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Michael Thorpe January 11th 06 11:05 AM

Measuring filter shape factor
 
Amongst all these political propaganda posts, I wonder if there is a
little room for a technical question related to radio please?

If so, here goes:

How does one measure the IF filter shape factor in a shortwave radio?

I am technically minded and do have a signal generator, etc., but I am
not sure of the exact procedure. Do I get the audio level at the peak
frequency, then detune both sides off the peak for -3dB of the
demodulated audio, note down the width between these points, then
detune to obtain for -50dB of the demodulated audio, get the width at
these points, and then the ratio of the two widths is the filter shape
factor?

I would appreciate a link to the exact procedure if there is one
(don't seem to be able to find this in Google) or an expert advice
please.

I would also appreciate advice as to what actual values of filter
shape are considered poor, good, excellent, etc...

Thanks in advance,
Michael


Arthur Pozner January 11th 06 08:08 PM

Measuring filter shape factor
 
Networksciences (original filter supplier for Drake) has a very
elaborate website on this subject. Try them first.


Dale Parfitt January 11th 06 09:23 PM

Measuring filter shape factor
 

"Michael Thorpe" wrote in message
news:43c4e407.4277000@news-server...
Amongst all these political propaganda posts, I wonder if there is a
little room for a technical question related to radio please?

If so, here goes:

How does one measure the IF filter shape factor in a shortwave radio?

I am technically minded and do have a signal generator, etc., but I am
not sure of the exact procedure. Do I get the audio level at the peak
frequency, then detune both sides off the peak for -3dB of the
demodulated audio, note down the width between these points, then
detune to obtain for -50dB of the demodulated audio, get the width at
these points, and then the ratio of the two widths is the filter shape
factor?

I would appreciate a link to the exact procedure if there is one
(don't seem to be able to find this in Google) or an expert advice
please.

I would also appreciate advice as to what actual values of filter
shape are considered poor, good, excellent, etc...

Thanks in advance,
Michael


Hi Michael,

Although I have never given it much thought, I don't believe one can fully
characterize a filter while it is installed in the receiver- certainly,
parameters such as insertion loss would not be easily measurable. Perhaps
programs like Spectran may give some rough insight.
My method is classic- the filter is removed, properly terminated and
connected as the DUT on a scalar network analyzer.
If you have a vector network analyzer available you could also observe group
delay- an important factor in narrow filters.
See Paul Kiciak's (N2PK) site for his clever VNA- ideally suited for
filters.
Dale W4OP




David January 11th 06 09:59 PM

Measuring filter shape factor
 
On Wed, 11 Jan 2006 21:23:09 GMT, "Dale Parfitt"
wrote:


"Michael Thorpe" wrote in message
news:43c4e407.4277000@news-server...
Amongst all these political propaganda posts, I wonder if there is a
little room for a technical question related to radio please?

If so, here goes:

How does one measure the IF filter shape factor in a shortwave radio?

I am technically minded and do have a signal generator, etc., but I am
not sure of the exact procedure. Do I get the audio level at the peak
frequency, then detune both sides off the peak for -3dB of the
demodulated audio, note down the width between these points, then
detune to obtain for -50dB of the demodulated audio, get the width at
these points, and then the ratio of the two widths is the filter shape
factor?

I would appreciate a link to the exact procedure if there is one
(don't seem to be able to find this in Google) or an expert advice
please.

I would also appreciate advice as to what actual values of filter
shape are considered poor, good, excellent, etc...

Thanks in advance,
Michael


Hi Michael,

Although I have never given it much thought, I don't believe one can fully
characterize a filter while it is installed in the receiver- certainly,
parameters such as insertion loss would not be easily measurable. Perhaps
programs like Spectran may give some rough insight.
My method is classic- the filter is removed, properly terminated and
connected as the DUT on a scalar network analyzer.
If you have a vector network analyzer available you could also observe group
delay- an important factor in narrow filters.
See Paul Kiciak's (N2PK) site for his clever VNA- ideally suited for
filters.
Dale W4OP


Look at the interstation atmospheric noise with a spectrum analyzer?



[email protected] January 11th 06 10:14 PM

Measuring filter shape factor
 
http://www.lazygranch.com/images/radio/cwfilter.gif
I did this test as follows:
1) radio in AM
2) AGC turned off
3) RF generator connector to antenna input
4) distortion analyzer connected to earphone output

Pick a frequency. I used 10Mhz. Set the RF generator and radio to that
frequency. Leave the radio dial alone. Sweep the RF generator manually
and measure the audio level from the distortion analyser. Plot the
results. This was a crystal filter, so you will need a RF generator
with 1Hz steps.

This is an in-situ measurement, i.e. this is not the same as just
testing the IF filter by itself. You need the distortion analyzer to
get the audio signal level independent from the noise.

All that said, Bush should be impeached.

Michael Thorpe wrote:
Amongst all these political propaganda posts, I wonder if there is a
little room for a technical question related to radio please?

If so, here goes:

How does one measure the IF filter shape factor in a shortwave radio?

I am technically minded and do have a signal generator, etc., but I am
not sure of the exact procedure. Do I get the audio level at the peak
frequency, then detune both sides off the peak for -3dB of the
demodulated audio, note down the width between these points, then
detune to obtain for -50dB of the demodulated audio, get the width at
these points, and then the ratio of the two widths is the filter shape
factor?

I would appreciate a link to the exact procedure if there is one
(don't seem to be able to find this in Google) or an expert advice
please.

I would also appreciate advice as to what actual values of filter
shape are considered poor, good, excellent, etc...

Thanks in advance,
Michael



dxAce January 11th 06 10:23 PM

Measuring filter shape factor
 


wrote:

http://www.lazygranch.com/images/radio/cwfilter.gif
I did this test as follows:
1) radio in AM
2) AGC turned off
3) RF generator connector to antenna input
4) distortion analyzer connected to earphone output

Pick a frequency. I used 10Mhz. Set the RF generator and radio to that
frequency. Leave the radio dial alone. Sweep the RF generator manually
and measure the audio level from the distortion analyser. Plot the
results. This was a crystal filter, so you will need a RF generator
with 1Hz steps.

This is an in-situ measurement, i.e. this is not the same as just
testing the IF filter by itself. You need the distortion analyzer to
get the audio signal level independent from the noise.

All that said, Bush should be impeached.


LMFAO at the misguided 'tard boy!

dxAce
Michigan
USA



David January 12th 06 12:17 AM

Measuring filter shape factor
 
On 11 Jan 2006 14:14:01 -0800, wrote:

http://www.lazygranch.com/images/radio/cwfilter.gif
I did this test as follows:
1) radio in AM
2) AGC turned off
3) RF generator connector to antenna input
4) distortion analyzer connected to earphone output

Pick a frequency. I used 10Mhz. Set the RF generator and radio to that
frequency. Leave the radio dial alone. Sweep the RF generator manually
and measure the audio level from the distortion analyser. Plot the
results. This was a crystal filter, so you will need a RF generator
with 1Hz steps.

This is an in-situ measurement, i.e. this is not the same as just
testing the IF filter by itself. You need the distortion analyzer to
get the audio signal level independent from the noise.

All that said, Bush should be impeached.

Can't you just use the random pink noise between stations, rather than
a sweep generator?


rkhalona January 12th 06 01:10 AM

Measuring filter shape factor
 

Michael Thorpe wrote:
Amongst all these political propaganda posts, I wonder if there is a
little room for a technical question related to radio please?

If so, here goes:

How does one measure the IF filter shape factor in a shortwave radio?

I am technically minded and do have a signal generator, etc., but I am
not sure of the exact procedure. Do I get the audio level at the peak
frequency, then detune both sides off the peak for -3dB of the
demodulated audio, note down the width between these points, then
detune to obtain for -50dB of the demodulated audio, get the width at
these points, and then the ratio of the two widths is the filter shape
factor?

I would appreciate a link to the exact procedure if there is one
(don't seem to be able to find this in Google) or an expert advice
please.

I would also appreciate advice as to what actual values of filter
shape are considered poor, good, excellent, etc...

Thanks in advance,
Michael


You need to generate a swept frequency response of the IF filter

Take a look at the following article on filter selectivity:

http://www.radio-electronics.com/inf...electivity.php

The shape factor is traditionally defined as

BW(-60dB)
SF =---------------
BW(-6dB)

(see the third figure in the article illustrating a typical filter
response and the meaning of the two bandwidths)

For an ideal filter (see second figure), this bandwidth ratio would be
equal to ONE (1.0).
The closer the shape factor is to 1.0, the sharper the selectivity. For
example, if you look at the specs for the Eton E1 on the following link
(Monitoring Times review)

http://www.monitoringtimes.com/html/...k-etone1xm.pdf

the shape factor for the 7 KHz filter would be:

SF = 12 KHz/7 KHz = 1.71 (not a very sharp filter, but not bad for a
radio of this type)

The other two filters have even worse shape factors. With DSP
receivers, these filters can be made extremely tight and shape factors
can be very close to 1.0.

Hope this is helpful. Perhaps Pete can chime in with a detailed
measurement procedure.

RK


[email protected] January 12th 06 01:12 AM

Measuring filter shape factor
 
Sine-wave measurements are more precise. My test is very close to real
life since it is testing the entire signal path, i.e. from antenna
input to audio output. I couldn't find the connector I made that taps
the line output, so I used the earphone output.

I have audio test gear that uses random noise with FFT analysis, in
addition to a swept sine. You always get more accurate results with a
swept sine. FFT analysis is only used when you need speed.

As you will notice from the graphical output, the noise floor is quite
high. I may do the test again BTW, you need a decent distortion
analyser for

David wrote:
On 11 Jan 2006 14:14:01 -0800, wrote:

http://www.lazygranch.com/images/radio/cwfilter.gif
I did this test as follows:
1) radio in AM
2) AGC turned off
3) RF generator connector to antenna input
4) distortion analyzer connected to earphone output

Pick a frequency. I used 10Mhz. Set the RF generator and radio to that
frequency. Leave the radio dial alone. Sweep the RF generator manually
and measure the audio level from the distortion analyser. Plot the
results. This was a crystal filter, so you will need a RF generator
with 1Hz steps.

This is an in-situ measurement, i.e. this is not the same as just
testing the IF filter by itself. You need the distortion analyzer to
get the audio signal level independent from the noise.

All that said, Bush should be impeached.

Can't you just use the random pink noise between stations, rather than
a sweep generator?



[email protected] January 12th 06 01:23 AM

Measuring filter shape factor
 
At the time I did my test, I had a "hole" in my generators. The audio
gear went as high as 100k, and the RF gear went as low at 1Mhz, but the
IF was 455Khz. Hence I tested the whole audio path.

The impedances in the radio itself will effect the performance of the
filter, so there is something to be said for in-situ measurements.

Oh yeah, note that Abramoff didn't donate any money to the Democrats.

rkhalona wrote:
Michael Thorpe wrote:
Amongst all these political propaganda posts, I wonder if there is a
little room for a technical question related to radio please?

If so, here goes:

How does one measure the IF filter shape factor in a shortwave radio?

I am technically minded and do have a signal generator, etc., but I am
not sure of the exact procedure. Do I get the audio level at the peak
frequency, then detune both sides off the peak for -3dB of the
demodulated audio, note down the width between these points, then
detune to obtain for -50dB of the demodulated audio, get the width at
these points, and then the ratio of the two widths is the filter shape
factor?

I would appreciate a link to the exact procedure if there is one
(don't seem to be able to find this in Google) or an expert advice
please.

I would also appreciate advice as to what actual values of filter
shape are considered poor, good, excellent, etc...

Thanks in advance,
Michael


You need to generate a swept frequency response of the IF filter

Take a look at the following article on filter selectivity:

http://www.radio-electronics.com/inf...electivity.php

The shape factor is traditionally defined as

BW(-60dB)
SF =---------------
BW(-6dB)

(see the third figure in the article illustrating a typical filter
response and the meaning of the two bandwidths)

For an ideal filter (see second figure), this bandwidth ratio would be
equal to ONE (1.0).
The closer the shape factor is to 1.0, the sharper the selectivity. For
example, if you look at the specs for the Eton E1 on the following link
(Monitoring Times review)

http://www.monitoringtimes.com/html/...k-etone1xm.pdf

the shape factor for the 7 KHz filter would be:

SF = 12 KHz/7 KHz = 1.71 (not a very sharp filter, but not bad for a
radio of this type)

The other two filters have even worse shape factors. With DSP
receivers, these filters can be made extremely tight and shape factors
can be very close to 1.0.

Hope this is helpful. Perhaps Pete can chime in with a detailed
measurement procedure.

RK



David January 12th 06 03:01 AM

Measuring filter shape factor
 
On 11 Jan 2006 17:12:45 -0800, wrote:

Sine-wave measurements are more precise. My test is very close to real
life since it is testing the entire signal path, i.e. from antenna
input to audio output. I couldn't find the connector I made that taps
the line output, so I used the earphone output.

I have audio test gear that uses random noise with FFT analysis, in
addition to a swept sine. You always get more accurate results with a
swept sine. FFT analysis is only used when you need speed.

As you will notice from the graphical output, the noise floor is quite
high. I may do the test again BTW, you need a decent distortion
analyser for

I built one of those Heathkit H-P 334A clones. Took me 3 days. Had
to leave it behind when I resigned.


David January 12th 06 03:03 AM

Measuring filter shape factor
 
On 11 Jan 2006 17:23:37 -0800, wrote:

At the time I did my test, I had a "hole" in my generators. The audio
gear went as high as 100k, and the RF gear went as low at 1Mhz, but the
IF was 455Khz. Hence I tested the whole audio path.

The impedances in the radio itself will effect the performance of the
filter, so there is something to be said for in-situ measurements.

Oh yeah, note that Abramoff didn't donate any money to the Democrats.

Read Rich Lowrie's latest editorial at National Review Online.


Brian Denley January 12th 06 03:36 AM

Measuring filter shape factor
 
Michael Thorpe wrote:
Amongst all these political propaganda posts, I wonder if there is a
little room for a technical question related to radio please?

If so, here goes:

How does one measure the IF filter shape factor in a shortwave radio?

I am technically minded and do have a signal generator, etc., but I am
not sure of the exact procedure. Do I get the audio level at the peak
frequency, then detune both sides off the peak for -3dB of the
demodulated audio, note down the width between these points, then
detune to obtain for -50dB of the demodulated audio, get the width at
these points, and then the ratio of the two widths is the filter shape
factor?

I would appreciate a link to the exact procedure if there is one
(don't seem to be able to find this in Google) or an expert advice
please.

I would also appreciate advice as to what actual values of filter
shape are considered poor, good, excellent, etc...

Thanks in advance,
Michael


Michael:
If you don't have a spectrum analyzer, you can use an oscope (setup for
x-y) while driving the filter (and x ) with a sweep function generator.
Remember that if you look at the IF output prior to the detector, you will
get a curve going positive and negative. If you look at the response after
the detector, it will look more like the IF filter shape that you expect.

--
Brian Denley
http://home.comcast.net/~b.denley/index.html



dxAce January 12th 06 03:54 AM

Measuring filter shape factor
 


wrote:

At the time I did my test, I had a "hole" in my generators. The audio
gear went as high as 100k, and the RF gear went as low at 1Mhz, but the
IF was 455Khz. Hence I tested the whole audio path.

The impedances in the radio itself will effect the performance of the
filter, so there is something to be said for in-situ measurements.

Oh yeah, note that Abramoff didn't donate any money to the Democrats.


LMFAO yet again at the Liberal 'tard boy!

dxAce
Michigan
USA



mike maghakian January 12th 06 04:17 AM

Measuring filter shape factor
 
check this page out:

http://www.radio-electronics.com/inf...electivity.php




"Michael Thorpe" wrote in message
news:43c4e407.4277000@news-server...
Amongst all these political propaganda posts, I wonder if there is a
little room for a technical question related to radio please?

If so, here goes:

How does one measure the IF filter shape factor in a shortwave radio?

I am technically minded and do have a signal generator, etc., but I am
not sure of the exact procedure. Do I get the audio level at the peak
frequency, then detune both sides off the peak for -3dB of the
demodulated audio, note down the width between these points, then
detune to obtain for -50dB of the demodulated audio, get the width at
these points, and then the ratio of the two widths is the filter shape
factor?

I would appreciate a link to the exact procedure if there is one
(don't seem to be able to find this in Google) or an expert advice
please.

I would also appreciate advice as to what actual values of filter
shape are considered poor, good, excellent, etc...

Thanks in advance,
Michael




Pete KE9OA January 12th 06 04:41 AM

Measuring filter shape factor
 
Good web page.....................I throw them on a network analyzer when I
want to measure them, but there are some pretty good ideas here.

Pete

"mike maghakian" wrote in message
...
check this page out:

http://www.radio-electronics.com/inf...electivity.php




"Michael Thorpe" wrote in message
news:43c4e407.4277000@news-server...
Amongst all these political propaganda posts, I wonder if there is a
little room for a technical question related to radio please?

If so, here goes:

How does one measure the IF filter shape factor in a shortwave radio?

I am technically minded and do have a signal generator, etc., but I am
not sure of the exact procedure. Do I get the audio level at the peak
frequency, then detune both sides off the peak for -3dB of the
demodulated audio, note down the width between these points, then
detune to obtain for -50dB of the demodulated audio, get the width at
these points, and then the ratio of the two widths is the filter shape
factor?

I would appreciate a link to the exact procedure if there is one
(don't seem to be able to find this in Google) or an expert advice
please.

I would also appreciate advice as to what actual values of filter
shape are considered poor, good, excellent, etc...

Thanks in advance,
Michael






[email protected] January 12th 06 05:06 AM

Measuring filter shape factor
 
I'm a National Review subscriber. Really. However, I don't read the
on-line version as it is routinely disinformation, i.e. articles that
don't make it to the magazine. If you subscribe to the magazine, they
will print retractions of what appears online.

I will say at NR is the only conservative mag worth reading. They never
stooped to the level of say the Spectator.

David wrote:
On 11 Jan 2006 17:23:37 -0800, wrote:

At the time I did my test, I had a "hole" in my generators. The audio
gear went as high as 100k, and the RF gear went as low at 1Mhz, but the
IF was 455Khz. Hence I tested the whole audio path.

The impedances in the radio itself will effect the performance of the
filter, so there is something to be said for in-situ measurements.

Oh yeah, note that Abramoff didn't donate any money to the Democrats.

Read Rich Lowrie's latest editorial at National Review Online.



Michael Thorpe January 12th 06 11:32 AM

Measuring filter shape factor
 
On Wed, 11 Jan 2006 21:23:09 GMT, "Dale Parfitt"
wrote:


"Michael Thorpe" wrote in message
news:43c4e407.4277000@news-server...
Amongst all these political propaganda posts, I wonder if there is a
little room for a technical question related to radio please?

If so, here goes:

How does one measure the IF filter shape factor in a shortwave radio?

I am technically minded and do have a signal generator, etc., but I am
not sure of the exact procedure. Do I get the audio level at the peak
frequency, then detune both sides off the peak for -3dB of the
demodulated audio, note down the width between these points, then
detune to obtain for -50dB of the demodulated audio, get the width at
these points, and then the ratio of the two widths is the filter shape
factor?

I would appreciate a link to the exact procedure if there is one
(don't seem to be able to find this in Google) or an expert advice
please.

I would also appreciate advice as to what actual values of filter
shape are considered poor, good, excellent, etc...

Thanks in advance,
Michael


Hi Michael,

Although I have never given it much thought, I don't believe one can fully
characterize a filter while it is installed in the receiver- certainly,
parameters such as insertion loss would not be easily measurable. Perhaps
programs like Spectran may give some rough insight.
My method is classic- the filter is removed, properly terminated and
connected as the DUT on a scalar network analyzer.
If you have a vector network analyzer available you could also observe group
delay- an important factor in narrow filters.
See Paul Kiciak's (N2PK) site for his clever VNA- ideally suited for
filters.
Dale W4OP


Thanks, Dale, for your input. I would have no problems measuring
filters when taken out of a receiver. But this is not always possible,
for example with modern DSP software-defined receivers. There you have
no choice, the filter is no longer just a component you can desolder,
so you do need to measure the entire receiver. Parameters such as
insertion loss is immaterial in such cases - all that matters is the
filter shape.

Michael


Michael Thorpe January 12th 06 11:43 AM

Measuring filter shape factor
 
On 11 Jan 2006 14:14:01 -0800, wrote:

http://www.lazygranch.com/images/radio/cwfilter.gif
I did this test as follows:
1) radio in AM
2) AGC turned off
3) RF generator connector to antenna input
4) distortion analyzer connected to earphone output

Pick a frequency. I used 10Mhz. Set the RF generator and radio to that
frequency. Leave the radio dial alone. Sweep the RF generator manually
and measure the audio level from the distortion analyser. Plot the
results. This was a crystal filter, so you will need a RF generator
with 1Hz steps.

This is an in-situ measurement, i.e. this is not the same as just
testing the IF filter by itself. You need the distortion analyzer to
get the audio signal level independent from the noise.


Many thanks, this is interesting. What I am still unsure about is how
you determine the -6dB and -60dB points using the distortion analyzer:
When you say "measure the audio level", what exactly do you measure,
the audio signal fundamental (i.e. filtered at the modulation
frequency)?

So in fact you are only using the distortion analyzer to filter the
audio and to measure the level? I don't have a distortion analyzer,
but I guess I could simply use an oscilloscope or an audio spectrum
analyzer (PC sound card based).

Michael


David January 12th 06 02:13 PM

Measuring filter shape factor
 
On 11 Jan 2006 21:06:53 -0800, wrote:

I'm a National Review subscriber. Really. However, I don't read the
on-line version as it is routinely disinformation, i.e. articles that
don't make it to the magazine. If you subscribe to the magazine, they
will print retractions of what appears online.

I will say at NR is the only conservative mag worth reading. They never
stooped to the level of say the Spectator.

David wrote:
On 11 Jan 2006 17:23:37 -0800,
wrote:

At the time I did my test, I had a "hole" in my generators. The audio
gear went as high as 100k, and the RF gear went as low at 1Mhz, but the
IF was 455Khz. Hence I tested the whole audio path.

The impedances in the radio itself will effect the performance of the
filter, so there is something to be said for in-situ measurements.

Oh yeah, note that Abramoff didn't donate any money to the Democrats.

Read Rich Lowrie's latest editorial at National Review Online.


He says the Abramoff scandal is 100% Republicans.


Mark Zenier January 12th 06 07:00 PM

Measuring filter shape factor
 
In article 43c63d58.6926500@news-server,
Michael Thorpe wrote:
On Wed, 11 Jan 2006 21:23:09 GMT, "Dale Parfitt"
wrote:


"Michael Thorpe" wrote in message
news:43c4e407.4277000@news-server...
Amongst all these political propaganda posts, I wonder if there is a
little room for a technical question related to radio please?

If so, here goes:

How does one measure the IF filter shape factor in a shortwave radio?

I am technically minded and do have a signal generator, etc., but I am
not sure of the exact procedure. Do I get the audio level at the peak
frequency, then detune both sides off the peak for -3dB of the
demodulated audio, note down the width between these points, then
detune to obtain for -50dB of the demodulated audio, get the width at
these points, and then the ratio of the two widths is the filter shape
factor?

I would appreciate a link to the exact procedure if there is one
(don't seem to be able to find this in Google) or an expert advice
please.

I would also appreciate advice as to what actual values of filter
shape are considered poor, good, excellent, etc...


Although I have never given it much thought, I don't believe one can fully
characterize a filter while it is installed in the receiver- certainly,
parameters such as insertion loss would not be easily measurable. Perhaps
programs like Spectran may give some rough insight.
My method is classic- the filter is removed, properly terminated and
connected as the DUT on a scalar network analyzer.
If you have a vector network analyzer available you could also observe group
delay- an important factor in narrow filters.
See Paul Kiciak's (N2PK) site for his clever VNA- ideally suited for
filters.


Thanks, Dale, for your input. I would have no problems measuring
filters when taken out of a receiver. But this is not always possible,
for example with modern DSP software-defined receivers. There you have
no choice, the filter is no longer just a component you can desolder,
so you do need to measure the entire receiver. Parameters such as
insertion loss is immaterial in such cases - all that matters is the
filter shape.


But when the whole system is put together, it's no longer "filter
shape factor", it's some other parameter, "adjacent signal rejection"
or something like that.

Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)

clifto January 12th 06 07:24 PM

Measuring filter shape factor
 
David wrote:
On 11 Jan 2006 21:06:53 -0800, wrote:
Read Rich Lowrie's latest editorial at National Review Online.


He says the Abramoff scandal is 100% Republicans.


Then he's stupid, or ignorant, or lying. 40 out of 45 Senate Democrats got
money from Abramoff.

Senator John Kerry (D-MA) received at least $98,550 in Abramoff-linked cash.
Senator Harry Reid (D-NV) received at least $68,941 in Abramoff-linked cash.
Senator Tom Harkin (D-IA) received at least $45,750 in Abramoff-linked cash.
Senator Hillary Clinton (D-NY) received at least $12,950 in Abramoff-linked cash.
Senator Patty Murray (D-WA) received at least $78,991 in Abramoff-linked cash.
Senator Chuck Schumer (D-NY) received at least $29,550 in Abramoff-linked cash.
Senator Debbie Stabenow (D-MI) received at least $6,250 in Abramoff-linked cash.
Senator Max Baucus (D-MT) received at least $22,500 in Abramoff-linked cash.
Senator Evan Bayh (D-IN) received at least $6,500 in Abramoff-linked cash.
Senator Joseph Biden (D-DE) received at least $1,250 in Abramoff-linked cash.
Senator Jeff Bingaman (D-NM) received at least $2,000 in Abramoff-linked cash.
Senator Barbara Boxer (D-CA) received at least $20,250 in Abramoff-linked cash.
Senator Maria Cantwell (D-WA) received at least $21,765 in Abramoff-linked cash.
Senator Tom Carper (D-DE) received at least $7,500 in Abramoff-linked cash.
Senator Kent Conrad (D-ND) received at least $8,000 in Abramoff-linked cash.
Senator Jon Corzine (D-NJ) received at least $7,500 in Abramoff-linked cash.
Senator Chris Dodd (D-CT) received at least $14,792 in Abramoff-linked cash.
Senator Byron Dorgan (D-ND) received at least $79,300 in Abramoff-linked cash.
Senator Dick Durbin (D-IL) received at least $14,000 in Abramoff-linked cash.
Senator Dianne Feinstein (D-CA) received at least $2,000 in Abramoff-linked cash.
Senator Russ Feingold (D-WI) received at least $1,250 in Abramoff-linked cash.
Senator Daniel Inouye (D-HI) received at least $9,000 in Abramoff-linked cash.
Senator Jim Jeffords (I-VT) received at least $2,000 in Abramoff-linked cash.
Senator Tim Johnson (D-SD) received at least $14,250 in Abramoff-linked cash.
Senator Ted Kennedy (D-MA) received at least $3,300 in Abramoff-linked cash.
Senator Mary Landrieu (D-LA) received at least $28,000 in Abramoff-linked cash.
Senator Pat Leahy (D-VT) received at least $4,000 in Abramoff-linked cash.
Senator Carl Levin (D-MI) received at least $6,000 in Abramoff-linked cash.
Senator Joe Lieberman (D-CT) received at least $29,830 in Abramoff-linked cash.
Senator Blanche Lincoln (D-AR) Received At Least $14,891 in Abramoff-linked cash.
Senator Barbara Mikulski (D-MD) received at least $10,550 in Abramoff-linked cash.
Senator Bill Nelson (D-FL) received at least $20,168 in Abramoff-linked cash.
Senator Ben Nelson (D-NE) Received At Least $5,200 in Abramoff-linked cash.
Senator Barack Obama (D-IL) received at least $7,500 in Abramoff-linked cash.
Senator Mark Pryor (D-AR) received at least $2,300 in Abramoff-linked cash.
Senator Jack Reed (D-RI) received at least $3,500 in Abramoff-linked cash.
Senator John Rockefeller (D-WV) received at least $4,000 in Abramoff-linked cash.
Senator Ken Salazar (D-CO) received at least $4,500 in Abramoff-linked cash.
Senator Paul Sarbanes (D-MD) received at least $4,300 in Abramoff-linked cash.
Senator Ron Wyden (D-OR) received at least $6,250 in Abramoff-linked cash.

--
If John McCain gets the 2008 Republican Presidential nomination,
my vote for President will be a write-in for Jiang Zemin.

[email protected] January 12th 06 07:39 PM

Measuring filter shape factor
 
There is a difference between getting money from tribes, and getting
money from Abramoff.

You should switch from kool-aid to beer.
clifto wrote:
David wrote:
On 11 Jan 2006 21:06:53 -0800, wrote:
Read Rich Lowrie's latest editorial at National Review Online.

He says the Abramoff scandal is 100% Republicans.


Then he's stupid, or ignorant, or lying. 40 out of 45 Senate Democrats got
money from Abramoff.

Senator John Kerry (D-MA) received at least $98,550 in Abramoff-linked cash.
Senator Harry Reid (D-NV) received at least $68,941 in Abramoff-linked cash.
Senator Tom Harkin (D-IA) received at least $45,750 in Abramoff-linked cash.
Senator Hillary Clinton (D-NY) received at least $12,950 in Abramoff-linked cash.
Senator Patty Murray (D-WA) received at least $78,991 in Abramoff-linked cash.
Senator Chuck Schumer (D-NY) received at least $29,550 in Abramoff-linked cash.
Senator Debbie Stabenow (D-MI) received at least $6,250 in Abramoff-linked cash.
Senator Max Baucus (D-MT) received at least $22,500 in Abramoff-linked cash.
Senator Evan Bayh (D-IN) received at least $6,500 in Abramoff-linked cash.
Senator Joseph Biden (D-DE) received at least $1,250 in Abramoff-linked cash.
Senator Jeff Bingaman (D-NM) received at least $2,000 in Abramoff-linked cash.
Senator Barbara Boxer (D-CA) received at least $20,250 in Abramoff-linked cash.
Senator Maria Cantwell (D-WA) received at least $21,765 in Abramoff-linked cash.
Senator Tom Carper (D-DE) received at least $7,500 in Abramoff-linked cash.
Senator Kent Conrad (D-ND) received at least $8,000 in Abramoff-linked cash.
Senator Jon Corzine (D-NJ) received at least $7,500 in Abramoff-linked cash.
Senator Chris Dodd (D-CT) received at least $14,792 in Abramoff-linked cash.
Senator Byron Dorgan (D-ND) received at least $79,300 in Abramoff-linked cash.
Senator Dick Durbin (D-IL) received at least $14,000 in Abramoff-linked cash.
Senator Dianne Feinstein (D-CA) received at least $2,000 in Abramoff-linked cash.
Senator Russ Feingold (D-WI) received at least $1,250 in Abramoff-linked cash.
Senator Daniel Inouye (D-HI) received at least $9,000 in Abramoff-linked cash.
Senator Jim Jeffords (I-VT) received at least $2,000 in Abramoff-linked cash.
Senator Tim Johnson (D-SD) received at least $14,250 in Abramoff-linked cash.
Senator Ted Kennedy (D-MA) received at least $3,300 in Abramoff-linked cash.
Senator Mary Landrieu (D-LA) received at least $28,000 in Abramoff-linked cash.
Senator Pat Leahy (D-VT) received at least $4,000 in Abramoff-linked cash.
Senator Carl Levin (D-MI) received at least $6,000 in Abramoff-linked cash.
Senator Joe Lieberman (D-CT) received at least $29,830 in Abramoff-linked cash.
Senator Blanche Lincoln (D-AR) Received At Least $14,891 in Abramoff-linked cash.
Senator Barbara Mikulski (D-MD) received at least $10,550 in Abramoff-linked cash.
Senator Bill Nelson (D-FL) received at least $20,168 in Abramoff-linked cash.
Senator Ben Nelson (D-NE) Received At Least $5,200 in Abramoff-linked cash.
Senator Barack Obama (D-IL) received at least $7,500 in Abramoff-linked cash.
Senator Mark Pryor (D-AR) received at least $2,300 in Abramoff-linked cash.
Senator Jack Reed (D-RI) received at least $3,500 in Abramoff-linked cash.
Senator John Rockefeller (D-WV) received at least $4,000 in Abramoff-linked cash.
Senator Ken Salazar (D-CO) received at least $4,500 in Abramoff-linked cash.
Senator Paul Sarbanes (D-MD) received at least $4,300 in Abramoff-linked cash.
Senator Ron Wyden (D-OR) received at least $6,250 in Abramoff-linked cash.

--
If John McCain gets the 2008 Republican Presidential nomination,
my vote for President will be a write-in for Jiang Zemin.



[email protected] January 12th 06 08:00 PM

Measuring filter shape factor
 
The distortion analyzer has a tracking bandpass filter. I'm using the
HP8903E, but for this purpose, even the 334B would do the trick. You
can use the analyzer to display the signal level of the sine wave
inpedentent of noise to the degree the bandpass filter can remove it.
[The 8903E reads amplitude, distortion, and frequency.]

I never reached the -60db point, because the signal was lost in the
noise. But you have to ask yourself, if the signal is in the noise, you
do care about the rejection?

In the dark ages, I was designing switched capacitor filters for modem
products. When you sold the chip as a Bell standard filter, you had to
implement that exact filter. However, the reality was the noise floor
and THD totally negated the effectiveness of the filter. [Power supply
rejection is a factor too.] So yeah, I could attenuate the alternate
(out of band) channel, but the filter noise was more significant than
what I was attenuating. Once the product became integrated, nobody
could see the filter implementation. The amount of filtering was
reduced to a level where the alternate channel (out of band) signal
level was minimum by picking a compromise between the number of poles
of filtering and the noise level of the amplifiers. Less poles of
filtering meant fewer all passes were required.

Now I'm not happy the noise floor of the radio crapped out at around
-45db. I don't know if measuring at the line outputs would have been
better. I need to do the measurement again.

It is quite possible that you can use your sound card to measure the
amplitude of the signal independent of the noise. BTW, I should have
mentioned I turned on the 1khz modulation on the RF signal generator.

My goal was to test a crystal filter I picked up at the flea market and
installed in my radio. [A good deal at $10.] One thing I learned is the
coupling capacitors make a difference in terms of the signal level. I'd
have to open the radio to see what I used, but I recall if the caps
were too small, the signal level was attenuated.


Michael Thorpe wrote:
On 11 Jan 2006 14:14:01 -0800, wrote:

http://www.lazygranch.com/images/radio/cwfilter.gif
I did this test as follows:
1) radio in AM
2) AGC turned off
3) RF generator connector to antenna input
4) distortion analyzer connected to earphone output

Pick a frequency. I used 10Mhz. Set the RF generator and radio to that
frequency. Leave the radio dial alone. Sweep the RF generator manually
and measure the audio level from the distortion analyser. Plot the
results. This was a crystal filter, so you will need a RF generator
with 1Hz steps.

This is an in-situ measurement, i.e. this is not the same as just
testing the IF filter by itself. You need the distortion analyzer to
get the audio signal level independent from the noise.


Many thanks, this is interesting. What I am still unsure about is how
you determine the -6dB and -60dB points using the distortion analyzer:
When you say "measure the audio level", what exactly do you measure,
the audio signal fundamental (i.e. filtered at the modulation
frequency)?

So in fact you are only using the distortion analyzer to filter the
audio and to measure the level? I don't have a distortion analyzer,
but I guess I could simply use an oscilloscope or an audio spectrum
analyzer (PC sound card based).

Michael



[email protected] January 12th 06 08:02 PM

Measuring filter shape factor
 
How exactly does one see 60db down?

Brian Denley wrote:
Michael Thorpe wrote:
Amongst all these political propaganda posts, I wonder if there is a
little room for a technical question related to radio please?

If so, here goes:

How does one measure the IF filter shape factor in a shortwave radio?

I am technically minded and do have a signal generator, etc., but I am
not sure of the exact procedure. Do I get the audio level at the peak
frequency, then detune both sides off the peak for -3dB of the
demodulated audio, note down the width between these points, then
detune to obtain for -50dB of the demodulated audio, get the width at
these points, and then the ratio of the two widths is the filter shape
factor?

I would appreciate a link to the exact procedure if there is one
(don't seem to be able to find this in Google) or an expert advice
please.

I would also appreciate advice as to what actual values of filter
shape are considered poor, good, excellent, etc...

Thanks in advance,
Michael


Michael:
If you don't have a spectrum analyzer, you can use an oscope (setup for
x-y) while driving the filter (and x ) with a sweep function generator.
Remember that if you look at the IF output prior to the detector, you will
get a curve going positive and negative. If you look at the response after
the detector, it will look more like the IF filter shape that you expect.

--
Brian Denley
http://home.comcast.net/~b.denley/index.html



clifto January 12th 06 10:00 PM

[OT] Measuring filter shape factor
 
wrote:
clifto wrote:
David wrote:
On 11 Jan 2006 21:06:53 -0800,
wrote:
Read Rich Lowrie's latest editorial at National Review Online.

He says the Abramoff scandal is 100% Republicans.


Then he's stupid, or ignorant, or lying. 40 out of 45 Senate Democrats got
money from Abramoff.


There is a difference between getting money from tribes, and getting
money from Abramoff.

You should switch from kool-aid to beer.


It took me all of 120 seconds to find this in the liberal Chicago Tribune:

http://www.chicagotribune.com/news/local/southsouthwest/chi-0601110210jan11,1,5780990.story?coll=chi-newslocalssouthwest-hed

"Kennedy on Tuesday also explained why Weller used $1,640 of his own money
to reimburse a lobbying firm where Abramoff once worked for a 1999 trip
to two Indian reservations in Louisiana and Mississippi.

"He visited those reservations at the request of former U.S. Rep. David
Funderburk (R-N.C.), and THOUGHT THE TRIBES HAD PAID FOR THE TRIP [emphasis
by clifto], Kennedy said. As soon as he confirmed otherwise, he repaid
the money from his own pocket, he said."


Here's one from liberal rag UnionLeader.com:

http://www.theunionleader.com/article.aspx?headline=Sullivan+defends+Democrats+k eeping+lobbyist%E2%80%99s+money&articleId=c0963d8c-692b-47e6-b316-f42c8053aeef

"Top Democrats received donations from scandal-plagued Washington
lobbyist Jack Abramoff?s Indian tribe clients for legitimate reasons
and are right to refuse to give up the money, the state?s Democratic
chairman says."


I bet if I took the time to search further, which I'm not going to bother
doing, I could find *tribal* money going to Democrats via Abramoff in mass
quantities.

Note that unlike most of the Republicans involved, Kennedy and Reid have
no intention of giving the money back or giving it to charity. They're
keeping it.

--
If John McCain gets the 2008 Republican Presidential nomination,
my vote for President will be a write-in for Jiang Zemin.

David January 13th 06 01:36 AM

[OT] Measuring filter shape factor
 
On Thu, 12 Jan 2006 16:00:51 -0600, clifto wrote:

wrote:
clifto wrote:
David wrote:
On 11 Jan 2006 21:06:53 -0800, wrote:
Read Rich Lowrie's latest editorial at National Review Online.

He says the Abramoff scandal is 100% Republicans.

Then he's stupid, or ignorant, or lying. 40 out of 45 Senate Democrats got
money from Abramoff.


There is a difference between getting money from tribes, and getting
money from Abramoff.

You should switch from kool-aid to beer.


It took me all of 120 seconds to find this in the liberal Chicago Tribune:

http://www.chicagotribune.com/news/local/southsouthwest/chi-0601110210jan11,1,5780990.story?coll=chi-newslocalssouthwest-hed

But the Indians didn't work for Abramoff.


Brian Denley January 13th 06 03:58 AM

Measuring filter shape factor
 
wrote:
How exactly does one see 60db down?



Very carefully!

--
Brian Denley
http://home.comcast.net/~b.denley/index.html



Telamon January 13th 06 04:47 AM

Measuring filter shape factor
 
In article 43c63f8a.7487750@news-server,
(Michael Thorpe) wrote:

On 11 Jan 2006 14:14:01 -0800,
wrote:

http://www.lazygranch.com/images/radio/cwfilter.gif
I did this test as follows:
1) radio in AM
2) AGC turned off
3) RF generator connector to antenna input
4) distortion analyzer connected to earphone output

Pick a frequency. I used 10Mhz. Set the RF generator and radio to that
frequency. Leave the radio dial alone. Sweep the RF generator manually
and measure the audio level from the distortion analyser. Plot the
results. This was a crystal filter, so you will need a RF generator
with 1Hz steps.

This is an in-situ measurement, i.e. this is not the same as just
testing the IF filter by itself. You need the distortion analyzer to
get the audio signal level independent from the noise.


Many thanks, this is interesting. What I am still unsure about is how
you determine the -6dB and -60dB points using the distortion analyzer:
When you say "measure the audio level", what exactly do you measure,
the audio signal fundamental (i.e. filtered at the modulation
frequency)?

So in fact you are only using the distortion analyzer to filter the
audio and to measure the level? I don't have a distortion analyzer,
but I guess I could simply use an oscilloscope or an audio spectrum
analyzer (PC sound card based).


rkhalona gave you the right definition of shape factor and a web page
that explains it.

BW(-60dB)
SF =---------------
BW(-6dB)

http://www.radio-electronics.com/inf...ty/selectivity.
php

The audio passband is often but not always defined at the IF stage with
a IF passband filter. The -6dB and -60dB is referenced to the filter
center IF frequency of 0dB. The filter is usually symmetrical and the SF
number refers to how fast the slope changes. Steeper is better. The -6dB
down point is usually considered the bandwidth of the filter.

With what you have the easiest thing to do would be to use the PC audio
spectrum analyzer. On a strong signal playing music use a max hold
function on the analyzer software and the passband of the filter should
become apparent. Look at where the high end response rolls off 6dB down
relative to what looks like a flat audio spectrum from low to middle
audio frequencies. Where the high frequencies roll of 6dB down from the
flat audio response range will be 1/2 the filter bandwidth.

For this to work the station you have are receiving must be have a wider
modulation bandwidth then you are using for an audio bandwidth filter so
this may only work for narrow filters.

If this does not work well enough then you will need an RF generator
that you can modulate at a frequency higher than the largest filter you
want to measure and use the PC analyzer as described above.

--
Telamon
Ventura, California

Telamon January 13th 06 05:10 AM

Measuring filter shape factor
 
In article ,
"Brian Denley" wrote:

wrote:
How exactly does one see 60db down?



Very carefully!


Things start getting pretty dark after 40dB down so be very careful!

--
Telamon
Ventura, California

Michael Thorpe January 13th 06 09:01 AM

Measuring filter shape factor
 
On Fri, 13 Jan 2006 04:47:07 GMT, Telamon
wrote:

In article 43c63f8a.7487750@news-server,
(Michael Thorpe) wrote:

On 11 Jan 2006 14:14:01 -0800,
wrote:

http://www.lazygranch.com/images/radio/cwfilter.gif
I did this test as follows:
1) radio in AM
2) AGC turned off
3) RF generator connector to antenna input
4) distortion analyzer connected to earphone output

Pick a frequency. I used 10Mhz. Set the RF generator and radio to that
frequency. Leave the radio dial alone. Sweep the RF generator manually
and measure the audio level from the distortion analyser. Plot the
results. This was a crystal filter, so you will need a RF generator
with 1Hz steps.

This is an in-situ measurement, i.e. this is not the same as just
testing the IF filter by itself. You need the distortion analyzer to
get the audio signal level independent from the noise.


Many thanks, this is interesting. What I am still unsure about is how
you determine the -6dB and -60dB points using the distortion analyzer:
When you say "measure the audio level", what exactly do you measure,
the audio signal fundamental (i.e. filtered at the modulation
frequency)?

So in fact you are only using the distortion analyzer to filter the
audio and to measure the level? I don't have a distortion analyzer,
but I guess I could simply use an oscilloscope or an audio spectrum
analyzer (PC sound card based).


rkhalona gave you the right definition of shape factor and a web page
that explains it.

BW(-60dB)
SF =---------------
BW(-6dB)

http://www.radio-electronics.com/inf...ty/selectivity.
php

The audio passband is often but not always defined at the IF stage with
a IF passband filter. The -6dB and -60dB is referenced to the filter
center IF frequency of 0dB. The filter is usually symmetrical and the SF
number refers to how fast the slope changes. Steeper is better. The -6dB
down point is usually considered the bandwidth of the filter.

With what you have the easiest thing to do would be to use the PC audio
spectrum analyzer. On a strong signal playing music use a max hold
function on the analyzer software and the passband of the filter should
become apparent. Look at where the high end response rolls off 6dB down
relative to what looks like a flat audio spectrum from low to middle
audio frequencies. Where the high frequencies roll of 6dB down from the
flat audio response range will be 1/2 the filter bandwidth.

For this to work the station you have are receiving must be have a wider
modulation bandwidth then you are using for an audio bandwidth filter so
this may only work for narrow filters.

If this does not work well enough then you will need an RF generator
that you can modulate at a frequency higher than the largest filter you
want to measure and use the PC analyzer as described above.

--
Telamon
Ventura, California


Yep, that's a very good method, thanks! To refine this, I might use a
noise generator modulating a signal generator (instead of using a
station music). This should show the passband nicer and more steady, I
think.

I do have a signal generator, and I guess I could make a noise
generator using a Zener diode followed by an amplifier. Let's see...

Thanks again.

Michael


Michael Thorpe January 13th 06 09:04 AM

Measuring filter shape factor
 
On 12 Jan 2006 12:00:25 -0800, wrote:

The distortion analyzer has a tracking bandpass filter. I'm using the
HP8903E, but for this purpose, even the 334B would do the trick. You
can use the analyzer to display the signal level of the sine wave
inpedentent of noise to the degree the bandpass filter can remove it.
[The 8903E reads amplitude, distortion, and frequency.]

I never reached the -60db point, because the signal was lost in the
noise. But you have to ask yourself, if the signal is in the noise, you
do care about the rejection?


Well I agree, but the point it is that I would like to be able to
compare my results to the actual manufactures' specifications of the
shape factor for various receivers. So if everyone defines the shape
factor as BW(-6dB)/BW(-60dB), then somehow I need to be able to
measure this. But I think I now have enough input from this group to
be able to do this. Thank you very much for your help.

In the dark ages, I was designing switched capacitor filters for modem
products. When you sold the chip as a Bell standard filter, you had to
implement that exact filter. However, the reality was the noise floor
and THD totally negated the effectiveness of the filter. [Power supply
rejection is a factor too.] So yeah, I could attenuate the alternate
(out of band) channel, but the filter noise was more significant than
what I was attenuating. Once the product became integrated, nobody
could see the filter implementation. The amount of filtering was
reduced to a level where the alternate channel (out of band) signal
level was minimum by picking a compromise between the number of poles
of filtering and the noise level of the amplifiers. Less poles of
filtering meant fewer all passes were required.

Now I'm not happy the noise floor of the radio crapped out at around
-45db. I don't know if measuring at the line outputs would have been
better. I need to do the measurement again.

It is quite possible that you can use your sound card to measure the
amplitude of the signal independent of the noise. BTW, I should have
mentioned I turned on the 1khz modulation on the RF signal generator.

My goal was to test a crystal filter I picked up at the flea market and
installed in my radio. [A good deal at $10.] One thing I learned is the
coupling capacitors make a difference in terms of the signal level. I'd
have to open the radio to see what I used, but I recall if the caps
were too small, the signal level was attenuated.


Michael Thorpe wrote:
On 11 Jan 2006 14:14:01 -0800,
wrote:

http://www.lazygranch.com/images/radio/cwfilter.gif
I did this test as follows:
1) radio in AM
2) AGC turned off
3) RF generator connector to antenna input
4) distortion analyzer connected to earphone output

Pick a frequency. I used 10Mhz. Set the RF generator and radio to that
frequency. Leave the radio dial alone. Sweep the RF generator manually
and measure the audio level from the distortion analyser. Plot the
results. This was a crystal filter, so you will need a RF generator
with 1Hz steps.

This is an in-situ measurement, i.e. this is not the same as just
testing the IF filter by itself. You need the distortion analyzer to
get the audio signal level independent from the noise.


Many thanks, this is interesting. What I am still unsure about is how
you determine the -6dB and -60dB points using the distortion analyzer:
When you say "measure the audio level", what exactly do you measure,
the audio signal fundamental (i.e. filtered at the modulation
frequency)?

So in fact you are only using the distortion analyzer to filter the
audio and to measure the level? I don't have a distortion analyzer,
but I guess I could simply use an oscilloscope or an audio spectrum
analyzer (PC sound card based).

Michael




Michael Thorpe January 13th 06 09:10 AM

Measuring filter shape factor
 
On Fri, 13 Jan 2006 05:10:44 GMT, Telamon
wrote:

In article ,
"Brian Denley" wrote:

wrote:
How exactly does one see 60db down?



Very carefully!


Things start getting pretty dark after 40dB down so be very careful!

--
Telamon
Ventura, California


Many thanks to everyone who invested their time and effort to help me
with my filter shape measurement problem. Your advice has been very
valuable to me and I am now back on track as a result. I will report
what I'll find.

Michael


[email protected] January 13th 06 04:55 PM

Measuring filter shape factor
 
I'm not sure why the XY display, but seeing 40db is about the limit.
You really need test equipment to get any meaningful results. Network
analysers that cover a few MHz aren't that expensive. You can also just
use a RF generator and power meter, which is a cheaper solution since
you don't need phase measurements to see attenuation.


Telamon wrote:
In article ,
"Brian Denley" wrote:

wrote:
How exactly does one see 60db down?



Very carefully!


Things start getting pretty dark after 40dB down so be very careful!

--
Telamon
Ventura, California



Brian Denley January 14th 06 03:39 AM

Measuring filter shape factor
 
wrote:
I'm not sure why the XY display, but seeing 40db is about the limit.
You really need test equipment to get any meaningful results. Network
analysers that cover a few MHz aren't that expensive. You can also
just use a RF generator and power meter, which is a cheaper solution
since you don't need phase measurements to see attenuation.



If you DON'T have a spectrum analyzer (most don't) or if you DON'T have
expensive test gear, a decent Oscope with x-y and a sweep generator can be
used as a poor man's spectrum analyzer. 50 years ago, there was no other
way to do it, in fact. If you look at, say, a Hammarlund receiver manual,
that's exactly the recommended way to adjust the IF filter response curve.
You don't have to go down to 60 db to see a bad shape factor.

--
Brian Denley
http://home.comcast.net/~b.denley/index.html



Telamon January 14th 06 04:07 AM

Measuring filter shape factor
 
In article 43c76b90.3683890@news-server,
(Michael Thorpe) wrote:

On Fri, 13 Jan 2006 04:47:07 GMT, Telamon
wrote:

In article 43c63f8a.7487750@news-server,
(Michael Thorpe) wrote:

On 11 Jan 2006 14:14:01 -0800,
wrote:

http://www.lazygranch.com/images/radio/cwfilter.gif
I did this test as follows:
1) radio in AM
2) AGC turned off
3) RF generator connector to antenna input
4) distortion analyzer connected to earphone output

Pick a frequency. I used 10Mhz. Set the RF generator and radio to that
frequency. Leave the radio dial alone. Sweep the RF generator manually
and measure the audio level from the distortion analyser. Plot the
results. This was a crystal filter, so you will need a RF generator
with 1Hz steps.

This is an in-situ measurement, i.e. this is not the same as just
testing the IF filter by itself. You need the distortion analyzer to
get the audio signal level independent from the noise.


Many thanks, this is interesting. What I am still unsure about is how
you determine the -6dB and -60dB points using the distortion analyzer:
When you say "measure the audio level", what exactly do you measure,
the audio signal fundamental (i.e. filtered at the modulation
frequency)?

So in fact you are only using the distortion analyzer to filter the
audio and to measure the level? I don't have a distortion analyzer,
but I guess I could simply use an oscilloscope or an audio spectrum
analyzer (PC sound card based).


rkhalona gave you the right definition of shape factor and a web page
that explains it.

BW(-60dB)
SF =---------------
BW(-6dB)

http://www.radio-electronics.com/inf...ty/selectivity.
php

The audio passband is often but not always defined at the IF stage with
a IF passband filter. The -6dB and -60dB is referenced to the filter
center IF frequency of 0dB. The filter is usually symmetrical and the SF
number refers to how fast the slope changes. Steeper is better. The -6dB
down point is usually considered the bandwidth of the filter.

With what you have the easiest thing to do would be to use the PC audio
spectrum analyzer. On a strong signal playing music use a max hold
function on the analyzer software and the passband of the filter should
become apparent. Look at where the high end response rolls off 6dB down
relative to what looks like a flat audio spectrum from low to middle
audio frequencies. Where the high frequencies roll of 6dB down from the
flat audio response range will be 1/2 the filter bandwidth.

For this to work the station you have are receiving must be have a wider
modulation bandwidth then you are using for an audio bandwidth filter so
this may only work for narrow filters.

If this does not work well enough then you will need an RF generator
that you can modulate at a frequency higher than the largest filter you
want to measure and use the PC analyzer as described above.

--
Telamon
Ventura, California


Yep, that's a very good method, thanks! To refine this, I might use a
noise generator modulating a signal generator (instead of using a
station music). This should show the passband nicer and more steady, I
think.

I do have a signal generator, and I guess I could make a noise
generator using a Zener diode followed by an amplifier. Let's see...


You are welcome. If the PC audio analyzer has a max hold function and
you modulate a an RF generator with a diode white noise source you will
have the high frequency roll off in seconds.

--
Telamon
Ventura, California

[email protected] January 14th 06 08:53 AM

Measuring filter shape factor
 
"Once worked??" Many people have visited Germany, where Hilter once
waged world war. Thus anyone who has been to Germany is a Nazi.

You can go to opensecrets.org and trace money given directly by Jack
Abramoff. Hopefull this link will do the trick:

http://www.opensecrets.org/indivs/search.asp?NumOfThou=0&txtName=abramoff%2C+jack&tx tState=%28all+states%29&txtZip=&txtEmploy=&txtCand =&txt2006=Y&txt2004=Y&txt2002=Y&Order=N

I see Tom Delay, Ted Stevens, Elizabeth Dole, Arlen Spector, etc.


clifto wrote:
wrote:
clifto wrote:
David wrote:
On 11 Jan 2006 21:06:53 -0800,
wrote:
Read Rich Lowrie's latest editorial at National Review Online.

He says the Abramoff scandal is 100% Republicans.

Then he's stupid, or ignorant, or lying. 40 out of 45 Senate Democrats got
money from Abramoff.


There is a difference between getting money from tribes, and getting
money from Abramoff.

You should switch from kool-aid to beer.


It took me all of 120 seconds to find this in the liberal Chicago Tribune:

http://www.chicagotribune.com/news/local/southsouthwest/chi-0601110210jan11,1,5780990.story?coll=chi-newslocalssouthwest-hed

"Kennedy on Tuesday also explained why Weller used $1,640 of his own money
to reimburse a lobbying firm where Abramoff once worked for a 1999 trip
to two Indian reservations in Louisiana and Mississippi.

"He visited those reservations at the request of former U.S. Rep. David
Funderburk (R-N.C.), and THOUGHT THE TRIBES HAD PAID FOR THE TRIP [emphasis
by clifto], Kennedy said. As soon as he confirmed otherwise, he repaid
the money from his own pocket, he said."


Here's one from liberal rag UnionLeader.com:

http://www.theunionleader.com/article.aspx?headline=Sullivan+defends+Democrats+k eeping+lobbyist%E2%80%99s+money&articleId=c0963d8c-692b-47e6-b316-f42c8053aeef

"Top Democrats received donations from scandal-plagued Washington
lobbyist Jack Abramoff?s Indian tribe clients for legitimate reasons
and are right to refuse to give up the money, the state?s Democratic
chairman says."


I bet if I took the time to search further, which I'm not going to bother
doing, I could find *tribal* money going to Democrats via Abramoff in mass
quantities.

Note that unlike most of the Republicans involved, Kennedy and Reid have
no intention of giving the money back or giving it to charity. They're
keeping it.

--
If John McCain gets the 2008 Republican Presidential nomination,
my vote for President will be a write-in for Jiang Zemin.



clifto January 14th 06 11:46 PM

Measuring filter shape factor
 
wrote:
"Once worked??" Many people have visited Germany, where Hilter once
waged world war. Thus anyone who has been to Germany is a Nazi.


Yeah, exactly. I see you liberals don't like Kennedy's excuse any better than
we conservatives do.

You can go to opensecrets.org and trace money given directly by Jack
Abramoff. Hopefull this link will do the trick:

http://www.opensecrets.org/indivs/search.asp?NumOfThou=0&txtName=abramoff%2C+jack&tx tState=%28all+states%29&txtZip=&txtEmploy=&txtCand =&txt2006=Y&txt2004=Y&txt2002=Y&Order=N

I see Tom Delay, Ted Stevens, Elizabeth Dole, Arlen Spector, etc.


I already posted two liberal rags that named a lot of Democrats involved in
the scandal. You can name all the lying liberal rags that don't mention them
as many times as you want, and it won't change that 40 out of 45 Senate
Democrats received tainted money from Abramoff.

--
If John McCain gets the 2008 Republican Presidential nomination,
my vote for President will be a write-in for Jiang Zemin.

[email protected] January 15th 06 04:56 AM

Measuring filter shape factor
 
You need to show a direct connection. Getting money from Indian Tribes
is not illegal.

I gather you left your thumb up your ass rather than look at the Open
Secrets link. Figures.

clifto wrote:
wrote:
"Once worked??" Many people have visited Germany, where Hilter once
waged world war. Thus anyone who has been to Germany is a Nazi.


Yeah, exactly. I see you liberals don't like Kennedy's excuse any better than
we conservatives do.

You can go to opensecrets.org and trace money given directly by Jack
Abramoff. Hopefull this link will do the trick:

http://www.opensecrets.org/indivs/search.asp?NumOfThou=0&txtName=abramoff%2C+jack&tx tState=%28all+states%29&txtZip=&txtEmploy=&txtCand =&txt2006=Y&txt2004=Y&txt2002=Y&Order=N

I see Tom Delay, Ted Stevens, Elizabeth Dole, Arlen Spector, etc.


I already posted two liberal rags that named a lot of Democrats involved in
the scandal. You can name all the lying liberal rags that don't mention them
as many times as you want, and it won't change that 40 out of 45 Senate
Democrats received tainted money from Abramoff.

--
If John McCain gets the 2008 Republican Presidential nomination,
my vote for President will be a write-in for Jiang Zemin.




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