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

"Earl Kiosterud" <someone@[EMAIL PROTECTED]
> writes:

> "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! :)

Hi Earl,

I see what you mean now. I'd say that comes as close to an "analog
alias" as you'll get. It is mathematically almost the same thing. (I say
almost since the analog system involves only two Dirac delta functions
while a digital one involves an infinite number.)

But I really don't think this is what was in Radium's mind when he
asked. 
-- 
%  Randy Yates                  % "...the answer lies within your soul
%% Fuquay-Varina, NC            %       'cause no one knows which side
%%% 919-577-9882                %                   the coin will fall."
%%%% <yates@[EMAIL PROTECTED]
>           %  'Big Wheels', *Out of the Blue*, ELO
http://www.digitalsignallabs.com