[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: This Weekend in Minneapolis: Central States VHF Society Meeting

Thanks for your quick reply.

I guess my reaction and comments were in anticipation of what you may hear
from a lot more satellite users.  The satellite community was "forced" by
the failure of mode-V on AO-40 to embrace microwaves and equip for mode-S.
I would say that many have found the process less "painful" and the mode
more useful than they anticipated.  So I was not writing just as a "rural

But now it appears we will have to go thru a similar process each time a
HEO is launched.  I am a mw ham so this generally is more acceptable to me,
but I also have a "painful" reality to face: living on 50% of what I
currently earn about the same time that Eagle will launch.

I understand that engineering projections show the 1270 and 2400 MHz bands
becoming unusable by hams.  From what I hear 5 GHz will be quickly
swallowed up by WiFi as well.  This is quite discouraging.  Frankly, I do
not understand why the current GPS satellite system is inadequate for
European use.  I am building a 1296 EME station at present and this sounds
like it will end up a total waste of money.  1296 EME is currently probably
the best band for eme in regards trade-offs of antenna size, cost, vs.
low-noise environment.  So long low noise!

Getting back to the mode-S issue, the presentation states that telemetry
will use S2 downlink.  It was my suggestion that a circuit path from the
mode-U receiver be provided to the mode-S2 exciter.  As I read it
everything is to be done digitally in SDX so this would not seem to require
much.  Is the problem that S2 Tx is only PSK?  I gather that this downlink
is considered immune from 2.4 GHz WiFi interference (?).

BTW you made no reference to my questions about bands above C-band.
Perhaps a UX or SX transponder could be included in the design since you
state that everything is still at the design level.  I understand if this
is not physically possible or if the energy budget makes it undoable.
10-GHz as a downlink band is presently available without extreme ham
engineering.  It used to be considered an "experimental" band but is
becoming quite populated by hams.  This is the highest frequency that isn't
experimental for hams.  I believe by 2010 that X-band may be as "easy" to
equip as S-band was for AO-40.  A lot of hams did that.

73's Ed - KL7UW

At 09:14 AM 7/25/2006 -0400, Robert McGwier wrote:
>In upcoming journal articles and in Eaglepedia documents showing the 
>detailed calculations upon which our statements are based,  we believe 
>that Tom is being very kind indeed when he calls S band a sewer on the 
>ground.   Furthermore,  as you can see from Tom's recent answers to the 
>candidate questions,   we have to plan on a satellite that we believe 
>cannot  be launched until 4+ years from now .   We cannot build a 
>satellite where we hope, by some miracle, conditions return to those we 
>had before AO-40 was launched or even those that prevailed at the end of 
>its life.   Our computations,   which will be checked again,  and 
>experiments done and supporting documentation will be provided to 
>support,  show that we CANNOT PROVIDE sufficient ERP at the spacecraft 
>for your old station to work as an S band weak signal downlink unless we 
>restrict the usable orbit for S band to a small fraction of the orbit 
>around apogee.  We fully understand that while S band may be usable by 
>you as an individual,  but it is irresponsible of us to design a 
>satellite where a small number of the current satellite users who live 
>in rural areas can use the mode.  We need to design a spacecraft where 
>we are attempting to use our crystal ball and current conditions to 
>forecast the environment we believe the satellite will operate in for at 
>least a decade.
>We are all sorry for the demise of AO-40,  we look forward to P3E which 
>itself may not be launched until 2008, but the following is a simple 
>fact:   we are not duplicating P3E.  Eagle is a different mission 
>entirely from an engineering and user standpoint.   We are not aiming 
>for a 50+ degree inclined orbit.  We are attempting to provide for 
>smaller antennas on the ground, provide for ENCOMM where it is legal, 
>and designing user ground terminals that will work with the spacecraft 
>when launched.   U/V is to be supported in as big a way as we can derive 
>power and provide antenna gain.  Again, this is to minimize the required 
>antenna on the ground.  As bad as 2 meters can be,  we believe it is not 
>as bad as S band will be. 
>Tom has not put in L band in this chart.  We do intend on having an L 
>band receiver (or two) on board.  HOWEVER,    it is almost the unanimous 
>feelings of the designers that this band is dead and we are simply 
>watching its death throes.  The Galileo/GNSS constellation has already 
>begun to eat into the L band allocation in Europe.  A single German TV 
>repeater operator caused the German telecom administration to act with a 
>sledge hammer against amateurs using L band.  
>It is simply irresponsible of us to ignore these issues and we will 
>not.  What we will do is work very hard indeed on stating our case with 
>supporting documentation.
>Let me say that nothing is as simple as "include a band and mode for a 
>test".   We will not do engineering that way.   We are going to 
>calculate and test and provide solid supportable instruments.
>have seen are now history because of the cold hard calculations we did 
>as engineered in a meeting in San Diego in late June.  What Tom and I 
>are presenting,  what Rick and I presented to the ARRL board,  what you 
>will see (much more fleshed out) in October is our current best opinion 
>of what it will take the AMSAT engineering team to deliver on the 
>mission statement the AMSAT board of directors has adopted.
>Edward R. Cole wrote:
>> At 01:01 AM 7/25/2006 -0400, Tom Clark, K3IO wrote:
>>> This coming weekend, Bob McGwier (N4HY) and I are presenting a paper on
>>> AMSAT's efforts on EAGLE and P3E at the Central States VHF Society
>>> meeting in Minneapolis. The following words come from Bruce, W9FZ:
>>> The 40th Annual Central States VHF Conference is just days away on July
>> 28th and 29th in Bloomington, MN. It's being held at the Ramada Mall of
>>> America (formerly The Thunderbird) and is just across the parking lot from
>> the Mall of America. More details can be seen at http://www.csvhfs.org/.
>>> Our paper contains a number of updates concerning EAGLE which you will
>> read about in the next Journal. But for an advance view, you can see our
>> CSVHFS paper, available as a ~3.9 MB PDF file at
>> http://mysite.verizon.net/~w3iwi/EAGLE_CSVHFS.pdf
>>> Sorry it's so long -- I hope you have a fast internet feed!
>>> 73 de Tom, K3IO (ex W3IWI)
>>> ----
>> Tom,
>> As I understand the conclusions from the CSVHFS presentation, Eagle is
>> proposed with:
>> Mode UV voice
>> Mode UV text
>> Mode S1C digital voice & video
>> Mode S2 tlm beacon
>> no mode L uplink
>> no mode S downlink
>> nothing stated about bands above C; what happened to mode UX or CX?
>> Well, I'm not too happy with this result since I have invested in 60w
>> mode-L and mode US & LS downlink equipment that will not have any use
>> (except the beacon).  Of course glad that mode UV is supported.  I am not
>> sure I see how this fits into replicating P3E.
>> Another issue is that mw satellite sub-bands do not coincide with
>> terrestrial sub-bands requiring additional equipment (e.g. my 2304, 3456,
>> 5760, and 10368 equipment is not usable for satellite operation).
>> I would suggest that Mode S (voice downlink) be included as a capablity to
>> test.  If enough ERP is provided this will overcome terrestrial WiFi
>> interference.  If not then we will have to surplus our mode-L and mode-S
>> stuff (ouch!).
>> I will be on a retirement budget by 2010 so the likelyhood of equiping for
>> new satellite mw modes is slim.
>> 73's,
>> Ed - KL7UW  
>> =========================================
>> http://www.qsl.net/al7eb - BP40iq 
>> 144-EME: FT-847, mgf-1801/1402, 4xM2-xpol-20, 170w
>> 432-EME: FT-847, mgf-1402, 1x21-ele (18.6 dBi), 60w
>> =========================================
>> ----
>> 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
>AMSAT VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats,
>"An expert is a man who has made all the mistakes which can be
>made in a very narrow field."  Niels Bohr
Ed - KL7UW  
http://www.qsl.net/al7eb - BP40iq 
144-EME: FT-847, mgf-1801/1402, 4xM2-xpol-20, 170w
432-EME: FT-847, mgf-1402, 1x21-ele (18.6 dBi), 60w
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