Cross Polarization.
We all know that vertical to vertical = Zero db loss from cross polarization. same with horizontal to horizontal
and
Right hand circular to RHC as well s LHC TO LHC
And then in theory, the "Infinite loss" when vert to horiz, and RHC to LHC But while in theory it says "Infinite" in practicality it's more like 30 to 40 db or so.
Now I did notice this effect when I had an antenna array that the db loss was NOT linear.
Like say at 45 degrees of polarity error, being half way in a linear world would be 15 to 20 db loss, but according to this pdf file it is only 3 db down.
And I do agree with this because I do remember when rotating the polarity little change was noticed till the last bit and the max deep part was very small.
Now does anyone know of a chart anywhere where the values for every degree of something really is? Like 45 deg is 3 db down, 50 deg =? 55 deg =? etc.
anyone?
Joe WB9SBD
sorry missed adding the pdf address that I referred to below, here it is,
http://www.tscm.com/polariza.pdf
Joe WB9SBD Sig The Original Rolling Ball Clock Idle Tyme Idle-Tyme.com http://www.idle-tyme.com On 1/9/2016 8:51 AM, Joe wrote:
Cross Polarization.
We all know that vertical to vertical = Zero db loss from cross polarization. same with horizontal to horizontal
and
Right hand circular to RHC as well s LHC TO LHC
And then in theory, the "Infinite loss" when vert to horiz, and RHC to LHC But while in theory it says "Infinite" in practicality it's more like 30 to 40 db or so.
Now I did notice this effect when I had an antenna array that the db loss was NOT linear.
Like say at 45 degrees of polarity error, being half way in a linear world would be 15 to 20 db loss, but according to this pdf file it is only 3 db down.
And I do agree with this because I do remember when rotating the polarity little change was noticed till the last bit and the max deep part was very small.
Now does anyone know of a chart anywhere where the values for every degree of something really is? Like 45 deg is 3 db down, 50 deg =? 55 deg =? etc.
anyone?
Joe WB9SBD
We all know that [matched polarity] = Zero db loss from cross
polarization.
And then in theory, the "Infinite loss" when cross polarized... [Pracically],it's more like 30 to 40 db or so [ or much less in the
presence of reflections]
Now does anyone know of a chart ... for every degree of something really
is?
Like 45 deg is 3 db down, 50 deg =? 55 deg =? etc.
The cosine table works for all angles.. The cosine of 45 degrees is 1/2 which is -3 dB etc...
Bob, Wb4APR
Well, the cosine of 45 degrees is actually 0.707. I suspect that the article is implying that the loss is linear. Since 45 degrees is half of 90 degrees, then you lose half the power, or -3dB. Following that logic, at 22.5 degrees you'd half one-fourth the power or -6dB, etc.
I have no idea if the article is correct, but the cosine of 45 degrees is 0.707
Steve AI9IN
----- Original Message ----- From: "Robert Bruninga" [email protected] To: "amsat bb" [email protected] Sent: Saturday, January 09, 2016 12:05 PM Subject: Re: [amsat-bb] Polarity
We all know that [matched polarity] = Zero db loss from cross
polarization.
And then in theory, the "Infinite loss" when cross polarized... [Pracically],it's more like 30 to 40 db or so [ or much less in the
presence of reflections]
Now does anyone know of a chart ... for every degree of something really
is?
Like 45 deg is 3 db down, 50 deg =? 55 deg =? etc.
The cosine table works for all angles.. The cosine of 45 degrees is 1/2 which is -3 dB etc...
Bob, Wb4APR _______________________________________________ Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
Steve Kristoff [email protected]
"A few chords strummed on a ukulele, enough to please a few others beside yourself, does more good in this world than the combined efforts of all the financiers and politicians that ever lived." - Frank Littig, Littig's New Harmony Self Instructor Chords for Ukulele, Banjuke or Taro Patch Fiddle, Chart Music Publishing House, Chicago, Illinois, 1924
It makes sense (to me) that it follows a cosine function. So, if your antenna is horizontal and the signal is at 30 degrees above the horizontal, you should be getting about 87% of the signal, which figures out to a loss of about -.6dB. If the signal is coming in at 45 degrees, you're getting about 71% of the signal, for a loss of about -1.5 dB. If the signal is at 60 degrees above horizontal you'll get about 50% of the signal, which is the -3dB loss. At 80 degrees above horizontal, you'll get about 17% of the signal, which is a -7.6 dB loss I know that is not what the article says, but if you're going by cosines, which makes sense to me, those should be the numbers. (I think maybe)
Steve AI9IN
----- Original Message ----- From: "Robert Bruninga" [email protected] To: "amsat bb" [email protected] Sent: Saturday, January 09, 2016 12:05 PM Subject: Re: [amsat-bb] Polarity
We all know that [matched polarity] = Zero db loss from cross
polarization.
And then in theory, the "Infinite loss" when cross polarized... [Pracically],it's more like 30 to 40 db or so [ or much less in the
presence of reflections]
Now does anyone know of a chart ... for every degree of something really
is?
Like 45 deg is 3 db down, 50 deg =? 55 deg =? etc.
The cosine table works for all angles.. The cosine of 45 degrees is 1/2 which is -3 dB etc...
Bob, Wb4APR _______________________________________________ Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
Steve Kristoff [email protected]
"A few chords strummed on a ukulele, enough to please a few others beside yourself, does more good in this world than the combined efforts of all the financiers and politicians that ever lived." - Frank Littig, Littig's New Harmony Self Instructor Chords for Ukulele, Banjuke or Taro Patch Fiddle, Chart Music Publishing House, Chicago, Illinois, 1924
Is the -1.5db vs -3db difference power vs voltage (which would be v**2/r and thus the loss of power is the square of the loss of voltage, which is double the db) ?
On Sat, Jan 9, 2016 at 12:34 PM, Steve Kristoff [email protected] wrote:
It makes sense (to me) that it follows a cosine function. So, if your antenna is horizontal and the signal is at 30 degrees above the horizontal, you should be getting about 87% of the signal, which figures out to a loss of about -.6dB. If the signal is coming in at 45 degrees, you're getting about 71% of the signal, for a loss of about -1.5 dB. If the signal is at 60 degrees above horizontal you'll get about 50% of the signal, which is the -3dB loss. At 80 degrees above horizontal, you'll get about 17% of the signal, which is a -7.6 dB loss I know that is not what the article says, but if you're going by cosines, which makes sense to me, those should be the numbers. (I think maybe)
Steve AI9IN
----- Original Message ----- From: "Robert Bruninga" [email protected] To: "amsat bb" [email protected] Sent: Saturday, January 09, 2016 12:05 PM Subject: Re: [amsat-bb] Polarity
We all know that [matched polarity] = Zero db loss from cross
polarization.
And then in theory, the "Infinite loss" when cross polarized... [Pracically],it's more like 30 to 40 db or so [ or much less in the
presence of reflections]
Now does anyone know of a chart ... for every degree of something really
is?
Like 45 deg is 3 db down, 50 deg =? 55 deg =? etc.
The cosine table works for all angles.. The cosine of 45 degrees is 1/2 which is -3 dB etc...
Bob, Wb4APR _______________________________________________ Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
Steve Kristoff
"A few chords strummed on a ukulele, enough to please a few others beside yourself, does more good in this world than the combined efforts of all the financiers and politicians that ever lived." - Frank Littig, Littig's New Harmony Self Instructor Chords for Ukulele, Banjuke or Taro Patch Fiddle, Chart Music Publishing House, Chicago, Illinois, 1924 _______________________________________________ Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
Sorry, I should have elaborated.... dB is a reference to power. ANd power is proportional to Voltage squared. So when the voltage of an RF field is down by 0.707 squared it is down by one half. Or - 3dB.
And when we use the cosine law we are referring to the angle off axis. So straight on is 0 angle and is 0 dB loss. 45 degrees is 3 dB down. But going another 22.5 degrees or 67.5 degrees off axis is 0.38 squared which is.144 which is -8.4 dB . Getting down to 90 degrees where the cosine is 0 might also seem confusing, but remember we are comparing "dB down" which is a ratio of the full power available, lets say 1, divided by the smaller power we would get at off angles. When we get to 90 degree off angle, and a cosine of 0 then we are comparing "1" straight on, divided by the "0" we get when we are cross polarized and so we get 1/0 which is infinitely "down"...
I guess there is a better way to explain it... but I have not had my coffee yet.
Bob
On Sat, Jan 9, 2016 at 12:20 PM, Steve Kristoff [email protected] wrote:
Well, the cosine of 45 degrees is actually 0.707. I suspect that the article is implying that the loss is linear. Since 45 degrees is half of 90 degrees, then you lose half the power, or -3dB. Following that logic, at 22.5 degrees you'd half one-fourth the power or -6dB, etc.
I have no idea if the article is correct, but the cosine of 45 degrees is 0.707
Steve AI9IN
----- Original Message ----- From: "Robert Bruninga" [email protected] To: "amsat bb" [email protected] Sent: Saturday, January 09, 2016 12:05 PM Subject: Re: [amsat-bb] Polarity
We all know that [matched polarity] = Zero db loss from cross
polarization.
And then in theory, the "Infinite loss" when cross polarized... [Pracically],it's more like 30 to 40 db or so [ or much less in the
presence of reflections]
Now does anyone know of a chart ... for every degree of something really
is?
Like 45 deg is 3 db down, 50 deg =? 55 deg =? etc.
The cosine table works for all angles.. The cosine of 45 degrees is 1/2 which is -3 dB etc...
Bob, Wb4APR _______________________________________________ Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
Steve Kristoff
"A few chords strummed on a ukulele, enough to please a few others beside yourself, does more good in this world than the combined efforts of all the financiers and politicians that ever lived." - Frank Littig, Littig's New Harmony Self Instructor Chords for Ukulele, Banjuke or Taro Patch Fiddle, Chart Music Publishing House, Chicago, Illinois, 1924 _______________________________________________ Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
It seems to me that a live test of these theories and calculations would be easy to perform. In an open space, separate two radios with dipole antennas. Onone radio transmit and read the receive level on the other radiowhile turning one of the antennas to a variety of polarizations. Be careful to avoid ground effects and Fresnel Zones. Let us know the results. ;o) GL/73, Bob K8BL
From: Steve Kristoff [email protected] To: amsat bb [email protected] Sent: Saturday, January 9, 2016 12:34 PM Subject: Re: [amsat-bb] Polarity
It makes sense (to me) that it follows a cosine function. So, if your antenna is horizontal and the signal is at 30 degrees above the horizontal, you should be getting about 87% of the signal, which figures out to a loss of about -.6dB. If the signal is coming in at 45 degrees, you're getting about 71% of the signal, for a loss of about -1.5 dB. If the signal is at 60 degrees above horizontal you'll get about 50% of the signal, which is the -3dB loss. At 80 degrees above horizontal, you'll get about 17% of the signal, which is a -7.6 dB loss I know that is not what the article says, but if you're going by cosines, which makes sense to me, those should be the numbers. (I think maybe)
Steve AI9IN
----- Original Message ----- From: "Robert Bruninga" [email protected] To: "amsat bb" [email protected] Sent: Saturday, January 09, 2016 12:05 PM Subject: Re: [amsat-bb] Polarity
We all know that [matched polarity] = Zero db loss from cross
polarization.
And then in theory, the "Infinite loss" when cross polarized... [Pracically],it's more like 30 to 40 db or so [ or much less in the
presence of reflections]
Now does anyone know of a chart ... for every degree of something really
is?
Like 45 deg is 3 db down, 50 deg =? 55 deg =? etc.
The cosine table works for all angles.. The cosine of 45 degrees is 1/2 which is -3 dB etc...
Bob, Wb4APR _______________________________________________ Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
Steve Kristoff [email protected]
"A few chords strummed on a ukulele, enough to please a few others beside yourself, does more good in this world than the combined efforts of all the financiers and politicians that ever lived." - Frank Littig, Littig's New Harmony Self Instructor Chords for Ukulele, Banjuke or Taro Patch Fiddle, Chart Music Publishing House, Chicago, Illinois, 1924
_______________________________________________ Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
participants (5)
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Joe -
R.T.Liddy -
Robert Bruninga -
Steve Kristoff