Wind/Solar Electrics ???

[SolarFlare]

Simple hetrodyne system will do that. No demodulating
required.

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[SolarFlare]

You can represent the bandwidth with double the
sampling rate as the bandwidth frequency but there is a
component missing from the sample information that has
to be known and is not part of the samples. Namely the
base frequency has to be added back into the formula.


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[Me]

So, if I have a signal with a 1000 hz carrier, with a bandwidth of 50 hz,
you think I can sample it at just 150 hz and get accurate reproduction?
That's just wrong.

It is the maximum frequency component in the signal that is important. The
bandwidth is not related unless the lower edge of the band is at 0 hz
(whereupon the upper side of the band is equal to the max frequency).

daestrom

You are getting your terms confused here guys. Nyquist requires that
you input both the Center Frequency, and Bandwidth when determining
the Sampling Rate. If the sampling is done at BaseBand then only the
Bandwidth is relevent. If the sampling is not done at baseband, then
the Center Frequency, and Bandwidth are required to determine samling
rate. Example, if the Bandwith of the signal is 3Kc and the sampling is
done at BaseBand then sample rate needed would 6Kc. If the sampling is
done at 100 Mhz with the same 3Kc bandwidth, then a 200.006 Mhz sampling
rate would be required.

It is much easyier to do DSP at baseBand, than at IF Frequencies, and if
you do DSP at IF Frequencies, the lower the IF Frequency, the easyier it
is to do, and the slower the DSP has to run.

Me

 

[SolarFlare]

If only the baseband frequency is sampled at 6kHz then
information is missing to recreate the original 100kHz
and the sampling information is insufficient to
recreate the original signal.


This is analogous to saying the number 1234 can be
represented by
(1234-234) / 1000 = 1

If I supply the number 1.0 you can regenerate the
number 1234 from it? Not true, without the rest of the
sampling information. The sample is incomplete.

Bandwidth sampling only cannot recreate the original
signal.

 

[wmbjk]

I'm still scratching my head over that one.


NT

He previously wrote about using either a 150 Ohm rheostat (other times
referred to as 150A or 200A), or 300k nichrome wire to control a few
Amps of field current on a small 12V automotive alternator. According
to the "designer" (who often refers to himself as a "solar power
consultant"), 150 Ohms didn't allow sufficiently low output, hence the
need for the nichrome wire. And as we all know, the prime
consideration on a home-power generator is low output. <snorf> Similar
wisdom surely underpins his other projects. For instance, liberal
application of 300k wire might be useful when building a max 150, peak
300, zero Watt inverter, or most any zero Watt inverter for that
matter. Perhaps strung around the property in large coils like razor
wire at Slinky Manor. ;-)

Wayne

 

[George Ghio]

Take the credit when you can as it does not happen that often.

 

[George Ghio]

Which part don't you understand

 

[George Ghio]

I'll pay that. Thank you for the correction. Spent too many hours under
the car, I guess.

Yes this is the problem. While there are people who will tell you anything
to make a sale, how do you know what you are really getting.

One test is the "Modified Square Wave" test.

When you hear these words you know you are dealing either with a shyster
or an ignorant person who should not be selling things he does not
understand.

Judging from your previous posts, I think you mean when you hear "Modified
*sine* wave", then you know you are dealing with shyster or an ignorant
person...."

A salesperson that says their unit puts out a modified *square* wave would
be a sign[sic] of a knowledgable salesperson.

daestrom

 

[Roger]

Also, some old systems used self-saturating reactors (magnetic amplifiers,
'magamps') for instrumentation. Things could take some severe environments,
but calibration tended to drift a lot. Required fairly frequent 'trip &
cals' to keep them in spec.

For the small and large stuff we used solid state SCRs while the
intermediate still used saturable core reactors. 10 years ago I think
they still had some mag amps, but the ones we had were pretty stable.

They use larger SCRs now, but I have the silicon wafer out of one that
is over 1 1/2" in diameter. They operated up to 480 and 1000 Amps
and ran near maximum for many hours. The SCRs themselves were about
the size of a hockey puck or slightly larger.

Now there was some power and I'd guess they use much larger systems
now.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

 

[Hal Murray]

So, if I have a signal with a 1000 hz carrier, with a bandwidth of 50 hz,

you think I can sample it at just 150 hz and get accurate reproduction?
That's just wrong.

No, that's the whole point of this discussion.

You have to understand aliasing. The signal you want aliases
down into the baseband. Your anti-aliaising filter has
to get rid of all the junk you don't want. In this case it
includes the baseband. Since there is no baseband signal
(or other out-of-band junk) you can reconstruct the original
signal.

It's a common trick with software radios.

You do need some extra information that doesn't go in through
the A/D channel. That's the design of the system, in particular
what the anti-aliasing filter lets through.

Maybe the reason that this is so confusing is that you also need
that info the the normal/baseband case. But since that's the normal
case we don't bother mentioning it.

 

[wmbjk]

daestrom wrote:>>

Judging from your previous posts, I think you mean when you hear "Modified
*sine* wave", then you know you are dealing with shyster or an ignorant
person...."

A salesperson that says their unit puts out a modified *square* wave would
be a sign[sic] of a knowledgable salesperson.

daestrom

I'll pay that. Thank you for the correction. Spent too many hours under
the car, I guess.

OHMYGOD! A blunder admitted! Who the hell are you and what have you
done with George Ghio?

Wayne

PS It's in everyone's best interest that you not be found out, so
don't forget to hide your pod.

 

[SolarFlare]

Where is the baseband information stored if it isn't
encoded into the sampling?

 

[Hal Murray]

Where is the baseband information stored if it isn't

encoded into the sampling?

I'm not sure what you are asking.

If you have a 1 MHz carrier with 1 KHz of bandwidth,
you might do something like sample at 10 KHz so
your anti-alias filter has some room to work with.
Then you feed the signal into a FFT and throw away
the buckets that the filter didn't get rid of.

You often pick the sampling frequency so the FFT buckets
(after aliasing) come out on convenient numbers.

If by "baseband" you mean the raw signal between 0 and X,
there isn't any information between 0 and X-tiny in a typical
narrow band modulated signal.

If you are doing the aliasing trick, the anti-aliasing filter
has to block the baseband junk (noise) or it will get into the
A/D and confuse things. It's the reverse of the "normal" anti-alias
filter that gets rid of the noise above the baseband so it doesn't
alias down and trash your signal.

 

[George Ghio]

George is alive and well and full of Christmas cheer.

Merry Christmas to all and may you all have a great solar new year.

Even you Wayne.

Yes this is the problem. While there are people who will tell you anything
to make a sale, how do you know what you are really getting.

One test is the "Modified Square Wave" test.

When you hear these words you know you are dealing either with a shyster
or an ignorant person who should not be selling things he does not
understand.

daestrom wrote:>>

Judging from your previous posts, I think you mean when you hear "Modified
*sine* wave", then you know you are dealing with shyster or an ignorant
person...."

A salesperson that says their unit puts out a modified *square* wave would
be a sign[sic] of a knowledgable salesperson.

daestrom

I'll pay that. Thank you for the correction. Spent too many hours under
the car, I guess.

OHMYGOD! A blunder admitted! Who the hell are you and what have you
done with George Ghio?

Wayne

PS It's in everyone's best interest that you not be found out, so
don't forget to hide your pod.

 

[SolarFlare]

You too George.

Merry Christmas to Wayne and all his socks.

George is alive and well and full of Christmas cheer.

Merry Christmas to all and may you all have a great solar new year.

Even you Wayne.

Yes this is the problem. While there are people who will tell you anything
to make a sale, how do you know what you are really getting.

One test is the "Modified Square Wave" test.

When you hear these words you know you are dealing either with a shyster
or an ignorant person who should not be selling things he does not
understand.

daestrom wrote:>>

Judging from your previous posts, I think you mean when you hear "Modified
*sine* wave", then you know you are dealing with shyster or an ignorant
person...."

A salesperson that says their unit puts out a modified *square* wave would
be a sign[sic] of a knowledgable salesperson.

daestrom

I'll pay that. Thank you for the correction. Spent too many hours under
the car, I guess.

OHMYGOD! A blunder admitted! Who the hell are you and what have you
done with George Ghio?

Wayne

PS It's in everyone's best interest that you not be found out, so
don't forget to hide your pod.

 

[SolarFlare]

The point is the sampling rate has to be done at just
over double the frequency of the signal and not the
bandwidth.

 

[Hal Murray]

The point is the sampling rate has to be done at just

over double the frequency of the signal and not the
bandwidth.

I'm sorry that I'm not smart enough to describe it in a way
that you can understand.

Maybe if you google for software-radio you will find something
that explains it in a way that makes sense.

 

[Rich Grise, but drunk]

I'll pay that. Thank you for the correction. Spent too many hours under
the car, I guess.

Just out of curiosity, is top-posting de rigeur on the
rec.ovulation.awning NG? Someone has crossposted this to sci.erectionics.
desire, and the convention there is to bottom- or mid- (or interspersed- )
post.

Just wondering - the clsoest I've been to aviating is I logged 4 hrs.
worth of lessons in a C-150, and onec I sat in the Republic Airlines
DC-9 simulator - that was a trip! My only other associations with
aircarft other than as a passenter is that I worked at a place that sold
little tiiny 28V 40A PSUs, and I'd rather jump out of an airplane (with
a proper aprachute, of course), than try to land one. ;-)

Thanks!
Rich

Yes this is the problem. While there are people who will tell you anything
to make a sale, how do you know what you are really getting.

One test is the "Modified Square Wave" test.

When you hear these words you know you are dealing either with a shyster
or an ignorant person who should not be selling things he does not
understand.

Judging from your previous posts, I think you mean when you hear "Modified
*sine* wave", then you know you are dealing with shyster or an ignorant
person...."

A salesperson that says their unit puts out a modified *square* wave would
be a sign[sic] of a knowledgable salesperson.

daestrom

 

[SolarFlare]

Which one do you have trouble reading?

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news[email protected]...

 

[[email protected]]

Which part don't you understand

I didnt seriously think you were going to stand by the above specs.
Since you are, enough said.


NT