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CX2SA > SATDIG 21.09.08 21:30l 947 Lines 33746 Bytes #999 (0) @ WW
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From: CX2SA@CX2SA.LAV.URY.SA
To : SATDIG@WW
Today's Topics:
1. Re: Polarity questions (Nate Duehr)
2. Antenna question (Michael Heim)
3. Re: Polarity questions (Anthony Monteiro)
4. re help needed on chip ID (Angus)
5. Re: Polarity questions (Robert Bruninga)
6. Re: Space-X to launch flight 4 (Iain Young, G7III)
7. [ans] ANS-265 AMSAT Weekly Bulletins (Dee)
8. Re: Polarity questions (Art McBride)
9. General Astrodynamics Library v0.4.0 Released (Paul Willmott)
10. Re: First impression (Clint Bradford)
11. Re: Polarity questions (Nate Duehr)
12. FS - Symek TNC3S high speed packet controller (st797(AT)dcpages.net)
----------------------------------------------------------------------
Message: 1
Date: Sun, 21 Sep 2008 00:29:15 -0600
From: Nate Duehr <nate(AT)natetech.com>
Subject: [amsat-bb] Re: Polarity questions
To: AMSAT BB <amsat-bb(AT)amsat.org>
Message-ID: <0CDE4541-9F8A-4052-868E-AA68D0F7DE6E(AT)natetech.com>
Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes
On Sep 20, 2008, at 2:07 PM, Edward Cole wrote:
>
>
> At 01:53 AM 9/20/2008, Luc Leblanc wrote:
>> On 20 Sep 2008 at 0:56, Nate Duehr wrote:
>> ======snip
That was a weird snip... made it look like my comments were left in
that question and statement from Luc.
I do have a question for the polarity gurus, however...
When *transmitting* circular vs. linear polarity, are the apparent
losses the reverse of the numbers being used for receiving? I am
inclined to think that has to be true.
Or to put it as a question: With all else being equal, including
antenna gain numbers...
How much more power has to be put into a circularly-polarized antenna
versus a linearly polarized one of the same gain, to have a distant
station receive the same signal if they're linearly polarized?
I'm purposely coming at this from the "other" direction... the
transmit side, instead of what is seen at the receiver.
This is mostly a mental exercise to see if I "get it". So if it's a
goofy way to analyze it, ignore that for a moment...
--
Nate Duehr, WY0X
nate(AT)natetech.com
------------------------------
Message: 2
Date: Sun, 21 Sep 2008 04:22:30 -0700 (PDT)
From: Michael Heim <kd0ar(AT)sbcglobal.net>
Subject: [amsat-bb] Antenna question
To: AMSAT-BB(AT)amsat.org
Message-ID: <698477.55580.qm(AT)web81507.mail.mud.yahoo.com>
Content-Type: text/plain; charset=iso-8859-1
I built one of Kent Britain's?"Cheap LEO Antennas" as a handheld antenna, and
I have a question.
I built mine on a 3/4 inch ID PVC boom.? works great!.? Anyway, there are a
good number of designs out there that use a folded dipole? for the driven
element, Kent's is of course "half" folded.? However each of these folded
elements I see, it is folded perpendicular to the plane of the antenna. (in
otherwords, if the antenna lays flat on the floor, the element fold?is
vertical)? I have a small 2 meter antenna that uses one and its perpendicular
also.? My question is, to simplify mounting? to a small diameter
insulated?boom, could such an element be placed "laying down", so the element
could be better supported by drilling 2 holes in the boom?? In a normal folded
element, balanced, I would assume the radiation center would be located at the
center between the 2 parallel rods.? The thoery that Kent uses for his states
that the "j" portion of his, the J is the matching section, and the half
wavelength rod, I?would then assume to be the radiator.
I'm building this one to replace a "permanent" station antenna, which uses tee
matches for the drivens.? Kent's is easier to build, and would be easier to do
if the element could be laid down on its side.? Would like to get your
thoughts on the thoery.? I?wouldnt think it would matter, as either way, its a
dipole, and they all radiate 360 degrees around the element.? Just trying to
figure out why theyre all designed in the orientation that they are.
?Michael Heim
ARS KD0AR
------------------------------
Message: 3
Date: Sun, 21 Sep 2008 07:46:58 -0400
From: Anthony Monteiro <aa2tx(AT)comcast.net>
Subject: [amsat-bb] Re: Polarity questions
To: Nate Duehr <nate(AT)natetech.com>, AMSAT BB <amsat-bb(AT)amsat.org>
Message-ID: <20080921114651.89LBkpP00EHSI(AT)mailbox5.ucsd.edu>
Content-Type: text/plain; charset="us-ascii"; format=flowed
At 02:29 AM 9/21/2008, Nate Duehr wrote:
>...
>I do have a question for the polarity gurus, however...
>
>When *transmitting* circular vs. linear polarity, are the apparent
>losses the reverse of the numbers being used for receiving? I am
>inclined to think that has to be true.
>...
>
>How much more power has to be put into a circularly-polarized antenna
>versus a linearly polarized one of the same gain, to have a distant
>station receive the same signal if they're linearly polarized?
Hi Nate,
This is a perfectly good question, Try this:
Let's say you have a horizontal RX antenna down range.
At the TX side, you have a horizontal and a vertical antenna
and they are quadrature phased so they make circular polarization.
Now your tx can put out 100 watts. The 100 watts gets split equally
between the horizontal and vertical antennas so you are putting 50
watts into the horizontal and 50 watts into the vertical.
The RX antenna down range doesn't know you are sending circular!
Since it is horizontal, it only responds to the horizontal signal.
It doesn't even see the vertical signal and it couldn't care less
about the phasing. It sees the 50 watts you put into the horizontal
antenna. The 50 watts you put into the vertical antenna is just wasted.
Now imagine you disconnect the vertical TX antenna and put all
100 watts into just the horizontal antenna. Now the RX antenna down
range sees the 100 watts you put into the horizontal antenna versus
the 50 watts you did before so you are up 3dB.
So, circular to linear, you wasted half your power and you lose 3dB.
Any good?
73,
Tony AA2TX
------------------------------
Message: 4
Date: Sun, 21 Sep 2008 13:17:13 +0100
From: "Angus" <angus(AT)young5769.freeserve.co.uk>
Subject: [amsat-bb] re help needed on chip ID
To: <AMSAT-BB(AT)amsat.org>
Message-ID: <A25B4E78181D4931BFF2EF8541629B97(AT)GusPC>
Content-Type: text/plain; charset="iso-8859-1"
Hi been to a local radio ralley and bought a nice looking ex mod board for ?1
(2USD) and found that its a an amplifier for 400-470mhz (board marked as such
but tuned somewhere I would have thought.
The chip inside is a single chip that is marked as 'TRW Bordeaux France MX7,5-
3 2.2880' anyone have any information on this chip at all, voltages, current
input/output power etc?
many thanks
regards
Gus M0IKB
--
I am using the free version of SPAMfighter for home users.
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------------------------------
Message: 5
Date: Sun, 21 Sep 2008 09:43:41 -0400
From: "Robert Bruninga" <bruninga(AT)usna.edu>
Subject: [amsat-bb] Re: Polarity questions
To: <AMSAT-BB(AT)amsat.org>
Message-ID: <F67AB0A093914210AF3D84E138CEDC36(AT)ewlab.usna.edu>
Content-Type: text/plain; charset="us-ascii"
Unless I am missing something, the technique below will give you
the free-space length, not the "in coax" length which can be 66%
of that length.
> If you want to know the velocity factor
> of a coax (known or un-known) try
> getting two eaqual lengths of coax which are physically
> 1/4wavelength long i.e. 50cms for 2mtrs.
> Short out ONE end (join the inner and outers together with a
> short a link as
> possible) and do this for both pieces of coax.
> We are going to make a coaxial dipole so these two shortened
> ends go on to a
> piece of feeder (try and keep this feeder as short as
> possible also but the
> dipole needs to be somewhere clear but does not to be 100
> feet up either).
> Yes you will need to support the dipole elements as they will
> just hang down
> so perhaps a piece of garden cane or some other RF invisible
material.
> Trim back both OPEN ends of the dipole until you get the
> lowest possible
> VSWR (on the centre frequency you want to use) and you should
> have very
> close to an electrically 1/2wave dipole for the coax you used
> (each side of
> the dipole will be a 1/4 wave long). You can use these
> figures for making a
> 1/4wave delay line or if your making a polarity control box
> you will need to
> know the lengths of both 1/2 and 1/4 of the coax you are
> going to use, the
> dipole will be considerably shorter than a normal wire dipole
> for the same
> frequency because we have used the velocity factor to help
reduce its
> length.
>
> If you think that the feeder you have used is radiating
> either do perhaps 6
> turns around a small 1" tube to make a balun at the feedpoint
> or alter the
> length of the feeder slightly, if theVSWR alters when you
> change the length
> of the feeder then the feeder is radiating.
>
> My two pennys worth, should help you get very close to the
> figures you need
> without the use of a GDO or an antenna analyser.
>
> regards
> Gus
>
>
> --
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>
>
> _______________________________________________
> Sent via AMSAT-BB(AT)amsat.org. Opinions expressed are those of
> the author.
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------------------------------
Message: 6
Date: Sun, 21 Sep 2008 14:38:13 +0100
From: "Iain Young, G7III" <g7iii(AT)g7iii.net>
Subject: [amsat-bb] Re: Space-X to launch flight 4
To: amsat-bb(AT)amsat.org
Message-ID: <48D64E45.8090900(AT)g7iii.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
G0MRF(AT)aol.com wrote:
> Hi all.
>
> I see Space X have an initial launch period scheduled for flight 4.
>
> The web site says anytime from Tuesday to Thursday (next week?) from their
> Kwajalein Atoll base in the Pacific.
>
> After the unfortunate loss of flight 3 due to a very minor glitch, does
> anyone know if the planned RazakSAT is flying of flight 4?
>
> Would be a shame if it isn't and the payload is a mass dummy only.
My understanding is that Flight 4, has a mass dummy. RazakSAT were
promised that they would fly after at least 1 fully successful
mission.
I'll be pleased just to see SpaceX get to orbit :)
73s
Iain
------------------------------
Message: 7
Date: Sun, 21 Sep 2008 09:41:05 -0400
From: Dee <morsesat(AT)optonline.net>
Subject: [amsat-bb] [ans] ANS-265 AMSAT Weekly Bulletins
To: AMSAT-BB(AT)amsat.org
Message-ID: <48D64EF1.8080506(AT)optonline.net>
Content-Type: text/plain; charset=us-ascii; format=flowed
AMSAT NEWS SERVICE
ANS-265
**************************************************************
*** 2008 AMSAT Space Symposium and Annual General Meeting ***
*** October 24-26 in Atlanta, Georgia ***
**** Please see the AMSAT-NA Website for INFO ****
**************************************************************
ANS is a free, weekly, news and information service of AMSAT North
America, The Radio Amateur Satellite Corporation. ANS reports on the
activities of a worldwide group of Amateur Radio operators who share an
active interest in designing, building, launching and communicating
through analog and digital Amateur Radio satellites.
Please send any amateur satellite news or reports to:
ans-editor(AT)amsat.org
In this edition:
* South African SumbandilaSat Launch Likely By Year-End 2008
* Richard Garriott W5KWQ ISS Operations Will Include SSTV
* Increased Solar Illumination Allows AO-16 Operations to Continue
* Flight 4 of Falcon 1
* Welcome Aboard AMSAT-Indonesia
* ARISS Status - 21 August 2008
SB SAT (AT) AMSAT $ANS-265.01
South African SumbandilaSat Launch Likely By Year-End 2008
AMSAT News Service Bulletin 265.01
From AMSAT HQ SILVER SPRING, MD.
September 21, 2008
To All RADIO AMATEURS
BID: $ANS-265.01
South African SumbandilaSat Launch Likely By Year-End 2008
ITAR-TASS published a news item stating that the first South African
satellite Sumbandila "is likely to be launched into orbit along with
a Russian spacecraft Meteor-M at the end of 2008, said the head of
the Federal Space Agency (Roskosmos), Anatoly Perminov.
"We are currently working toward adapting this cluster of satellite
launch with the spacecraft Meteor-M, which will be launched this year."
Perminov added that "in the near future to meet with experts from South
Africa, perhaps even with the head of the South African Space Agency,
to discuss the matter." According to Roscosmos, the South African side
is ready to launch its first spacecraft to the new Russian launch
vehicle Soyuz-2 ".
ITAR-TASS said that in return for launch services Russia will have
the opportunity to place on the territory of South Africa a tracking
station to receive f telemetry from upper stages of launch vehicles.
[Editor Note:] AMSAT South Africa has designed and built a control
system to facilitate the following operations:
+ V/U voice transponder with an uplink in the 2 meter band and a
downlink in the 70cm band.
+ A parrot repeater (voice digipeater)
+ A voice beacon
[ANS thanks ITAR-TASS for the above information]
/EX
SB SAT (AT) AMSAT $ANS-265.02
Richard Garriott W5KWQ ISS Operations Will Include SSTV
AMSAT News Service Bulletin 265.02
From AMSAT HQ SILVER SPRING, MD.
September 21, 2008
To All RADIO AMATEURS
BID: $ANS-265.02
Richard Garriott W5KWQ ISS Operations Will Include SSTV
September 18, 2008
Silver Spring, Maryland
Richard Garriott, W5KWQ, to communicate with Students and Ham Radio
Operators World-wide through the Amateur Radio Station on-board the
International Space Station (ISS)
Through multiple agreements with NASA, the Russian Space Agency, RSC
Energia, Space Adventures Ltd, and ARISS (Amateur Radio on the Inter-
national Space Station), Richard Garriott will fly to ISS and will
communicate with students, ham radio operators, friends, and family
world-wide using the ARISS amateur radio station on-board the ISS.
Richard Garriott, with the amateur radio callsign, W5KWQ is the sixth
private citizen to be flown by the Russian space agency to the ISS. A
legendary video game programmer and designer, Garriott will be travel-
ing to orbit this October and will speak with hundreds of students
while thousands more listen in during a series of ten-minute ham radio
contacts. His on-orbit stay on Soyuz and ISS is planned for October 12
through 22, 2008.
The locales for the worldwide student contacts include eight Challenger
Learning Centers in the U.S., the Austin Liberal Arts and Sciences
Academy in Austin, Texas, the Pinehurst School in Ashland, Oregon,
the Budbrooke School in the U.K., and the National Space Challenge in
Kuala Lumpur, Malaysia. Garriott also plans to have random chats with
scouts world-wide as part of the amateur radio "Jamboree on the Air"
which is planned for October 18 and 19.
"An important aspect of Richard Garriott's mission is to encourage
students' interest in science and technology through the amateur radio
contacts," said Rosalie White, ARISS International Secretary-Treasurer
and ARISS Program Manager for ARRL (American Radio Relay League).
"ARISS team members from all over the world volunteer their time every
day so that students receive opportunities that we hope will cause them
to study harder and learn more about any educational subject."
The connection from the ISS to individual student locations will be
established through an amateur radio station set up directly at the
school or through the ARISS network of worldwide amateur radio ground
stations utilized to link Garriott directly with students. The amateur
radio system works similar to the way mission control centers in the
United States and Russia talk to their space explorers.
To date, the ARISS international working group volunteer team has
conducted over 360 school contacts with crew members using ham radio
on the ISS. The team has also set up radio contacts for family members
of space explorers via ham radio. And have enabled countless contacts
between the ISS crew members and hams on the ground. All previous
Space Adventures private citizens who have flown to ISS have used the
ARISS equipment to talk to school students, ham radio operators and
friends and family.
As part of Richard Garriott's science investigations, he will be
taking highdefinition photographs of many parts of the Earth and
comparing them to photos taken on previous space missions. In con-
junction with his Earth science investigation, Mr. Garriott is flying
special amateur radio electronics that will enable him to send and
receive low resolution images from space, comparable to cell phone
images. Through this ham radio system, called Slow-Scan Television
(SSTV), Garriott will beam down images of the Earth to schools and ham
radio operators on the ground so that they can actively participate
in his mission.
Frank Bauer, KA3HDO, ARISS International Chairman and AMSAT Vice
President for Human Spaceflight Programs, states: "The ARISS team
is quite excited about Richard's flight. He is very interested in
bringing the wonders of space to those of us on Earth and he sees
amateur radio as a great mechanism to make that happen. Through
his school and scout voice contacts, his SSTV image downlinks and
his communications with the world-wide amateur radio community, we
see his mission as being "action packed" from an amateur radio
perspective."
Bauer continues, "What is extra special is that Richard Garriott's
flight coincides almost 25 years from when his father, Owen Garriott,
made history as the first ham radio operator to communicate with
radio amateurs from space on the STS-9 Space Shuttle mission." Owen
Garriott's call sign is W5LFL. Richard also hopes to link up with
his father via amateur radio during his flight.
Currently, Mr. Garriott is finishing his final spaceflight preparations
at the Gagarin Cosmonaut Training Centre (GCTC) located in Star City,
Russia. His launch date is scheduled for October 12, 2008, with ISS
docking planned for October 14 and undocking planned for October 22.
Mr. Garriott was trained thoroughly to be a member of the Soyuz TMA-13/
17S crew.
Since its first flight with Owen Garriott, in November 1983, Ham Radio
has flown on more than two-dozen space shuttle missions, on the Mir
Space Station and on the ISS. ARISS is the first and longest continuous
operating educational outreach program to fly on the ISS. ARISS is an
internationally-based working group, sponsored by the national amateur
radio organizations and the international AMSAT (Radio Amateur Satellite
Corporation) organizations from each country as well as the ISS space
agency partners. In the United States, ARISS is sponsored by the Ameri-
can Radio Relay League (ARRL), the Radio Amateur Satellite Corporation-
North America (AMSAT-NA) and the National Aeronautics and Space Admin-
istration (NASA). NASA's education office provides support to ARISS
and guidance in the development of ARISS educational objectives.
The primary purpose of ARISS is to allow students engaged in a science
and technology curriculum to speak with an astronaut orbiting the
Earth on the International Space Station. Using amateur radio,
students ask questions about life in space or other space-related
topics. Students fully participate in the ARISS contact by helping
set up an amateur radio ground station at the school and then using
that station to talk directly with the on-board crew member. Prep-
aration for the experience motivates the children to learn about
radio waves, space technology, science, geography and the space
environment. In many cases, the students help write press releases
and give presentations on the contact to their fellow students and
to the local community. Through this hands-on experience, students
are engaged and educated in the Science, Technology, Engineering and
Mathematics (STEM) fields, and are inspired to pursue STEM-related
careers.
For more information about amateur radio on the ISS and Richard
Garriott's flight, go to:
http://www.ariss.org
http://richardinspace.com
http://spaceadventures.com
http://www.arrl.org
http://www.amsat.org
http://www.spaceflight.nasa.gov/station/reference/radio/index.html
http://dln.nasa.gov/dln/content/catalog/details/?cid=634
http://www.nasa.gov/mission_pages/station/science /EXperiments/ARISS.html
Scout Jamboree on the Air:
http://www.scout.org/jota
Frank H. Bauer, KA3HDO
AMSAT-NA V.P. for Human Spaceflight Programs
ARISS International Chairman
[ANS thanks ARISS for the above information]
/EX
SB SAT (AT) AMSAT $ANS-265.03
Increased Solar Illumination Allows AO-16 Operations to Continue
AMSAT News Service Bulletin 265.03
From AMSAT HQ SILVER SPRING, MD.
September 21, 2008
To All RADIO AMATEURS
BID: $ANS-258.03
Increased Solar Illumination Allows AO-16 Operations to Continue
AO-16 Command Station, Mark N8MH commanded AO-16 ON and restored it to
voice mode on September 15. Mark commented, "At the time of my message
we are up to 30 hours of continuous uptime, which is a 'good thing.'
Our predictions regarding sustained activities seem to be right on the
mark. Recording your observations about AO-16 at http://oscar.dcarr.org/
has been, and will continue to be, very helpful to us."
It is possible that the transmitter will turn OFF; this requires some
commanding to get it running again, which means a pass over the Eastern
US coast is required for a change in status. The command team is hoping
that the bird will remain ON more often than OFF for the next several
weeks.
Illumination projects (and subsequent temperature predictions) suggest
that AO-16 might be able to sustain operations until early November. So,
if you want some AO-16 contacts, you had better get them before then.
After November 2008, it may be a long, long, time before the orbit pro-
vides favorable temperatures for the bird to remain operational for
more than a few seconds or minutes at a time.
Current operational mode for AO-16
Mode FM Voice Repeater ( Downlink is DSB)
Uplink : 145.9200 MHz FM
Downlink 437.0260 MHz SSB
[ANS thanks Mark, N8MH for the above information]
/EX
SB SAT (AT) AMSAT $ANS-265.04
Flight 4 of Falcon 1
AMSAT News Service Bulletin 265.04
From AMSAT HQ SILVER SPRING, MD.
September 21, 2008
To All RADIO AMATEURS
BID: $ANS-265.04
Flight 4 of Falcon 1
As mentioned in my update last month, we do expect to conduct a launch
countdown in late September - as scheduled.
Having said that, it is still possible that we encounter an issue that
needs to be investigated, which would delay launch until the next
available window in late October. If preparations go smoothly, we will
conduct a static fire on Saturday and launch sometime between Tuesday
and Thursday (California time).
The SpaceX team worked hard to make this launch window, but we also took
the time to review data from Flight 3 in detail. In addition to us
reviewing the data, we had several outside experts check the data and
conclusions. No flight critical problems were found apart from the
thrust transient issue.
Flight 5 production is well underway with an expected January completion
date, Flight 6 parts are on order and Flight 7 production will begin
early next year. We are now in steady state production of Falcon 1 at a
rate of one vehicle every four months, which we will probably step up to
one vehicle every two to three months in 2010.
--Elon--
[ANS thanks Lee, KU4OS for the above information]
EX/
SB SAT (AT) AMSAT $ANS-265.05
Welcome Aboard AMSAT-Indonesia
AMSAT News Service Bulletin 265.05
From AMSAT HQ SILVER SPRING, MD.
September 21, 2008
To All RADIO AMATEURS
BID: $ANS-265.05
Welcome Aboard AMSAT-Indonesia
Hakim Satar YB0AN, contacted AMSAT-NA President Rick Hambly W2GPS
this week with the announcement that AMSAT-Indonesia has formed.
Rick replied, "Congratulations on the new AMSAT. I have added you
to the AMSAT Web site and included various AMSAT-NA mail groups
on this reply so everyone will receive the good news."
Two web links are available:
http://www.amsat-id.net
http://www.amsat.org/amsat-new/links/Asia.php
[ANS thanks Hakim Satar YB0AN, President AMSAT-Indonesia for
the above information]
/EX
SB SAT (AT) AMSAT $ANS-265.06
ARISS Status - 21 September 2008
AMSAT News Service Bulletin 265.06
From AMSAT HQ SILVER SPRING, MD.
September 21, 2008
To All RADIO AMATEURS
BID: $ANS-265.06
ARISS Status Report for the Week of September 15, 2008
1. Upcoming School Contact - Status
The ARISS team continues working to schedule the next contact. Contact
approvals for the week have been delayed due to the closure of Johnson
Space Center, which was closed for Hurricane Ike.
2. Boy Scouts Contact Successful
On Saturday, September 13, Prairielands Council Scouts attending the
Space Jamboree at Chanute Air Force Base in Rantoul, Illinois partici-
pated in an ARISS contact with Greg Chamitoff, KD5PKZ. Telebridge station
WH6PN in Hawaii assisted with the contact. Thirteen Scouts were able
to ask 17 questions of the astronaut during the pass. Scout leaders
replayed the question and answer session later in the day for all 3,000
Scouts attending the Jamboree. The audio was fed into the EchoLink AMSAT
server and Internet Radio Linking Project (IRLP) Reflector 9010.
The News-Gazette printed a press release for the event:
http://www.news-gazette.com/news/local/2008/09/12/scouts_at_jamboree_set_to_
talk_with_space_station_astronauts
3. ARISS at Launchfest
On Saturday, September 13, the public was invited to Goddard Space
Flight Center in Greenbelt, Maryland to attend Launchfest. There were
plenty of exhibits and demonstrations of space related activities
including model rocket launches and space robots. The event also
celebrated NASA's 50th anniversary. ARISS members supported Launchfest
and distributed ARISS lithographs.
4. Garriott Prepares for Ham Radio Activities
Spaceflight participant Richard Garriott, W5KWQ, is scheduled to launch
on October 12 with the Expedition 18 crew. He plans to take part in
several ARISS activities while onboard the ISS. His activities include
speaking with children at Challenger Learning Centers throughout the
U.S. He mentioned his radio training in his recent blog. See:
http://www.richardinspace.com/index.cfm?fuseaction=blog.welcome&theyear=&the
month=&view=77#77
[ANS thanks Carol, KB3LKI, for the above information]
/EX
In addition to regular membership, AMSAT offers membership in the
President's Club. Members of the President's Club, as sustaining donors
to AMSAT Project Funds, will be eligible to receive additional benefits.
Application forms are available from the AMSAT Office.
73,
This week's ANS Editor,
Dee Interdonato, NB2F
nb2f at amsat dot org
------------------------------
Message: 8
Date: Sun, 21 Sep 2008 08:35:38 -0700
From: "Art McBride" <kc6uqh(AT)cox.net>
Subject: [amsat-bb] Re: Polarity questions
To: "'Nate Duehr'" <nate(AT)natetech.com>, "'AMSAT BB'"
<amsat-bb(AT)amsat.org>
Message-ID: <743786DCB77A4B25A6103BF8844D6C92(AT)kc6uqh>
Content-Type: text/plain; charset="us-ascii"
Nate,
The advantages of circular when both antennas are circular is not the 3 dB
gain, but the ability to except the rotation of the antenna without signal
change and cancellation of the first reflection (reduction of multipath
fading) which produces steady signals.
Yagi types are subject to receiving reflections from the side and are only
circular polarization on the on axis lobe. Off axis reverse circular
rejection is limited to the forward gain and side lobe rejection of a Yagi
antenna. Helix and QFH antennas are circular over the entire envelope.
The use of dish reflectors on frequencies of 1.2 GHz and above is
recommended. There are several designs, one in an old AMSAT Journal of a
patch feed and polarity switch that works well as a RH/LH circular feed for
the popular TVRO satellite dishes that are abundant.
Art,
KC6UQH
-----Original Message-----
From: amsat-bb-bounces(AT)amsat.org [mailto:amsat-bb-bounces(AT)amsat.org] On
Behalf Of Nate Duehr
Sent: Saturday, September 20, 2008 11:29 PM
To: AMSAT BB
Subject: [amsat-bb] Re: Polarity questions
On Sep 20, 2008, at 2:07 PM, Edward Cole wrote:
>
>
> At 01:53 AM 9/20/2008, Luc Leblanc wrote:
>> On 20 Sep 2008 at 0:56, Nate Duehr wrote:
>> ======snip
That was a weird snip... made it look like my comments were left in
that question and statement from Luc.
I do have a question for the polarity gurus, however...
When *transmitting* circular vs. linear polarity, are the apparent
losses the reverse of the numbers being used for receiving? I am
inclined to think that has to be true.
Or to put it as a question: With all else being equal, including
antenna gain numbers...
How much more power has to be put into a circularly-polarized antenna
versus a linearly polarized one of the same gain, to have a distant
station receive the same signal if they're linearly polarized?
I'm purposely coming at this from the "other" direction... the
transmit side, instead of what is seen at the receiver.
This is mostly a mental exercise to see if I "get it". So if it's a
goofy way to analyze it, ignore that for a moment...
--
Nate Duehr, WY0X
nate(AT)natetech.com
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------------------------------
Message: 9
Date: Sun, 21 Sep 2008 12:08:48 -0300
From: Paul Willmott <pwillmott(AT)northrock.bm>
Subject: [amsat-bb] General Astrodynamics Library v0.4.0 Released
To: amsat-bb(AT)amsat.org
Message-ID: <BAE25EFC-DE81-4FB4-8324-B27BAAA3A50C(AT)northrock.bm>
Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes
Version 0.4.0 of the General Astrodynamics Library has been released.
It can be downloaded from the project website here:
http://homepage.mac.com/pclwillmott/GAL/index.html
Updates in this release:
Higher precision ephemerides for the Sun, Planets, and Pluto.
Implemented using VSOP87. Heliocentric and barycentric routines for
position and velocity provided.
Support added for classical Keplerian models, circular, elliptical,
parabolic, and hyperbolic orbits and trajectories supported. Keplerian
propagation implemented using the Universal formulation.
Release includes some additional support files, and minor updates.
Work continues with the atmosphere, and remaining force models.
The General Astrodynamics Library (GAL) is a numerical library for C
and C++ programmers. It is free software under the GNU General Public
License.
The library provides a wide range of astrodynamical routines such as
ephemerides, earth orientation, and orbit propagation. There are over
250 functions in total with an extensive test suite.
Paul Willmott, VP9MU
AMSAT-BDA
------------------------------
Message: 10
Date: Sun, 21 Sep 2008 08:53:05 -0700 (GMT-07:00)
From: Clint Bradford <clintbrad4d(AT)earthlink.net>
Subject: [amsat-bb] Re: First impression
To: amsat-bb(AT)amsat.org
Message-ID:
<8404460.1222012385231.JavaMail.root(AT)mswamui-
thinleaf.atl.sa.earthlink.net>
Content-Type: text/plain; charset=UTF-8
>>..I too am frustrated by the almost complete abscense of any thing related
to AMSAT or the satellites coming out of QST....
We have no one to blame but ourselves if WE miss the opportunity to submit
articles to QST. They would WELCOME well-written articles on the topic.
Clint Bradford, K6LCS
--------------------------------------
Clint Bradford, K6LCS / KAF3359
909-241-7666 - cell
------------------------------
Message: 11
Date: Sun, 21 Sep 2008 09:48:59 -0600
From: Nate Duehr <nate(AT)natetech.com>
Subject: [amsat-bb] Re: Polarity questions
To: AMSAT BB <amsat-bb(AT)amsat.org>
Message-ID: <48D66CEB.6030005(AT)natetech.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Great answers guys... that made it perfectly clear!
Nate WY0X
------------------------------
Message: 12
Date: Sun, 21 Sep 2008 05:48:30 -0500
From: st797(AT)dcpages.net
Subject: [amsat-bb] FS - Symek TNC3S high speed packet controller
To: amsat-bb(AT)amsat.org
Message-ID: <1764835703.20080921054830(AT)dcpages.net>
Content-Type: text/plain; charset=us-ascii
Hello,
I have a nice used Symek TNC3S high speed packet controller
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MESELX:IT&item=3
20301584793
Good for satellite or ground high speed packet.
Search ebay item 320301584793 if the link above breaks.
--
Best regards,
st797 mailto:st797(AT)dcpages.net
------------------------------
_______________________________________________
Sent via amsat-bb(AT)amsat.org. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
http://amsat.org/mailman/listinfo/amsat-bb
End of AMSAT-BB Digest, Vol 3, Issue 477
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