[amsat-bb] Re: Different ways to do mobile ham radio operation...

Tim - N3TL n3tl at bellsouth.net
Tue Oct 6 09:21:05 PDT 2009


Thank you for this post. I hope you don't mind if I add a couple thoughts:

1 - Brunton (and, I suspect, others) makes a baseplate compass (the kind used for orienteering) that includes an elevation scale on one end of the base plate. Brunton used to make one that was intended for those mounting satellite dishes, and that scale went up to 60 degrees elevation. Their current model only goes to 30 degrees, but it still proves useful in visualizing an upcoming pass.

2 - Nothing beats observing visible passes of the International Space Station as practice for satellite passes. Because it orbits lower than our amateur satellite, passes unfold a few minutes more quickly than, say, a pass of AO-51. Even so, I found that several years of watching visible passes really paid off when it came to visualizing a pass.

3 - Use easily indetifiable landmarks to help guide you through a pass. AOS, for example, occurs in a line with that mailbox off there to my left. Mid-pass will be almost directly above the chimney of that home over there. And LOS will occur in a line with that street light.

73 to all,

Tim - N3TL

From: Mark VandeWettering <kf6kyi at gmail.com>
To: amsat-bb at amsat.org
Sent: Tuesday, October 6, 2009 11:26:15 AM
Subject: [amsat-bb] Different ways to do mobile ham radio operation...

There has been a lot of discussion about using PDAs and the like to do
satellite orbit prediction.  Indeed, I've thought about writing my
own satellite prediction stuff for the iphone, but haven't bothered
yet, mostly because i find that having another electronic device that
I am staring at while I am pointing an antenna with one hand and
playing with the HT in the other isn't at all helpful.    Here's how I
work a pass:

1. Early in the day (hours ahead of time) I run a prediction for the
satellite of interest.  Minimally, you need to know the time of the
AOS and LOS, the maximum altitude of pass, and azimuth at which these
events occur.
2. Make sure you know where north is.  From your home QTH, it
probably is easy, but I carry a compass for mobile operation just in
3. You need to know what time it is.  Accuracy to 30 seconds is
probably reasonable for hand held operation, where you might not work
down to the horizons anyway.
4. At AOS, aim your antenna near the horizon at the AOS azimuth.
Don't bother sweeping left and right all that much if you are pretty
sure of your directions: the sat will come up on target.  For 70cm
downlinks, start 10khz high for the LEO sats we currently have up.
5. Work the pass.  If you know the azimuth and altitude and time for
the max elevation, you can with a glance at your watch "interpolate"
the satellite pass pretty reasonably.  It may help to have a couple of
other times/locations along the path, but isn't strictly necessary,
particularly if you have full duplex, since you'll be able to hear how
you are doing in working the pass.

Honestly, having an interactive display wouldn't be all that useful
during the pass.  For one thing, I don't have another hand to hold
it.  Additionally, it's not like the satellite is going to do
anything unexpected: it will be coming up exactly as expected, and
setting exactly as expected.

One thing I am working at is a script to create Google Calendar events
that are automatically synched to my iphone.  That way, I can get the
details of each pass automatically a day in advance.  Just having
that static data on my phone (which I am seldom without) suffices for
95 percent of all my operating needs.

I should thank WB4APR and K7AGE for their satellite operation tips.
Bob points out that satellite orbits are regular, and hence can be
easily predicted ahead of time, and a simple printout will show you
within a minute or so when the pass will occur...


Randy, K7AGE used a printout of the pass taped to his HT in one of his
videos, which I did when I started, but later I realized that if I
just "rehearsed" the pass in my head and had a watch, it wasn't

73, Mark K6HX
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