating newcomers?

** New comers to ham radio generally get an " education " all right.

> The amount of effort is nothing like it used to be, you can earn a ham
> license in a weekend.

** Hmmm - that bodes well for giving new comers advice an all matters
electronic.....

> You just need to answer 75% of 50 multiple choice
> questions corrent about basic electronics, radio theory and law. No
> morse code. No circuit drawings, etc.

** Same goes for the jokers you will find on the ham radio bands.

Like this guy:

Geoffrey S. Mendelson N3OWJ/4X1GM

BTW

The amateur bands have been damn near silent here in Australia for decades.

The hobby is all but dead.

CB radio, the internet and GSM phones have destroyed it.

.... Phil

== 6 of 21 ==
Date: Sun, Mar 20 2011 5:29 am
From: "Geoffrey S. Mendelson"

Michael A. Terrell wrote:
> You've got to be kidding. I know a lot of hams who don't even own a
> soldering iron. They ship their radios off for factory service, unlike
> 40 years ago.

Totally irrelevant. I know a lot of people who can barely figure out
how to put gasoline in their cars, but that does not mean there are is no one
who knows how they work, and repair and "upgrade" their cars.

It's like this group. You ask a question and you get answers. Most of them
are not worth the paper they were never printed upon.

You go to a web forum, you get the same results. You ask a bunch of hams and
you get an answer. Not from all of them, but from one or two who know
what they are talking about.

Geoff.

--
Geoffrey S. Mendelson N3OWJ/4X1GM
Those who cannot remember the past are condemned to misquote it.

== 7 of 21 ==
Date: Sun, Mar 20 2011 5:31 am
From: "William Sommerwerck"

>> I'm looking for an online electronics forum (web-based)
>> where I can post some questions.

> Get a ham license. Then you can find people who actively
> design and build things, like to talk about them and would
> gladly help you.

Amateur radio has largely become a plug 'n play hobby. Hams still build
antennas, and sometimes high-power finals, but other than small projects and
accessories, they mostly buy things. Don't expect to walk into a shack and
find a home-brew receiver these days.

One of the purposes in licensing amateur radio operators was to build a base
of people with both theoretical and practical knowledge of electronics. It's
not clear that it still does this.

== 8 of 21 ==
Date: Sun, Mar 20 2011 5:39 am
From: "William Sommerwerck"

>> Ideally, I'd like a forum where rank amateurs like me can post
>> questions that may be answered by "respected regulars" with
>> lotsa knowledge on the subject.

> I think you have to refine your overall goals/interests. There are
> many places you can find out "how to use an op amp"
> (or, "how an op amp works", etc.).

> But, what you *want* to use that op amp for is probably where
> you will get far more pertinent information/advice if you can
> refine your needs better.

> E.g., using an op amp to design a battery charger is different
> than using an op amp to buffer the pickup from an electric
> guitar or to implement a feedback loop in a robotic servo
> controller.

> A place that will give you "textbook" advice on how an op
> amp works (or can be applied) will leave you wondering,
> "OK, now how do I use that to ______?"

Not so! If you understand The Basic Rule in op-amp circuit design, you'll
see that there is no difference among these applications. Nor will you be
wondering how to do something.

National Semiconductor had an on-line seminar "explaining" op-amp circuit
design -- hostessed by a woman, of course -- and nowhere in it is The Basic
Rule even hinted at.

And Bob Pease had the nerve to tell me that my editing didn't improve the
quality of his (or others') writing!

== 9 of 21 ==
Date: Sun, Mar 20 2011 6:04 am
From: "Geoffrey S. Mendelson"

William Sommerwerck wrote:
> Amateur radio has largely become a plug 'n play hobby. Hams still build
> antennas, and sometimes high-power finals, but other than small projects and
> accessories, they mostly buy things. Don't expect to walk into a shack and
> find a home-brew receiver these days.

That's true. But you will find home brew (or at least kit) QRP rigs,
audio and microphone amps, and similar items.

Except in the UK, where one of the requirments for getting their "foundation"
license is to have built something.

> One of the purposes in licensing amateur radio operators was to build a base
> of people with both theoretical and practical knowledge of electronics. It's
> not clear that it still does this.

It still does. Like everyone who uses a computer, most people could never
program their way out of a paper bag, there is a large population of hams
who can't design or build anything. But there is still a small percentage,
say 10% that do. In the US, that's about 60,000 or so. Enough that David
should not have trouble finding one.

The main objective of ham radio was to have a pool of radio operators
ready in case of an emergency. In 1920 that meant being able to send and
receive Morse code. In 2011, that means knowing how to set up and operate an
FM two way radio, and how to take and pass messages correctly with little
or no instuctions and not panicing.

Geoff.

--
Geoffrey S. Mendelson N3OWJ/4X1GM
Those who cannot remember the past are condemned to misquote it.

== 10 of 21 ==
Date: Sun, Mar 20 2011 8:56 am
From: D Yuniskis

On 3/20/2011 5:39 AM, William Sommerwerck wrote:
>>> Ideally, I'd like a forum where rank amateurs like me can post
>>> questions that may be answered by "respected regulars" with
>>> lotsa knowledge on the subject.
>
>> I think you have to refine your overall goals/interests. There are
>> many places you can find out "how to use an op amp"
>> (or, "how an op amp works", etc.).
>
>> But, what you *want* to use that op amp for is probably where
>> you will get far more pertinent information/advice if you can
>> refine your needs better.
>
>> E.g., using an op amp to design a battery charger is different
>> than using an op amp to buffer the pickup from an electric
>> guitar or to implement a feedback loop in a robotic servo
>> controller.
>
>> A place that will give you "textbook" advice on how an op
>> amp works (or can be applied) will leave you wondering,
>> "OK, now how do I use that to ______?"
>
> Not so! If you understand The Basic Rule in op-amp circuit design, you'll
> see that there is no difference among these applications. Nor will you be
> wondering how to do something.

No, you only "get" to that point with experience. There
are different design issues involved in each of the above
applications. If you understand how an op amp works
"in theory", you can look at an EXISTING circuit and suss
out the functionality that the op amp is providing. But,
that doesn't mean that you would be able to come up with
the particular circuit topology that is avoiding some
particular *real* (vs theoretical) limitation of that
*particular* op amp and/or leveraging some particular
characteristic thereof.

If it could all be boiled down to a simple rule, then
EVERYONE would be able to design perfect circuits "first
time, every time" -- with/without SPICE.

I want to design a 2KW, 2KV SMPS and use an op amp to
compute the error term. Should be no different than
designing a pickup for an electric guitar, right?
Should I expect to have either/both of those designs
on my desk, this afternoon, *completed*??
error

== 11 of 21 ==
Date: Sun, Mar 20 2011 9:30 am
From: D Yuniskis

On 3/20/2011 5:31 AM, William Sommerwerck wrote:
>>> I'm looking for an online electronics forum (web-based)
>>> where I can post some questions.
>
>> Get a ham license. Then you can find people who actively
>> design and build things, like to talk about them and would
>> gladly help you.
>
> Amateur radio has largely become a plug 'n play hobby. Hams still build
> antennas, and sometimes high-power finals, but other than small projects and
> accessories, they mostly buy things. Don't expect to walk into a shack and
> find a home-brew receiver these days.

I think that is a matter of simple economics. You can buy
finished, tested, "legit" product for less than you can
purchase the components needed to build same. And, often,
getting those components is tedious -- unless you have a
business account to which you can add the order (or, buy
THAT SORT OF COMPONENTS in big enough quantities that a
sales rep will sample you a few pieces). Most electronic
suppliers don't want to deal with small orders. And, the
places that *will* have hefty markups (or don't carry the
more exotic components).

> One of the purposes in licensing amateur radio operators was to build a base
> of people with both theoretical and practical knowledge of electronics. It's
> not clear that it still does this.

I think dropping the code requirement was a clear acknowledgement
of this. Now they're just trying to hold onto their frequency
allocations. :-/

And, in practical terms, there are fewer and fewer things that
even a motivated ham can design or repair in a modern household
(contrast this with how "capable" he/she would be in a 1960's
household)

== 12 of 21 ==
Date: Sun, Mar 20 2011 10:00 am
From: "William Sommerwerck"

>> Not so! If you understand The Basic Rule in op-amp circuit
>> design, you'll see that there is no difference among these
>> applications. Nor will you be wondering how to do something.

> No, you only "get" to that point with experience. There
> are different design issues involved in each of the above
> applications. If you understand how an op amp works
> "in theory", you can look at an EXISTING circuit and suss
> out the functionality that the op amp is providing. But,
> that doesn't mean that you would be able to come up with
> the particular circuit topology that is avoiding some
> particular *real* (vs theoretical) limitation of that
> *particular* op amp and/or leveraging some particular
> characteristic thereof.
>
> If it could all be boiled down to a simple rule, then
> EVERYONE would be able to design perfect circuits "first
> time, every time" -- with/without SPICE.
>
> I want to design a 2KW, 2KV SMPS and use an op amp to
> compute the error term. Should be no different than
> designing a pickup for an electric guitar, right?
> Should I expect to have either/both of those designs
> on my desk, this afternoon, *completed*??

I probably overstated the case, but understanding Basic Principles can be a
major leg-up to creating a workable design.

A person who doesn't understand The Basic Rule of Op-Amp Circuit Operation
is going to have a lot of trouble.

I might add that, several years ago, I asked the English gentleman who
worked with Bob Pease at National to tell me what that Rule was -- and bang,
he said it right out, without any hints.

== 13 of 21 ==
Date: Sun, Mar 20 2011 10:18 am
From: Jeff Liebermann

On Sun, 20 Mar 2011 05:09:04 +0000 (UTC), "Geoffrey S. Mendelson"
<gsm@mendelson.com> wrote:

>David Nebenzahl wrote:
>> I'm looking for an online electronics forum (web-based) where I can post
>> some questions.

>Get a ham license. Then you can find people who actively design and build
>things, like to talk about them and would gladly help you.

Locally, we have about 2800 licensed hams in the county, of which I
would guess about 500 are at least semi-active, 100 regularly attend
various club meetings, 50 bother to build things, and perhaps 4 are
qualified to design anything useful. While it's possible to get some
help with design and construction from ham radio, it really depends on
whom you contact.

This is the age of specialization. I can design and advise on some
aspects of RF and repair. In other areas, I'm clueless. You would do
best by finding a forum, blog, newsgroup, or mailing list that covers
the specific area that you're interested in asking questions. Don't
be fooled by the names or lack of traffic. There are often forums
where most of the answers are by email from those that just don't want
their names and advice subject to public scrutiny. For example, I've
found that the LEAST useful forum for solving Apple computer related
problems is Apple's own forums. Just post your question and see what
happens. If you get a dozen one-line useless bad guesses, move on.

As always, the quality of the answers depend heavily on the quality of
the question. Without a clue as the nature of the question, vague
answers, like this one, will be epidemic.

--
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

== 14 of 21 ==
Date: Sun, Mar 20 2011 10:21 am
From: "Michael A. Terrell"

"Geoffrey S. Mendelson" wrote:
>
> Michael A. Terrell wrote:
> > You've got to be kidding. I know a lot of hams who don't even own a
> > soldering iron. They ship their radios off for factory service, unlike
> > 40 years ago.
>
> Totally irrelevant. I know a lot of people who can barely figure out
> how to put gasoline in their cars, but that does not mean there are is no one
> who knows how they work, and repair and "upgrade" their cars.
>
> It's like this group. You ask a question and you get answers. Most of them
> are not worth the paper they were never printed upon.
>
> You go to a web forum, you get the same results. You ask a bunch of hams and
> you get an answer. Not from all of them, but from one or two who know
> what they are talking about.

Right. Sure. Maybe in your small world. I recently went to the
local ham radio club's hamfest. 99% of the items for sale were cheap
chinese crap that is even cheaer on Ebay. the hams that knew what they
were doing have either quit the hobby, or are now 'Silent Keys'. I saw
more computer related items than radio, and the couple vendors with
components had no one at their tables.

--
You can't fix stupid. You can't even put a Band-Aid� on it, because it's
Teflon coated.

== 15 of 21 ==
Date: Sun, Mar 20 2011 10:21 am
From: Meat Plow

On Sun, 20 Mar 2011 05:09:04 +0000, Geoffrey S. Mendelson wrote:

> David Nebenzahl wrote:
>> I'm looking for an online electronics forum (web-based) where I can
>> post some questions.
>
> Get a ham license. Then you can find people who actively design and
> build things, like to talk about them and would gladly help you.
>
> Not quite a web forum, but more personal.
>
> Geoff.

Just renewed my ticket for the 2nd time. You might find a few hams that
dabble in design but only because that's what they do for a living.

The best way to learn besides OTJ training is to read. There isn't a day
that passes that I don't read out of some old school books containing
fundamental electronics. You need to understand why electronics work,
and some mathematics involving calculating loads, current, power sine
waves etc...first. I did it ass-backwards learning on the bench first
using test equipment without knowing much about the fundamentals.

--
Live Fast Die Young, Leave A Pretty Corpse

== 16 of 21 ==
Date: Sun, Mar 20 2011 10:26 am
From: "Michael A. Terrell"

"Geoffrey S. Mendelson" wrote:
>
> William Sommerwerck wrote:
> > Amateur radio has largely become a plug 'n play hobby. Hams still build
> > antennas, and sometimes high-power finals, but other than small projects and
> > accessories, they mostly buy things. Don't expect to walk into a shack and
> > find a home-brew receiver these days.
>
> That's true. But you will find home brew (or at least kit) QRP rigs,
> audio and microphone amps, and similar items.
>
> Except in the UK, where one of the requirments for getting their "foundation"
> license is to have built something.
>
> > One of the purposes in licensing amateur radio operators was to build a base
> > of people with both theoretical and practical knowledge of electronics. It's
> > not clear that it still does this.
>
> It still does. Like everyone who uses a computer, most people could never
> program their way out of a paper bag, there is a large population of hams
> who can't design or build anything. But there is still a small percentage,
> say 10% that do. In the US, that's about 60,000 or so. Enough that David
> should not have trouble finding one.
>
> The main objective of ham radio was to have a pool of radio operators
> ready in case of an emergency. In 1920 that meant being able to send and
> receive Morse code. In 2011, that means knowing how to set up and operate an
> FM two way radio, and how to take and pass messages correctly with little
> or no instuctions and not panicing.

More like 1975, not 2011 and this isn't Israel.

There are plenty of commercial FM radios around, and all the county
radios are digital. The only amateur related emergency gear is the
club's HF station, near the county offices. They don't have a spare
tower, or antennas that could be erected in a couple hours and there is
no way in hell they could put up a replacement commercial digital radio
base station or cell phone tower, even if they had months.

--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.

== 17 of 21 ==
Date: Sun, Mar 20 2011 10:36 am
From: "Michael A. Terrell"

D Yuniskis wrote:
>
> On 3/20/2011 5:39 AM, William Sommerwerck wrote:
> >>> Ideally, I'd like a forum where rank amateurs like me can post
> >>> questions that may be answered by "respected regulars" with
> >>> lotsa knowledge on the subject.
> >
> >> I think you have to refine your overall goals/interests. There are
> >> many places you can find out "how to use an op amp"
> >> (or, "how an op amp works", etc.).
> >
> >> But, what you *want* to use that op amp for is probably where
> >> you will get far more pertinent information/advice if you can
> >> refine your needs better.
> >
> >> E.g., using an op amp to design a battery charger is different
> >> than using an op amp to buffer the pickup from an electric
> >> guitar or to implement a feedback loop in a robotic servo
> >> controller.
> >
> >> A place that will give you "textbook" advice on how an op
> >> amp works (or can be applied) will leave you wondering,
> >> "OK, now how do I use that to ______?"
> >
> > Not so! If you understand The Basic Rule in op-amp circuit design, you'll
> > see that there is no difference among these applications. Nor will you be
> > wondering how to do something.
>
> No, you only "get" to that point with experience. There
> are different design issues involved in each of the above
> applications. If you understand how an op amp works
> "in theory", you can look at an EXISTING circuit and suss
> out the functionality that the op amp is providing. But,
> that doesn't mean that you would be able to come up with
> the particular circuit topology that is avoiding some
> particular *real* (vs theoretical) limitation of that
> *particular* op amp and/or leveraging some particular
> characteristic thereof.
>
> If it could all be boiled down to a simple rule, then
> EVERYONE would be able to design perfect circuits "first
> time, every time" -- with/without SPICE.
>
> I want to design a 2KW, 2KV SMPS and use an op amp to
> compute the error term. Should be no different than
> designing a pickup for an electric guitar, right?

Wrong. A pickup for a guitar doesn't require a stable reference
voltage to regulate it's output.

> Should I expect to have either/both of those designs
> on my desk, this afternoon, *completed*??

Look at national Semiconductor's 'Simple Switcher' line, or Linear's
free Switchercad spice program and use ICs that are tailored to SMPS
applications. If your opamp circuit takes too long to stabilize, you'll
have an expensive failure and maybe a fire.

Switchercad III can be downloaded here:
http://www.linear.com/software/

There is a Yahoo user group at:
http://groups.yahoo.com/group/LTspice/

--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.

== 18 of 21 ==
Date: Sun, Mar 20 2011 10:41 am
From: D Yuniskis

On 3/20/2011 10:00 AM, William Sommerwerck wrote:
>>> Not so! If you understand The Basic Rule in op-amp circuit
>>> design, you'll see that there is no difference among these
>>> applications. Nor will you be wondering how to do something.
>>
>> If it could all be boiled down to a simple rule, then
>> EVERYONE would be able to design perfect circuits "first
>> time, every time" -- with/without SPICE.
>
> I probably overstated the case, but understanding Basic Principles can be a
> major leg-up to creating a workable design.

But, isn't that so of everything? :> I enjoy watching
folks "design by app-note" -- cutting and pasting together
circuit fragments from various publications -- and wondering
why their designs don't work.

"Um, if you UNDERSTOOD what you had /designed/, you would
understand why it WON'T work!"

This is where The Trades have a leg up (in theory) on The Sciences.
In the former, there is a hands-on learning process where you see
the practical aspects of what you are learning *before* you are
deemed "qualified" to practice that skill. In the latter, you
get an abstract exposure to things (to be fair, often a wider
range of "things" since "paper is cheap") but aren't qualified
to use *any* of them before you are "certified" (diploma-ed).

:<

M Crichton's novels are typically based on this "lack of
(full) experience" -- Man having "getting" technology
before he has "earned" it (i.e., has the wisdom to know
how to *use* it).

== 19 of 21 ==
Date: Sun, Mar 20 2011 11:03 am
From: D Yuniskis

On 3/20/2011 10:18 AM, Jeff Liebermann wrote:
> On Sun, 20 Mar 2011 05:09:04 +0000 (UTC), "Geoffrey S. Mendelson"
> <gsm@mendelson.com> wrote:
>
>> David Nebenzahl wrote:
>>> I'm looking for an online electronics forum (web-based) where I can post
>>> some questions.
>
>> Get a ham license. Then you can find people who actively design and build
>> things, like to talk about them and would gladly help you.
>
> Locally, we have about 2800 licensed hams in the county, of which I
> would guess about 500 are at least semi-active, 100 regularly attend
> various club meetings, 50 bother to build things, and perhaps 4 are
> qualified to design anything useful.

Expressed in your characteristic "dry" manner... :>

But, illustrates the point, well. Yet, doesn't say how accessible
those "4" are nor where their interests lie. E.g., you would be
hard-pressed to get me to help you design an audio amp out of
discretes -- but, could probably keep me obsessed with trying to
cut power consumption by half a milliwatt on a battery powered
device! (and I'm a *helpful* soul ;-)

A lot also depends on how dense that population of "experts" is,
as well. E.g., our county is 9,200 sq mi with a population of just
over 1,000,000. So, 90 people / sq mile. *If* we have those 2800
hams, here (no idea), that would be one ham for every 4 sq mi. That
can make accessing that "expert" a bit problematic (I find learning
is usually faster "in person").

And, if the hams (and population, in general) are not evenly
distributed throughout the county, it only gets worse (potentially).
E.g., there are *no* electronic suppliers, here, within driving
distance. The closest possible (overpriced) retailer is clear across
town (and would never have the types of components that I am
interested in).

> While it's possible to get some
> help with design and construction from ham radio, it really depends on
> whom you contact.
>
> This is the age of specialization.

Exactly! The days of being able to keep a drawer full of transistors,
diodes, resistors, etc. and hack together an amplifier -- or a logic
gate (!) -- are long behind us. Sure, you can still do it, but there
is no point. I can recall building 8 digit counters out of discretes
with nixie displays... would I bother wasting my time on that *now*??
(though I *have* been sorely tempted to build a Difference Engine).

> I can design and advise on some
> aspects of RF and repair. In other areas, I'm clueless. You would do
> best by finding a forum, blog, newsgroup, or mailing list that covers
> the specific area that you're interested in asking questions. Don't

Agreed. ------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

> be fooled by the names or lack of traffic. There are often forums
> where most of the answers are by email from those that just don't want
> their names and advice subject to public scrutiny. For example, I've
> found that the LEAST useful forum for solving Apple computer related
> problems is Apple's own forums. Just post your question and see what
> happens. If you get a dozen one-line useless bad guesses, move on.
>
> As always, the quality of the answers depend heavily on the quality of
> the question. Without a clue as the nature of the question, vague
> answers, like this one, will be epidemic.

Wear rubber soled shoes, remove all jewelry, keep one hand in your
pocket and *play*! It's not *chemistry* where you have to worry
about losing eyebrows or other body parts when you make a mistake :>
All you have to lose is a little *money*!

(and, depending on what you are playing with, many devices nowadays
can take a LOT of abuse -- short circuit protection, etc. -- so you
don't have to worry about replacing components every two ohnoseconds!)

== 20 of 21 ==
Date: Sun, Mar 20 2011 11:42 am
From: mike

Jeff Liebermann wrote:
> On Sun, 20 Mar 2011 05:09:04 +0000 (UTC), "Geoffrey S. Mendelson"
> <gsm@mendelson.com> wrote:
>
>> David Nebenzahl wrote:
>>> I'm looking for an online electronics forum (web-based) where I can post
>>> some questions.
>
>> Get a ham license. Then you can find people who actively design and build
>> things, like to talk about them and would gladly help you.
>
> Locally, we have about 2800 licensed hams in the county, of which I
> would guess about 500 are at least semi-active, 100 regularly attend
> various club meetings, 50 bother to build things, and perhaps 4 are
> qualified to design anything useful. While it's possible to get some
> help with design and construction from ham radio, it really depends on
> whom you contact.

Valid point, although I think you exaggerate a bit.

Now, give those same numbers for the denizens of sci.electronics.repair.
Maybe two numbers, with and without the profuse few who insist
on pushing the SNR toward zero.

I'd also like to hear your estimate of the percentage that even
attempt to add USEFUL new information that helps answer the
original question. Percentages by post will be different than percentage
by author.
And the percentage that just want to argue for the sake of arguing,
name calling, backstabbing, "hey look how smart I think I am", etc.

On any subject, it's important to ask someone who knows what he's talking
about.
Unfortunately, there are precious few of them.
Most get drowned out by the multitude.
Some of them ARE hams.
-.-

>
> This is the age of specialization. I can design and advise on some
> aspects of RF and repair. In other areas, I'm clueless. You would do
> best by finding a forum, blog, newsgroup, or mailing list that covers
> the specific area that you're interested in asking questions. Don't
> be fooled by the names or lack of traffic. There are often forums
> where most of the answers are by email from those that just don't want
> their names and advice subject to public scrutiny. For example, I've
> found that the LEAST useful forum for solving Apple computer related
> problems is Apple's own forums. Just post your question and see what
> happens. If you get a dozen one-line useless bad guesses, move on.
>
> As always, the quality of the answers depend heavily on the quality of
> the question. Without a clue as the nature of the question, vague
> answers, like this one, will be epidemic.
>

== 21 of 21 ==
Date: Sun, Mar 20 2011 12:17 pm
From: Meat Plow

On Sun, 20 Mar 2011 13:21:16 -0400, Michael A. Terrell wrote:

> "Geoffrey S. Mendelson" wrote:
>>
>> Michael A. Terrell wrote:
>> > You've got to be kidding. I know a lot of hams who don't even own
>> > a
>> > soldering iron. They ship their radios off for factory service,
>> > unlike 40 years ago.
>>
>> Totally irrelevant. I know a lot of people who can barely figure out
>> how to put gasoline in their cars, but that does not mean there are is
>> no one who knows how they work, and repair and "upgrade" their cars.
>>
>> It's like this group. You ask a question and you get answers. Most of
>> them are not worth the paper they were never printed upon.
>>
>> You go to a web forum, you get the same results. You ask a bunch of
>> hams and you get an answer. Not from all of them, but from one or two
>> who know what they are talking about.
>
>
> Right. Sure. Maybe in your small world. I recently went to the
> local ham radio club's hamfest. 99% of the items for sale were cheap
> chinese crap that is even cheaer on Ebay. the hams that knew what they
> were doing have either quit the hobby, or are now 'Silent Keys'. I saw
> more computer related items than radio, and the couple vendors with
> components had no one at their tables.

When a few of us used to go in on a table at a hamfest we'd go dig in the
attic or basement for a bunch of junk to sell. I used to go to Dayton Oh
every year but that started being a joke. Most junk and computers. A few
vendors from Kenwood, Yaesu, Alinco, MFD etc.. Not like it was 20 years
ago.

--
Live Fast Die Young, Leave A Pretty Corpse

==============================================================================
TOPIC: USB device interfering AM radio
http://groups.google.com/group/sci.electronics.repair/t/3ab7201fcff1b0c6?hl=en
==============================================================================

== 1 of 3 ==
Date: Sun, Mar 20 2011 6:15 am
From: Man-wai Chang

I just discovered this. And I also found that the AC to USB power
adaptor does not have a metal ground pin.

So would this AM interference be gone after getting a better AC to USB
power adaptor?

--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and Farce be with you!
/( _ )\ (x86_64 Ubuntu 9.10) Linux 2.6.38
^ ^ 21:13:01 up 2 days 47 min 0 users load average: 0.00 0.07 0.08
不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 (CSSA):
http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa

== 2 of 3 ==
Date: Sun, Mar 20 2011 10:05 am
From: Jeff Liebermann

On Sun, 20 Mar 2011 21:15:04 +0800, Man-wai Chang
<toylet.toylet@gmail.com> wrote:

>I just discovered this. And I also found that the AC to USB power
>adaptor does not have a metal ground pin.

It's double insulated and therefore does not need a protective
grounded plug.

>So would this AM interference be gone after getting a better AC to USB
>power adaptor?

Yes. What you're hearing are harmonics of the 20-50Khz switching
frequency in the power supply. These are suppose to meed FCC Part 15
incidental and conducted radiation specifications. Except for name
brand manufacturers, most of these wall warts do not meet the specs
(by my measurements). There's no way to easily predict which wall
wart is any better than any other, leaving you with trial and error to
make your selection. Fortunately, USB power adapters are cheap and
common, so you should be able to find one that's fairly clean (and
return the others).

Also, note that your unspecified model AM radio may also be
contributory. My guess(tm) is that you have both the USB power
adapter and the radio plugged into the same outlet or power strip.
Conducted radiation, through the power lines is another component of
the problem. Your radio may be susceptible to junk pickup from the
power lines, or for really cheap junk, use the power cord as an
antenna. Clamp on ferrite beads (more like ferrite blocks) are
available to block conducted radiation and pickup.

<http://en.wikipedia.org/wiki/Electromagnetic_compatibility>
<http://www.radiolabs.com/Articles/amnoise.html>
<http://www.stevelarkins.freeuk.com/images/computer_rfi_solution2.jpg>

--
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

== 3 of 3 ==
Date: Sun, Mar 20 2011 10:24 am
From: Meat Plow

On Sun, 20 Mar 2011 21:15:04 +0800, Man-wai Chang wrote:

> I just discovered this. And I also found that the AC to USB power
> adaptor does not have a metal ground pin.
>
> So would this AM interference be gone after getting a better AC to USB
> power adaptor?

The adapter may be a switch mode supply and you are hearing a harmonic
spur of the frequency the supply uses to function on. A switch to non-
switch mode supply would cure your problem.

--
Live Fast Die Young, Leave A Pretty Corpse

==============================================================================
TOPIC: BAD SEXY SEEMS
http://groups.google.com/group/sci.electronics.repair/t/58152be38535fb6f?hl=en
==============================================================================

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