[Namaste-dev] Re: link budget

Michelle w5nyv at yahoo.com
Thu May 29 06:37:12 PDT 2008


I don't think the OpenKM server is open for business quite yet. 
Dave just yesterday (successfully) worked through two issues with me (very low file-size limits and batch upload restrictions) and another set of issues with internet explorer compatibility was raised with someone else. Also, I noticed either a feature or a bug with uploading identical files. I don't want the revision rolled when the exact same file is uploaded over again, but that seems to be what happens.
Since OpenKM hasn't "gone public" quite yet, I'll put the documents up on the website and in the feed. 
-Michelle W5NYV

----- Original Message ----
From: Matt Ettus <matt at ettus.com>
To: Howie AB2S <howie at aosusa.com>
Cc: Namaste-dev at amsat.org
Sent: Wednesday, May 28, 2008 10:06:02 PM
Subject: [Namaste-dev] Re: link budget

Howie AB2S wrote:
> OK, I know I am coming to the table a little late and I may have 
> missed something, BUT... from what I have been able to gleen from the 
> information posted so far; the satellite transponder will be a bent 
> pie (no onboard regeneration), with a global beam (about 18 dBi 
> antenna) and a 20W SSPA (EIRP about 31 dBW). The small ground station 
> will use a .5M antenna and 10W SSPA (EIRP 37 dBW). Using this 
> information and assuming typical Intelsat performance parameters of 
> SFD (Saturation Flux Density) of about -78 dB/m2, G/T of 0 dB/K and 
> modest Input and output back-off on satellite transponder, this link 
> will not work if these two stations are trying to communicate in 
> anything other than possibly CW. Given all of the above assumptions, 
> the nearest thing to a practical point to point link that I can come 
> up with is 16 kbps using 10 Watts and 2.4M (6') antennas at each end, 
> this was assuing a threshold Eb/N0 of 4.3db and BPSK modulation. So 
> what am I missing here? ........Howie AB2S


The ACP will definitely not be a bent pipe.  It will be demodulation, 
multiplexing, and remodulating the packets which are sent up to it.  It 
will act more like an ethernet switch than a repeater or transponder.  I 
don't know if you have access to the new OpenKM server that Dave put up, 
but if you do, you can read my docs.  I have several presentations up 
there, plus some air interface proposal documents.  In case you don't 
have access, I have attached a presentation I have given a number of 
times about the ACP.  It is longer (but slightly older) than the one I 
gave at Dayton.

We are also hoping to have more like 50W of power out of the ACP.

Matt



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