It's 18:40 z and I'm 'listening' (I think) to WWRB. There is some religious
fervert doing his thing. At first I thought it was a pirate as the
frequency seemed to be drifting up and down.

This guy is shouting so loud into the mic, that I came across his splatter
as high as 20 khz and more above his broadcast frequency. In my recent SWL
experience, I found that most AM signals could be detected at less than +/-
10 khz (usually 5) from the broadcast frequency. He's on 12.172 (I think).
My meter seems to be resting on +30. His lower sideband is unclear, being
interrupted by other powerhouse stations.

In the ILG database, WWRB's modulation is listed as DAB. What is this, and
are SW broadcasters limited to 100% modulation as are (were?) amateur and
commercial broadcasters? What is a reasonable bandwidth for an AM station.

HankG

"HankG" wrote:

In my recent SWL
experience, I found that most AM signals could be detected at less than
+/-
10 khz (usually 5) from the broadcast frequency. He's on 12.172 (I
think).
My meter seems to be resting on +30. His lower sideband is unclear, being
interrupted by other powerhouse stations.

It's not easy to determine the bandwidth of a station by using a receiver.
For instance, just because you can hear "something" from a station as you
tune your receiver over a 20 kHz range doesn't mean the station is 20 kHz
wide. You have to take the bandwidth and shape factor of your receiver's
i.f. section into account. The strength of the signal will also affect what
you observe.

For instance, a steady unmodulated carrier has essentially zero bandwidth.
But if you tune across it in lsb or usb mode, you will hear the heterodyne
over at least a few kHz. That's a funtion of your receiver, not the
transmitted sugnal.

The correct way to characterize a station's bandwidth is with a spectrum
analyzer.

Art N2AH

In article ,
"Arthur Harris" wrote:

"HankG" wrote:

In my recent SWL experience, I found that most AM signals could be
detected at less than +/- 10 khz (usually 5) from the broadcast
frequency. He's on 12.172 (I think). My meter seems to be resting
on +30. His lower sideband is unclear, being interrupted by other
powerhouse stations.

It's not easy to determine the bandwidth of a station by using a
receiver. For instance, just because you can hear "something" from a
station as you tune your receiver over a 20 kHz range doesn't mean
the station is 20 kHz wide. You have to take the bandwidth and shape
factor of your receiver's i.f. section into account. The strength of
the signal will also affect what you observe.

For instance, a steady unmodulated carrier has essentially zero
bandwidth. But if you tune across it in lsb or usb mode, you will
hear the heterodyne over at least a few kHz. That's a funtion of your
receiver, not the transmitted sugnal.

The correct way to characterize a station's bandwidth is with a
spectrum analyzer.

Spectrum analyzers are generally expensive items. Got a source for a
modern one that covers 1 to 30 MHz that does not cost a lot?

--
Telamon
Ventura, California

"beerbarrel" wrote in message
...
On Sun, 09 Jan 2005 23:12:13 GMT, Telamon
wrote:

In article ,
"Arthur Harris" wrote:

"HankG" wrote:

In my recent SWL experience, I found that most AM signals could be
detected at less than +/- 10 khz (usually 5) from the broadcast
frequency. He's on 12.172 (I think). My meter seems to be resting
on +30. His lower sideband is unclear, being interrupted by other
powerhouse stations.

It's not easy to determine the bandwidth of a station by using a
receiver. For instance, just because you can hear "something" from a
station as you tune your receiver over a 20 kHz range doesn't mean
the station is 20 kHz wide. You have to take the bandwidth and shape
factor of your receiver's i.f. section into account. The strength of
the signal will also affect what you observe.

For instance, a steady unmodulated carrier has essentially zero
bandwidth. But if you tune across it in lsb or usb mode, you will
hear the heterodyne over at least a few kHz. That's a funtion of your
receiver, not the transmitted sugnal.

The correct way to characterize a station's bandwidth is with a
spectrum analyzer.

Spectrum analyzers are generally expensive items. Got a source for a
modern one that covers 1 to 30 MHz that does not cost a lot?


O.K., guys, I got it. Don't really need to know the station's bandwidth.
It's just that I've never heard a station sound exactly like that.

How about my question modulation (limit ?), and any idea what DAB
stands for?

HankG

HankG wrote:

"beerbarrel" wrote in message
...
On Sun, 09 Jan 2005 23:12:13 GMT, Telamon
wrote:

In article ,
"Arthur Harris" wrote:

"HankG" wrote:

In my recent SWL experience, I found that most AM signals could be
detected at less than +/- 10 khz (usually 5) from the broadcast
frequency. He's on 12.172 (I think). My meter seems to be resting
on +30. His lower sideband is unclear, being interrupted by other
powerhouse stations.

It's not easy to determine the bandwidth of a station by using a
receiver. For instance, just because you can hear "something" from a
station as you tune your receiver over a 20 kHz range doesn't mean
the station is 20 kHz wide. You have to take the bandwidth and shape
factor of your receiver's i.f. section into account. The strength of
the signal will also affect what you observe.

For instance, a steady unmodulated carrier has essentially zero
bandwidth. But if you tune across it in lsb or usb mode, you will
hear the heterodyne over at least a few kHz. That's a funtion of your
receiver, not the transmitted sugnal.

The correct way to characterize a station's bandwidth is with a
spectrum analyzer.

Spectrum analyzers are generally expensive items. Got a source for a
modern one that covers 1 to 30 MHz that does not cost a lot?


O.K., guys, I got it. Don't really need to know the station's bandwidth.
It's just that I've never heard a station sound exactly like that.

How about my question modulation (limit ?), and any idea what DAB
stands for?

DAB = Digital Audio Broadcasting.

dxAce
Michigan
USA

HankG wrote:

O.K., guys, I got it. Don't really need to know the station's
bandwidth.
It's just that I've never heard a station sound exactly like that.

How about my question modulation (limit ?),

You can't exceed 100% modulation on negative peaks because the
modulation envelope can't be less than zero. There are "super
modulation" techniques that allow a bit over 100% on positive peaks.

As for bandwidth, if there is no distortion, the bandwidth of an AM
station should be twice the highest audio frequency transmitted. For
high fidelity voice modulation, the sibilants (mostly "s" and "t"
sounds) may have frequency components up to nearly 10 kHz. Music can go
higher than that. So unless the higher audio frequencies are filtered,
the bandwidth of an AM station could be 20 or 30 kHz (not good with the
5 kHz channel spacing on shortwave). Just for reference, I believe the
allowable bandwidth for an AM broadcast station in the US is 10 kHz.
Art N2AH