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CX2SA > SATDIG 17.06.05 21:28l 199 Lines 7042 Bytes #999 (0) @ WW
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Subj: AMSAT-BB-digest V2004 #745 2/7
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Sent: 050617/2018Z @:CX2SA.LAV.URY.SA #:63007 [Minas] FBB7.00e $:63007-CX2SA
From: CX2SA@CX2SA.LAV.URY.SA
To : SATDIG@WW
Message: 4
Date: Fri, 17 Jun 2005 08:00:15 -0400
From: Joe Fitzgerald
Subject: [amsat-bb] Planetary Society requests amateur assistance.
The following is from the famous orbital detective Ted Molczan on the Hearsat
mailing list:
**********************************************************************
Long-time SeeSat-L contributor Vladimir Agapov has contacted me and confirmed
that amateur radio observations will be highly useful to the Cosmos 1 project.
For example, accurate radio frequency measurements for Doppler calculations
(even AOS, LOS or zero-Doppler times).
The Russian company "Space Informatics and Analytical Systems JSC" ("KIA
Systems") has developed various software for measurements processing,
catalogue
maintenance etc., and is responsible for ballistic and navigation support of
the
Solar Sail flight, under contract to Lavochkin Association, which developed
and
produced the spacecraft for the Planetary Society.
KIA Systems has created a special e-mail account, to which I will forward all
radio observations that I receive via HearSat-L or directly, including each
observer's name, station name and coordinates.
Please include the precision of frequency and time measurements. Timing
accuracy
need not be better than 0.001 s.
Information on the spacecraft's radio frequencies is provided here:
http://www.planetary.org/solarsail/parameters.html
"The spacecraft will broadcast telemetry at two different frequencies:
401.5275
MHz (UHF band) and 2250 MHz (S-band). However, the broadcast will not be
continuous; it is turned only when the spacecraft passes over one of the
ground
stations in our network."
Information on the tracking stations is provided here:
http://www.planetary.org/solarsail/tracking_stations.html
http://planetary.org/solarsail/images/ground_station_map_800x442.jpg
During the first day after launch, it would be highly desirable to report
observations as soon as possible.
Scheduled Launch Time: June 21, 2005 at 19:46:09 UTC
Ted Molczan
- ----
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------------------------------
Message: 5
Date: Fri, 17 Jun 2005 08:56:14 -0400
From: "Robert Bruninga"
Subject: Re: [amsat-bb] Eggbeaters
There are 3 things to think about when using OMNI
antennas for Satellites.
1) Satellites spend 67% of all in-view times below 20 deg
2) Satellites below 20 deg are 6 to 10 dB further away
3) You cannot afford ANY coax loss (use a preamp)
Thus, assuming you have a preamp, a good base
station antenna will work well for about 50% of the
time when the satellite is below about 15 deg IF THE
SATELLITE IS STRONG ENOUGH TO BE HEARD IN THE
FIRST PLACE. But the main lobe of such antennas
is only on the horizon and there is a big null from about
15 deg up to about 45 deg. Thus if the signal
is too weak on the horizon to be heard anyway,
then no only do you not hear it there, but now you
have null higher up, where it is closer in and you
would be able to hear it on a 1/4 wave low gain
whip.
Conversly, a hemispherical antenna has equal
gain everywhere (usually inadequate on low
elevations where the bird is 6 to 10 dB farther
away and also where it spends 67% of its time.
But when the bird gets closer (higher) then
this antenna gives solid performance (but for
less than 1/3rd of the pass.
So it all goes back to one thing. You cannot have
high gain on the horizon witout having a null higher
up, and if you have gain higher up, then you miss
most of the time on the horizon. BUT IF THE
SATELLITE IS SUCH THAT IT CANNOT BE HEARD
ON THE HORIZON ANYWAY without gain, then
dont bother. Go with a omni such as a 1/4 whip
over a gorund plane and just plan on only hearing
the 30% of all pass times when the satellite is
closer in (and above the trees) and hear it well.
But always use a preamp.
I dont think there are any amateur satellites other
than the ISS that fall into the category of workable
at the horizon on an omni.
de WB4APR, Bob
>>> "Dale - KL7XJ" 06/17/05 1:39 AM >>>
Art,
I agree with what you stated. Another thing about EB ant is
that you need the radials below the antenna. The EB was one of
my first satellite antennas. I improved the reception with the preamp.
It is now my back up antenna system. I have both 2m and 70cm
EB's mounted on my tower at about 40 '. I use crossed yagis for both
bands on a separate tower for satellite work now. I am also mounting
S band and L band antennas with G5500 rotors after field day.
Happy Fathers Day!
73's
Dale/KL7XJ
- ----- Original Message -----
From: "KC6UQH"
To: "Dale - KL7XJ"
Sent: Thursday, June 16, 2005 7:45 PM
Subject: Re: [amsat-bb] Eggbeaters
> Dale,
> I suggest that a 1 wave per side QFH is better than a egg beater, circular
> polarized and will work to a few degrees above the horizon.
>
> Art, KC6UQH
> ----- Original Message -----
> From: "Dale - KL7XJ"
> To: "John Henderson"
> Cc: <amsat-bb@amsat.org>
> Sent: Thursday, June 16, 2005 7:40 PM
> Subject: Re: [amsat-bb] Eggbeaters
>
>
>> A preamp will definitely help. I have one at about 40' using 9913 coax.
>> I do have a preamp mounted right below the antenna. I used the antenna
>> without preamp for a long time when UO14 was alive. But they sure do
>> make
> a
>> differance on the recieve end.
>>
>> Dale/KL7XJ
>> #30600
>> ----- Original Message -----
>> From: "John Henderson"
>> To: "AMSAT-BB" <amsat-bb@amsat.org>
>> Sent: Thursday, June 16, 2005 5:56 PM
>> Subject: [amsat-bb] Eggbeaters
>>
>>
>> >I have constructed, very carefully I might add, a 70cm eggbeater II, got
>> > the swr down to 1.1/1 at 435-438 .Stone deaf at 25' height and 40 foot
>> > run of 9913.
>> > I must have too much attenuation in the line into the shack. I don't
>> > have any N connectors on hand so there are a couple of 259's in the
>> > line.
>> >
>> > Am I wasting my time and $$ or will a mast preamp help?
>> >
>> > 73, John
>> > N4NAB/ FM14lq
>> > AMSAT # 32411
>> > ----
>> > Sent via amsat-bb@amsat.org. Opinions expressed are those of the
>> > author.
>> > Not an AMSAT member? Join now to support the amateur satellite program!
>> > To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>> ----
>> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
>> Not an AMSAT member? Join now to support the amateur satellite program!
>> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
- ----
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
- ----
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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