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Author Topic: Operating sats: Are they all the same?  (Read 5674 times)

KF4TEK

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Operating sats: Are they all the same?
« on: September 29, 2001, 12:40:43 PM »

When I discovered that there were amateur radio satellites accessible to me with my current HT and a few hours' work constructing a respectable downlink antenna, I was thrilled. I got up early Saturday morning to climb to the top of a nearby hill to get the best chances of hearing voices from AO-27. Shortly after the projected time, I heard them! What were they saying?

<callsign one> <callsign two> <gridsquare>
<callsign two> <callsign one> <another gridsquare> QSL, thanks

<callsign three> <gridsquare>
<callsign four> static... static...  ...thanks...

And that was all, on and on for 10 long minutes.

I couldn't even figure out where these hams were because I didn't have a gridsquare map in front of me (and I haven't memorized it.) It was all I could do to follow the callsigns whipping back and forth, my HT in one hand with two fingers fiddling with the tuning knob, the homemade beam in my other hand twisting around in the sky trying to keep the signal up. I'm sure I looked quite foolish. And I'm glad that my friend, who has recently gotten his call and is becoming interested in ham radio, couldn't make it. It was one big contest in the sky.

And it's been the same any time I've gone out to listen to AO-27. Now, some folks love contesting, and that's fine. But what I want to know is this:

Are there any satellites out there devoted to something other than <callsign> <callsign> <gridsquare>?  I was thinking of picking up some used  VHF SSB equipment and a downconverter to monitor AO-40, but if it's going to be more of the same, I'm not interested.

Can anyone tell me what operating the other sats is like? There's nothing worse than spending a lot of effort getting somewhere only to find it it's not where you want to be.

Thanks much in advance,
Mike - KF4TEK
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KQ6EA

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Operating sats: Are they all the same?
« Reply #1 on: September 30, 2001, 11:59:06 PM »

Welcome to the world of Low Earth Orbit (LEO) FM satellites! Because they can only support ONE QSO at a time, what you heard was actually the correct operating procedure. If you want to carry on a conversation with someone, you'll need a satellite that has a passband wider than one FM signal. You'll need at least a 2M SSB transmitter to use as your uplink, and either a 70cm or 10M receiver to listen to the downlink. The Russian 'RS' series of sats generally use 2M up, 10M down, although RS-13 can also have a 15M uplink. FO-20 and FO-29 use a 2M uplink, and a 70cm downlink, and since they have a higher orbit, can be in range for 20 minutes or so. AO-40 uses a 70cm or 23cm (1269MHz) uplink with a 13cm (2401 MHz) downlink. Downlink equipment is readily available, as you've already found out, and they recently tested the 24GHz transmitter. One thing you MUST have is the capability to simultaneously receive while you transmit, known as full-duplex. You must be able to find your own downlink to use the satellite. Otherwise you run the risk of 'stepping on' a QSO in progress. AMSAT (www.amsat.org) has many excellent operating guides on their website, and I suggest you start there. They cover all the basics you need to get started, and will answer many of your questions. Welcome to satellite operating! 73, Jim  KQ6EA
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W9GB

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Operating sats: Are they all the same?
« Reply #2 on: November 07, 2001, 10:33:24 AM »

First, check the amsat.org web site.

All information on satellites can be found their and international links.

The satellites will vary depending upon their orbits (e.g. Low Earth Orbit, Highe Earth Orbit, Geostationary), ARRL Handbook has chapter on this.
There are NO amateur geostationary satellties today.

The LEO orbits have the advantage that they are physcially closer to you ( 150 - 300 miles up ) and require less power and smaller antennas to work.  The disadvantage is that they fly by very quickly (going at least 17,000 mph), so a "useable" pass is 10 - 15 minutes maximum.  The Alpha ISS faces these same challenges.

This is also why you see interest in digital modes on LEO (packet, APRS, etc.)

Now if you are looking for "rag chew" satellites, this was the mission of the "Phase 3" satellites.  The 2 current Phase 3 sats are AO-10 and AO-40.

AO-10 (Oscar 10)

Carries Mode B and Mode L transponders.
Radiation damage has caused the failure of the main computer memory and batteries no longer function.  Provides good communications when it has favorable sun angles (in sunlight for solar power).  Still provides good trans-atlantic and trans-pacific coverage.

W4SM, still functions as "station controller" and provides periodic updates on satellite reports.







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Are there any satellites out there devoted to something other than <callsign> <callsign> <gridsquare>? I was thinking of picking up some used VHF SSB equipment and a downconverter to monitor AO-40, but if it's going to be more of the same, I'm not interested.

Can anyone tell me what operating the other sats is like? There's nothing worse than spending a lot of effort getting somewhere only to find it it's not where you want to be.
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