The average value of a signal is its DC value. To receive and reproduce
a signal with a non-zero DC component means that your antenna, as well
as your receiver, has to have response to DC. To generate such a signal
would require a static electric and/or magnetic field, which can't
propagate. So it's not possible for a signal you're receiving to have a
non-zero average value.

If it doesn't seem to be zero, there's something wrong with your
measurement system.

Roy Lewallen, W7EL

Thank you for all your help.

Richard, just because someone writes from an academic institution doesn't
mean they have had an academic education. This institution provides to
anyone who is willing to pay from the whole city and its surroundings with a
connection. I, for one, don't have one and it has just been recently, since
I started to work here that I have become interested from looking around and
talking to people during my shifts. Just because I am trying to learn by my
own means doesn't mean you have to rub my lack of knowledge in.

Once again, thank you all for your help.


"Galilea" wrote in message
...
Hello, thank you for reading this post.

When analysing wideband impulse signals from a wideband antenna I have
realised that the average signal magnitude is not zero. I have thought
this
is because the reactance of the antenna at different frequencies varies
and
since it is a wideband antenna there can be energy measured since it is
only
for an extremely small period of time of 2-4 us. However, I am not sure
and
would greatly appreciate the views of this newsgroup.

"Roy Lewallen" wrote
The average value of a signal is its DC value. To receive and reproduce a
signal with a non-zero DC component means that your antenna, as well as
your receiver, has to have response to DC. To generate such a signal would
require a static electric and/or magnetic field, which can't propagate. So
it's not possible for a signal you're receiving to have a non-zero average
value.
________________

Pure DC doesn't radiate, but there can be a DC component in the modulation
of an RF wave that does radiate. An example is analog broadcast television,
which has a highly asymmetric RF waveform. It can transmit a constant (DC)
video value of any amplitude between reference black at 75% modulation and
reference white at 12-1/2% modulation.

RF

"Roy Lewallen" wrote in message
...
The average value of a signal is its DC value. To receive and reproduce
a signal with a non-zero DC component means that your antenna, as well
as your receiver, has to have response to DC. To generate such a signal
would require a static electric and/or magnetic field, which can't
propagate. So it's not possible for a signal you're receiving to have a
non-zero average value.

sure it is. and while the 'static' field itself doesn't propagate the
leading edge of a step from 0 to some 'static' value can propagate and if
you measure as it passes you will see the received signal go from 0 to the
static value and then stay there.

On Sun, 6 Feb 2005 08:03:39 -0600, "Richard Fry"
wrote:

It can transmit a constant (DC) video value of any amplitude

Hi OM,

This is absurd. Video is a modulation being carried on RF, no one
broadcasts baseband on anything but copper.

The equally absurd notion offered here originally of DC offset being
RECEIVED is another fanciful illusion. Any such measurement was
clearly an error of measurement or understanding.

73's
Richard Clark, KB7QHC

On Sun, 6 Feb 2005 15:59:36 -0000, "Dave" wrote:

leading edge of a step from 0 to some 'static' value

Hi Dave,

....negates the usage of "static" - clearly.

A step pulse is not "static" and in fact contains an infinite range of
frequencies all of which are NOT DC. This is called the genii out of
the bottle and no one here can (but no doubt will try to) put it back.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message...
On Sun, 6 Feb 2005 08:03:39 -0600,
"Richard Fry" wrote:

It can transmit a constant (DC) video value of any amplitude

Hi OM,

This is absurd. Video is a modulation being carried on RF, no one
broadcasts baseband on anything but copper.
__________________

Before calling this reality absurd, consider that a television station
transmits a video signal in/on an RF channel. The demodulated video
waveform in the TV receiver will be identical to the baseband video signal
applied to the TV tx -- including its DC components (subject to any
distortions along the transmission path).

If it wasn't ~ identical, a TV set could never "fade to black" when the
original image did, and low-luminance colors such as blue, red, brown etc
would be impossible to reproduce with their original chromaticity.

RF (ex-RCA Field Engineer, and installer of
hundreds of TV color studio and film cameras)

"Richard Clark" wrote in message
On Sun, 6 Feb 2005 15:59:36 -0000, "Dave" wrote:

leading edge of a step from 0 to some 'static' value

...negates the usage of "static" - clearly.

A step pulse is not "static" and in fact contains an infinite range of
frequencies all of which are NOT DC. This is called the genii out of
the bottle and no one here can (but no doubt will try to) put it back.
______________

You mis-read. There is a DC component _required_ to convey the steady
voltage values preceding and following the step pulse transition. He's not
saying that the step pulse transition itself is comprised of "DC."

RF

On Sun, 6 Feb 2005 10:46:48 GMT, "Galilea" wrote:

Just because I am trying to learn by my
own means doesn't mean you have to rub my lack of knowledge in.

This is reverse elitist soap opera.

Since you are unresponsive to technical discussion, let's talk about
manners. Littering your posts with apologies does not excuse rude
behavior. This is rubbing your nose into your lack of knowledge in
newsgroup etiquette (and teaching you about flaming). Responding to
others (much as you've done to me here) through YOUR own postings
quite clearly marks you as being indifferent to the standards of
protocol and this arrives clearly through ignorance.

In any society, bohemian or in the dress circle of the opera, it
doesn't take much native intelligence to FIRST observe how people
conduct themselves and THEN participate after having noted the rules
of the game.

73's
Richard Clark, KB7QHC

On Sun, 6 Feb 2005 12:06:38 -0600, "Richard Fry"
wrote:

Before calling this reality absurd, consider that a television station
transmits a video signal in/on an RF channel. The demodulated video
waveform in the TV receiver will be identical to the baseband video signal
applied to the TV tx -- including its DC components (subject to any
distortions along the transmission path).

Hi OM,

OK, this is after the reality: what you offer is either absurd, or
non-nutritive didacticism.

Throw enough capacitance on the output of a detector and you will get
nothing but D.C. and never observe an average of zero. So What? The
forced presumption that you should is laughable. The original
question is so clouded with speculation that elbowing fantasy into a
response allows for any statement to qualify as an "authoritative
answer." Save this stuff for White House Social Security math -
mathbonics?

73's
Richard Clark, KB7QHC