Nothing heard on the 7 AM EDT 65 degree pass over Orlando.

On Apr 12, 2011, at 2:51 AM, [email protected] wrote:

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> Today's Topics:
> 
>   1. Re: The Need for Phonetics (Jim Shorney)
>   2.  ARISsat-1 not heard (John Heath)
>   3.  ARISSat-1 update (Gould Smith)
>   4. Re: ARRISSat Reception 14.45 UTC (Joe Fitzgerald)
>   5.  Arissat still silent (P. Pakr)
>   6.  Nothing Heard in VK of ARISSat-1 (Colin Hurst)
>   7.  Nice view of ISS ... (Viktor Kudielka)
>   8. Re: ARRISSat Reception 14.45 UTC (Phil Karn)
>   9. Re: ARRISSat Reception 14.45 UTC (KF1BUZ)
>  10.  Nothing Heard 2M ARISSat-1 9:32PM PDT (Clint Bradford)
>  11.  Just an hour from now ... (Clint Bradford)
>  12.  R50KEDR Heard on 14.190 (John Heath)
>  13.  ARISSat-1 No Signal (John Spasojevich)
>  14. Re: ARISSat-1 No Signal (KF1BUZ)
>  15.  Nothing here either: 0606z pass over California (Greg D.)
>  16.  Nothing Heard From ARISSat-1 In DO33 (B J)
>  17.  Not Heard 1106 PM PDT (Clint Bradford)
>  18.  satellite average elevation (Bob- W7LRD)
>  19.  Nothing heard over Nashville 0610 (Alan P. Biddle)
>  20. Re: ARRISSat Reception 14.45 UTC (Phil Karn)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Mon, 11 Apr 2011 19:03:22 -0500
> From: "Jim Shorney" <[email protected]>
> Subject: [amsat-bb] Re: The Need for Phonetics
> To: "amsat-bb" <[email protected]>
> Message-ID: <[email protected]>
> Content-Type: text/plain; charset="iso-8859-1"
> 
> On Mon, 11 Apr 2011 14:17:49 -0700, Jeff Moore wrote:
> 
>> <==  Could it be that they understand the quicksand you're standing on?
> 
> 
> No. We know from long experience (35+ years in my case) that Glen is right.
> 
> 73
> 
> -Jim
> 
> 
> --
> Ham Radio NU0C
> Lincoln, Nebraska, U.S.S.A.
> TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, 
> HyGain 3750, IBM PS/2 - all vintage, all the time!
> 
> "Give a man a URL, and he will learn for an hour; teach him to Google, and he 
> will learn for a lifetime."
> 
> HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/
> http://incolor.inetnebr.com/jshorney
> http://www.nebraskaghosts.org
> 
> 
> 
> 
> ------------------------------
> 
> Message: 2
> Date: Tue, 12 Apr 2011 01:22:39 +0100 (BST)
> From: John Heath <[email protected]>
> Subject: [amsat-bb]  ARISsat-1 not heard
> To: Amsat <[email protected]>
> Message-ID: <[email protected]>
> Content-Type: text/plain; charset=iso-8859-1
> 
> 0107? AOS pass in range UK - nothing heard on 145.950
> 
> 73 john g7hia
> 
> ------------------------------
> 
> Message: 3
> Date: Mon, 11 Apr 2011 20:35:42 -0400
> From: "Gould Smith" <[email protected]>
> Subject: [amsat-bb]  ARISSat-1 update
> To: <[email protected]>
> Message-ID: <0EE1E8CB77EF40158B1BCB10C560994B@GouldMainPC>
> Content-Type: text/plain;     charset="iso-8859-1"
> 
> As Armando, N8IGJ noted in his earlier email, NASA as published an update of 
> today's activities ( it can be found at 
> :http://www.nasa.gov/directorates/somd/reports/iss_reports/index.html) 
> .Contained this document is a section about ARISSat
> 
> Dmitri performed hardware setup and test activation of the TEKh-43 
> Radioskaf-B "Kedr" microsatellite in the MRM2 Poisk module, connecting it to 
> an 825M3 Orlan battery and checking out its 430 MHz transmitter from the 
> satellite control panel. [The small satellite was named Kedr in honor of the 
> call sign of Yuri Gagarin. It will be activated onboard the station tomorrow, 
> April 12, i.e., Cosmonautics Day, when the world celebrates the anniversaries 
> of the first human flight into space and the first Space Shuttle flight. 
> Development, manufacturing and launch of Kedr is the first phase in Russia's 
> integrated program approved by UNESCO, with the goal to create and operate 
> mini-satellites with a mass less than 100 kg by combined efforts of students 
> across the world. Once Kedr is activated, it will transmit 25 greetings in 15 
> languages, pictures of Earth, and telemetry data from science hardware and 
> support systems, as well as historical audio recordings. 50 years after 
> Gagarin's !
 fl!
> ight all ham radio operators across the world thus will have a unique 
> opportunity to hear the famous "Poyekhali" (Let's Go!) from Earth orbit.]
> 
> Some clarifications:
> ARISSat-1, RadioSkaf-V, RadioSkaf-B, Kedr are all names for the same 
> satellite.
> It is doubtful that the satellite will transmit pictures of earth as it is 
> inside the ISS.
> ARISSat-1 only transmits on 2M. The ARISS team has arranged for the TM-D700 
> transceiver aboard the ISS to also transmit the ARISSat signals on 437.55 MHz.
> There are 24 different messages that will transmit in a sequence, one of 
> which is the Gagarin-ground station conversation.
> The crew operates on UTC time and sleeps from 2130Z - 0600Z usually so 
> probably no activity until after 0600Z
> The 12 April schedule found at  
> http://www.nasa.gov/pdf/534825main_041211_tl.pdf  doesn't specifically list 
> an activity to turn on ARISsat-1
> Keep listening, we'll let you know more as we know more.
> 
> 73,
> Gould, WA4SXM
> 
> ------------------------------
> 
> Message: 4
> Date: Mon, 11 Apr 2011 20:47:28 -0400
> From: Joe Fitzgerald <[email protected]>
> Subject: [amsat-bb] Re: ARRISSat Reception 14.45 UTC
> To: [email protected]
> Message-ID: <[email protected]>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
> On 4/11/2011 1:44 PM, Phil Karn wrote:
>> Since it's already connected to the station antenna, it sure would be nice
>> if they could just plug it directly into the ISS power supply, switch it on
>> full duty cycle, and just *leave* it for a couple of, oh, years.
> 
> Phil,
> 
> I am curious to see how your BPSK1000 fares on a rapidly tumbling 
> platform.  Let's hope ISS doesn't start tumbling more than once per orbit!
> 
> If you do convince them to leave the ISS powered up on board ISS, we 
> could evaluate rapit deep fades in the channel by putting middle school 
> students  in charge of holding an arrow antenna.
> 
> -Joe KM1P
> 
> 
> ------------------------------
> 
> Message: 5
> Date: Tue, 12 Apr 2011 01:02:59 +0200
> From: "P. Pakr" <[email protected]>
> Subject: [amsat-bb]  Arissat still silent
> To: [email protected]
> Message-ID: <[email protected]>
> Content-Type: text/plain ; charset="UTF-8"
> 
> Next pass over Czech, nothing heard here :-(
> 73! Petr
> 
> 
> ------------------------------
> 
> Message: 6
> Date: Tue, 12 Apr 2011 10:52:47 +0930
> From: "Colin Hurst" <[email protected]>
> Subject: [amsat-bb]  Nothing Heard in VK of ARISSat-1
> To: "amsat-bb" <[email protected]>
> Message-ID: <C8B6CE92B219472DBF5394B1577A6723@Athlon>
> Content-Type: text/plain;     charset="us-ascii"
> 
> Had a nice pass at 0045utc 12/4/2011, 67 degrees elevation.
> No signals heard.
> 73
> Colin VK5HI
> 
> 
> 
> ------------------------------
> 
> Message: 7
> Date: Tue, 12 Apr 2011 03:39:11 +0000
> From: Viktor Kudielka <[email protected]>
> Subject: [amsat-bb]  Nice view of ISS ...
> To: [email protected]
> Message-ID: <[email protected]>
> Content-Type: text/plain; charset=us-ascii
> 
> ... over Vienna at 03:25UTC with 47 degrees elevation.
> Automatic antenna tracking seems to be nearly perfect,
> but no signal ?
> The CW decoder of ARISSatTLM produced a random string of
> characters including ...HIHI... 
> 73, Viktor OE1VKW
> 
> 
> 
> ------------------------------
> 
> Message: 8
> Date: Mon, 11 Apr 2011 20:58:54 -0700
> From: Phil Karn <[email protected]>
> Subject: [amsat-bb] Re: ARRISSat Reception 14.45 UTC
> To: Joe Fitzgerald <[email protected]>
> Cc: [email protected]
> Message-ID: <[email protected]>
> Content-Type: text/plain; charset=UTF-8
> 
> On Mon, Apr 11, 2011 at 5:47 PM, Joe Fitzgerald 
> <[email protected]>wrote:
> 
>> 
>> I am curious to see how your BPSK1000 fares on a rapidly tumbling
>> platform.  Let's hope ISS doesn't start tumbling more than once per orbit!
>> 
> 
> It's a pretty sensitive mode, but it still won't work with a zero-watt
> transmitter.
> 
> 
>> 
>> If you do convince them to leave the ISS powered up on board ISS, we
>> could evaluate rapit deep fades in the channel by putting middle school
>> students  in charge of holding an arrow antenna.
>> 
>> 
> My concern is that the on/off cycling won't play well with my convolutional
> interleaver. It takes 16.384 seconds to fill the interleaver at AOS. You
> might get decoded data up to 8 seconds earlier than that if what you do get
> is very clean, but there's little margin for additional error correction.
> 
> And when the transmitter switches off, the interleaver will drain over
> 16.384 seconds as it fills with noise. If the signal in the last 16.384
> seconds before switch-off is unusually strong, you may be able to decode
> data up to 8 seconds before LOS. But anywhere from 8 to 16 seconds will be
> chopped off *each end* of each already very short  40-60 second
> transmission.
> 
> I designed this signal to deal well with occasional deep fades lasting up to
> 1-1.5 seconds -- not for total "fades" lasting 2 minutes at a time. Had I
> known that this "emergency low power mode" was actually going to be used, I
> would have designed the whole mode completely differently, with block
> interleaving aligned to the transmit on/off times.
> 
> The golden rule of the modem designer: "know your channel". Optimizing for
> one impairment usually pessimizes it for something else.
> 
> 
> ------------------------------
> 
> Message: 9
> Date: Mon, 11 Apr 2011 21:22:28 -0700
> From: KF1BUZ <[email protected]>
> Subject: [amsat-bb] Re: ARRISSat Reception 14.45 UTC
> To: <[email protected]>, "'Joe Fitzgerald'" <[email protected]>
> Cc: [email protected]
> Message-ID: <00f101cbf8c9$3ceed0b0$b6cc7210$@com>
> Content-Type: text/plain;     charset="us-ascii"
> 
> Well its 421 am they will be awake around 0600 am utc.. 2 hours from now,
> then we will see if they flippa da switcha
> 
> Kf1buz
> 
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On
> Behalf Of Phil Karn
> Sent: Monday, April 11, 2011 8:59 PM
> To: Joe Fitzgerald
> Cc: [email protected]
> Subject: [amsat-bb] Re: ARRISSat Reception 14.45 UTC
> 
> On Mon, Apr 11, 2011 at 5:47 PM, Joe Fitzgerald
> <[email protected]>wrote:
> 
>> 
>> I am curious to see how your BPSK1000 fares on a rapidly tumbling 
>> platform.  Let's hope ISS doesn't start tumbling more than once per orbit!
>> 
> 
> It's a pretty sensitive mode, but it still won't work with a zero-watt
> transmitter.
> 
> 
>> 
>> If you do convince them to leave the ISS powered up on board ISS, we 
>> could evaluate rapit deep fades in the channel by putting middle 
>> school students  in charge of holding an arrow antenna.
>> 
>> 
> My concern is that the on/off cycling won't play well with my convolutional
> interleaver. It takes 16.384 seconds to fill the interleaver at AOS. You
> might get decoded data up to 8 seconds earlier than that if what you do get
> is very clean, but there's little margin for additional error correction.
> 
> And when the transmitter switches off, the interleaver will drain over
> 16.384 seconds as it fills with noise. If the signal in the last 16.384
> seconds before switch-off is unusually strong, you may be able to decode
> data up to 8 seconds before LOS. But anywhere from 8 to 16 seconds will be
> chopped off *each end* of each already very short  40-60 second
> transmission.
> 
> I designed this signal to deal well with occasional deep fades lasting up to
> 1-1.5 seconds -- not for total "fades" lasting 2 minutes at a time. Had I
> known that this "emergency low power mode" was actually going to be used, I
> would have designed the whole mode completely differently, with block
> interleaving aligned to the transmit on/off times.
> 
> The golden rule of the modem designer: "know your channel". Optimizing for
> one impairment usually pessimizes it for something else.
> _______________________________________________
> Sent via [email protected]. Opinions expressed are those of the author.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
> 
> 
> 
> ------------------------------
> 
> Message: 10
> Date: Mon, 11 Apr 2011 21:47:09 -0700
> From: Clint Bradford <[email protected]>
> Subject: [amsat-bb]  Nothing Heard 2M ARISSat-1 9:32PM PDT
> To: AMSAT BB <[email protected]>
> Message-ID: <[email protected]>
> Content-Type: text/plain; CHARSET=US-ASCII
> 
> Another poor pass for me ... nothing heard.
> 
> BUT AT 11:06PM PDT - a whopper of a pass. Followed by a pass in the morning 
> that should be VISIBLE!
> 
> ("Honey, brew another pot o' coffee, will you please?")
> 
> Clint, K6LCS
> 909-241-7666 - cell 
> 
> 
> ------------------------------
> 
> Message: 11
> Date: Mon, 11 Apr 2011 22:09:42 -0700
> From: Clint Bradford <[email protected]>
> Subject: [amsat-bb]  Just an hour from now ...
> To: AMSAT BB <[email protected]>
> Message-ID: <[email protected]>
> Content-Type: text/plain; CHARSET=US-ASCII
> 
> Added a photo of me working (unsuccessfully) a pass of the ISS this evening 
> (9:32PM PDT, Riverside, CA DM13).
> 
> In the background, FirstOrbit.org's incredible film that will be released to 
> the world tomorrow - a re-creation of Yuri's 108-minute flight, taken by 
> modern cameras aboard the ISS.
> 
> http://gallery.me.com/clintbradford#100077
> 
> Clint, K6LCS
> Skype - clintbradford
> 
> 
> ------------------------------
> 
> Message: 12
> Date: Tue, 12 Apr 2011 06:20:53 +0100 (BST)
> From: John Heath <[email protected]>
> Subject: [amsat-bb]  R50KEDR Heard on 14.190
> To: Amsat <[email protected]>
> Message-ID: <[email protected]>
> Content-Type: text/plain; charset=utf-8
> 
> 0520 UTC
> 
> The gagarin station R50KEDR on 14.190 working split listening 5 up.
> 
> Weak signal at my QTH in southern England
> 
> 73 john g7hia
> 
> ------------------------------
> 
> Message: 13
> Date: Tue, 12 Apr 2011 00:08:25 -0500
> From: John Spasojevich <[email protected]>
> Subject: [amsat-bb]  ARISSat-1 No Signal
> To: [email protected]
> Message-ID: <[email protected]>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> Nothing heard on the 0437 UTC pass in Montgomery, IL  76 degrees elevation,
> nice night though.
> 
> John - AG9D
> 
> 
> ------------------------------
> 
> Message: 14
> Date: Mon, 11 Apr 2011 23:16:30 -0700
> From: KF1BUZ <[email protected]>
> Subject: [amsat-bb] Re: ARISSat-1 No Signal
> To: "'John Spasojevich'" <[email protected]>, <[email protected]>
> Message-ID: <00f201cbf8d9$2accaf00$80660d00$@com>
> Content-Type: text/plain;     charset="us-ascii"
> 
> Nothing heard over reno, no packet or anything..
> 
> Slacking space doods!!
> Kf1buz
> 
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On
> Behalf Of John Spasojevich
> Sent: Monday, April 11, 2011 10:08 PM
> To: [email protected]
> Subject: [amsat-bb] ARISSat-1 No Signal
> 
> Nothing heard on the 0437 UTC pass in Montgomery, IL  76 degrees elevation,
> nice night though.
> 
> John - AG9D
> _______________________________________________
> Sent via [email protected]. Opinions expressed are those of the author.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
> 
> 
> 
> ------------------------------
> 
> Message: 15
> Date: Mon, 11 Apr 2011 23:23:27 -0700
> From: "Greg D." <[email protected]>
> Subject: [amsat-bb]  Nothing here either: 0606z pass over California
> To: <[email protected]>
> Message-ID: <[email protected]>
> Content-Type: text/plain; charset="iso-8859-1"
> 
> 
> No signal on 145.950 here in Cal.  With my luck they probably started the 15 
> min timer just before LOS...
> 
> By the way, confirming the earlier post about inconsistent KEPs.  Gpredict 
> updates from Celestrak, and was slightly behind Predict which I had loaded 
> from Amsat.org website.  (I use Gpredict for pass prediction and eye candy 
> during a pass; predict drives my rotor and Doppler shift radio client.)
> 
> Greg  KO6TH
> 
>                                         
> 
> ------------------------------
> 
> Message: 16
> Date: Mon, 11 Apr 2011 23:25:29 -0700 (PDT)
> From: B J <[email protected]>
> Subject: [amsat-bb]  Nothing Heard From ARISSat-1 In DO33
> To: [email protected]
> Message-ID: <[email protected]>
> Content-Type: text/plain; charset=us-ascii
> 
> I listened until 0620 UTC but it was a low-elevation pass.  The next 3 will 
> be over 30 degrees.
> 
> 73s
> 
> Bernhard VA6BMJ @ DO33FL
> 
> 
> 
> ------------------------------
> 
> Message: 17
> Date: Mon, 11 Apr 2011 23:35:36 -0700
> From: Clint Bradford <[email protected]>
> Subject: [amsat-bb]  Not Heard 1106 PM PDT
> To: AMSAT BB <[email protected]>
> Message-ID: <[email protected]>
> Content-Type: text/plain; CHARSET=US-ASCII
> 
> Darn .... Nada heard on an excellent pass of the ISS at 1106PM PDT.
> 
> But I think the astronauts were just awakened at the top o' the hour.
> 
> OK - 5:30-ish AM PDT next pass over Southern CA DM13-land!
> 
> Clint
> Skype - clintbradford
> 
> 
> ------------------------------
> 
> Message: 18
> Date: Tue, 12 Apr 2011 06:35:48 +0000 (UTC)
> From: Bob- W7LRD <[email protected]>
> Subject: [amsat-bb]  satellite average elevation
> To: [email protected]
> Message-ID:
>       
> <1639302076.3920933.1302590148277.javamail.r...@sz0126a.emeryville.ca.mail.comcast.net>
>       
> Content-Type: text/plain; charset=utf-8
> 
> 
> 
> I saw on this bb a site or note that shows the overall?average elevatation.? 
> As I remember it elevation is surprisingly low for most passes.? Where can I 
> find it? 
> 
> 73 Bob W7LRD 
> 
> 
> ------------------------------
> 
> Message: 19
> Date: Tue, 12 Apr 2011 01:41:15 -0500
> From: "Alan P. Biddle" <[email protected]>
> Subject: [amsat-bb]  Nothing heard over Nashville 0610
> To: "AMSAT-BB" <[email protected]>
> Message-ID: <0D3F14EBAC99494FA86A73A7FD1D8543@WA4SCA>
> Content-Type: text/plain;     charset="us-ascii"
> 
> All,
> 
> Silence over Nashville on the 0610 UTC pass.  All but 2 of the passes during
> the scheduled period of activation will be "in the weeds" from an elevation
> standpoint at my QTH.
> 
> Did get a nice I/Q recording of the passband, though.
> 
> 
> Alan
> WA4SCA
> 
> -----------------------------------
> 
> The prospect of domination of the
> nation's scholars by Federal employment,
> project allocations, and the power of money
> is ever present - and is gravely to be
> regarded.
> 
> President Dwight D. Eisenhower
> 
> 
> 
> 
> ------------------------------
> 
> Message: 20
> Date: Mon, 11 Apr 2011 23:50:44 -0700
> From: Phil Karn <[email protected]>
> Subject: [amsat-bb] Re: ARRISSat Reception 14.45 UTC
> To: Joe Fitzgerald <[email protected]>
> Cc: [email protected]
> Message-ID: <[email protected]>
> Content-Type: text/plain; charset=UTF-8
> 
> To elaborate:
> 
> BPSK-1000 uses "convolutional interleaving" with a depth of 16,384 symbols.
> The symbol rate is 1 kHz (1,000 symbols/sec) so it takes 16.384 seconds for
> a data symbol to pass through both the transmit and receive interleave
> buffers. The transmitter delay changes a lot from one symbol to the next,
> but every symbol experiences the same *total* (transmitter + receiver)
> delay: 16,384 symbol times or 16.384 seconds. The idea of any interleaver is
> to chop up (short) fades and spread them out in time so that they can be
> easily corrected by the Viterbi error correction algorithm (which deals well
> with random thermal noise but not with burst errors).
> 
> The usual rule of thumb is that an interleaver can easily handle a complete
> fade lasting up to 10% of its length, as long as you give it time to recover
> between fades. That would be 1.6 seconds, which seemed plenty long for a
> continuously transmitting LEO spacecraft on 2 meters.
> 
> Of course, you pay a price in delay -- there's no way around it. I have
> Sirius Satellite Radio in my car, and it always cuts out 4 seconds *after* I
> drive into the parking garage at work. It doesn't come back until (at least)
> 4 seconds *after* I drive out and it sees the satellite(s) again. The reason
> is exactly the same -- an interleaver that takes care of brief fades but not
> the really long ones caused by driving into a parking garage.
> 
> I chose convolutional interleaving for BPSK-1000 because it has half the
> delay of block interleaving for the same fade performance.
> 
> Convolutional interleavers also operate continuously, a good match to
> ARISSat-1's continuous transmitter. At AOS, your deinterleaver is still full
> of noise received earlier; it takes 16.384 seconds to flush it all out and
> feed "solid" data to the decoder. During that time, it ramps from pure noise
> to pure signal, and at some point it starts correcting what it sees.
> Depending on how strong the signal is, that may happen before the flushing
> is complete. I.e., it might reconstruct some of the missing symbols sent
> before your AOS.
> 
> Similarly there is a slow ramp from solid signal down to pure noise over
> 16.384 seconds at LOS.
> 
> See how this helps handle fading? Even an abrupt, complete fade starts the
> same, slow 16-second ramp down from signal to noise. If the fade ends only a
> second or two later, the rampdown won't have progressed very far and the
> decoder will still see mostly signal when the trend reverses and ramps back
> up to pure signal. That takes a few extra seconds, but the error correction
> can easily handle it all -- as long as the fade isn't *too* long.
> Interleaving takes a signal that may be solid one moment and gone the next
> and smooths it out so that the signal-to-noise ratio changes only slowly. It
> literally averages the signal-to-noise ratio.
> 
> Since even a short LEO pass is usually several minutes long, these 16 second
> fill/drain intervals didn't seem like a big deal. Besides, we've already had
> a similar problem since the old days of the uncoded Phase III block
> telemetry format. You might have AOS in the middle of a frame and have to
> wait for the next one to start before you can decode anything. Interleaving
> isn't really any worse.
> 
> The problem is that I didn't count on having the transmitter turned on for
> only 40-60 seconds at a time. So....if the transmissions are only 40 sec,
> and if you have to wait 16.384 seconds for the interleaver to fill, and you
> can't rely on the last 16.384 seconds as the interleaver drains, that leaves
> 40 - 2*16.384 = 7.232 seconds of solid, noise-free "middle" to work with.
> 
> As I recall, ARISSat-1 data frames can be up to 512 bytes long. Ignoring
> HDLC flags, bit stuffing, CRC, etc, that's 4K bits. At a data rate of 500
> bps (the FEC is rate 1/2), 512 bytes will take 4096/500 = 8.192 seconds to
> transmit.
> 
> 8.192 seconds is longer than 7.232 seconds.
> 
> Ooops.
> 
> But wait, there's more. If the satellite sends a series of back-to-back 512
> byte frames, and the transmitter comes on  too late after one has already
> started, you'll have to wait for it to end before you can begin decoding the
> next one. Meanwhile, the clock is quickly ticking down until the transmitter
> goes OFF again...
> 
> Double oops.
> 
> Now this probably overstates the problem a bit. Being the engineer that I
> am, this is a very conservative analysis -- I made the most pessimistic
> assumption at each step. After all, I was stunned when somebody streamed
> BPSK-1000 over the net with a lossy MP3 encoder and it *decoded*; I never
> thought that would work.
> 
> Error correction can fill in for a remarkable variety of ills. In reality,
> the satellite won't send a continuous stream of 512 byte frames. In reality,
> the key-down intervals may be more than 40 seconds. So I actually won't be
> too terribly surprised if the thing actually works. But it won't perform
> anything like it will when the satellite is eventually operated in its
> intended 100% duty cycle mode.
> 
> 
> ------------------------------
> 
> _______________________________________________
> Sent via [email protected]. Opinions expressed are those of the author.
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> 
> 
> End of AMSAT-BB Digest, Vol 6, Issue 207
> ****************************************



Lou McFadin
W5DID
ARISS US Hardware manager


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