It is late and I have been up a little too long.
I have spent an hour wading through my reffrence books,
and the ITU web pages.

Earlier today I found a reffrence that states that the
"standard Pre/De-emphasis is 75uS", and implies that
this is also true for HF.

I thought that 75uS was for non-Dolby FM,50Us for US TV and
European FM and that MW/AM and HF/AM had no pre/de-emphasis.
Have I lost what is left of my mind?

I have been trying to decide on the best pivot point for my
tone-tilt. Craig at Kiwa used 700Hz. The best diagram I found
was from a guitar link and was designed to be used with spring
reverbs and had the pivot at 1KHz. I have been experimenting
and think I may have to have two, one for 700Hz for male voices,
and one about 1.4KHz for females.

Does anyone have and use a Kiwa MAP unit?
Is the 700Hz too low to be really efective on female voices?

Thanks
Terry

wrote in message
ups.com...
It is late and I have been up a little too long.
I have spent an hour wading through my reffrence books,
and the ITU web pages.

Earlier today I found a reffrence that states that the
"standard Pre/De-emphasis is 75uS", and implies that
this is also true for HF.

I thought that 75uS was for non-Dolby FM,50Us for US TV and
European FM and that MW/AM and HF/AM had no pre/de-emphasis.
Have I lost what is left of my mind?

It's not quite as simple as that. All broadcast audio is processed. Here's
a brief history:

http://www.bext.com/histproc.htm

Clear Channel is adopting IBOC and has developed a coincidental interest in
reducing the bandwidth of AM audio:

http://www.rwonline.com/reference-ro...andwidth.shtml


I have been trying to decide on the best pivot point for my
tone-tilt. Craig at Kiwa used 700Hz. The best diagram I found
was from a guitar link and was designed to be used with spring
reverbs and had the pivot at 1KHz. I have been experimenting
and think I may have to have two, one for 700Hz for male voices,
and one about 1.4KHz for females.

There might also be a station to station difference. Stations can process
their audio differently.

Frank Dresser

FM stations in the United Stated use a 75uS deemphasis while European FM
stations use a 50uS deemphasis. The reason for this is because the FM
transmitting stations use a preemphasis, boosting the transmitted treble
response above a certain frequency. The end result of this technique is a
better signal to noise ratio at the receiving end.
Without a deemphasis network in your FM receiver, the received audio would
sound trebly, similar to, but not exactly not like listening to a dolby
encoded tape on a non-dolby tape playback machine.
AM stations do not use any preemphasis so a deemphasis network after the
detector in your receiver is not required.
It is true that digital modes such as IBOC are being use on the MW band, but
this is a totally different technique.

Pete

"Frank Dresser" wrote in message
...

wrote in message
ups.com...
It is late and I have been up a little too long.
I have spent an hour wading through my reffrence books,
and the ITU web pages.

Earlier today I found a reffrence that states that the
"standard Pre/De-emphasis is 75uS", and implies that
this is also true for HF.

I thought that 75uS was for non-Dolby FM,50Us for US TV and
European FM and that MW/AM and HF/AM had no pre/de-emphasis.
Have I lost what is left of my mind?

It's not quite as simple as that. All broadcast audio is processed.
Here's
a brief history:

http://www.bext.com/histproc.htm

Clear Channel is adopting IBOC and has developed a coincidental interest
in
reducing the bandwidth of AM audio:

http://www.rwonline.com/reference-ro...andwidth.shtml


I have been trying to decide on the best pivot point for my
tone-tilt. Craig at Kiwa used 700Hz. The best diagram I found
was from a guitar link and was designed to be used with spring
reverbs and had the pivot at 1KHz. I have been experimenting
and think I may have to have two, one for 700Hz for male voices,
and one about 1.4KHz for females.

There might also be a station to station difference. Stations can process
their audio differently.

Frank Dresser

"Pete KE9OA" wrote in message
...

[snip]

AM stations do not use any preemphasis so a deemphasis network after the
detector in your receiver is not required.

It's my understanding that there's no FCC standard for AM stations to
preemphasize their audio, but nearly all do in order to compensate for the
normal roll off. I have an old school high fidelity AM receiver, and AM
stations usually sound rather shrill on the "Hi-Fi" IF bandwidth position.

A quick google search brings up:

"In 1977 Orban Associates introduced "Optimod-AM." This unit contained a
high-slope receiver equalizer to pre-compensate for the highly rolled-off
radios of the time, "

http://www.bext.com/histproc.htm

"and Omnia exclusives like a pre-emphasis section placed behind the
multi-band limiters to create a more consistent, natural sound."

http://www.omniaaudio.com/am.htm


It is true that digital modes such as IBOC are being use on the MW band,
but
this is a totally different technique.

Pete


I brought up IBOC because Clear Channel wants all AM radio stations to limit
their audio bandwidth to 5 - 6 kHz. One of the reasons for the change was
given:

"1. Increased modulation efficiency. By eliminating the broadcast of the
high-frequency energy, we can increase the amount of energy that is in the
20 Hz to 5 kHz region. Let's not forget that due to pre-emphasis, higher
frequencies are boosted and will have a more profound effect on total
modulation than lower frequencies will."

http://www.rwonline.com/reference-ro...andwidth.shtml

I don't know if the IBOC stations use a different preemphasis on the analog
channel than the non IBOC stations.

Frank Dresser

Hi Frank,

I didn't realize that..........I thought that the older AM stations took
greater pains to have flatter high frequency response. I do remember
listening to stations such as WGN on my old McIntosh MR-55, and they sounded
very good. The same stations on my Dynaco AF-6 tuner in its wide bandwidth
sounded shrill, as you describe.
As far as AM receivers, they do not have a deemphasis circuit following the
detector. With FM receivers, it is a different story.
Thanks for the info!

Pete

"Frank Dresser" wrote in message
...

"Pete KE9OA" wrote in message
...

[snip]

AM stations do not use any preemphasis so a deemphasis network after the
detector in your receiver is not required.

It's my understanding that there's no FCC standard for AM stations to
preemphasize their audio, but nearly all do in order to compensate for the
normal roll off. I have an old school high fidelity AM receiver, and AM
stations usually sound rather shrill on the "Hi-Fi" IF bandwidth position.

A quick google search brings up:

"In 1977 Orban Associates introduced "Optimod-AM." This unit contained a
high-slope receiver equalizer to pre-compensate for the highly rolled-off
radios of the time, "

http://www.bext.com/histproc.htm

"and Omnia exclusives like a pre-emphasis section placed behind the
multi-band limiters to create a more consistent, natural sound."

http://www.omniaaudio.com/am.htm


It is true that digital modes such as IBOC are being use on the MW band,
but
this is a totally different technique.

Pete


I brought up IBOC because Clear Channel wants all AM radio stations to
limit
their audio bandwidth to 5 - 6 kHz. One of the reasons for the change was
given:

"1. Increased modulation efficiency. By eliminating the broadcast of the
high-frequency energy, we can increase the amount of energy that is in the
20 Hz to 5 kHz region. Let's not forget that due to pre-emphasis, higher
frequencies are boosted and will have a more profound effect on total
modulation than lower frequencies will."

http://www.rwonline.com/reference-ro...andwidth.shtml

I don't know if the IBOC stations use a different preemphasis on the
analog
channel than the non IBOC stations.

Frank Dresser

"Pete KE9OA"
As far as AM receivers, they do not have a deemphasis circuit
following the detector. With FM receivers, it is a different story.
___________

But in effect, almost every AM receiver has de-emphasis -- it is the result
of the "haystack" amplitude response of their RF/IF circuits driving the 2nd
detector. Higher modulating frequencies are rolled off, sometimes very
severely.

The problem with trying to compensate for it at the AM tx is that the amount
needed for "flat" system response varies considerably from rx to rx, and
even with carrier frequency. Even so, many MW/SW AM stations do boost their
highs, trying to get some of it to pass through the narrowband receivers
typically in use these days.

RF

Petet thanks for jumping in. I found this refference while searching
the FCC archive. I thought it was wrong, but just wanted to verify it.

Terry

Anytime Terry!

Pete

wrote in message
oups.com...
Petet thanks for jumping in. I found this refference while searching
the FCC archive. I thought it was wrong, but just wanted to verify it.

Terry

Pete KE9OA wrote:

FM stations in the United Stated use a 75uS deemphasis while European FM
stations use a 50uS deemphasis. The reason for this is because the FM
transmitting stations use a preemphasis, boosting the transmitted treble
response above a certain frequency. The end result of this technique is a
better signal to noise ratio at the receiving end.
Without a deemphasis network in your FM receiver, the received audio would
sound trebly, similar to, but not exactly not like listening to a dolby
encoded tape on a non-dolby tape playback machine.
AM stations do not use any preemphasis so a deemphasis network after the
detector in your receiver is not required.


Actually, since NRSC II, yes they do. Part of this was to
accomodate AM stereo and make the audio competitive with FM on
receivers with sufficiently narrow IF bandwidth to accomodate
largely interference free reception. NRSC II also brickwalled audio
below 10K, so preemphasis helped overcome the top end losses from
shoddily designed IF strips.

On a vintage wideband receiver, NRSC II sounds unusually bright.
And on an NRSC II receiver the audio quality isn't really what
anyone would call high fidelity. Or even medium fidelity. It was a
feel good response to cutting the nuts off AM's potential for decent
audio in order to accomodate interference free listening as
nighttime powers were increased for local AM's.

Neither the AM stereo nor the better receiver audio developed as
expected. Tell me you're surprised. With the exception of some
dedicated receiver manufacturers focussing on AM audio quality, like
Fanfare, or builders who produced the limited number of AMAX
certifed receivers, most AM manufacturers took NRSC II as a license
to build cheaper receivers letting the preemphasis at the
transmitter compensate for poorer circuit designs.








It is true that digital modes such as IBOC are being use on the MW band, but
this is a totally different technique.

Pete

"Frank Dresser" wrote in message
...

wrote in message
roups.com...

It is late and I have been up a little too long.
I have spent an hour wading through my reffrence books,
and the ITU web pages.

Earlier today I found a reffrence that states that the
"standard Pre/De-emphasis is 75uS", and implies that
this is also true for HF.

I thought that 75uS was for non-Dolby FM,50Us for US TV and
European FM and that MW/AM and HF/AM had no pre/de-emphasis.
Have I lost what is left of my mind?

It's not quite as simple as that. All broadcast audio is processed.
Here's
a brief history:

http://www.bext.com/histproc.htm

Clear Channel is adopting IBOC and has developed a coincidental interest
in
reducing the bandwidth of AM audio:

http://www.rwonline.com/reference-ro...andwidth.shtml


I have been trying to decide on the best pivot point for my
tone-tilt. Craig at Kiwa used 700Hz. The best diagram I found
was from a guitar link and was designed to be used with spring
reverbs and had the pivot at 1KHz. I have been experimenting
and think I may have to have two, one for 700Hz for male voices,
and one about 1.4KHz for females.

There might also be a station to station difference. Stations can process
their audio differently.

Frank Dresser

Frank Dresser wrote:

It's not quite as simple as that. All broadcast audio is processed.
Here's
a brief history:

http://www.bext.com/histproc.htm

Clear Channel is adopting IBOC and has developed a coincidental
interest in
reducing the bandwidth of AM audio:

http://www.rwonline.com/reference-ro...andwidth.shtml


There might also be a station to station difference. Stations can
process
their audio differently.

Frank Dresser
---------------------------------------------------
I am aware of "standard" audio processing, but the refference giving
75uS on AM through me for a minor loop. Up too long and the old brain
was a little too fogged. I tried several local AM stations with 75uS
and 50uS
and they soundeed very muffled. The exact oppositte of what I am trying
to do.

I do remember when WLW (700KHz) used to run real clasical music
programs on Sunday afternoon, and they clearly broadcast up to at least
10KHz. The cymbols were crystal clear. But that was 35~40 uears ago.

Terry