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Author Topic: HEO satellites ??  (Read 1817 times)
AF4XK
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Posts: 96




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« on: March 15, 2010, 02:52:56 PM »

Hello folks.

I am trying to get up to speed on satellite operating so I've been reading quite a bit lately on the subject.

What I don't understand yet is: are there any High Earth Orbit satellites available to us now?

Is a DXCC possible via sats? If so which ones should I focus on.

Thanks and 73.
chuck
af4xk
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XE1VE3OQC
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Posts: 20




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« Reply #1 on: March 20, 2010, 05:36:58 AM »

Hi Chuck,
As of now no, as you know since Oscar 10 died a while ago there has been nothing from AMSAT and DL-AMSAT is proposing a launch sometime later this year or early next with an apogee of 40,000km. Check with the AMSAT Germany site for additional info.
I have begun setting up my system in anticipation for the HEO´s.

Glenn,VE3OQC/XE1
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AF4XK
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« Reply #2 on: March 20, 2010, 05:45:10 AM »

Thanks Glenn.

In reading the various web info on satellites it seems much of it is dated so it's difficult to know what's current and applicable.

Anyway, as far as the LEO satellites, what would you say is the average distance of a qso?

And lastly, is most of the LEO activity on the FM satellites or the CW/SSB ones?

thanks and 73.
chuck
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WD4ELG
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« Reply #3 on: March 20, 2010, 10:02:59 PM »

The satellites are a mix:  some are FM repeaters (AO-51 and AO-27) others are CW/SSB (AO-7, FO-29, VO-52).  I think the latest (XW-1?) is a mix, either one or the other depending upon the ground control station.

Tim, N3TL, has made many trans-oceanic contacts on AO-7, and I think he only needs Alaska for WAS.  It depends upon the height, and AO-7 is (I seem to remember) higher, and VO-52 is one of the lower ones.

Anyway, I personally have worked from NC to Calif on several of the birds with just 5 watts and a hand-held Elk antenna.
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K4PP
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Posts: 64




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« Reply #4 on: March 21, 2010, 04:26:14 AM »

Are these sats actually put into a high earth orbit, or is it a highly eliptical orbit with apogee at those altitudes and much lower perigee?

K4PRP
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XE1VE3OQC
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« Reply #5 on: March 21, 2010, 09:07:51 AM »

Hi Chuck,
The longest contact I have made using AO-7 was 6,800 kms and most recently on AO-7 mode B,was 6,378 kms into GH14 Brazil.It depends on a number of factors. One, the AOS (Aquistion of Satellite) of the satellite into your area which depends on altitude, Two, Field of view from your particular station and Three, your antennas. I have used 10x10 on the UHF uplink with 10 watts and have always had excellent results on AO-52.The same for AO-7, lately I have experimented with 20x20 on the uplink and is 1-2 S units better....sometimes.
As for the modes, I have leaned towards the SSB birds since 1977 just my preference, I have never had the desire to work the fm birds. This may be different for many people and I encourage the use of all modes.
Equipment is also not expensive. Example, my ¨basic¨setup uses a Ten Tec 2510B (circa 1985) for the uplink and a FT-817 as the receiver for AO-52. On AO-7 I use a FT-790RII on TX with a IC-290a as the receive. Works well and my yagis are all homebrew crossed RHCP/LHCP.
Fun...that is what it´s all about.

Glenn,VE3OQC/XE1 Dl91
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XE1VE3OQC
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« Reply #6 on: March 21, 2010, 09:22:26 AM »

Some orbits are the Molniya type which maintain an apogee for some 12-14 hours, which means less tracking and less doppler shift. UHF doppler shift is 10-15 khz on LEO´s.The next Phase 3 may be a type of Molniya orbit with a mean distance of 40,000 kms at apogee that will enable you to work half of the world on a pass.Antennas become a factor with 20x20 on UHF and at least 20 watts and 12x12 on VHF for receive and perhaps a good preamp.

Glenn,VE3OQC/XE1
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XE1VE3OQC
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« Reply #7 on: March 21, 2010, 09:28:32 AM »

The Radio Amateur´s Satellite handbook from 1998 is full of excellent information and is required reading!!.This is available from ebay for a very reasonable price. The newest one, The ARRL Satellite Handbook is not very well written and is more of an introduction. The few projects that are in there require a Phd to build them and are from the Phase 3D era.
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AF4XK
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Posts: 96




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« Reply #8 on: March 22, 2010, 02:35:27 PM »

Thanks again Glenn. I'm on the lookout for the suggested handbook.

One last question: as far as your antennas, what do you mean by 10x10 and 20x20?

73.
chuck
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XE1VE3OQC
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Posts: 20




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« Reply #9 on: March 22, 2010, 06:25:50 PM »

Hi Chuck,

What is meant by that is 10 vertical and 10 horizontal elements which are separated by an electrical 1/4 wavelength and fed in phase which in turn gives circular right hand polarization or left hand, depends on the feeding of the driven elements.You will see these antennas mounted in a X pattern on sat mounts. Sounds more complicated than it really is.
To get an idea look at M2 crossed yagis for 435 Mhz and you will see the way the elements are spaced.
By the way, if you choose to go with commercial units the M2 ones are the best choice for now and for the future HEO´s. Hy-Gain does not give you real circular polarization but a form of linear polarization, (Vertical/Horizontal) and their feed and relay system is quite questionable.
A lot of the old material for satellites such as books and how to set up a station still applies today, just some of the sat´s are no longer operational.
AO-7 for example was ¨dead¨ for about 23 years and then a shorted battery supply brought the bird back to life,..not bad for something made in the garages of Canada the U.S. and Germany in 1974.

One final note, basic earth station antennas are one-half of your OSCAR setup,don´t skimp on the antennas and coax.My antennas are only 24´from my radio room so that is not an issue.

Cheers,
Glenn,VE3OQC/XE1
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AF4XK
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Posts: 96




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« Reply #10 on: March 23, 2010, 02:58:00 PM »

Great info Glenn. I appreciate it.

73
chuck
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