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HOWTO: Working FM Ham Satellites
radio : by Tommy - January 22nd 2011, 03:37PM
radio
A local ham recently asked me the best way to talk on ham radio satellites using what he already has on hand. It doesn't take much, although some more specialized equipment does make it much easier, but the point is - you don't need much beyond what you may already own if you have a basic VHF/UHF station. The following is my email to him:

Which birds to target and how to track them
"The best satellites to start with are AO-27, AO-Echo and SaudiSat-1C. (Satellites go by different names depending on where you're getting your info.)

I usually direct people to Heavens-Above to get the latest pass information. The exact time and angle of each pass varies from day to day, so you either need tracking software or a website to tell you when the next pass is over your location. With Heavens Above, you need to enter your longitude and latitude, so it can figure out the information for you.

I've put in the longitude and latitude in for my QTH here in Longview on this link:
http://www.heavens-above.com/main.aspx?Lat=32.5560&Lng=-94.7474&Alt=365&Loc=N5DUX&TZ=CST
(change the location by editing the link or click on the link under Configuration at the top of the page)

When you go to the website, you'll be shown a lot of different links. For our purposes, we're interested in "Radio Amateur Satellites". Click on that link.

Now you'll be presented a table of all the various satellites that Heavens Above is tracking. I usually find the satellites I'm interested in working, then look over at the "maximum elevation" - this is how high in the sky the "bird" will get. Generally the higher the pass, the better chance of hitting the satellite you'll have. If all you're using is a vertical, 45-degree passes will give you a good shot. But anything greater than 30-degrees should be doable. Because you're not on a directional antenna, you don't need to really worry about the azimuth of the pass. Someday, you may find that you'd like to get a yagi and then direction of the pass will matter.

( edit: Heavens-Above is a good reference, but since most people have to jump through a few hoops to enter their Longitude and Latitude, I've been recommending N2YO more and more. Heavens-Above will show a good table of information so you can see everything at a glance, but if you know the satellites you're wanting to work, check out the table at N2YO's Amateur Satellite listing.)

What frequency?
So, now you know when the passes are occurring, now you need to set the frequency. Here are the uplink and downlink frequencies for these 3 satellites. Note the tone. Remember, you talk on the uplink, receive on the downlink.

nameuplinkdownlinkPL
AO-Echo145.880435.150-
AO-27145.850436.795-
SaudiSat-1C145.850436.79567.0
Int'l Space Sation144.490145.800-

Doppler
Ok, so there are your frequencies. Those are the "actual" frequencies. Remember, Doppler shift does play a part in satellite communications. You will need to go UP a few kHz as the satellite is coming TOWARD you and DOWN a few kHz as it goes past you. (When it is perpendicular to your position, the frequency will be right on the actual frequency.) If that makes your head hurt, just know to start about 15-20kHz above the actual. As the signal gets more "scratchy" sounding, you'll know it's time to drop ~5kHz.

Listen first!
Listen, listen, listen. Just because you can't hear it, doesn't mean it can't hear you! It's a repeater in many respects, and if you're calling and calling and calling, you're tying it up so others can't use it. If you plan to operate chiefly during daytime hours, you'll hear A LOT of guys crowding onto the satellite each pass. You'll hear quick, rapid-fire exchanges. "N5DUX Echo Mike-22" "Ok, N5DUX, EM22 - this is W1AW, FN31" "Roger W1AW, FN31, 73." - and that's all it is usually. A quick exchange of grid squares, seldom a signal report and rarely much conversation. That is, during the day. At night it's a different story. When all the "sane" people are asleep, you can get on an FM satellite and have a full QSO for the duration of the pass, sometimes up to 15 minutes - always remember though, you have an entire continent of hams that may be wanting on the satellite too, so keep some space between exchanges.

So, tune your radio to the downlink frequency, find the next pass and see if you can hear the satellite.

Recording
A tip I've picked up along the way: The operators are going to be throwing out their info very quickly, so you may need to make a recording of the pass, so you can go back and replay the whole thing to get a second chance of copying their info.

Once you know you can hear the signals, throw out your callsign and see if someone comes back. It's just a really busy repeater, so don't give up. Also, realize that since you're only using a vertical, you won't have as strong of a signal as others will, so you may get stepped on or not heard. Don't give up - try later in the evening when not many are on.

CW telemetry
If you have a dual-band antenna, that would be even better for working sats from a vertical. A mono-band 70cm will work fine for receiving, but for transmitting the uplink you'll need a resonant antenna on 2m.

That's not to say you can't have fun with the 70cm alone. If you have a multimode 70cm radio, you can also copy telemetry data from other satellites that is sent down in CW. It's not the most exciting stuff right away, but copy one satellite over a period of a few days and you can monitor how it's on board temperature swings as it passes in/out of the sun/earth's shadow and stuff like that. It's just fun to copy CW from a little satellite 200+ miles away. The one I copy most often (when I do try to copy) is RS-30 Yubileiny. Unfortunately it isn't tracked on Heaven-Above, so I have to use this other website that's pretty handy, N2YO.com
Yubileiny's track: http://www.n2yo.com/?s=32953

After you decode the info, check out how to "decode" the info by Googling for "RS-30 telemetry", or use a tool like those found here for free: http://www.dk3wn.info/software.shtml Check out the telemetry hypothesis section here to decode the seemingly random strings of info: http://www.ne.jp/asahi/hamradio/je9pel/yubilein.htm

So there you have it, a beginner's guide to getting on the birds with stuff you probably already have. For further reading, check out this page from AMSAT and, of course, scour Google for all it's worth!

update: It should be noted that as of sometime in Spring 2011, AO-Echo began experiencing difficulties with its onboard batteries. The command team cannot keep the control system loaded effectively taking AO-Echo offline. AO Echo is as good as dead until further notice.

update #2: AO-Echo is back online now. Thanks for the heads up Schrockwell. Echo is online running at 2/3 her input power and running 1W output. Note the changed frequencies. These are not the same frequencies Echo has been using since launch. There are the "QRP" frequencies.

update #3: AO-Echo is dead, so long little guy.
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tags: satellite ham radio intro howto
+ Tommy G.
  Jan 23, 2011 00:37
  
#18768
Audio clip of Col Doug Wheelock aboard ISS talking to me in Fall 2009: http://www.issfanclub.com/node/29725

reply

+ Grendel
  Oct 16, 2011 18:04
  
#18781
Audio recording of me working as W1AW from ARRL HQ: http://www.youtube.com/watch?v=N5aGriCx-YA

reply




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