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CX2SA > SATDIG 12.03.18 17:27l 797 Lines 29514 Bytes #999 (0) @ WW
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Sent: 180312/1521Z @:CX2SA.SAL.URY.SOAM #:37617 [Salto] FBB7.00e $:AMSATBB1393
From: CX2SA@CX2SA.SAL.URY.SOAM
To : SATDIG@WW
Today's Topics:
1. Re: AO-91 and circular polarization? (Nick Hart)
2. W3HQX Perry F. Crabill SK (Larry)
3. Re: AO-91 and circular polarization? (Todd Deckard)
4. Re: AO-91 and circular polarization? (Todd W Deckard)
5. ZF2AE Grand Cayman - ZF2AE/ZF8 Little Cayman QRT - LOTW Soon
(Adrian Engele)
6. Re: AO-91 and circular polarization? (Mike)
7. Re: AO-91 and circular polarization? (Mike Thompson)
8. Re: AO-91 and circular polarization? (Paul Andrews)
9. Oscar satellite status page (alex weimer)
10. Re: Oscar satellite status page (Alan)
11. Re: AO-91 and circular polarization? (Mvivona)
----------------------------------------------------------------------
Message: 1
Date: Sun, 11 Mar 2018 19:21:53 -0700
From: "Nick Hart" <nickhart@???.???>
To: Jerry Buxton <n0jy@?????.???>, <amsat-bb@?????.???>
Subject: Re: [amsat-bb] AO-91 and circular polarization?
Message-ID: <683wcLcu29776Set.1520821313@?????.???.???.???>
Content-Type: text/plain; charset=utf-8
If you can make the direction switchable without adding too much weight, that
can be helpful.
We did an ARISS QSO this week and switched the polarity in the middle of it.
It was just the best thing for that particular pass.
------ Original Message ------
Received: Sun, 11 Mar 2018 04:49:46 PM PDT
From: Jerry Buxton <n0jy@?????.???>
To: amsat-bb@?????.???
Subject: Re: [amsat-bb] AO-91 and circular polarization?
Todd,
Correct is not really a consideration, the way I see it.? Will a CP
antenna work?? Yes.? Polarization should not matter for AO-92.? (BTW I
presume you mean AO-92, not AO-91 in which case L band just flat won't
work no matter the antenna, period.)???? :-)
I use RHCP because I built my antenna for AO-51 and that is was in use
at the time.? I believe that when CP is used on a satellite, at least in
the AMSAT history, it has been RHCP most of the time so building for
RHCP may have advantages for future satellites.
Jerry Buxton, N?JY
On 3/11/2018 15:44, Todd W Deckard wrote:
> Would it be correct to use a CP antenna on the L-band uplink for AO-91? If
so which polarization?
>
> Just purchased an ICOM X-2 on ebay that gets me 1.2ghz and the temps are
getting civilized so it?s about time to get back on the air ...
>
> My elev. over azimuth system is already swinging more mass than it was
geared for and i?m looking to cook up a small antenna that doesn?t add too
much straw to the camel.
>
> I would like to go Helical just because ...
>
> if anyone has an alternate suggestion I?d listen to any and all.
>
> Thanks
> Todd
> KE0CMD
> Sent from my iPhone
> _______________________________________________
> Sent via AMSAT-BB@?????.???. 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
_______________________________________________
Sent via AMSAT-BB@?????.???. 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
------------------------------
Message: 2
Date: Mon, 12 Mar 2018 05:43:28 +0000
From: Larry <lmwatbullrun@??????.???>
To: amsat-bb@?????.???
Subject: [amsat-bb] W3HQX Perry F. Crabill SK
Message-ID: <5AA61380.4070808@??????.???>
Content-Type: text/plain; charset=windows-1252
To all Metro DC area amateur radio operators:
I am saddened to report to the amateur radio community that Perry F.
Crabill, W3HQX, member of AMSAT, born in 1920, formerly of Washington DC
and suburban Maryland and until his passing of Winchester Virginia, is
now a Silent Key at age 97, as reported in Friday's Winchester Star.
Perry was first licensed as W3HQX in "19ought38" as he was wont to say,
worked for C&P telephone for many years, served in the US Navy in World
War Two as a radio technician (passing the difficult Eddy test,) and was
active for almost 70 years in a variety of amateur radio activities.
Known affectionately by the 147.300 repeater's "Question Of the Day"
group as "The Professor", Perry had a wide range of on-the-air
acquaintances.
We are diminished by his passing.
There will be a memorial service and celebration of his life held on
Saturday March 24th at 3:00 PM at the Jones Funeral Home at 228 S.
Pleasant Valley Road, Winchester, VA 22601, 540-662-2523,
http://www.jonesfuneralhomes.com/ This memorial service is open to
the public and especially to all members of the amateur community. On
display will be the early logbooks from W3HQX, including his first
dating from August of 1938, QSL cards, and other memorabilia from his
long life.
Please forward this announcement to any who may be interested. Those
who knew Perry are welcome to share anecdotes from Perry's life; those
may be presented at the service or forwarded to Larry Wright, W8ANT for
inclusion.
Larry Wright W8ANT
__
------------------------------
Message: 3
Date: Mon, 12 Mar 2018 02:51:25 +0000
From: Todd Deckard <tdeckard@?????.???>
To: Jerry Buxton <n0jy@?????.???>
Cc: "amsat-bb@?????.???? <amsat-bb@?????.???>
Subject: Re: [amsat-bb] AO-91 and circular polarization?
Message-ID: <B4DF4797-CAD5-4AA0-AB3D-431C1FC0DD79@?????.???>
Content-Type: text/plain; charset="utf-8"
Greetings Jerry,
thank you for this (yes I meant AO-92).
If I understand, you are saying the the satellite uses a conventional linear
antenna.
However AO-92 is easy enough to access that a 3db loss from the polarity
mismatch b/t linear and circular is not significant.
Correct?
Todd
Sent from my iPhone
> On Mar 11, 2018, at 6:46 PM, Jerry Buxton <n0jy@?????.???> wrote:
>
> Todd,
>
> Correct is not really a consideration, the way I see it. Will a CP
> antenna work? Yes. Polarization should not matter for AO-92. (BTW I
> presume you mean AO-92, not AO-91 in which case L band just flat won't
> work no matter the antenna, period.) :-)
>
> I use RHCP because I built my antenna for AO-51 and that is was in use
> at the time. I believe that when CP is used on a satellite, at least in
> the AMSAT history, it has been RHCP most of the time so building for
> RHCP may have advantages for future satellites.
>
> Jerry Buxton, N?JY
------------------------------
Message: 4
Date: Mon, 12 Mar 2018 06:01:29 -0500
From: Todd W Deckard <twdeckard@?????????.???>
To: amsat-bb@?????.???
Subject: Re: [amsat-bb] AO-91 and circular polarization?
Message-ID: <03AE117A-AD97-4130-94A9-D33C10D300EF@?????????.???>
Content-Type: text/plain; charset=utf-8
Greetings Jerry,
thank you for this (yes I meant AO-92).
If I understand, you are saying the the satellite uses a conventional linear
antenna.
However AO-92 is easy enough to access that a 3db loss from the polarity
mismatch b/t linear and circular is not significant.
Correct?
Todd
Sent from my iPhone
> On Mar 11, 2018, at 6:46 PM, Jerry Buxton <n0jy@?????.???> wrote:
>
> Todd,
>
> Correct is not really a consideration, the way I see it. Will a CP
> antenna work? Yes. Polarization should not matter for AO-92. (BTW I
> presume you mean AO-92, not AO-91 in which case L band just flat won't
> work no matter the antenna, period.) :-)
>
> I use RHCP because I built my antenna for AO-51 and that is was in use
> at the time. I believe that when CP is used on a satellite, at least in
> the AMSAT history, it has been RHCP most of the time so building for
> RHCP may have advantages for future satellites.
>
> Jerry Buxton, N?JY
>
>> On 3/11/2018 15:44, Todd W Deckard wrote:
>> Would it be correct to use a CP antenna on the L-band uplink for AO-91?
If so which polarization?
>>
>> Just purchased an ICOM X-2 on ebay that gets me 1.2ghz and the temps are
getting civilized so it?s about time to get back on the air ...
>>
>> My elev. over azimuth system is already swinging more mass than it was
geared for and i?m looking to cook up a small antenna that doesn?t add too
much straw to the camel.
>>
>> I would like to go Helical just because ...
>>
>> if anyone has an alternate suggestion I?d listen to any and all.
>>
>> Thanks
>> Todd
>> KE0CMD
>> Sent from my iPhone
>> _______________________________________________
>> Sent via AMSAT-BB@?????.???. 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
>
>
------------------------------
Message: 5
Date: Mon, 12 Mar 2018 12:37:27 +0000 (UTC)
From: Adrian Engele <aa5uk@?????.???>
To: AMSAT BB <amsat-bb@?????.???>
Subject: [amsat-bb] ZF2AE Grand Cayman - ZF2AE/ZF8 Little Cayman QRT -
LOTW Soon
Message-ID: <1517010521.14673749.1520858247849@????.?????.???>
Content-Type: text/plain; charset=UTF-8
Folks,
I am now back in Chicago from my vacation as of yesterday. This was going to
be a "light on satellite" operation and it appears I worked more passes than
originally planned.I know I made many people happy but also disappointed a
few due to equipment and location issues.
I will be transcribing the recordings in the coming days and uploading to
LOTW and eQSL hopefully by next weekend, so please be patient for the EK99
grid
Although I prefer LOTW, if you did send me a card with an SASE I will
respond with a very cool card in return.
I am very casual operator and I don't get much on the satellites. Thanks for
pulling me out in the pileups on FO-29 and AO-7.? Sorry I? did not do more
FM satellites. That one AO-92 pass was enough for me to pass on doing more.
Plus there are some local ZF stations that do periodically get on FM sats.
Please do look into using other satellites like CAS-4B or EO-88. I got on a
few passes that were completely empty. These are loud, easy to use and easy
to work linear satellites.
QRT for 2018. Thanks again!
73, Adrian AA5UK - ZF2AE
------------------------------
Message: 6
Date: Mon, 12 Mar 2018 09:24:04 -0400
From: Mike <mvivona@?????.???>
To: Todd Deckard <tdeckard@?????.???>
Cc: "amsat-bb@?????.???? <amsat-bb@?????.???>
Subject: Re: [amsat-bb] AO-91 and circular polarization?
Message-ID: <8BF55510-459F-4604-83A4-3DD970685835@?????.???>
Content-Type: text/plain; charset=utf-8
Not sure where the 3db loss when on the opposite polarity came from. It is
more on the order of 20db or more.
I am a TV broadcast engineer and we take video and data feeds via various
satellites. I can be locked into a bird in the vertical polarity and looking
at the spectrum analyzer you can see all the carriers nice and tall. If I
rotate the polarity all the signals go completely away and are replaced by
all the carriers on the opposite pole. Broadcast satellites transmit two
feeds on the same frequency only separated by polarity. This wouldn?t be
possible at only a 3db loss.
That?s why you must rotate your arrow antennas to follow the spin on the
birds else the signal completely disappears.
Michael KC4ZVA
EL98
> On Mar 11, 2018, at 10:51 PM, Todd Deckard <tdeckard@?????.???> wrote:
>
> Greetings Jerry,
>
> thank you for this (yes I meant AO-92).
>
> If I understand, you are saying the the satellite uses a conventional
linear antenna.
>
> However AO-92 is easy enough to access that a 3db loss from the polarity
mismatch b/t linear and circular is not significant.
>
> Correct?
> Todd
>
> Sent from my iPhone
>
>> On Mar 11, 2018, at 6:46 PM, Jerry Buxton <n0jy@?????.???> wrote:
>>
>> Todd,
>>
>> Correct is not really a consideration, the way I see it. Will a CP
>> antenna work? Yes. Polarization should not matter for AO-92. (BTW I
>> presume you mean AO-92, not AO-91 in which case L band just flat won't
>> work no matter the antenna, period.) :-)
>>
>> I use RHCP because I built my antenna for AO-51 and that is was in use
>> at the time. I believe that when CP is used on a satellite, at least in
>> the AMSAT history, it has been RHCP most of the time so building for
>> RHCP may have advantages for future satellites.
>>
>> Jerry Buxton, N?JY
> _______________________________________________
> Sent via AMSAT-BB@?????.???. 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
------------------------------
Message: 7
Date: Mon, 12 Mar 2018 08:36:55 -0500
From: Mike Thompson <zryder94@?????.???>
To: Mike <mvivona@?????.???>
Cc: Todd Deckard <tdeckard@?????.???>, "amsat-bb@?????.????
<amsat-bb@?????.???>
Subject: Re: [amsat-bb] AO-91 and circular polarization?
Message-ID:
<CAGD5MUES5jue61sqYCH-8SfHYLD6sqvrvhyrqRY=Akua2=p6aw@????.?????.???>
Content-Type: text/plain; charset="UTF-8"
The 3dB mentioned is a result of the polarity mismatch between CP and
linear polarization. Mike is correct that there is 20dB or more when one CP
is mismatched with another CP, or one linear is mismatched with another
linear, but from linear to CP it's only ever about 3dB. IIRC, AO-92 uses a
1/4w whip for 70cm as the receive antenna for the L-band converter, so
using a CP antenna on the ground will work just fine, and you will always
have a 3dB loss, but it will be consistent. If I was building an antenna
for that purpose, that I was going to operate beyond reach of the antenna,
I would use CP as well.
On Mon, Mar 12, 2018 at 8:24 AM, Mike via AMSAT-BB <amsat-bb@?????.???>
wrote:
> Not sure where the 3db loss when on the opposite polarity came from. It is
> more on the order of 20db or more.
> I am a TV broadcast engineer and we take video and data feeds via various
> satellites. I can be locked into a bird in the vertical polarity and
> looking at the spectrum analyzer you can see all the carriers nice and
> tall. If I rotate the polarity all the signals go completely away and are
> replaced by all the carriers on the opposite pole. Broadcast satellites
> transmit two feeds on the same frequency only separated by polarity. This
> wouldn?t be possible at only a 3db loss.
> That?s why you must rotate your arrow antennas to follow the spin on the
> birds else the signal completely disappears.
>
> Michael KC4ZVA
> EL98
>
>
> > On Mar 11, 2018, at 10:51 PM, Todd Deckard <tdeckard@?????.???> wrote:
> >
> > Greetings Jerry,
> >
> > thank you for this (yes I meant AO-92).
> >
> > If I understand, you are saying the the satellite uses a conventional
> linear antenna.
> >
> > However AO-92 is easy enough to access that a 3db loss from the polarity
> mismatch b/t linear and circular is not significant.
> >
> > Correct?
> > Todd
> >
> > Sent from my iPhone
> >
> >> On Mar 11, 2018, at 6:46 PM, Jerry Buxton <n0jy@?????.???> wrote:
> >>
> >> Todd,
> >>
> >> Correct is not really a consideration, the way I see it. Will a CP
> >> antenna work? Yes. Polarization should not matter for AO-92. (BTW I
> >> presume you mean AO-92, not AO-91 in which case L band just flat won't
> >> work no matter the antenna, period.) :-)
> >>
> >> I use RHCP because I built my antenna for AO-51 and that is was in use
> >> at the time. I believe that when CP is used on a satellite, at least in
> >> the AMSAT history, it has been RHCP most of the time so building for
> >> RHCP may have advantages for future satellites.
> >>
> >> Jerry Buxton, N?JY
> > _______________________________________________
> > Sent via AMSAT-BB@?????.???. 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
>
> _______________________________________________
> Sent via AMSAT-BB@?????.???. 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
>
------------------------------
Message: 8
Date: Mon, 12 Mar 2018 10:31:39 -0400
From: Paul Andrews <w2hro.fn20@?????.???>
To: Mike <mvivona@?????.???>
Cc: Todd Deckard <tdeckard@?????.???>, "amsat-bb@?????.????
<amsat-bb@?????.???>
Subject: Re: [amsat-bb] AO-91 and circular polarization?
Message-ID:
<CAOsf+NQ_0-cr6dAPfHsSbWcL=50H_EEAK1q4TFPxV2DRowr-_g@????.?????.???>
Content-Type: text/plain; charset="UTF-8"
Mike KC4ZVA,
All US Domestic Communication satellite in C-Band and Ku-band used
orthogonal linear polarization. This is also known as "Frequency
Reuse" first deployed by RCA in the 1970s. In a well designed
commercial satellite system isolation between the Horizontal (0 deg)
and the Vertical (90 deg) polarization should exceed 30 dB.
Isolation is greatest at exactly a 90-degree offset between H-pol and
V-pol. At a 45 deg offset, polarization isolation is only 3db.
When adjusting a commercial satellite dish, it is better to "null out"
the cross-pol that "peak" the co-pol. Circular polarization is still
used on some Intelsat standard International satellite links.
I believe FO-29 is the only amateur satellite to use a circularly
polarized antenna on the spacecraft. All of the CubeSats use small
linear polarized antennas.
The primary reason to use a circularly polarized (CP) ground antenna
with a Cubesat is to avoid the deep (-20 to -30 dB) signal null when
the ground antenna is orthogonal (90 deg orientation offset) with the
satellite antenna. There will still be times when the CubeSat antenna
is pointed away from the earth and even a circular antenna will not
help. Since most Cubesate tumble, these LP to LP nulls never last
very long but they are an irritation during a QSO.
When using a CP ground antenna, you are effectively using a signal
(wavefront) that contains both an H-pol and V-pol component that will
always be at 45 deg offset to the linear polarized satellite antenna.
When using a CP signal you are making a decision to "give up" 3 dB
100% of the time in signal to avoid the occasional -20 to -30 dB
signal nulls possible in a linear pol to linear pol system.
If you watch a satellite operator using a hand help Arrow antenna -
they are constantly peaking the antenna in direction and polarization.
If the Arrow was a CP antenna there would be a lot less "arm twisting"
but the Arrow would be 3 dB less efficient 100% of the time.
If your goal is CubeSat operation a CP antenna could be a good choice.
It doesn't matter if the CP antenna is RHCP or LHCP because you are
working a linear polarization satellite. If you are working FO-29
and your launch an LHCP signal and FO-29 is expecting an RHCP signal -
you will experience a -20 to -30 dB loss because RHCP into LHCP will
exhibit high isolation.
CubeSats have relatively strong signals and I highly recommend
experimentation with small helical antennas and cross-pol yagis. You
will have a lot of fun. If you want to get some arm and shoulder
exercise use the Arrow antenna but the results will be very good.
73 - Paul - W2HRO
On Mon, Mar 12, 2018 at 9:24 AM, Mike via AMSAT-BB <amsat-bb@?????.???> wrote:
> Not sure where the 3db loss when on the opposite polarity came from. It is
more on the order of 20db or more.
> I am a TV broadcast engineer and we take video and data feeds via various
satellites. I can be locked into a bird in the vertical polarity and looking
at the spectrum analyzer you can see all the carriers nice and tall. If I
rotate the polarity all the signals go completely away and are replaced by
all the carriers on the opposite pole. Broadcast satellites transmit two
feeds on the same frequency only separated by polarity. This wouldn?t be
possible at only a 3db loss.
> That?s why you must rotate your arrow antennas to follow the spin on the
birds else the signal completely disappears.
>
> Michael KC4ZVA
> EL98
>
>
>> On Mar 11, 2018, at 10:51 PM, Todd Deckard <tdeckard@?????.???> wrote:
>>
>> Greetings Jerry,
>>
>> thank you for this (yes I meant AO-92).
>>
>> If I understand, you are saying the the satellite uses a conventional
linear antenna.
>>
>> However AO-92 is easy enough to access that a 3db loss from the polarity
mismatch b/t linear and circular is not significant.
>>
>> Correct?
>> Todd
>>
>> Sent from my iPhone
>>
>>> On Mar 11, 2018, at 6:46 PM, Jerry Buxton <n0jy@?????.???> wrote:
>>>
>>> Todd,
>>>
>>> Correct is not really a consideration, the way I see it. Will a CP
>>> antenna work? Yes. Polarization should not matter for AO-92. (BTW I
>>> presume you mean AO-92, not AO-91 in which case L band just flat won't
>>> work no matter the antenna, period.) :-)
>>>
>>> I use RHCP because I built my antenna for AO-51 and that is was in use
>>> at the time. I believe that when CP is used on a satellite, at least in
>>> the AMSAT history, it has been RHCP most of the time so building for
>>> RHCP may have advantages for future satellites.
>>>
>>> Jerry Buxton, N?JY
>> _______________________________________________
>> Sent via AMSAT-BB@?????.???. 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
>
> _______________________________________________
> Sent via AMSAT-BB@?????.???. 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
------------------------------
Message: 9
Date: Mon, 12 Mar 2018 10:52:24 -0400 (EDT)
From: alex weimer <ingejack@???.???>
To: amsat-bb@?????.???
Subject: [amsat-bb] Oscar satellite status page
Message-ID: <1982899497.5152.1520866344151@???????.???.???>
Content-Type: text/plain; charset=UTF-8
has anyone else had a problem with the Amsat Satellite status page. It seems
several of us when clicking on a satellite get no response as to who entered
the info. However when you enter the info, it takes but all you see is
whether it is red blue or yellow, Not who entered the info as normal.. What
is the procedure for correcting this problem ?? JACK KC7MG
------------------------------
Message: 10
Date: Mon, 12 Mar 2018 10:04:32 -0500
From: "Alan" <wa4sca@?????.???>
To: "'alex weimer'" <ingejack@???.???>, <amsat-bb@?????.???>
Subject: Re: [amsat-bb] Oscar satellite status page
Message-ID: <000001d3ba13$6de33c70$49a9b550$@?????.???>
Content-Type: text/plain; charset="us-ascii"
The maintainers are aware of the problem and looking at it. Thanks for the
report.
73,
Alan
WA4SCA
<-----Original Message-----
<From: AMSAT-BB [mailto:amsat-bb-bounces@?????.???? On Behalf Of alex
<weimer
<Sent: Monday, March 12, 2018 09:52 AM
<To: amsat-bb@?????.???
<Subject: [amsat-bb] Oscar satellite status page
<
<has anyone else had a problem with the Amsat Satellite status page. It
seems
<several of us when clicking on a satellite get no response as to who
entered
<the info. However when you enter the info, it takes but all you see is
whether
<it is red blue or yellow, Not who entered the info as normal.. What is the
<procedure for correcting this problem ?? JACK KC7MG
<_______________________________________________
<Sent via AMSAT-BB@?????.???. 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
------------------------------
Message: 11
Date: Mon, 12 Mar 2018 11:14:10 -0400
From: Mvivona <Mvivona@?????.???>
To: Mike Thompson <zryder94@?????.???>
Cc: Todd Deckard <tdeckard@?????.???>, "amsat-bb@?????.????
<amsat-bb@?????.???>
Subject: Re: [amsat-bb] AO-91 and circular polarization?
Message-ID: <8F0B9C7B-5CE9-4749-AD86-D13F09EE2F7B@?????.???>
Content-Type: text/plain; charset=utf-8
Ahh, between CP and linear. Sorry, I should have read more carefully.
Michael Vivona
Sent from my iPad
On Mar 12, 2018, at 9:36 AM, Mike Thompson <zryder94@?????.???> wrote:
The 3dB mentioned is a result of the polarity mismatch between CP and linear
polarization. Mike is correct that there is 20dB or more when one CP is
mismatched with another CP, or one linear is mismatched with another linear,
but from linear to CP it's only ever about 3dB. IIRC, AO-92 uses a 1/4w whip
for 70cm as the receive antenna for the L-band converter, so using a CP
antenna on the ground will work just fine, and you will always have a 3dB
loss, but it will be consistent. If I was building an antenna for that
purpose, that I was going to operate beyond reach of the antenna, I would
use CP as well.
> On Mon, Mar 12, 2018 at 8:24 AM, Mike via AMSAT-BB <amsat-bb@?????.???>
wrote:
> Not sure where the 3db loss when on the opposite polarity came from. It is
more on the order of 20db or more.
> I am a TV broadcast engineer and we take video and data feeds via various
satellites. I can be locked into a bird in the vertical polarity and looking
at the spectrum analyzer you can see all the carriers nice and tall. If I
rotate the polarity all the signals go completely away and are replaced by
all the carriers on the opposite pole. Broadcast satellites transmit two
feeds on the same frequency only separated by polarity. This wouldn?t be
possible at only a 3db loss.
> That?s why you must rotate your arrow antennas to follow the spin on the
birds else the signal completely disappears.
>
> Michael KC4ZVA
> EL98
>
>
> > On Mar 11, 2018, at 10:51 PM, Todd Deckard <tdeckard@?????.???> wrote:
> >
> > Greetings Jerry,
> >
> > thank you for this (yes I meant AO-92).
> >
> > If I understand, you are saying the the satellite uses a conventional
linear antenna.
> >
> > However AO-92 is easy enough to access that a 3db loss from the polarity
mismatch b/t linear and circular is not significant.
> >
> > Correct?
> > Todd
> >
> > Sent from my iPhone
> >
> >> On Mar 11, 2018, at 6:46 PM, Jerry Buxton <n0jy@?????.???> wrote:
> >>
> >> Todd,
> >>
> >> Correct is not really a consideration, the way I see it. Will a CP
> >> antenna work? Yes. Polarization should not matter for AO-92. (BTW I
> >> presume you mean AO-92, not AO-91 in which case L band just flat won't
> >> work no matter the antenna, period.) :-)
> >>
> >> I use RHCP because I built my antenna for AO-51 and that is was in use
> >> at the time. I believe that when CP is used on a satellite, at least in
> >> the AMSAT history, it has been RHCP most of the time so building for
> >> RHCP may have advantages for future satellites.
> >>
> >> Jerry Buxton, N?JY
> > _______________________________________________
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>
> _______________________________________________
> Sent via AMSAT-BB@?????.???. AMSAT-NA makes this open forum available
> to all interested persons worldwide without requiring membership. Opinions
expressed
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AMSAT-NA.
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------------------------------
Subject: Digest Footer
_______________________________________________
Sent via amsat-bb@?????.???.
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 member? Join now to support the amateur satellite program!
http://www.amsat.org/mailman/listinfo/amsat-bb
------------------------------
End of AMSAT-BB Digest, Vol 13, Issue 93
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