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[aprssig] PCSAT2 Downlink Challenge

Phillip B. Pacier ad6nh at arrl.net
Sat Jul 30 16:53:25 UTC 2005


Whatever you end up with, send your PCSat2 9600 telemetry to 
satgate.aprsca.net:20150

73
Phil - AD6NH

Robert Bruninga wrote:

>Unattended 9600 baud fixed antenna data capture:
>
>There are many variables at work here for optimizing data
>capture unattended from weak satellite signal.  Remember
>with global APRS-Intenret links, the only thing that counts
>will be the SUM of everyone's efforts, so not any one station
>needs to get all data.  In fact, a single fixed antenna and
>because of doppler, it is impossible to get all data without
>changing direction of beam or doppler.  But we can each 
>optimize our fixed station to make our best contribution.
>Even if only one pass a day..  There are many variables.
>
>1) Weakest signal near horizon must have beam
>2) But least doppler change is at horizon
>2) Strongest signal above 30 deg, but maximum doppler change
>3) 19" whip is excellent gain at 435 (7 dBi) but only for >30 deg
>4) But high doppler (over 8 KHz in 2 minutes) >30 deg
>5) Your latitude determines if most passes are north, south
>    and your area might favor east or west.
>6) Also you might live on east coast or west coast.  If on east
>coast, you should have fixed antenna to favor passes to east
>that no one else will hear, on west coast, favor to the west.
>
>Best combination will be different for everyone.  Or, everyone
>just gets a small part on an OMNI and APRS network puts
>it all together into good total...  hummh...
>
>  
>
>>>>aprssig at ei7ig.org 07/30/05 7:01 AM >>>
>>>>        
>>>>
>>1)   You need to replace the antennas!
>>    
>>
>No rotators here unfortunately, so a 19" Whip it will have to be  
>then.  Though from reading and re-reading Bob's post, and knowing  
>that these stations will be un-manned should we just leave the rigs  
>on the downlink frequency and hope to receive with little or no  
>doppler at the centre of the pass, or should we tune/scan between the  
>frequencies most likely at the beginning/end of the pass?
>  
>
>>2)   For work at 9600, you must tap the receive signal off the  
>>radio's discriminator output
>>    
>>
>
>Ok, I'll try the linux soundmodem interface again later... I think I  
>hung the soundcard driver trying 9k6 last night, i have the cables  
>already made up to interface to the FT-847.
>
>I did a bit of playing with the TH-D7 this morning and i have it  
>running under Linux in Kiss mode.  Though I've come across a few web  
>pages that seem to suggest that its very unreliable at 9K6 in kiss  
>mode. Has anyone had any experience of this? bearing in mind we are  
>only trying to catch a few packets of data would this suffice for a  
>9K6 downlink?
>
>I've got the machine time synced using ntp and this should give me  
>the correct output, listen -t -p 70cm | tee PC2_$(date +%y%m%d_%H%M) 
>_EI7IG.txt
>
>  
>
>>3)   The TS2000 appears,
>>
>>    
>>
>So for the EI8JA's TS-2000, kiss mode and add 19" Whip, AGW (which he  
>has) and AGW monitor. Excellent, one hopefulle sorted.
>
>  
>
>>If you have a PC with sufficient "horsepower" (approximately  
>>Pentium II 300 or higher) and a soundcard with a stereo line input,  
>>the AGW PE  softmodem can be configured to act as TWO TNCs, one on  
>>the left channel and one on the right channel, emulating something  
>>like a Kantronics 9612 dual-port..   You could set one to 1200 baud  
>>connected to one radio via the speaker output, and one to 9K6  
>>connected to the other radio via the discriminator output.   Note  
>>that you MUST have a line-level input to get the stereo input; the  
>>mic input (often the ONLY input on laptops) is single-channel  
>>(MONO) and can't use this feature of AGW PE.
>>    
>>
>
>Thats a very interesting idea, I'll put that to John, as he could  
>then use both rigs one on the 'big vertical' and one on the 19" Whip,
>
>Thanks for the reply.
>
>Regards
>de John
>EI7IG
>
>
>
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>  
>




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