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Author Topic: SAT?  (Read 20267 times)
N5TEN
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« on: August 20, 2012, 09:46:24 AM »

Anyone know what this SAT pair is?  Uplink 145.850 FM Downlink 436.875 FM

Right now I'm hitting it by pointing my antennas due west from my QTH in No. Calif. I can't find this exact pair anywhere on AMSAT yet, so I sent them an email. I'm very new to this SAT thing, so forgive me if I'm missing something about it.

Thanks
N5TEN/AE
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WD9EWK
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« Reply #1 on: August 23, 2012, 04:46:01 PM »

Anyone know what this SAT pair is?  Uplink 145.850 FM Downlink 436.875 FM

Right now I'm hitting it by pointing my antennas due west from my QTH in No. Calif. I can't find this exact pair anywhere on AMSAT yet, so I sent them an email. I'm very new to this SAT thing, so forgive me if I'm missing something about it.


The 145.850 MHz uplink is used by two satellites, AO-27 and SO-50.  The downlink for these two satellites is around 436.795 MHz +/- for Doppler.  You would need to transmit with a 67.0 Hz tone to be heard through SO-50, and AO-27 does not require a PL tone.

73!
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Patrick WD9EWK/VA7EWK
http://www.wd9ewk.net/
N5TEN
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« Reply #2 on: August 23, 2012, 05:41:24 PM »

Hey thanks for coming back to me, but I'm really trying to get to the bottom of this frequency pair.  I have a basic understanding of sat operations, the PL enable/operation with SO-50, and I'm able to track the AO-27. This doesn't seem to be either sat.

Anyone know what pair this could possibly be? Can either of these sats reflect my TX without a PL enable, or tracking up with down/up links and just the pair: 436.875 downlink and 145.850 downlink?

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KQ6EA
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« Reply #3 on: September 02, 2012, 08:51:11 PM »

Satellites don't "reflect" your signal. They repeat it. SO-50 needs two PL tones; one to enable the timer onboard, and a second to pass your uplink signal.
AO-27 doesn't need a PL, but is only turned on for a few minutes of each pass. Listen for the "packet" burst at the beginning of a pass, and then at the end.
The ONLY two operational satellites with a 145.850 uplink are SO-50 and AO-27. Their downlinks are both 436.7950.
AO-7 has an uplink of 145.800~145.900, but its downlink is 29.400~29.500.
How do you know you're "hitting it"?
Can you hear any other stations on it?

Jim
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N5TEN
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« Reply #4 on: September 02, 2012, 09:02:15 PM »

Satellites don't "reflect" your signal. They repeat it. SO-50 needs two PL tones; one to enable the timer onboard, and a second to pass your uplink signal.
AO-27 doesn't need a PL, but is only turned on for a few minutes of each pass. Listen for the "packet" burst at the beginning of a pass, and then at the end.
The ONLY two operational satellites with a 145.850 uplink are SO-50 and AO-27. Their downlinks are both 436.7950.
AO-7 has an uplink of 145.800~145.900, but its downlink is 29.400~29.500.
How do you know you're "hitting it"?
Can you hear any other stations on it?

Jim

I can hit "it" (whatever it is) only at certain times during the day. Sometimes I follow "it" with my beam from south west to due west and then it eventually disappears. I have never heard anyone on it. It's an echo'y fluttering come back on my voice which dissipates over time as whatever it is travels. I'm pretty sure it's not SO-50 (no private line needed (PL)). I have no idea if it's AO-27, but probably not because of the downlink.

That is why I'm so stumped on this. Could it be a bounce from something traveling in space?

Thanks.
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KQ6EA
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« Reply #5 on: September 02, 2012, 09:13:56 PM »

Extremely unlikely unless you're using a huge antenna array and full legal limit. These things are just too small to reflect any meaningful signal, and even if you could hear it, it would be on the same frequency you're transmitting on
Is there any delay between when you key up and you hear your own downlink coming back to you?
What are you using for a radio, and what antenna?
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N5TEN
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« Reply #6 on: September 02, 2012, 09:26:59 PM »

That's what I figured.

Yes, I hear the downlink and it fades in and out as the thing moves. I'm using a Yaesu FT-847 with a 10 element 2m beam (horizontal), with a 5 element UHF horizontal yagi. No meaningful delay. My voice comes through as I speak, but it's obviously filtered through whatever I'm going through and it's only when the "object" is in the south west to due western sky.  And only on those specific frequencies...with slight deviation.

Ideas?

By the way...I emailed AMSAT about it and got no response.
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KQ6EA
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« Reply #7 on: September 02, 2012, 09:39:35 PM »

"No meaningful delay"

You're hearing your own 3rd harmonic. It's very common to have this happen when you're first getting started, and it's easily corrected.

AMSAT has an article on a cheap, easy fix, and it's what I use.

http://www.amsat.org/amsat-new/articles/Mode-J/
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N5TEN
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« Reply #8 on: September 02, 2012, 10:08:34 PM »

I wish it were that easy to explain. Remember, I can only hit it during the day at certain times for a limited amount of time and only in the south west or due west directions, with other directions fading the signal completely as the rotor turns out of those headings. This only happens at certain times during the day with my voice coming back to me clearly with slight flutter and echo, but only when the rotor is pointed West or South West.

Right now, I have nothing there.  No echo or voice or noise or anything on TX.
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KQ6EA
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« Reply #9 on: September 02, 2012, 10:15:06 PM »

If there's NO delay, it can't be a satellite.
Laws of physics and all that stuff.....

Another check to make is to use an online tracking program, and cycle through the satellites listed the next time this happens, and see if there are any in range.
Heavens Above is one:
http://www.heavens-above.com/

And AMSAT has another:
http://www.amsat.org/amsat-new/tools/predict/satloc.php?lang=en&satellite=AO-51
« Last Edit: September 02, 2012, 10:19:02 PM by KQ6EA » Logged
N5TEN
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« Reply #10 on: September 02, 2012, 10:17:53 PM »

How long of a delay are we talking about?  seconds? milliseconds? There is a delay, but it's like speed of sound kind of delay...not long. What's the length of a sat delay?
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N5TEN
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« Reply #11 on: September 02, 2012, 10:19:37 PM »

Maybe I'll get a cross mast and separate the antennas more...see what happens. I'm skeptical about the desense thing because of the other variables involved. Believe me...I thought of it. uggh.
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KQ6EA
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« Reply #12 on: September 02, 2012, 10:20:25 PM »

It depends on the altitude of the satellite. Definitely noticeable on a satellite like AO-7, and less, but still noticable, on satellites like AO-27.
You're using FM, right?
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N5TEN
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« Reply #13 on: September 02, 2012, 10:27:05 PM »

Yeah...FM. If it were harmonics and desense, you'd think it would replicate every single time. This situation only happens at certain times in the late afternoon, early evening and only when I point my antennas at it in the western sky.

There's nothing in front of the antennas when I point them west, other than my Rohn 25 tower about 20 feet away and south of the angle of where I am getting the response....

I'll do some more experimenting and see what other things I can notice about it tomorrow.
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KQ6EA
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« Reply #14 on: September 07, 2012, 07:57:57 PM »

Any progress yet?

I'm very curious as to what you find.

Jim
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