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.

is this surprising? what did you expect to find, and why?? why do you
think 2-4us is a small period of time, and why does that matter?? what is
an 'impulse' signal that you are measuring?? and how do you define 'signal
magnitude??

"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.

"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.


Are you saying the DC value is not 0 ?

Tam/WB2TT

Tam/WB2TT wrote:
"Galilea" wrote
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.

Are you saying the DC value is not 0 ?

He seems to be saying the DC value is not 0 for a sampling
time period of 2-4 uS which would of course be true for a
sine wave if, e.g., an odd number of positive cycles were
sampled along with an even number of negative cycles. Or
if the frequency was lower than 250 kHz. Plus all the
signals and noise are superposed.
--
73, Cecil http://www.qsl.net/w5dxp


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Cecil Moore wrote:

Tam/WB2TT wrote:

"Galilea" wrote

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.

Are you saying the DC value is not 0 ?


He seems to be saying the DC value is not 0 for a sampling
time period of 2-4 uS which would of course be true for a
sine wave if, e.g., an odd number of positive cycles were
sampled along with an even number of negative cycles. Or
if the frequency was lower than 250 kHz. Plus all the
signals and noise are superposed.

Chances are fair that something is doing some rectifying somewhere.

ac6xg

Jim Kelley wrote:
Chances are fair that something is doing some rectifying somewhere.

It later occurred to me that wind/snow noise is
carried by static DC charged particles.
--
73, Cecil http://www.qsl.net/w5dxp


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Cecil Moore wrote:
Jim Kelley wrote:

Chances are fair that something is doing some rectifying somewhere.


It later occurred to me that wind/snow noise is
carried by static DC charged particles.

DC stands for Direct Current. What is a static, direct current, charged
particle?

73,
Tom Donaly, KA6RUH

Tom Donaly, KA6RUH wrote:
"DC stands for Direct Current. What is static, direct current, charged
particle?

Tom addressed Cecil Moore, W5DXP. I`ll risk a breach of protocol and
respond though I was not addressed.

Put a charge on a speck of dust, snow flake, or rain drop. Propel it
through space by any means. The moving charge is an electric current.
What kind of current depends on its trajectory. A unidirectional
atraight trip is without doubt a d-c flow.

If the chrge is propelled regularly back and forth, it possibly
qualifies as a-c.

If the charge lands on a bare antenna wire, it likely will abruptly give
some of its charge to the antenna wire. In this case, the singular event
is a pulse and a static discharge.

Best regards, Richard Harrison, KB5WZI

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

"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