On Mon, 09 Apr 2007 21:53:38 -0500, jakdedert
wrote:

+++james wrote:
+++ On Fri, 6 Apr 2007 20:10:23 -0400, "Radiosrfun"
+++ wrote:
+++
+++ +++"james" wrote in message
+++ ...
+++ +++ On Thu, 05 Apr 2007 19:57:47 +0200, Giulia
+++ +++ wrote:
+++ +++
+++ ++++++Hi ,
+++ ++++++i have a problem with a president jackson cb ,
+++ ++++++in tx there is about 100hz noise (i tx with car battery no PSU),
+++ ++++++the noise there is even if carrier is unmodulted (fm and am mode)....
+++ ++++++Can someone halp me ?
+++ ++++++Schemtics are aviable and i can use an oscilloscope.........
+++ ++++++
+++ ++++++Giulia
+++ +++ *************
+++ +++
+++ +++ 100Hz?????
+++ +++
+++ +++ That is a subaudible frequency.
+++ +++ How could anyone detect it without a scope?
+++ +++
+++ +++ james
+++ +++
+++ +++The range of "normal" human hearing is 20-20,000 Hz. How is 100 Hz
+++ +++"subaudible"?
+++ +++
+++ ****************
+++
+++ That maybe true but the Human ear does not perceive sounds with a flat
+++ response for that frequency range. Instead as frequency goes very low
+++ and also very high the power density for a given frequency may have to
+++ increase or decrease. The human ear does not have a flat range of
+++ sensitivity.
+++
+++ Also in communications the Human voice has very little power below
+++ 300Hz. Therefore most communications equiptment considered below 300
+++ Hz as subaudible. A well designed receiver for voice communications
+++ should reject frequencies below 300Hz. In fact they should also reject
+++ frequencies above about 3KHz also.
+++
+++ The range of 300 to 3000 Hz is where the ear is most sensitive to
+++ frequencies. Also the Human voice contains most of its power between
+++ this range.
+++
+++ james
+++
+++
+++
+++You're backpedaling.
+++
+++What you clearly said was that it could not be detected without a scope.
+++ Then you come up with a bunch of gobbledeegook about 'well designed
+++receivers'. That's not the point, and that's not what you said.
+++
+++Suffice to say that you were simply wrong. 100 Hz is clearly audible.
+++It doesn't take a scope to detect. A pair of common ears is all that's
+++necessary. Whether it should be heard in a CB receiver is debatable,
+++but if it's there, there's no reason why one shouldn't be able to hear it.
+++
+++jak
**************

I stated how could one detect it without a scope? please reread my
post and comprehend better.


100 Hz is hearable or percieved. As I stated before there is a subtle
difference bwetween audible and hearable. Yes you can "hear" 100Hz if
increase the signal power compared to a 1000Hz tone. But at equal
power desity, a 100 Hz tone by most people is not "hearable" or
audible. The same goes for the higher end of the audio spectrum.
Granted some have better sensitivity to a wider spectrum of audiio
frequencies.

Besides this tangent has gone far beyond the scope of the original
post and realy was not my intention. My intention was to discuss the
detection of the offending signal with and without a scope. Not to
discuss what is audible to your ear or the frequency response of your
hearing.

thank you

james