[amsat-bb] AO 7 comments

Jim Danehy jdanehy at cinci.rr.com
Sat Nov 15 21:50:00 PST 2008

Mark (WD4ELG)

Thanks for the comment on my CW signal . . . I prefer CW so I attempt to generate some activity on AO 7 whenever I can . . .  hope to catch you on Sunday . . . 

RE : doppler . . . . my experience is that doppler is pretty dynamic rather than static . . . a lot of variables such as height, angle to your QTH that change from pass to pass . . . I use SatPC32 to control the doppler . . .  i have made up a little chart for the non-FM birds and dial in the adjustment (to the uplink)  before the pass . . . . I notice that on AO7 when I work Europe (a very low elevation for me) that I need to dial in a lot more adjustment (almost 2 khz)  . . . . I use an Icom 910H and its RIT is limited to 1 khz which is a little bit of a pain  . . . . i have the RIT on and like to be able to use it on stations that do not use computer control of their rigs . . . I do not think  you can "nail" the frequency consistently . . .  in my experience on the non-FM satellites it is just something you take into account . . .

You ask about the activity level too . . . well all of the non-FM satellites suffer from relative  lack of use compared to the FM satellites. Doppler is not as much of a factor because of the FM signal's width  . . . . I use the AFC (automatic frequency control) on my 910 too in FM mode which really solves the (doppler) problem . . . I think the doppler effect on non FM signals is really too much for many of the users . . . that signal really moves around albeit in the same direction . . . use of a computer to control it reduces the number of successful users . . .  I do hear people struggling (as I did) to get the doppler issue under control . . . I also think that there is a lot more FM rigs in use compared to the multi mode rigs . . .  thus more relative activity . . in sorting through my collection of QSLs from satellite QSOs I find that there is a preponderance of HTs  . .  I do not use an HT even on the FM birds . .  

One more thing : AO 7 is really old ( 1974 ) and suffers from old age (very sensitive to the use of high power) I usually use 5 watts on CW . . .  today I worked K9CIS who was using  7/10ths of a watt . . . we rag chewed for 10 minutes . . . anyone who uses excess power causes the transponder on AO 7  to sound choppy  with the offending signal being heard up and down the band in 3 or 4 places, often making AO 7 unusable for many. . . I stick to CW and use the CW filter which helps me overcome the hash that is generated by stations using too much power . . . .  folks really need to keep their ERP (effective radiated power) down to 100 watts or less on AO7. That means if you are using 25 watts output your antenna should not exceed 6 db gain (a factor of 4 times). Most satellite users on non FM birds use yagis that have 10 db + or more gain which means they should keep their power to 10 watts . . . unfortunately that remains a problem . . .more is less in that situation . . 

Look forward to exchanging reports with you . . .

73  Jim W9VNE

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