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From: Michael A. Terrell on 18 Feb 2010 11:36

John Fields wrote:
>
> On Wed, 17 Feb 2010 15:50:21 -0800, Peter Bennett
> <peterbb(a)somewhere.invalid> wrote:
>
> >On Wed, 17 Feb 2010 11:44:01 -0800 (PST), George Herold
> ><ggherold(a)gmail.com> wrote:
> >
> >>On Feb 16, 1:22 am, MRW <mr.whate...(a)gmail.com> wrote:
> >>> Hello group,
> >>>
> >>> I posted a screen capture of an image showing a basic Amplitude Shift
> >>> Key modulation:http://imgur.com/Ahwya.jpg
> >>>
> >>> The image shows the a diagram and equation. The equation is ASK(t) =
> >>> s(t)*sin(2*pi*f*t). I assume s(t) is the baseband signal and
> >>> sin(2*pi*f*t) is the carrier frequency.
> >>>
> >>> In the image, is it possible for s(t) to have a higher frequency as
> >>> sin(2*pi*f*t)? Please explain.
> >>>
> >>> Thanks!
> >>
> >>OK I'm probabbly being an idiot here... But is that picture right?
> >>You don't want the carrier to go to zero amplitude do you? Isn't this
> >>like AM radio?
> >>
> >>George H.
> >
> >I think I'd call that on-off keying.
>
> ---
> Agreed, but, taken to the lowest level of ASK, zero carrier and some
> level of carrier defines the difference between mark and space.
> ---
>
> >For amplitude-shift keying, I'd
> >expect one or more intermediate levels, not just off and on. Perhaps
> >full amplitude and 50% (or a couple more intermediate levels to encode
> >multiple bits in each interval.)
>
> ---
> Using ASK in the way you describe it, what would you expect the maximum
> data transfer rate to be?
>
> JF

WWVB gets one baud.


--
Greed is the root of all eBay.
From: John Fields on 18 Feb 2010 17:44
On Thu, 18 Feb 2010 11:36:23 -0500, "Michael A. Terrell"
<mike.terrell(a)earthlink.net> wrote:

>
>John Fields wrote:
>>
>> On Wed, 17 Feb 2010 15:50:21 -0800, Peter Bennett
>> <peterbb(a)somewhere.invalid> wrote:
>>
>> >On Wed, 17 Feb 2010 11:44:01 -0800 (PST), George Herold
>> ><ggherold(a)gmail.com> wrote:
>> >
>> >>On Feb 16, 1:22 am, MRW <mr.whate...(a)gmail.com> wrote:
>> >>> Hello group,
>> >>>
>> >>> I posted a screen capture of an image showing a basic Amplitude Shift
>> >>> Key modulation:http://imgur.com/Ahwya.jpg
>> >>>
>> >>> The image shows the a diagram and equation. The equation is ASK(t) =
>> >>> s(t)*sin(2*pi*f*t). I assume s(t) is the baseband signal and
>> >>> sin(2*pi*f*t) is the carrier frequency.
>> >>>
>> >>> In the image, is it possible for s(t) to have a higher frequency as
>> >>> sin(2*pi*f*t)? Please explain.
>> >>>
>> >>> Thanks!
>> >>
>> >>OK I'm probabbly being an idiot here... But is that picture right?
>> >>You don't want the carrier to go to zero amplitude do you? Isn't this
>> >>like AM radio?
>> >>
>> >>George H.
>> >
>> >I think I'd call that on-off keying.
>>
>> ---
>> Agreed, but, taken to the lowest level of ASK, zero carrier and some
>> level of carrier defines the difference between mark and space.
>> ---
>>
>> >For amplitude-shift keying, I'd
>> >expect one or more intermediate levels, not just off and on. Perhaps
>> >full amplitude and 50% (or a couple more intermediate levels to encode
>> >multiple bits in each interval.)
>>
>> ---
>> Using ASK in the way you describe it, what would you expect the maximum
>> data transfer rate to be?
>>
>> JF
>
> WWVB gets one baud.

---
Yeah, but its not ASK in the sense that one level defines a 1 and
another defines a 0, it's more like PWM with a carrier floor and the
length of time the transmitter stays at the low floor level before it
gets keyed on to full power out determines whether the bit sent is a 1
or a zero.

http://tf.nist.gov/stations/wwvbtimecode.htm

http://en.wikipedia.org/wiki/WWVB#Modulation_Format

Pretty damn clever, in my book...

JF
From: Michael A. Terrell on 19 Feb 2010 15:20

John Fields wrote:
>
> On Thu, 18 Feb 2010 11:36:23 -0500, "Michael A. Terrell"
> <mike.terrell(a)earthlink.net> wrote:
>
> >
> >John Fields wrote:
> >>
> >> On Wed, 17 Feb 2010 15:50:21 -0800, Peter Bennett
> >> <peterbb(a)somewhere.invalid> wrote:
> >>
> >> >On Wed, 17 Feb 2010 11:44:01 -0800 (PST), George Herold
> >> ><ggherold(a)gmail.com> wrote:
> >> >
> >> >>On Feb 16, 1:22 am, MRW <mr.whate...(a)gmail.com> wrote:
> >> >>> Hello group,
> >> >>>
> >> >>> I posted a screen capture of an image showing a basic Amplitude Shift
> >> >>> Key modulation:http://imgur.com/Ahwya.jpg
> >> >>>
> >> >>> The image shows the a diagram and equation. The equation is ASK(t) =
> >> >>> s(t)*sin(2*pi*f*t). I assume s(t) is the baseband signal and
> >> >>> sin(2*pi*f*t) is the carrier frequency.
> >> >>>
> >> >>> In the image, is it possible for s(t) to have a higher frequency as
> >> >>> sin(2*pi*f*t)? Please explain.
> >> >>>
> >> >>> Thanks!
> >> >>
> >> >>OK I'm probabbly being an idiot here... But is that picture right?
> >> >>You don't want the carrier to go to zero amplitude do you? Isn't this
> >> >>like AM radio?
> >> >>
> >> >>George H.
> >> >
> >> >I think I'd call that on-off keying.
> >>
> >> ---
> >> Agreed, but, taken to the lowest level of ASK, zero carrier and some
> >> level of carrier defines the difference between mark and space.
> >> ---
> >>
> >> >For amplitude-shift keying, I'd
> >> >expect one or more intermediate levels, not just off and on. Perhaps
> >> >full amplitude and 50% (or a couple more intermediate levels to encode
> >> >multiple bits in each interval.)
> >>
> >> ---
> >> Using ASK in the way you describe it, what would you expect the maximum
> >> data transfer rate to be?
> >>
> >> JF
> >
> > WWVB gets one baud.
>
> ---
> Yeah, but its not ASK in the sense that one level defines a 1 and
> another defines a 0, it's more like PWM with a carrier floor and the
> length of time the transmitter stays at the low floor level before it
> gets keyed on to full power out determines whether the bit sent is a 1
> or a zero.
>
> http://tf.nist.gov/stations/wwvbtimecode.htm
>
> http://en.wikipedia.org/wiki/WWVB#Modulation_Format
>
> Pretty damn clever, in my book...


Especially when you consider when they first used it. A 10 dB carrier
reduction to modulate the carrier in the early days of electronics, and
was used to control clocks all over the country. A lot of metrology
labs used a Fluke VLF receiver & WWVB for their frequency standard,
until GPS based systems replaced it. I still have my Fluke receiver,
but I will need to build a new PLL 10 MHz standard.

BTW, I found my homebrew copper 60 KHz loop for WWVB yesterday. I
finally feel well enough to start cleaning out the small shop building,
so I can get back to the bench. :) It is only 18 * 28 feet, but it
suffered the least hurricane damage a few years ago. I tossed out a
truckload of damaged cardboard boxes and very rusty hardware. I have a
fairly clear shot towards WWVB from here, unlike the last place I lived.


--
Greed is the root of all eBay.
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