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