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From: Tim Wescott on 17 Feb 2010 17:25
On Wed, 17 Feb 2010 13:32:35 -0800, George Herold wrote:

> On Feb 17, 3:45 pm, John Fields <jfie...(a)austininstruments.com> wrote:
>> On Wed, 17 Feb 2010 11:44:01 -0800 (PST), George Herold
>>
>>
>>
>>
>>
>> <ggher...(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?
>>
>> ---
>> Yeah.
>> ---
>>
>> >You don't want the carrier to go to zero amplitude do you?  Isn't this
>> >like AM radio?
>>
>> ---
>> No; in this case the presence of a carrier denotes a transmission of a
>> "1", say, and the length of time the carrier is ON defines how many 1's
>> will be transmitted.
>>
>> Conversely, the absence of a carrier denotes the transmission of a zero
>> and the length of time there is no carrier defines how many zeros will
>> be transmitted.
>>
>> JF- Hide quoted text -
>>
>> - Show quoted text -
>
> Thanks John, That makes sense... sorta. Not the most 'robust' way to
> send data. Lose of the carrier means a zero... or that you've just lost
> the carrier.

'xactly. But a very _easy_ way to send data -- just turn the transmitter
on and off.

--
www.wescottdesign.com
From: Peter Bennett on 17 Feb 2010 18:50
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. 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.)


--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca
From: John Fields on 17 Feb 2010 20:03
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
From: Jon on 17 Feb 2010 20:35

"Peter Bennett" <peterbb(a)somewhere.invalid> wrote in message
news:310pn5pctm9t6a4l6433ukmgdhv58m244p(a)news.supernews.com...
> 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. 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.)

The loss would be a constant power drain on the battery of say, a
wireless mouse or keyboard.



--- news://freenews.netfront.net/ - complaints: news(a)netfront.net ---
From: Tim Wescott on 17 Feb 2010 22:41
On Wed, 17 Feb 2010 19:03:21 -0600, 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


Do you mean when it's working correctly, or most of the time?


--
www.wescottdesign.com
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