ADC limitations for bandpass/IF sampling

[clam]

I want to sample a 1MHz RF signal at 20kHz (i.e., IF/Bandpass sampling fo
downconversion. Is there any limiting factor on the ADC that I need t
consider? e.g., does the ADC need special circuit? or smal
sample-and-hold delay time?

CJLam

[Bhaskar Thiagarajan]

"clam" <[email protected]> wrote in message
news:[email protected] ...
> I want to sample a 1MHz RF signal at 20kHz (i.e., IF/Bandpass sampling for
> downconversion. Is there any limiting factor on the ADC that I need to
> consider? e.g., does the ADC need special circuit? or small
> sample-and-hold delay time?
>
> CJLam

You need to be sure that the analog bandwidth of the ADC is higher than
1MHz. You should find this as a parameter in the data sheet.
Also, I'm assuming your BW of the RF signal is not much more than about
5kHz.

Cheers
Bhaskar

[Richard Owlett]

Bhaskar Thiagarajan wrote:
> "clam" <[email protected]> wrote in message
> news:[email protected] ...
>
>>I want to sample a 1MHz RF signal at 20kHz (i.e., IF/Bandpass sampling for
>>downconversion. Is there any limiting factor on the ADC that I need to
>>consider? e.g., does the ADC need special circuit? or small
>>sample-and-hold delay time?
>>
>>CJLam
>
>
> You need to be sure that the analog bandwidth of the ADC is higher than
> 1MHz. You should find this as a parameter in the data sheet.
> Also, I'm assuming your BW of the RF signal is not much more than about
> 5kHz.
>
> Cheers
> Bhaskar
>
>

I assume Bhaskar means at least the sample acquisition time is less than
..5 microsecond [ That's how I would apply Nyquist to the situation. ]

Given that assumption and assuming the 20kHz sampling rate is not locked
to the 1 MHz carrier, I can not see what information could be obtained.

Obviously I'm missing something.

[Eric Jacobsen]

On Tue, 13 Dec 2005 13:43:23 -0600, "clam" <[email protected]>
wrote:

>I want to sample a 1MHz RF signal at 20kHz (i.e., IF/Bandpass sampling for
>downconversion. Is there any limiting factor on the ADC that I need to
>consider? e.g., does the ADC need special circuit? or small
>sample-and-hold delay time?
>
>CJLam

Yes, the sample-and-hold time is important, but shouldn't be too
difficult for a 1MHz input. For IF sampling this is one of the more
important parameters.

As Bhaskar mentioned, the input BW of the front end has to support the
desired input spectrum. Getting a narrow enough IF filter at 1MHz to
support such a low signal bandwidth might be tricky, so I'm assuming
you've got reasonable control of the input spectrum.

Eric Jacobsen
Minister of Algorithms, Intel Corp.
My opinions may not be Intel's opinions.
http://www.ericjacobsen.org

[Jerry Avins]

Richard Owlett wrote:
> Bhaskar Thiagarajan wrote:

>> You need to be sure that the analog bandwidth of the ADC is higher than
>> 1MHz. You should find this as a parameter in the data sheet.
>> Also, I'm assuming your BW of the RF signal is not much more than about
>> 5kHz.
>>
>> Cheers
>> Bhaskar
>>
>>
>
> I assume Bhaskar means at least the sample acquisition time is less than
> .5 microsecond [ That's how I would apply Nyquist to the situation. ]

No. He means that the electronics between the analog input and the
sampler will pass 1 MHz without significant attenuation or phase shift.
(It's also important that the aperture uncertainty be as good as would
be needed to sample at the full (2 MHz) rate.)

> Given that assumption and assuming the 20kHz sampling rate is not locked
> to the 1 MHz carrier, I can not see what information could be obtained.
>
> Obviously I'm missing something.

Yes. Read the chapter on sub-band sampling in Rick's book. (You located
it on the shelf behind you.)

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Bhaskar Thiagarajan]

"Richard Owlett" <[email protected]> wrote in message
news:[email protected]...
> Bhaskar Thiagarajan wrote:
> > "clam" <[email protected]> wrote in message
> > news:[email protected] ...
> >
> >>I want to sample a 1MHz RF signal at 20kHz (i.e., IF/Bandpass sampling
for
> >>downconversion. Is there any limiting factor on the ADC that I need to
> >>consider? e.g., does the ADC need special circuit? or small
> >>sample-and-hold delay time?
> >>
> >>CJLam
> >
> >
> > You need to be sure that the analog bandwidth of the ADC is higher than
> > 1MHz. You should find this as a parameter in the data sheet.
> > Also, I'm assuming your BW of the RF signal is not much more than about
> > 5kHz.
> >
> > Cheers
> > Bhaskar
> >
> >
>
> I assume Bhaskar means at least the sample acquisition time is less than
> .5 microsecond [ That's how I would apply Nyquist to the situation. ]

No - as Jerry has already explained, one of the important things that
limits undersampling is the BW of the front-end of the ADC. Usually the
analog front-end of an ADC will be several tens of times (say 10x) the max
sampling rate it can support.

The sampling rate only needs to be higher than twice the BW of the signal
for satisfying Nyquist (this relates to my 5kHz remark...I used 5k and not
10k to give room for practical considerations like filter roll-off and
such).

Cheers
Bhaskar

>
> Given that assumption and assuming the 20kHz sampling rate is not locked
> to the 1 MHz carrier, I can not see what information could be obtained.
>
> Obviously I'm missing something.
>

[Steve Underwood]

Bhaskar Thiagarajan wrote:

>"Richard Owlett" <[email protected]> wrote in message
>news:[email protected]...
>
>
>>Bhaskar Thiagarajan wrote:
>>
>>
>>>"clam" <[email protected]> wrote in message
>>>news:[email protected] ...
>>>
>>>
>>>
>>>>I want to sample a 1MHz RF signal at 20kHz (i.e., IF/Bandpass sampling
>>>>
>>>>
>for
>
>
>>>>downconversion. Is there any limiting factor on the ADC that I need to
>>>>consider? e.g., does the ADC need special circuit? or small
>>>>sample-and-hold delay time?
>>>>
>>>>CJLam
>>>>
>>>>
>>>You need to be sure that the analog bandwidth of the ADC is higher than
>>>1MHz. You should find this as a parameter in the data sheet.
>>>Also, I'm assuming your BW of the RF signal is not much more than about
>>>5kHz.
>>>
>>>Cheers
>>>Bhaskar
>>>
>>>
>>>
>>>
>>I assume Bhaskar means at least the sample acquisition time is less than
>>.5 microsecond [ That's how I would apply Nyquist to the situation. ]
>>
>>
>
>No - as Jerry has already explained, one of the important things that
>limits undersampling is the BW of the front-end of the ADC. Usually the
>analog front-end of an ADC will be several tens of times (say 10x) the max
>sampling rate it can support.
>
>
It is important to take care in how you define "ADC" in this context. To
so many people these days, it implies a chip, and that is how they think
of an ADC.

The key thing is the bandwidth up to the sampler, and the aperature of
the sampler itself. These days the sampler is typically within a
monolithic IC, and you cannot affect its performance. However, if you
are using an ADC chip with a low performance sampler you could put a
high performance external one in front of it, and get the overall result
you need. In fact, you can use a super duper external sampler, and
multiple slower ADCs. You pass successive narrow samples to the ADCs in
turn, and combine their outputs into a final high speed sample stream.
This form of polyphase sampling is much loved by those of a masochistic
tendency, for the pain and misery it can cause. :-) It is a nightmare to
get multiple ADCs like this to track over time and temperatures.

>The sampling rate only needs to be higher than twice the BW of the signal
>for satisfying Nyquist (this relates to my 5kHz remark...I used 5k and not
>10k to give room for practical considerations like filter roll-off and
>such).
>
>Cheers
>Bhaskar
>
>
>
>>Given that assumption and assuming the 20kHz sampling rate is not locked
>>to the 1 MHz carrier, I can not see what information could be obtained.
>>
>>Obviously I'm missing something.
>>
>>
Everyone misses something, even if its only their lost youth. :-)

Regards,
Steve

[Joerg]

Hello Bhaskar,

> No - as Jerry has already explained, one of the important things that
> limits undersampling is the BW of the front-end of the ADC. Usually the
> analog front-end of an ADC will be several tens of times (say 10x) the max
> sampling rate it can support.
>

If the ADC input circuitry doesn't offer such bandwidth you can sample
and hold. It's really no big deal if done right. I often sample via a
diode bridge driven from a toroid so that I don't have to worry about
the charge injection of CMOS switches.

Regards, Joerg

http://www.analogconsultants.com

[Jerry Avins]

Steve Underwood wrote:

...

> Everyone misses something, even if its only their lost youth. :-)

Ooh! I have to remember that one!

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Joerg]

Hello Steve,

> This form of polyphase sampling is much loved by those of a masochistic
> tendency, for the pain and misery it can cause. :-) It is a nightmare to
> get multiple ADCs like this to track over time and temperatures.
>

Nah, there are situations where you simply have to do it or else the
project would die. Done it a few times.

The trick is not to rely on any manual alignment whatsoever but to run a
little uC alongside and then provide auto-adjust circuitry for all three
variables for all ADCs minus one. Gain, offset and clock phase. It's not
really rocket science. On one project they parked a big TI DSP just for
that purpose. In the end its 'employment rate' hovered around a percent
or two, almost idle. The cost for the analog parts and the DACs to set
the trim levels was about $15 or so, peanuts compared to the cost of one
of the ADCs. This was not a one-off project but it remained in
production for about seven years until a faster and cheaper ADC type
came out where we could get it done without multi-phase.

Regards, Joerg

http://www.analogconsultants.com

[Richard Owlett]

Jerry Avins wrote:
> Steve Underwood wrote:
>
> ...
>
>> Everyone misses something, even if its only their lost youth. :-)
>
>
> Ooh! I have to remember that one!
>
> Jerry

I was wonder to what Jerry was responding so I did a Google of comp.dsp
for Author=Underwood and found the relevant message.

My ISP provides a Supernews account, that message does not appear.

*HOWEVER* his 12/10 message "Re: Happy Hmas!" appears on Supernews, but
not on Google search ;}

Aside to Steve re his post
Never fought battles you implied but reminded me of two aspects of "good
old days"
-- chopper stabilized op amps
-- multi ampere ground loops in audio racks of a radio station

[Chris Bore]

The ADC need only be suitable for the 20 kHz sampling.

But the analog hold circuit must be capable of the 1 MHz.

Chris
=====================
Chris Bore
www.bores.com


clam wrote:
> I want to sample a 1MHz RF signal at 20kHz (i.e., IF/Bandpass sampling for
> downconversion. Is there any limiting factor on the ADC that I need to
> consider? e.g., does the ADC need special circuit? or small
> sample-and-hold delay time?
>
> CJLam

[Bhaskar Thiagarajan]

"Joerg" <[email protected]> wrote in message
news:qJ_nf.33643$q%[email protected] om...
> Hello Steve,
>
> > This form of polyphase sampling is much loved by those of a masochistic
> > tendency, for the pain and misery it can cause. :-) It is a nightmare to
> > get multiple ADCs like this to track over time and temperatures.
> >
>
> Nah, there are situations where you simply have to do it or else the
> project would die. Done it a few times.
>
> The trick is not to rely on any manual alignment whatsoever but to run a
> little uC alongside and then provide auto-adjust circuitry for all three
> variables for all ADCs minus one. Gain, offset and clock phase. It's not
> really rocket science. On one project they parked a big TI DSP just for
> that purpose. In the end its 'employment rate' hovered around a percent
> or two, almost idle. The cost for the analog parts and the DACs to set
> the trim levels was about $15 or so, peanuts compared to the cost of one
> of the ADCs. This was not a one-off project but it remained in
> production for about seven years until a faster and cheaper ADC type
> came out where we could get it done without multi-phase.

Neat! I know of a few who've done this although I'm not masochistic enough
(sounds like you are :-))
Sometimes there are no other options and these kinds of approaches are
warranged - but in the case of the OP, I'd bet there are several viable
ones.

Cheers
Bhaskar


> Regards, Joerg
>
> http://www.analogconsultants.com

[Steve Underwood]

Richard Owlett wrote:
> Jerry Avins wrote:
>
>> Steve Underwood wrote:
>>
>> ...
>>
>>> Everyone misses something, even if its only their lost youth. :-)
>>
>>
>>
>> Ooh! I have to remember that one!
>>
>> Jerry
>
>
> I was wonder to what Jerry was responding so I did a Google of comp.dsp
> for Author=Underwood and found the relevant message.
>
> My ISP provides a Supernews account, that message does not appear.
>
> *HOWEVER* his 12/10 message "Re: Happy Hmas!" appears on Supernews, but
> not on Google search ;}
>
> Aside to Steve re his post
> Never fought battles you implied but reminded me of two aspects of "good
> old days"
> -- chopper stabilized op amps
> -- multi ampere ground loops in audio racks of a radio station

Steve Underwood has no weirdness, but newsgroups generally do. :-)

Google groups usually has everything. However, other news servers
typically seem to miss stuff. Sometimes a little, and sometimes a lot. I
often go to Google groups to figure out what a thread was really about.

Steve

[Joerg]

Hello Bhaskar,


> Neat! I know of a few who've done this although I'm not masochistic enough
> (sounds like you are :-))


I am not a masochist, at least I hope not. We just didn't have any other
choice back then to get to 12 bits. But I have to confess that I
really like those challenges. And when some folks say that it cannot be
done it's even more fun to get it done :-)

Regards, Joerg

http://www.analogconsultants.com

[Jerry Avins]

Joerg wrote:
> Hello Bhaskar,
>
>
>> Neat! I know of a few who've done this although I'm not masochistic
>> enough
>> (sounds like you are :-))
>
>
>
> I am not a masochist, at least I hope not. We just didn't have any other
> choice back then to get to 12 bits. But I have to confess that I really
> like those challenges. And when some folks say that it cannot be done
> it's even more fun to get it done :-)
>
> Regards, Joerg
>
> http://www.analogconsultants.com

Back in 1962 interviewed for a position at RCA Labs. One question was
about making 10 watts of square wave at 100 MHz. All I could do was tick
off all the tube types that couldn't do it and profess ignorance of any
semiconductors that might. The interviewer agreed that those avenues
were closed, but added, "I need it, so what should I do?" A said that
the only way I could think of was to synthesize is by generating the
components separately. I said it would be a dog to tweak the phases, but
that it could be made stable enough in the lab. He told me "That's what
we did" and I got the job. Sometimes the hard way is the only way.

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Steve Underwood]

Jerry Avins wrote:

> Joerg wrote:
>
>> Hello Bhaskar,
>>
>>
>>> Neat! I know of a few who've done this although I'm not masochistic
>>> enough
>>> (sounds like you are :-))
>>
>>
>>
>>
>> I am not a masochist, at least I hope not. We just didn't have any
>> other choice back then to get to 12 bits. But I have to confess that
>> I really like those challenges. And when some folks say that it
>> cannot be done it's even more fun to get it done :-)
>>
>> Regards, Joerg
>>
>> http://www.analogconsultants.com
>
>
> Back in 1962 interviewed for a position at RCA Labs. One question was
> about making 10 watts of square wave at 100 MHz. All I could do was
> tick off all the tube types that couldn't do it and profess ignorance
> of any semiconductors that might. The interviewer agreed that those
> avenues were closed, but added, "I need it, so what should I do?" A
> said that the only way I could think of was to synthesize is by
> generating the components separately. I said it would be a dog to
> tweak the phases, but that it could be made stable enough in the lab.
> He told me "That's what we did" and I got the job. Sometimes the hard
> way is the only way.
>
> Jerry

I remember getting to 12 bits at 3M samples/second in the 1970s, using
four 750k sample/second Philbrick ADCs polyphased. In those days using a
processor to manage them wasn't on (though there were dead times in
their operation, every few seconds, where we could have done some kind
of calibration). Being large bricks, with several chips inside, making
them thermally track wasn't easy. Yeah, sometimes the hard way is the
only way. However, it sucks up so much of your time trying to deal with
this stuff, it seriously detracts from doing the interesting stuff with
the digitised data. I've never been big on brute force solutions.

The next system used a form of pipelined ADC, with each chip handling 2
bits of the final result. These were made by Quantel (the TV effects
people). They were dramatically better (though still somewhat
problematic) without really using devices that were inherently faster.
Maybe the smart way was better than the hard way? :-)

Regards,
Steve

[Richard Owlett]

Jerry Avins wrote:
> Richard Owlett wrote:
>
>> Bhaskar Thiagarajan wrote:
>
>
>>> You need to be sure that the analog bandwidth of the ADC is higher than
>>> 1MHz. You should find this as a parameter in the data sheet.
>>> Also, I'm assuming your BW of the RF signal is not much more than about
>>> 5kHz.
>>>
>>> Cheers
>>> Bhaskar
>>>
>>>
>>
>> I assume Bhaskar means at least the sample acquisition time is less
>> than .5 microsecond [ That's how I would apply Nyquist to the
>> situation. ]
>
>
> No. He means that the electronics between the analog input and the
> sampler will pass 1 MHz without significant attenuation or phase shift.
> (It's also important that the aperture uncertainty be as good as would
> be needed to sample at the full (2 MHz) rate.)
>
>> Given that assumption and assuming the 20kHz sampling rate is not
>> locked to the 1 MHz carrier, I can not see what information could be
>> obtained.
>>
>> Obviously I'm missing something.
>
>
> Yes. Read the chapter on sub-band sampling in Rick's book.

I assume you mean "Sampling Bandpass Signals" in Chapter 2.
I "understood" each of his math steps but I still miss big picture.
Math seems to clash with my concept of physical reality.
[part of reason I never got my EE degree? ;]


> (You located it on the shelf behind you.)

It moved next to recliner.

>
> Jerry

[Joerg]

Hello Steve,

> I remember getting to 12 bits at 3M samples/second in the 1970s, using
> four 750k sample/second Philbrick ADCs polyphased. In those days using a
> processor to manage them wasn't on (though there were dead times in
> their operation, every few seconds, where we could have done some kind
> of calibration). Being large bricks, with several chips inside, making
> them thermally track wasn't easy. Yeah, sometimes the hard way is the
> only way. However, it sucks up so much of your time trying to deal with
> this stuff, it seriously detracts from doing the interesting stuff with
> the digitised data. I've never been big on brute force solutions.
>

We could have done it without a micro because all it did was regulate
out the deviations while applying a test signal, one function at a time.
So a three bit shift register and some analog "glue" would have worked.
But we used a DSP because they had already parked one on the board, it
was there when I came and they didn't want to take it back out. IIRC it
already had one rather mundane job like a slow RS232 comm. Yawn. It was
like using a Ferrari to go grocery shopping.

Regards, Joerg

http://www.analogconsultants.com

[Jerry Avins]

Richard Owlett wrote:

...

> I assume you mean "Sampling Bandpass Signals" in Chapter 2.
> I "understood" each of his math steps but I still miss big picture.
> Math seems to clash with my concept of physical reality.
> [part of reason I never got my EE degree? ;]

I'm with you there: math is useful to me for quantifying, but not very
much for conceptualizing. I always have a niggling doubt about my
understanding of things I can explain only with math. I think I
understand sampling subband signals.

Shannon tells you that you need at a bit more than two samples per cycle
to nail down a frequency component, and that the smaller that bit is,
the more samples it takes for it to come clear.* Believe him. (He didn't
need to tell me because I learned how to extract Fourier components by
hand.) The penalty for not sampling fast enough is aliasing.

Aliasing isn't necessarily bad; there are times when it doesn't bother
us at all. Consider a sampler running at 10 KHz. Frequencies in the
sampled signal from 0 to 5 KHz will be sampled just fine. Those from 5
to 10 KHz will alias and end up looking like they ran from 5 to 0 kHz --
an inversion. Frequencies from 10 to 15 KHz will look like (be aliases
of) the frequencies from 0 to 5 KHz. A mess? Only maybe.

Normally, before the signal is sampled. it will be run through a lowpass
filter to cut off everything above, say, 4.5 KHz, and the reconstruction
filter will be similar. Suppose instead that we use bandpass filters
that pass 5.5 to 9.5 KHz. Can you see that the signal /in that band/
will be faithfully reproduced? If "yes", I don't have to write more. If
"no", tell me what eludes you.

...

Jerry
__________________________________________
* We're talking obtainable samples here. I'll give up on you if you
argue from infinite precision just to be ornery.
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Joerg]

Hello Jerry,
>
> Back in 1962 interviewed for a position at RCA Labs. One question was
> about making 10 watts of square wave at 100 MHz. All I could do was tick
> off all the tube types that couldn't do it and profess ignorance of any
> semiconductors that might. The interviewer agreed that those avenues
> were closed, but added, "I need it, so what should I do?" A said that
> the only way I could think of was to synthesize is by generating the
> components separately. I said it would be a dog to tweak the phases, but
> that it could be made stable enough in the lab. He told me "That's what
> we did" and I got the job. Sometimes the hard way is the only way.
>

Synthesizing is a cool method. It's interesting to think about problems
while having to limit the parts to what was around in the early 60's.

Depending on what transition time was needed maybe it could have been
done with tubes. A couple of 2C39 come to mind which were pretty cheap,
at least as mil surplus. The output transformer would be quite
challenging and in those days you could not get that designed with CAD
like today. The noise from the air cooling might also have been
considered a nuisance by the interviewer.

Regards, Joerg

http://www.analogconsultants.com

[Jerry Avins]

Joerg wrote:
> Hello Jerry,
>
>>
>> Back in 1962 interviewed for a position at RCA Labs. One question was
>> about making 10 watts of square wave at 100 MHz. All I could do was
>> tick off all the tube types that couldn't do it and profess ignorance
>> of any semiconductors that might. The interviewer agreed that those
>> avenues were closed, but added, "I need it, so what should I do?" A
>> said that the only way I could think of was to synthesize is by
>> generating the components separately. I said it would be a dog to
>> tweak the phases, but that it could be made stable enough in the lab.
>> He told me "That's what we did" and I got the job. Sometimes the hard
>> way is the only way.
>>
>
> Synthesizing is a cool method. It's interesting to think about problems
> while having to limit the parts to what was around in the early 60's.
>
> Depending on what transition time was needed maybe it could have been
> done with tubes. A couple of 2C39 come to mind which were pretty cheap,
> at least as mil surplus. The output transformer would be quite
> challenging and in those days you could not get that designed with CAD
> like today. The noise from the air cooling might also have been
> considered a nuisance by the interviewer.

It was a power supply for a then classified computer using tunnel
diodes. Since square-wave current into a low impedance was needed, they
used a capacitative ballast impedance. The resulting differentiation
reduced the necessary amplitude the higher harmonics from 1/n to 1/n^2.
The 7th harmonic was overkill.

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Joerg]

Hello Jerry,
>
> It was a power supply for a then classified computer using tunnel
> diodes. Since square-wave current into a low impedance was needed, they
> used a capacitative ballast impedance. The resulting differentiation
> reduced the necessary amplitude the higher harmonics from 1/n to 1/n^2.
> The 7th harmonic was overkill.
>

That would have been tough with a tube. Did they ever de-classify it and
put some info on the web?


> Engineering is the art of making what you want from things you can get. <

That's why engineering was more fun in the old days. It was tougher.
There was no Digikey and you had to make do with whatever the radio or
TV industry used. I remember concocting state registers and ring
counters with Ge transistor because they wanted over $5 for one RTL chip
which exceeded my allowance. And even at that price they probably were
from a 're-labeler'. Bulk waste days were field days because one could
harvest tons of tubes for free and create cool stuff with them.

Regards, Joerg

http://www.analogconsultants.com

[Jerry Avins]

Joerg wrote:
> Hello Jerry,

...

> That would have been tough with a tube. Did they ever de-classify it and
> put some info on the web?

Not that I know. I don't think I'm talking out of turn by giving the
name: Project Lightning.

...

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Spehro Pefhany]

On Thu, 15 Dec 2005 20:44:25 -0500, the renowned Jerry Avins
<[email protected]> wrote:

>Joerg wrote:
>> Hello Jerry,
>
> ...
>
>> That would have been tough with a tube. Did they ever de-classify it and
>> put some info on the web?
>
>Not that I know. I don't think I'm talking out of turn by giving the
>name: Project Lightning.
>
>Jerry

It's mentioned here:
http://www.stanford.edu/group/mmdd/SiliconValley/Flamm/Flamm_TargetComputer.html

which leads to this 1980 article (abstract only, they want $19 for the
article):

http://csdl2.computer.org/persagen/DLAbsToc.jsp?resourcePath=/dl/mags/an/&toc=comp/mags/an/1980/01/a1toc.xml&DOI=10.1109/MAHC.1980.10012



Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
[email protected] Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

[Al Clark]

Joerg <[email protected]> wrote in
news:[email protected]. com:

> Hello Jerry,
>>
>> It was a power supply for a then classified computer using tunnel
>> diodes. Since square-wave current into a low impedance was needed,
>> they used a capacitative ballast impedance. The resulting
>> differentiation reduced the necessary amplitude the higher harmonics
>> from 1/n to 1/n^2. The 7th harmonic was overkill.
>>
>
> That would have been tough with a tube. Did they ever de-classify it
> and put some info on the web?
>
>
> > Engineering is the art of making what you want from things you can
> > get. <
>
> That's why engineering was more fun in the old days. It was tougher.

Its wasn't tougher, just different.

One of the changes that I think will affect our profession is that it is
very difficult for a kid to get started if he wants to build hardware.

You probably need several thousand dollars of used equipment to start
(microscope, good soldering iron, etc.) This is a lot of money for a 16
year old kid.

Of course, we didn't have personal computers.....


> There was no Digikey and you had to make do with whatever the radio or
> TV industry used.

I used to go to the local shop for parts, then Radio Shack....


I remember concocting state registers and ring
> counters with Ge transistor because they wanted over $5 for one RTL
> chip which exceeded my allowance. And even at that price they probably
> were from a 're-labeler'. Bulk waste days were field days because one
> could harvest tons of tubes for free and create cool stuff with them.
>
> Regards, Joerg
>
> http://www.analogconsultants.com








--
Al Clark
Danville Signal Processing, Inc.
--------------------------------------------------------------------
Purveyors of Fine DSP Hardware and other Cool Stuff
Available at http://www.danvillesignal.com

[Steve Underwood]

Al Clark wrote:
> Joerg <[email protected]> wrote in
> news:[email protected]. com:
>
>
>>Hello Jerry,
>>
>>>It was a power supply for a then classified computer using tunnel
>>>diodes. Since square-wave current into a low impedance was needed,
>>>they used a capacitative ballast impedance. The resulting
>>>differentiation reduced the necessary amplitude the higher harmonics
>>>from 1/n to 1/n^2. The 7th harmonic was overkill.
>>>
>>
>>That would have been tough with a tube. Did they ever de-classify it
>>and put some info on the web?
>>
>>
>>
>>>Engineering is the art of making what you want from things you can
>>>get. <
>>
>>That's why engineering was more fun in the old days. It was tougher.
>
>
> Its wasn't tougher, just different.
>
> One of the changes that I think will affect our profession is that it is
> very difficult for a kid to get started if he wants to build hardware.
>
> You probably need several thousand dollars of used equipment to start
> (microscope, good soldering iron, etc.) This is a lot of money for a 16
> year old kid.
>
> Of course, we didn't have personal computers.....

Its very hard for any of us to prototype now. BGA, QFN, everything else
new seems like a "get your hands off" kinda device. Professionally this
forces us to use simulations of one sort or another to a high degree.
Any school kid can do the same on their PC. There are a number of free
tools (e.g. Octave) to keep the cost really low. They all have PCs, so
that's a non-issue.

So..... at a hands on level what you say is kind of true. However, the
wealth of things they can do with a PC these days I think allows them to
go much farther in interesting engineering than I could when I was young.

One practical consideration:

When I was 12, my father let me build valve/tube equipment running on
400V to 500V. He was an electro-mechanical engineer, so he fully
understood what he was letting me do. There is *absolutely* *no* *way*
my two kids are going to do that when they are 12 :-)

[...]

Steve

[Jerry Avins]

Steve Underwood wrote:

...

> Its very hard for any of us to prototype now. BGA, QFN, everything else
> new seems like a "get your hands off" kinda device. Professionally this
> forces us to use simulations of one sort or another to a high degree.
> Any school kid can do the same on their PC. There are a number of free
> tools (e.g. Octave) to keep the cost really low. They all have PCs, so
> that's a non-issue.
>
> So..... at a hands on level what you say is kind of true. However, the
> wealth of things they can do with a PC these days I think allows them to
> go much farther in interesting engineering than I could when I was young.

Hands-on matters. Today we have college students and beyond who glibly
compute complex baseband signals on a single twisted pair, and wonder
how to proceed with their simulations. It's east to forget that no
matter how small things become, they're still made up of parts that
interact.

> One practical consideration:
>
> When I was 12, my father let me build valve/tube equipment running on
> 400V to 500V. He was an electro-mechanical engineer, so he fully
> understood what he was letting me do. There is *absolutely* *no* *way*
> my two kids are going to do that when they are 12 :-)

Acquaintances and neighbors were aghast that I let my kids use tools
like saws and chisels before first grade. I explained that I was careful
to teach them how to use such tools -- in general and specifically --
without hurting themselves. I too drew a line. I allowed them to use
tools that could cut a finger, but not one that could cut a finger off.

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Rocky]

Steve Underwood wrote:
> When I was 12, my father let me build valve/tube equipment running on
> 400V to 500V. He was an electro-mechanical engineer, so he fully
> understood what he was letting me do. There is *absolutely* *no* *way*
> my two kids are going to do that when they are 12 :-)

I think it can be one of the best ways to really learn. It's hard to
get a heart-stopping shock in the base of a biscuit tin. Maybe a few
white spots on the fingers from touching the HT line.

Kids will experiment and do far more life threatening things that that.

My biggest scare building a 4 tube radio was when a second-hand HT
smoothing cap exploded, covering the ceiling with black spots and other
goo while we were fault finding.

Regards
Rocky

[Al Clark]

"Rocky" <[email protected]> wrote in news:1134751225.596897.33290
@g47g2000cwa.googlegroups.com:

> Steve Underwood wrote:
>> When I was 12, my father let me build valve/tube equipment running on
>> 400V to 500V. He was an electro-mechanical engineer, so he fully
>> understood what he was letting me do. There is *absolutely* *no* *way*
>> my two kids are going to do that when they are 12 :-)
>
> I think it can be one of the best ways to really learn. It's hard to
> get a heart-stopping shock in the base of a biscuit tin. Maybe a few
> white spots on the fingers from touching the HT line.
>
> Kids will experiment and do far more life threatening things that that.
>
> My biggest scare building a 4 tube radio was when a second-hand HT
> smoothing cap exploded, covering the ceiling with black spots and other
> goo while we were fault finding.
>
> Regards
> Rocky
>
>

I still call powering up a circuit the first time, the smoke test.

Its been a long time since one actually smoked (they don't always work,
but they tend to be a lot more benign).

When I was a kid, they usually smoked. I think that about half the kids in
my EE class were reasonably competent technicians. This is rarely the case
today. OTOH, most of the students are C programmers.

I'm not criticizing, young techies. I think they are not very different
than us grey beards (or female equivalents) when we were their age. They
just have different resources and opportunities. I do think that most of
them lack good hardware skills, which is unfortunate. Sometimes the best
software is code and sometimes its solder.


--
Al Clark
Danville Signal Processing, Inc.
--------------------------------------------------------------------
Purveyors of Fine DSP Hardware and other Cool Stuff
Available at http://www.danvillesignal.com

[Richard Owlett]

Al Clark wrote:
[*SNIP*]
>>>Engineering is the art of making what you want from things you can
>>>get. <
>>
>>That's why engineering was more fun in the old days. It was tougher.
>
>
> Its wasn't tougher, just different.
>
> One of the changes that I think will affect our profession is that it is
> very difficult for a kid to get started if he wants to build hardware.
>
> You probably need several thousand dollars of used equipment to start
> (microscope, good soldering iron, etc.) This is a lot of money for a 16
> year old kid.
>
> Of course, we didn't have personal computers.....
>

*WHAT* ?

just how do you justify that monetary outlay?

I'll use myself as an example ;}

I am routinely giving grief to regulars on
comp.dsp
comp.speech.research
comp.speech.users
comp.lang.forth
sci.geo.satellite-nav
alt.satellite.gps
comp.arch.embedded


I have not expended dollars, but I've made some *THINK* ;)







>
>
>>There was no Digikey and you had to make do with whatever the radio or
>>TV industry used.
>
>
> I used to go to the local shop for parts, then Radio Shack....
>
>
> I remember concocting state registers and ring
>
>>counters with Ge transistor because they wanted over $5 for one RTL
>>chip which exceeded my allowance. And even at that price they probably
>>were from a 're-labeler'. Bulk waste days were field days because one
>>could harvest tons of tubes for free and create cool stuff with them.
>>
>>Regards, Joerg
>>
>>http://www.analogconsultants.com
>
>
>
>
>
>
>
>
>

[Joerg]

Hello Jerry,

> Hands-on matters. Today we have college students and beyond who glibly
> compute complex baseband signals on a single twisted pair, and wonder
> how to proceed with their simulations. It's east to forget that no
> matter how small things become, they're still made up of parts that
> interact.
>

I had several cases where they could not understand my module specs. And
my prose is quite ok since even (older) mechanical engineers never have
problems with that. Some of the new grads can't even solder. It's pathetic.


> Acquaintances and neighbors were aghast that I let my kids use tools
> like saws and chisels before first grade. I explained that I was careful
> to teach them how to use such tools -- in general and specifically --
> without hurting themselves. I too drew a line. I allowed them to use
> tools that could cut a finger, but not one that could cut a finger off.
>

Probably because you were good parents and your kids paid attention to
what you taught them. I remember a trip in the mid west when a big truck
pulled up next to us at the market. A little boy hopped out, maybe 14 or
15. "Are you allowed to drive that thing?" "Ahm, well, ahem, pa kinda
ruined his back and we really need some stuff for the farm". He had been
in front of us for 10 miles or so and all I could say is he drove like a
pro, very safely.

Regards, Joerg

http://www.analogconsultants.com

[Joerg]

Hello Al,

> Its wasn't tougher, just different.
>

Maybe not tougher but more expensive. Even in 2005 Dollars our
allowances were much smaller than today's.


> One of the changes that I think will affect our profession is that it is
> very difficult for a kid to get started if he wants to build hardware.
>

Nah. Recently I needed some CD4000 chips right away so I drove into town
and picked them up at an electronics store. All between 30 and 50 cents
a piece. When I grew up you couldn't touch any of these for under $4.
Just imagine what that would be in 2005 Dollars.

Now you can buy a uC for a couple Dollars and program it for free by
just making a serial cable and hooking up a little level translation.
Back then any kind of processor cost more than a decent bicycle and
wouldn't work without external RAM. I paid more than $25 for one lone
memory chip which offered a whopping 1k (kilobits, not kilobytes). I'd
really needed 2k but that was way out of reach. Oh, and I had to punch
in the data with buttons until blisters showed up. The only computer was
at my fathers work, a huge IBM mainframe.

When I built a small frequency counter I had to wait a few weeks before
its sensitivity could become better than 1Vpp. That's because an AF126
was almost $10 at the local radio repair store. Too much. So when the
snow and ice became manageable I did a (rather scary) bicycle tour of
about 20 miles because the store in town had it for under $5. That AF126
had to be treated like a princess on the pea so as not to fry it, ever.
I mounted it in a socket so it could be used in another circuit while I
didn't need to run the counter.

Nowadays you can get a whole bag of similar speed BJTs for a Dollar or two.

Regards, Joerg

http://www.analogconsultants.com

[Al Clark]

Richard Owlett <[email protected]> wrote in
news:[email protected]:

> Al Clark wrote:
> [*SNIP*]
>>>>Engineering is the art of making what you want from things you can
>>>>get. <
>>>
>>>That's why engineering was more fun in the old days. It was tougher.
>>
>>
>> Its wasn't tougher, just different.
>>
>> One of the changes that I think will affect our profession is that it
>> is very difficult for a kid to get started if he wants to build
>> hardware.
>>
>> You probably need several thousand dollars of used equipment to start
>> (microscope, good soldering iron, etc.) This is a lot of money for a
>> 16 year old kid.
>>
>> Of course, we didn't have personal computers.....
>>
>
> *WHAT* ?
>
> just how do you justify that monetary outlay?

Microscope with Boom & Light: $500-$1000
Soldering Station $150
Oscilloscope $250-$750
Handtools $50-$250

Signal Generator, Multimeter, etc.
Solder, Flux, Antistat Mat, etc...

This is before buying parts.


Sure, you can still buy thru hole parts for many things, but I think
you will find that you cannot avoid SMT parts for very long.





--
Al Clark
Danville Signal Processing, Inc.
--------------------------------------------------------------------
Purveyors of Fine DSP Hardware and other Cool Stuff
Available at http://www.danvillesignal.com

[Peter K.]

Al Clark <[email protected]> writes:

> I still call powering up a circuit the first time, the smoke test.
>
> Its been a long time since one actually smoked (they don't always work,
> but they tend to be a lot more benign).

When I was tutoring 1st year engineering labs, by far the biggest
mistake students had made when they said "it doesn't work" was to
leave the power supply off.

I _know_ it's bad, but I used to shout <BANG> when they turned the
power supply on. :-)

And nine times out of ten, everything worked. There were just two
times I remember anything "letting the smoke out". Once it was an
electrolytic capacitor that went <BANG> and the other time the
students got some diodes to glow faintly red... and they we'ren't
SUPPOSED to be LEDs.

Ciao,

Peter K.

[Vladimir Vassilevsky]

Peter K. wrote:


> When I was tutoring 1st year engineering labs, by far the biggest
> mistake students had made when they said "it doesn't work" was to
> leave the power supply off.
>
> I _know_ it's bad, but I used to shout <BANG> when they turned the
> power supply on. :-)
>

The engineers who work on the power electronics are usually very good
engineers. Many of them are stutterers also. Perhaps the folks who were
not that good just didn't survive.

VLV

[Jerry Avins]

Peter K. wrote:
> Al Clark <[email protected]> writes:
>
>
>>I still call powering up a circuit the first time, the smoke test.
>>
>>Its been a long time since one actually smoked (they don't always work,
>>but they tend to be a lot more benign).
>
>
> When I was tutoring 1st year engineering labs, by far the biggest
> mistake students had made when they said "it doesn't work" was to
> leave the power supply off.

When I was doing audio service, a fellow brought me a newly wired
Heathkit power amplifier to fix. When I asked him what the problem was,
he said, "I don't know. I didn't have the guts to turn it on."

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Ron N.]

Steve Underwood wrote:
> When I was 12, my father let me build valve/tube equipment running on
> 400V to 500V. He was an electro-mechanical engineer, so he fully
> understood what he was letting me do. There is *absolutely* *no* *way*
> my two kids are going to do that when they are 12 :-)

I attended a talk given my Gorden Moore recently. When asked how
he got interested in chemistry, he talked about using the stuff in
his chemistry set to blow things up. When asked later about
the declining interest in science education in the US, he lamented
that maybe it's because you can't get the fun chemistry sets any
longer.


IMHO. YMMV.
--
rhn A.T nicholson d.O.t C-o-M

[Joerg]

Hello Peter,

> I _know_ it's bad, but I used to shout <BANG> when they turned the
> power supply on. :-)
>

My first boss used to walk around, look over your shoulder, reach onto
the board, touch a chip or an electrolytic, quickly retract his hand and
say "ouch, why does this get hot?"

(None of this ever got hot, usually...)

Regards, Joerg

http://www.analogconsultants.com

[Joerg]

Hello Al,

> Microscope with Boom & Light: $500-$1000


How 'bout #3 magnifier glasses (a buck at the Dollar Store) and a loupe
on the swivel arm of a discarded drafting table lamp (pretty much free)?

Regards, Joerg

http://www.analogconsultants.com

[Tim Wescott]

Vladimir Vassilevsky wrote:

>
>
> Peter K. wrote:
>
>
>> When I was tutoring 1st year engineering labs, by far the biggest
>> mistake students had made when they said "it doesn't work" was to
>> leave the power supply off.
>>
>> I _know_ it's bad, but I used to shout <BANG> when they turned the
>> power supply on. :-)
>>
>
> The engineers who work on the power electronics are usually very good
> engineers. Many of them are stutterers also. Perhaps the folks who were
> not that good just didn't survive.
>
> VLV
>
-- and the folks who aren't that nervous?

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

[Tim Wescott]

Peter K. wrote:

> Al Clark <[email protected]> writes:
>
>
>>I still call powering up a circuit the first time, the smoke test.
>>
>>Its been a long time since one actually smoked (they don't always work,
>>but they tend to be a lot more benign).
>
>
> When I was tutoring 1st year engineering labs, by far the biggest
> mistake students had made when they said "it doesn't work" was to
> leave the power supply off.
>
> I _know_ it's bad, but I used to shout <BANG> when they turned the
> power supply on. :-)
>
> And nine times out of ten, everything worked. There were just two
> times I remember anything "letting the smoke out". Once it was an
> electrolytic capacitor that went <BANG> and the other time the
> students got some diodes to glow faintly red... and they we'ren't
> SUPPOSED to be LEDs.
>
> Ciao,
>
> Peter K.

I had a coworker for a while who could make a perfect 120-cycle buzz,
loudly, just like a piece of power electronics about to go up in smoke.

I think if we hadn't been doing stuff that was all DC we would have
dragged him out and shot him...

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

[Joerg]

Hello Tim,

> I had a coworker for a while who could make a perfect 120-cycle buzz,
> loudly, just like a piece of power electronics about to go up in smoke.
>
> I think if we hadn't been doing stuff that was all DC we would have
> dragged him out and shot him...
>

This was from the days when smoking was still allowed in labs: Engineer
drinks coffee. Nature calls. While engineer is at the ceramics
department someone shoves a screw cap with a not-quite-extinguished butt
under the prototype. Engineer comes back. Smoke billowing out of
prototype. Engineer panics and rips all supplies off.

Regards, Joerg

http://www.analogconsultants.com

[Jerry Avins]

Joerg wrote:
> Hello Tim,
>
>> I had a coworker for a while who could make a perfect 120-cycle buzz,
>> loudly, just like a piece of power electronics about to go up in smoke.
>>
>> I think if we hadn't been doing stuff that was all DC we would have
>> dragged him out and shot him...
>>
>
> This was from the days when smoking was still allowed in labs: Engineer
> drinks coffee. Nature calls. While engineer is at the ceramics
> department someone shoves a screw cap with a not-quite-extinguished butt
> under the prototype. Engineer comes back. Smoke billowing out of
> prototype. Engineer panics and rips all supplies off.

A long piece of spaghetti stock artfully arranged with one end under the
chassis and the other where it can be blown into allows for more precise
timing.

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Peter K.]

Joerg <[email protected]> writes:

> This was from the days when smoking was still allowed in labs:
> Engineer drinks coffee. Nature calls. While engineer is at the
> ceramics department someone shoves a screw cap with a
> not-quite-extinguished butt under the prototype. Engineer comes
> back. Smoke billowing out of prototype. Engineer panics and rips all
> supplies off.

Yes, I heard a similar story... but it involved someone putting one
end of a vaccuum cleaner hose under a piece of equipment, standing
behind a partition and blowing smoke from their cigarette into the
other end of the hose (so that it looked like smoke was coming from
the piece of equipment).

:-)

Ciao,

Peter K.

[Peter K.]

Jerry Avins <[email protected]> writes:

> A long piece of spaghetti stock artfully arranged with one end under
> the chassis and the other where it can be blown into allows for more
> precise timing.

Aha! So you're the culprit! :-)

Ciao,

Peter K.

[Joerg]

Hello Peter,

> Yes, I heard a similar story... but it involved someone putting one
> end of a vaccuum cleaner hose under a piece of equipment, standing
> behind a partition and blowing smoke from their cigarette into the
> other end of the hose (so that it looked like smoke was coming from
> the piece of equipment).
>

I guess the screw cap method gave it more authenticity. The plastic in
there caused a smell that resembled frying cables.

Regards, Joerg

http://www.analogconsultants.com

[Al Clark]

Joerg <[email protected]> wrote in news:Cb0pf.33828
[email protected]:

> Hello Al,
>
>> Microscope with Boom & Light: $500-$1000
>
>
> How 'bout #3 magnifier glasses (a buck at the Dollar Store) and a loupe
> on the swivel arm of a discarded drafting table lamp (pretty much free)?
>
> Regards, Joerg
>
> http://www.analogconsultants.com

I solder using a microscope at about 7x. With practice, you know exactly
where your hands are (and the soldering tip). I don't think I've tried
soldering my fingers for several years.

I inspect at higher magnification.

A good light ring on the microscope really helps as well.

I have never tried 3x reading glasses. Maybe I will get a pair.



--
Al Clark
Danville Signal Processing, Inc.
--------------------------------------------------------------------
Purveyors of Fine DSP Hardware and other Cool Stuff
Available at http://www.danvillesignal.com

[Joerg]

Hello Al,

> I solder using a microscope at about 7x. With practice, you know exactly
> where your hands are (and the soldering tip). I don't think I've tried
> soldering my fingers for several years.
>

I used to solder under a video microscope where you have to look up at
the monitor. It's just a matter of practice but the microscopes get in
the way with larger circuit boards.


> I inspect at higher magnification.
>

I do as well. What I want to try out some day is to hook up a Nikon
Coolpix camera. It seems that those digital cameras have a downside in
that they can output NTSC while running but not digital data. So I
either have to get a video card for the lab computer or schlepp the
video monitor onto the top shelf.


> A good light ring on the microscope really helps as well.


I often use a bright halogen lamp that can be swiveled around to give
the best illumination. It can be very handy to find hair cracks and stuff.

>
> I have never tried 3x reading glasses. Maybe I will get a pair.
>

They are cool. But try to get some that are narrow enough so that you
can peek over the top. It prevents from bumping into stuff or knocking
things over (my keyboard could tell as story about that).

Regards, Joerg

http://www.analogconsultants.com

[Al Clark]

Joerg <[email protected]> wrote in
news:[email protected]. net:

> Hello Al,
>
>> I solder using a microscope at about 7x. With practice, you know
>> exactly where your hands are (and the soldering tip). I don't think
>> I've tried soldering my fingers for several years.
>>
>
> I used to solder under a video microscope where you have to look up at
> the monitor. It's just a matter of practice but the microscopes get in
> the way with larger circuit boards.
>
>
>> I inspect at higher magnification.
>>
>
> I do as well. What I want to try out some day is to hook up a Nikon
> Coolpix camera. It seems that those digital cameras have a downside in
> that they can output NTSC while running but not digital data. So I
> either have to get a video card for the lab computer or schlepp the
> video monitor onto the top shelf.

With the advancement and falling prices of digital cameras, this is a
very interesting idea.
>
>
>> A good light ring on the microscope really helps as well.
>
>
> I often use a bright halogen lamp that can be swiveled around to give
> the best illumination. It can be very handy to find hair cracks and
> stuff.

I have a small halogen lamp on the bench as well. The main catch is that
it gets warm. The fiberoptic light ring is much better.




>
>>
>> I have never tried 3x reading glasses. Maybe I will get a pair.
>>
>
> They are cool. But try to get some that are narrow enough so that you
> can peek over the top. It prevents from bumping into stuff or knocking
> things over (my keyboard could tell as story about that).

Thanks for the comments and ley us know if the camera idea works.

Al






>
> Regards, Joerg
>
> http://www.analogconsultants.com
>



--
Al Clark
Danville Signal Processing, Inc.
--------------------------------------------------------------------
Purveyors of Fine DSP Hardware and other Cool Stuff
Available at http://www.danvillesignal.com

[Jerry Avins]

Al Clark wrote:

...

> I have a small halogen lamp on the bench as well. The main catch is that
> it gets warm. The fiberoptic light ring is much better.
>
>
>
>
>
>>>I have never tried 3x reading glasses. Maybe I will get a pair.
>>>
>>
>>They are cool. But try to get some that are narrow enough so that you
>>can peek over the top. It prevents from bumping into stuff or knocking
>>things over (my keyboard could tell as story about that).
>
>
> Thanks for the comments and ley us know if the camera idea works.

A perf-board ring holding white LEDs makes a good cheap cool light ring.
They're relatively easy to make; if they aren't already articles of
commerce, they soon will be.

If anyone's interested, I'll post a picture of the 3X telescopic
magnifiers. You've probably seen your dentist use one. I can see around
them. My first wife said they made me look like a bug-eyed monster.

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Al Clark]

Jerry Avins <[email protected]> wrote in
news:[email protected]:

> Al Clark wrote:
>
> ...
>
>> I have a small halogen lamp on the bench as well. The main catch is
>> that it gets warm. The fiberoptic light ring is much better.
>>
>>
>>
>>
>>
>>>>I have never tried 3x reading glasses. Maybe I will get a pair.
>>>>
>>>
>>>They are cool. But try to get some that are narrow enough so that you
>>>can peek over the top. It prevents from bumping into stuff or
>>>knocking things over (my keyboard could tell as story about that).
>>
>>
>> Thanks for the comments and ley us know if the camera idea works.
>
> A perf-board ring holding white LEDs makes a good cheap cool light
> ring. They're relatively easy to make; if they aren't already articles
> of commerce, they soon will be.

There you go, You can start your own ebay business. This is a very good
idea. Light rings (even used) are expensive.


>
> If anyone's interested, I'll post a picture of the 3X telescopic
> magnifiers. You've probably seen your dentist use one. I can see
> around them. My first wife said they made me look like a bug-eyed
> monster.
>
> Jerry



--
Al Clark
Danville Signal Processing, Inc.
--------------------------------------------------------------------
Purveyors of Fine DSP Hardware and other Cool Stuff
Available at http://www.danvillesignal.com

[Jerry Avins]

Joerg wrote:
> Hello Al,
>
>> I solder using a microscope at about 7x. With practice, you know
>> exactly where your hands are (and the soldering tip). I don't think
>> I've tried soldering my fingers for several years.
>>
>
> I used to solder under a video microscope where you have to look up at
> the monitor. It's just a matter of practice but the microscopes get in
> the way with larger circuit boards.
>
>
>> I inspect at higher magnification.
>>
>
> I do as well. What I want to try out some day is to hook up a Nikon
> Coolpix camera. It seems that those digital cameras have a downside in
> that they can output NTSC while running but not digital data. So I
> either have to get a video card for the lab computer or schlepp the
> video monitor onto the top shelf.
>
>
>> A good light ring on the microscope really helps as well.
>
>
>
> I often use a bright halogen lamp that can be swiveled around to give
> the best illumination. It can be very handy to find hair cracks and stuff.
>
>>
>> I have never tried 3x reading glasses. Maybe I will get a pair.
>>
>
> They are cool. But try to get some that are narrow enough so that you
> can peek over the top. It prevents from bumping into stuff or knocking
> things over (my keyboard could tell as story about that).

I bought a no-name stereo microscope body for less than $50 and
refurbished it. Then I made a mount for it in part from an old telescope
focuser, and equipped it with eyepieces from my collection. (I bought a
new pair eventually.) The magnification is about 8 and 15. Nowadays, I
use it mostly for removing splinters in my hand because it supports
itself. I use 7X, 10X, and 15X Hastings triplet magnifiers; the 10X is
on my key ring. For soldering jewelry, I sometimes use a pair of 3X
Galilean telescopes. The long working distance -- about a foot -- means
I don't need a heat-shield mask.

I built a vertical illuminator into an old medical microscope, using a
discarded light source from a metallurgical microscope. An eyepiece tube
that accommodates 1-1/4 telescope eyepieces together with a 4X objective
gives me a decently wide monocular field at 32X, and of course, I can go
much higher. Working with inverted images takes getting used to, though.

I made an adapter that lets me use a C-mount camera instead of an
eyepiece. The sensor array is much smaller than a microscope's field, so
one sees the central part only at higher-than-wanted magnification.
Eventually, I added a positive lens to the adapter that reduces the
image size on the array, giving a broader field. I call it a wrolab lens
-- Barlow, backwards. (There's one in my C-5 telescope to reduce the
f-number from 10 to 6.3.) Putting the image up on a TV monitor takes a
lot of eyestrain out of repeated inspections. Besides, it's fun to show
grandchildren the activity in a drop of puddle water.

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[[email protected]]

Jerry Avins wrote:
....
> If anyone's interested, I'll post a picture of the 3X telescopic
> magnifiers. You've probably seen your dentist use one. I can see around
> them. My first wife said they made me look like a bug-eyed monster.

Can't you post a picture with you as bug-eyed monster :-) ?

[Peter K.]

[email protected] writes:

> Jerry Avins wrote:
> ...
> > If anyone's interested, I'll post a picture of the 3X telescopic
> > magnifiers. You've probably seen your dentist use one. I can see around
> > them. My first wife said they made me look like a bug-eyed monster.
>
> Can't you post a picture with you as bug-eyed monster :-) ?

A must! :-)

Ciao,

Peter K.

[Jerry Avins]

[email protected] wrote:
> Jerry Avins wrote:
> ...
>
>>If anyone's interested, I'll post a picture of the 3X telescopic
>>magnifiers. You've probably seen your dentist use one. I can see around
>>them. My first wife said they made me look like a bug-eyed monster.
>
>
> Can't you post a picture with you as bug-eyed monster :-) ?

OK: http://users.rcn.com/jyavins/BEM.jpg

I'm looking with 3 power at the statue of Lincoln seated inside the
Lincoln Memorial on the back of a penny. That's a good distance, but the
field is small; about 2" as they're mounted. 2.5" if moved closer to the
eyes.

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[[email protected]]

Jerry Avins wrote:

> [email protected] wrote:
> > Jerry Avins wrote:
> > ...
> >
> >>If anyone's interested, I'll post a picture of the 3X telescopic
> >>magnifiers. You've probably seen your dentist use one. I can see around
> >>them. My first wife said they made me look like a bug-eyed monster.
> >
> >
> > Can't you post a picture with you as bug-eyed monster :-) ?
>
> OK: http://users.rcn.com/jyavins/BEM.jpg

Neat! But do you have one from upfront? A _really_ scary one?

[Jerry Avins]

[email protected] wrote:
> Jerry Avins wrote:
>
>
>>[email protected] wrote:
>>
>>>Jerry Avins wrote:
>>>...
>>>
>>>
>>>>If anyone's interested, I'll post a picture of the 3X telescopic
>>>>magnifiers. You've probably seen your dentist use one. I can see around
>>>>them. My first wife said they made me look like a bug-eyed monster.
>>>
>>>
>>>Can't you post a picture with you as bug-eyed monster :-) ?
>>
>>OK: http://users.rcn.com/jyavins/BEM.jpg
>
>
> Neat! But do you have one from upfront? A _really_ scary one?

Your wish is my command. http://users.rcn.com/jyavins/BEM.htm

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[[email protected]]

Jerry Avins wrote:

> [email protected] wrote:
> > Jerry Avins wrote:
> >
> >
> >>[email protected] wrote:
> >>
> >>>Jerry Avins wrote:
> >>>...
> >>>
> >>>
> >>>>If anyone's interested, I'll post a picture of the 3X telescopic
> >>>>magnifiers. You've probably seen your dentist use one. I can see around
> >>>>them. My first wife said they made me look like a bug-eyed monster.
> >>>
> >>>
> >>>Can't you post a picture with you as bug-eyed monster :-) ?
> >>
> >>OK: http://users.rcn.com/jyavins/BEM.jpg
> >
> >
> > Neat! But do you have one from upfront? A _really_ scary one?
>
> Your wish is my command. http://users.rcn.com/jyavins/BEM.htm

Hahaha! That third one is just like I imagined! When she is a bit
older, I'll show this photo to Viviana when she was naughty :-).

Regards,
Andor

[Peter K.]

Jerry Avins <[email protected]> writes:

>
> Your wish is my command. http://users.rcn.com/jyavins/BEM.htm
>

Thanks, Jerry. ;-)

Ciao,

Peter K.

[Peter K.]

[email protected] writes:

> Hahaha! That third one is just like I imagined! When she is a bit
> older, I'll show this photo to Viviana when she was naughty :-).

Andor, thanks for suggesting the photos of Jerry. :-)

Ciao,

Peter K.

[Jerry Avins]

Peter K. wrote:
> [email protected] writes:
>
>
>>Hahaha! That third one is just like I imagined! When she is a bit
>>older, I'll show this photo to Viviana when she was naughty :-).
>
>
> Andor, thanks for suggesting the photos of Jerry. :-)

I made them a little easier to look at.

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯