WD0E Explains MICROSAT Antenna Polarization

 From: Dave Cowdin <cowdin@pogo.den.mmc.com>

Subject: ANS-331 BULLETINS

Newsgroups: local.amsat

Date: Sun, 28 Nov 1993 11:12:40 -0700 (MST)

 

SB SAT @ AMSAT   $ANS-331.01

MICROSAT ANTENNA POLARIZATION

 

HR AMSAT NEWS SERVICE BULLETIN 331.01 FROM AMSAT HQ

SILVER SPRING, MD NOVEMBER 27, 1993

TO ALL RADIO AMATEURS BT

BID: $ANS-331.01

 

WD0E Explains MICROSAT Antenna Polarization

 

There have been quite a few question raised recently regarding the sense of

polarization of the MICROSATs.  Jim White (WD0E) sheds some light on the

subject with the following: "There has been a certain amount of confusion

about the sense of the polarization of the MICROSAT down links.  The

following is an attempt to clarify it.  The two transmitters in each

MICROSAT are connected to the canted turnstile downlink antenna through a

hybrid.  The two input ports they are connected to are out of phase with

each other.  So when one transmitter is on the sense of the downlink will

be RHCP and when the other is on it will be LHCP.  When we switch trans-

mitters, we also switch polarization sense.  No sense is 'normal'.  During

construction there was no attempt to make a particular transmitter a

particular sense.  The limiting factor was how to fit the semi-rigid cables

connecting all the various parts together in the tiny space inside the

transmitter module.  Additionally, since one of the objectives of the

MICROSAT Project was to create satellites that could be used with very

simple portable ground stations using simple omni-directional antennas,

there was no need to be concerned about sense.  When receiving with a

circularly polarized ground antennas, miss-matched sense can make several

dB of difference at times.  The most strongly circular signal will be

received by the ground station when the bottom of the satellite is

pointed directly at it.  For stations at about 35 to 50 degrees north or

south latitude, this happens when the satellites are directly overhead and

slightly lower in latitude.  (For all but LO-19 the turnstile is pointed

down in the northern hemisphere, for LO-19 it's down in the southern

hemisphere).  At other times the sense is effected by a variety of other

influences and cannot be relied on.  If you have a circularly polarized

Yagi with swit-chable sense you can do a test yourself to see which

transmitter provides which sense.  Throughout a pass, but particularly when

the satellite is nearly overhead, switch the antenna sense every few

seconds and see which is stronger.  At times you will notice a large

difference (AO-16 is 5 S units different on my TS-811).  The sense that

provides the strongest signal over the majority of the pass is the sense of

the downlink for that trans-mitter.  And for all but DOVE, it also

correlates to the frequency, since the 70 cm transmitters are all on

different frequencies.  DOVE is a special case since it's two transmitters

are on nearly the same frequency.  To make the correlations yourself on

DOVE you would need to do the same test as above, but also check which

transmitter is in use as indicated by the STATUS line.  We normally run

TX#2 on DOVE because it is more efficient.

Here is a chart I have hanging on my wall to remind me of which sense to

use."

 

WD0E welcomes confirmations of these observations:

 

WO-18:

437.075 PSK LHCP (this TX is bad and not normally used)

437.100 RC RHCP (normally in use)

 

LO-19:

437.153 PSK LHCP

437.125 RC/CW RHCP

 

AO-16:

437.025 PSK LHCP (not presently in use)

437.050 RC RHCP (in use now)

 

DO-17:

145.825 TX#1 LHCP

145.825 TX#2 RHCP (normally used, and in use now)

 

[The AMSAT News Service (ANS) would like to thank Jim White (WD0E) for this

bulletin item.  Jim White's Internet address is: wd0e@amsat.org]

 

/EX

SB SAT @ AMSAT   $ANS-331.02

LANDLINE BBS WITH ANS BULLEINS

 

HR AMSAT NEWS SERVICE BULLETIN 331.02 FROM AMSAT HQ

SILVER SPRING, MD NOVEMBER 27, 1993

TO ALL RADIO AMATEURS BT

BID: $ANS-331.02

 

 

The AMSAT BBS Network now includes the following BBS's:

 

 

     CompuServe's HAMNET

Phone: (Local Access)

Location: USA

Baud Rate: Up To 14,400bps

Sysop: Scott Loftness (W3VS)

 

     Western Pacific Database

Phone: 415-453-2854

Location: San Rafael, CA

Baud Rate: Up to 14,400bps V.32bis

Sysop: Daniel C. Dufficy (KH8AF)

 

     The ARRL BBS

Phone: 203-666-0578

Location: Newington, CT

Baud Rate: Up To 14,400bps

Sysop: Luck Hurder (KY1T)

 

     California Amateur Radio Emergency Services (CARES) BBS

Phone: 916-323-4826

Location: Sacramento, CA

Sysop: Gorden Fuller (WB6OVH)

 

     AMSAT East Coast Bulletin Board

Phone: 201-261-2780

Location: New Milford, New Jersey

Baud Rate: Up to 14,400bps

Sysop: Mel Roman (KA2UPD)

 

     HAM>LINK<RBBS

Phone: 612-426-0000

Location: St. Paul, Minnesota

Baud Rate: Up to 9600bps V.32

Sysop: John Desmond (K0TG)

 

     OCA/AMSAT BBS

Phone: 714-738-4331

Location: Fullerton, CA

Baud Rate: Up to 24000bps

Sysop: John Wisniowski (N6DBF)

 

     DRIG BBS

Phone: 214-394-7438

Location: Carrolton, TX

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Sysop: Jeff Wallach  (N5ITU)

 

     GEnie's Radio, Electronics, & Broadcasting RoundTable

Phone: Call 800-638-9638 for information and local access phone number

Location: USA

Baud Rate: Up To 9600bps

Sysop: Larry Ledlow  (NA5E)

 

     PC-Ham (Reliable) BBS

Phone: 301-593-9067

Location: Silver Springs, MD

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Sysop: Joe Kasser  (W3/G3ZCZ)

 

     The WireNet BBS

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Location: Birmingham, Alabama

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     Top of The Rock BBS

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Location: Lilburn, GA

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Sysop: Steve Driggs  (KB4ZTN)

 

     USS Enterprise 1701-D BBS

Phone: 717-752-1468

Location: Berwick, PA

Baud Rate: Up To 2400bps

Sysop: Bill Barnes  (N3JIX)

 

If you run a BBS and would like to join The AMSAT BBS Network, we want to

hear from you.  Tell us the name of your BBS, phone number, location (city,

state), baud rate, sysop's name and callsign, and Internet and/or

CompuServe address.  Also, what AMSAT, ARRL, etc. files do you post each

week?

 

     You can contact me on:

                           >INTERNET:n6dbf@amsat.org

                                     or

                            CompuServe:  70233,75

 

 

73, John Wisniowski (N6DBF)

    AMSAT-NA, BBS Coordinator

 

/EX

SB SAT @ AMSAT   $ANS-331.03

AMSAT OPS NET SCHEDULE

 

HR AMSAT NEWS SERVICE BULLETIN 331.03 FROM AMSAT HQ

SILVER SPRING, MD NOVEMBER 27, 1993

TO ALL RADIO AMATEURS BT

BID: $ANS-331.03

 

Current AMSAT Operations Net Schedule For AO-13

 

AMSAT Operations Nets are planned for the following times.  Mode-B Nets

are conducted on AO-13 on a downlink frequency of 145.950 MHz.  If, at the

start of the OPS Net, the frequency of 145.950 MHz is being used for a QSO,

OPS Net enthusiasts are asked to move to the alternate frequency of 145.955

MHz.

 

 Date           UTC    Mode     Phs     NCS     Alt NCS

 

12-Dec-93       0435   B       180      W9ODI   WB6LLO

 3-Jan-94       0200   B       160      WA5ZIB  N7NQM

 

Any stations with information on current events would be most welcomed.

Also, those interested in discussing technical issues or who have questions

about any particular aspect of OSCAR statellite operations, are encouraged

to join the OPS Nets.  In the unlikely event that either the Net Control

Station (NCS) or the alternate NCS do not call on frequency, any

participant is invited to act as the NCS.

 

**************************************

 

Slow Scan Television on AO-13

 

SSTV sessions will be held on immediately after the OPS Nets a downlink

on a Mode-B downlink frequency 145.960 MHz.

 

/EX

SB SAT @ AMSAT   $ANS-331.04

WEEKLY OSCAR STATUS REPORTS

 

HR AMSAT NEWS SERVICE BULLETIN 331.04 FROM AMSAT HQ

SILVER SPRING, MD NOVEMBER 27, 1993

TO ALL RADIO AMATEURS BT

BID: $ANS-331.04

 

Weekly OSCAR Status Reports: 27-NOV-93

 

AO-13: Current Transponder Operating Schedule:

L QST *** AO-13 TRANSPONDER SCHEDULE ***  1993 Nov 15-Jan 31

Mode-B  : MA   0 to MA  95 !                   / Eclipses, max

Mode-B  : MA  95 to MA 180 ! OFF Dec 07 - 24. <  duration 136

Mode-B  : MA 180 to MA 218 !                   \ minutes.

Mode-S  : MA 218 to MA 220 !<- S beacon only

Mode-S  : MA 220 to MA 230 !<- S transponder; B trsp. is OFF

Mode-BS : MA 230 to MA 256 !        Blon/Blat 240/-5

Omnis   : MA 250 to MA 150 !  Move to attitude 180/0, Jan 31

AO-13 will experience another partial solar eclipse on 1993 Dec 13 [Mon].

It sees the Moon eclipse the Sun from 10:09 - 10:59 UTC with a maximum 53%

obscuration at 10:34 UTC.  This is Orbit #4211 MA 73-92.  The encounter

will be "visible" on the telemetry to stations throughout the USA and

Japan.  Reports would be appreciated.  Stations who observed this

spectacular eclipse of Dec 13 will know what to look for.  Eclipses of sun

by earth commence on Dec 07 [Tue] and continue until Dec 24 [Fri].  The

eclipses are of course total.  The maximum lasts 2 hours and 16 minutes,

and is the longest AO-13 has ever experienced.  The telemetry during these

outages is very interesting, particularly the spacecraft temperatures; some

reach -40 C.  The Mode-B transponder will be OFF from MA 95 to 180 during

this two week period.  [G3RUH/DB2OS/VK5AGR]

 

FO-20: The following is the FO-20 operating schedule:

              Analog mode: 01-Dec-93  08:43 -to- 07-Dec-93 7:16  UTC

                           15-Dec-93  07:41 -to- 22-Dec-93 8:05  UTC

       Digital mode: otherwise noted above.  In December, analog mode and

      digital mode will be ON alternately for a week, respectively.

       [JJ1WTK]

 

RS-12: RS-12 was very active on the East Coast and Midwest passes

       during this last week.  Not so active on the West Coast passes.

       XE1YMY has been worked many times by RS-12 users in Canada, Arizona,

       and Texas.  Also, a YV5 station was heard calling on 15M with

       no responses!  And one can also hear JA stations calling on RS-12 in

       the late evening West Coast passes.  [KF5WY]

 

The AMSAT NEWS Service (ANS) is looking for volunteers to contribute weekly

OSCAR status reports.  If you have a favorite OSCAR which you work on a

regular basis and would like to contribute to this bulletin, please send

your observations to WD0HHU at his CompuServe address of 70524,2272, on

INTERNET at wd0hhu@amsat.org, or to his local packet BBS in the Denver, CO

area, WD0HHU @ W0LJF.#NECO.CO.USA.NOAM.  Also, if you find that the current

set of orbital elements are not generating the correct AOS/LOS times at

your QTH, PLEASE INCLUDE THAT INFORMATION AS WELL.  The information you

provide will be of value to all OSCAR enthusiasts.

 

/EX