Re: Are purely-analog audio devices immune to aliasing?

"Randy Yates" <yates@[EMAIL PROTECTED]
> wrote in message
news:m31w46svgx.fsf@[EMAIL PROTECTED]
> "Chronic Philharmonic" <karl.uppiano@[EMAIL PROTECTED]
> writes:
>
>> "Randy Yates" <yates@[EMAIL PROTECTED]
> wrote in message
>> news:m3k5hzj58s.fsf@[EMAIL PROTECTED]
>>> "Green Xenon [Radium]" <glucegen1@[EMAIL PROTECTED]
> writes:
>>>
>>>> Hi:
>>>>
>>>> Is it true that purely-analog audio devices [such as analog cassette,
>>>> AM radio, and the pre-digital telephone systems*] are immune to
>>>> aliasing?
>>>
>>> Yes.
>>
>> Well... AM radio is not immune to aliasing, although we rarely
encounter it
>> in practice
>
> How would AM ever alias?
> -- 
> %  Randy Yates                  % "Midnight, on the water...
> %% Fuquay-Varina, NC            %  I saw...  the ocean's daughter."
> %%% 919-577-9882                % 'Can't Get It Out Of My Head'
> %%%% <yates@[EMAIL PROTECTED]
>           % *El Dorado*, Electric Light Orchestra
> http://www.digitalsignallabs.com

An AM radio station operating at 1 MHz would have to have the baseband
limited to 500 KHz, 
or aliases would appear.  For example a 600 KHz baseband component would
appear at 400 KHz. 
This obviously ain't gonna happen in any real world situation, but imagine
an AM station 
operating at 10 KHz.  It would have to keep the audio limited to below
it's Nyquist 
frequency of 5 Khz.

I'm using the term Nyquist frequency somewhat incorrectly, as it
technically applies to 
sampled systems.  But it still works, and we know what we mean! :)
-- 
Earl