Satellites - Some newbie questions

[VK4WDM]

On the 14th of Dec I had my first ever satellite QSO when I worked VK3MQ via A0-83 which was a real buzz Since then I have failed to make anymore two way contacts, but I am receiving stations quite well on AO-85, JAS-2, and for the first time today, SO-50.

I have only been using my fixed elevation terrestrial yagis but I am going to rig up a simple way of elevating them using just a piece of rope attached to the boom. I am also in the process of making a hand-held antenna but the current weather is not the best for running round the yard pointing a yagi at the sky - the neighbors already think I am

My questions are:

1. How accurate does the elevation have to be? It will be difficult to continuously change it throughout the pass using my rope method. Would setting it at the average elevation for the pass be OK?

2. JAS-2 Downlink is 435.8 to 435.9 MHz and the uplink is 145.9 to 146.0 MHz. If I hear a station calling, say, on 435.6 what uplink frequency would I use?

3. JAS-2 Downlink is USB. Is the uplink USB or LSB?

I am a complete newbie at satellite ops so please be easy with the jargon

73

Wayne VK4WDM (but still learning new things)

[VK3ZAZ]

1. How accurate does the elevation have to be?

Broad give or take ten degrees


It will be difficult to continuously change it throughout the pass using my rope method.
Yes will be a juggling act. but if you get two simple rotors like stole you can make easy elevate and azimuth rotor system.


Would setting it at the average elevation for the pass be OK?

Yes you can slant the yagi because only one pass is directly overhead usually.

FYI I did this with OSCAR 6 and 7 way back in 1974

Also ran a program in fortran that printed out az el in dot matrix,
Ran program in an NEC 1601A mini computer reading punch cards in FORTRAN to track az and el


using "imperative programming" -- do this, then do that, as directed.
it analysed the things I told it to do, and sorted everything out, and decided the order.
then ran to servos turning the Stolle motors on and off and getting position feedback via selsyn motors
Someone is going to say WTF??--.

[VK4WDM]

Hi Steve

feedback via selsyn motors. Yes, I used those a way back when you could pick them up for a few bucks and prop pitch motors for only a few bucks more My first VHF beams had such a system and it worked very well, but I have not seen that sort of gear for sale for years. I do have a Stolle rotator somewhere that might still work, but I will give the calibrated rope a try first.

73 and all the best for the New Year!

Wayne VK4WDM

[VK3ALB]

2. JAS-2 Downlink is 435.8 to 435.9 MHz and the uplink is 145.9 to 146.0 MHz. If I hear a station calling, say, on 435.6 what uplink frequency would I use?

3. JAS-2 Downlink is USB. Is the uplink USB or LSB?

I am a complete newbie at satellite ops so please be easy with the jargon

73

Wayne VK4WDM (but still learning new things)

Hi Wayne, the specification for the satellite says that it is a linear inverting transponder. I understand this means that the passband is flipped hence the sideband inversion. I'll take your word that the downlink is USB so you would choose LSB on the uplink. Without taking Doppler into account you can assume that the lowest frequency on the downlink passband equates to the highest frequency in the uplink passband. So in your example it should mean 145.90 up = 435.9 down and 146.00 up = 435.80 down.

If you hear a station calling on 435.6 it's probably terrestrial

[VK4WDM]

Hi Lou

I was definitely receiving sigs on JAS-2 on USB. I take your point on the sig at 435.6 (although it could be aliens ).

73

Wayne VK4WDM

[VK5EI]

Hi Wayne,

FO-29 or Fuji Oscar 29 (Jas-2) is a great SSB bird to work and well done for your contact with Rob.


1. How accurate does the elevation have to be? It will be difficult to continuously change it throughout the pass using my rope method. Would setting it at the average elevation for the pass be OK?

Before you start changing your antenna try to work the satellite while its low in the horizon. You should have success to at least 20 deg. There are other guys getting into this bird using no elevation as well.

2. JAS-2 Downlink is 435.8 to 435.9 MHz and the uplink is 145.9 to 146.0 MHz. If I hear a station calling, say, on 435.6 what uplink frequency would I use?

Normally you use the middle of the passband.
Downlink is 435.850 USB
Uplink is 145.950 LSB plus or minus doppler shift.

Tune with your RX VFO to the station your are hearing then adjust your TX uplink frequency until you hear yourself.

Doppler tracking is easily achieved using PC satellite controlling software, I use SatPC32, if you do not use tracking software keep your overs short that way you and the other station can keep up with the doppler shift.
Also much less doppler shift when the bird is at low elevation.

3. JAS-2 Downlink is USB. Is the uplink USB or LSB?
Correct.


Good luck and if you want to do a test send me a email and I will listen out for you.


73

[VK2AZ]

Hi Wayne,
I have a fixed elevation of 25deg on my 5ele 2m and 6 ele 70cm horizontal beams.
I have been working like this for about a year and a half and have great success.
It can be a little challenging at times, particularly with the sats that change polarisation a lot as they spin, but I know you love a good challenge

Over the last couple of days I have made many QSOs on 6 of the sats available.

Joe VK5EI, is the master of the sats, so anything he tells you is correct - aye Joe

Regards

Hilary
VK2IUW

--

[VK7ZA]

While I'm no expert at this, I'm on the journey, so have done a significant amount of fiddling and reading over the past six months or so. As such, take this as the knowledge of an enthusiastic amateur, rather than a satellite guru.

A three element 2m antenna, and a seven element 70cm yagi give you a 50deg beam. If you then use a fixed antenna elevation of 45 degrees or so, you will have quite good coverage with only a patch of fading on passes where the satellite goes over at an elevation close to 90deg. The fading doesn't last long either as that's the fastest relative period of the pass.

Lance

[VK4WDM]

All very helpful, thank you.

I am building a three element 2m and seven element 70cm yagi and I will mount it at a 45 degree angle. I have found a spare rotator so I can mount it on a separate mast and leave the terrestrial array alone.

73

Wayne VK4WDM

[VK5EI]

Another method used is to mount both 2m and 70cm on the same boom. (as per pic). 30 degree elevation will be plenty for your experiment.

To reduce fading on signals caused by polarization change you could also mount the antennas with a 45 degree slant, this method is also popular.

Thanks for your comment Hilary, I have learnt a lot from other Satellite operators sharing there experiences, that's what it all about

73
Joe

[VK3ANZ]

2. JAS-2 Downlink is 435.8 to 435.9 MHz and the uplink is 145.9 to 146.0 MHz. If I hear a station calling, say, on 435.6 what uplink frequency would I use?

Many places will actually quote these frequencies as "Downlink: 435.900-435.800; Uplink: 145.900-146.000".
The thing to note is the order of the upper and lower frequencies (as in the 'downlink' entry) which will show you that the band is linear (a frequency range is given) and inverted (higher then lower frequency, whereas the order is the opposite for the uplink frequency range).
Susan