[amsat-bb] AO-73 - Evening transponder time increasing in NorthernHemisphere

Mvivona Mvivona at yahoo.com
Tue Aug 18 13:20:24 UTC 2015

Recently you may have heard me attempting to find myself on the bandpass. I am tuning manually, but can never get a clean downlink of my voice. Also, I only show up on my spectrum as a small spike and others show up nice and strong. 
I have tried several times to work it with not much luck. I am using an IC910H, dual Arrow antennas on rotor, no preamp yet, but my coax is quite short with about 3db loss on the 70cm and almost nothing on the 2m. On a high pass I can hear myself, but I can never get my audio to sound right. It always sounds like I'm not on frequency as my voice is always real high pitched through the tuning range. I'm hitting the bird with about 200W ERP. I thought I might be getting into my frontend with harmonics due to my antennas being only about 3 ft apart so I also tried using an eggbeater for the uplink and setting it 20ft away. Granted that dropped my ERP to about 100W, but still the same outcome, but with 100W I could barely hear my downlink. I can hear others nice and strong and they are clean sounding. I also tried a different radio just for the heck of it, but the same outcome. 
I use dual fed coax and switch polarity as the bird rotates. 
My settings are:
Uplink - 435.130 - 435.150 LSB
Downlink - 145.950 - 145.970 USB

Michael Vivona
Sent from my iPad

On Aug 18, 2015, at 8:14 AM, Clayton W5PFG <w5pfg at amsat.org> wrote:

One thing I might add: often I encounter stations spending a lot of time trying to find themselves on the transponder.  I suspect they are trying to calibrate their SatPC32/MacDoppler/gpredict.  Sadly, they spend so much time doing so that they miss out on the precious transponder time.  Ditting/hola/test-test-test without sending a callsign doesn't even make for a good SWL report.

I would suggest stations NOT try using computer control and enjoy the transponder with manual control.

Chances are if you are not hearing your own downlink on AO-73, you probably either have a poor antenna/feedline OR (more likely) you are not listening in the correct corresponding downlink frequency for your uplink frequency into the transponder. AO-73 is VERY easy to hear!


> On 8/17/2015 21:13, Paul Stoetzer wrote:
> Good evening,
> As we're nearly two months pass the Summer Solstice here in the
> Northern Hemisphere, transponder time is increasing on evening passes
> over North America. Here in Washington, DC, on the 0155Z pass, I had 6
> minutes and 10 seconds of pass time from AOS until the satellite
> entered sunlight and the transponder switched off. I heard and worked
> PV8DX at my AOS, but no other stations were heard.
> AO-73 is currently the only amateur satellite consistently available
> during regular evening hours, even if not for an entire pass, so let's
> hear some more activity! It's really quite an easy satellite to work
> with the strong downlink.
> 73,
> Paul, N8HM
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