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Galaxy Nation Explore the other side of the universe. Discuss AM/FM, XM, DISH, DirecTV, HD Radio, and all mp3 players. Here you can also discuss the ins and outs of tomorrow's radio technology...where music and satellites collide. Who said it's not rocket science?!?

 
 
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Old 08-02-2005, 05:44 PM   #1
NHTracker
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Default Can any techie with satellite experience answer this?

I have noticed that about an hour before the western satellite sets over the equator I no longer receive a signal from that satellite at all in New Hampshire and most of New England for that matter. According to my satellite tracking program the satellite is still 14 to 22 degrees above the horizon in New Hampshire yet, I can't receive a signal from it. This is even with my car next to an open field completely void of trees with a southwestern view. It just doesn't make sense to me.

The way I know that I'm only receiving one sat is by the signal strength meter. When three bars are present it indicates that both sats are being received. When only two or one bars are received I'm only receiving one.

The very second the western sat is deactivated and the eastern one takes over at the equator I bounce right up to three bars. Obviously this is because the eastern sat is much higher than 22 degrees in the sky relative to my location when the switch occurs.

My discontent with this is due to the fact that during this "critical hour" prior to the sat swap my radio drops out like crazy, especially where foliage and overpasses are concerned. Without that second sat my radio, and others in my area, cannot receive the crucial 4 second delay to augment service when the northern sat is blocked by something while driving.

For example, on Sunday the sat swap occured at 1:39PM EDT. From 12:30PM until the switch at 1:39PM I was driving on I-95 from Augusta to the Portland area. Prior to 12:30 I was receiving three bars consistently as I-95 is pretty much in the open. From 12:30 to 12:50 I would bounce from two to three bars, even though I was still in the clear for the most part. From 12:50 to 1:39 I received no more than two bars period. Because the reciever was no longer able to receive a signal from secondary sat I lost the 4 second backup delay. This meant that every single overpass I'd drive under no matter how small (Most overpasses on I-95 in New England are not very wide) I'd get a dropout 4 seconds AFTER I completely cleared the overpass. The reason is obvious, unable to receive the 4 second delay from the secondary sat (which is transmitted simultaneously with the "live" feed from the northern sat), apparently because it is too low in the sky to be received in New England one hour before the switch at the equator, the receiver is unable to compensate for the data lost while driving under the overpass now matter how brief. At that point the receiver uses up it's own internal 4 second buffer and subsequently drops 4 seconds after you have long since cleared the overpass. It's very annoying to say the least. Of course after the sat switch at 1:39 I no longer had any problems with overpasses.

It's really too bad that Sirius didn't untilize XM's diversity. BOTH of XM sats broadcast a primary and 4 second delayed signal. Therefore it's not a problem if you pass under an overpass while only receiving a signal from one of their sats, as you already have the 4 seconds of unplayed data stored in the receiver. As long as you clear the overpass within 4 seconds your golden. Of course the same goes for Sirius, except with Sirius you MUST receive the signal from both sats prior to a temporary obstruction in order to prevent a dropout. But what the heck are you supposed to do when Sirius allows their sat to drop so low on the horizon for the New England region? I also imagine that those in the Pacific Northwest suffer from the same problem we do except their problems begin when the switch is made to the eastern sat.

Can't Sirius solve this problem by changing the orbit path so that the east and west sats can handoff at say 10 degrees north latitude instead of the equator in order to guarentee that both east and west sats will be high enough in the sky for the northern corners of the country at all times to maintain diversity? It would make sense wouldn't it?

BTW: I move to Houston, TX next week and won't have to worry about this issue anymore thankfully. Also my observations of this problem span the three years I have been with Sirius. No matter what equipment I have used the results are still the same.
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Old 08-03-2005, 12:30 PM   #2
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Ahh, finally someone who states the same problem I've been writing about! Search back under this space nation and read the posts I've made on this in the past! Here in the Northeast, the times you state change very slowly as the months go by and the sats also move (look at an online sat finder like orbitron) and you'll see that the exact same problem/drop you have today at a certain time will be the same when the sats move (time wise) a few weeks down the road. SO that it's a problem with the orbit of the given sat.

As for Sirius changing the sats in any fashion, be it however slight. Not a chance. Sirius likes the higher orbit (as they say) as they feel it is more beneficial rather than harmful.

FYI, now that I have my TERK6 antanna at home, the lowest I get is one bar, no more drops. Before it I'd get a drop 1-3 times a day for a minute or so.
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Old 08-03-2005, 07:01 PM   #3
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Default Re: Can any techie with satellite experience answer this?

Quote:
Originally Posted by NHTracker
BOTH of XM sats broadcast a primary and 4 second delayed signal.
My understanding is that each XM satellite transmits 2 "ensembles", each of which are at a different frequency. But I think that each ensemble represents 1/2 of the XM data stream (i.e. about half of their channels; each ensemble is 1.84 MHz wide). So even if there is a 4-second delay between these ensembles, it's not as if each XM satellite transmits the entire XM package, at different frequencies, 4 seconds apart. There isn't the space to do this given that each satellite only has about 3.8 MHz of bandwidth. See Figure 3 at:

http://beradio.com/features/radio_fi...own_satellite/

This is in contrast to the Sirius system, in which each satellite transmits the entire package at one frequency per satellite (as you point out).
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Old 08-03-2005, 07:07 PM   #4
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First a correction and then a suggestion. XM does not send the signal and the signal time delayed from each satelite (neither XM or Sirius has the bandwidth to send their signal out in 4 copies). XM3 (east coast one) is the live one (I think). XM1 and 2 the west coast ones send the 4 second delay.

Now for the suggestion:
Even though the satelite radio antennas are omni-directional, they are adjusted for a particular elevation range. The Sirius antennas are adjusted to look mostly for signals coming from higher elavations (where the satelites are most likely to be) The XM antennas are adjusted for lower elevations (where their satelites are most likely to be). So the suggestion would be to try using an XM antenna with your tuner and see if that improves your reception during the time of day that the second satelite is lower in the sky.
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Old 08-04-2005, 10:55 AM   #5
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Quote:
they are adjusted for a particular elevation range

Intersting blackstar, that makes sense and is another positive argument for antenna diversity systems. Having multiple antennas "tuned" to varying quandrants in the sky. Extreme but interesting.
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Old 08-04-2005, 07:13 PM   #6
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Even still, I just don't understand why Sirius would believe that elevations of 11 to 20 degrees in some of the most densely forested areas of the country is acceptable. Even if I could get a signal from those elevations it wouldn't matter because almost everything you could imagine would block it.
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Old 08-05-2005, 11:24 AM   #7
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Quote:
Even if I could get a signal from those elevations it wouldn't matter because almost everything you could imagine would block it.
Makes you wonder why so many buy XM doesn't it? I am curious about this because my antenna locations would block those low elevations yet I get perfect signal all day. Perhaps it is my elevation relative.
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Old 08-07-2005, 08:49 PM   #8
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Quote:
Originally Posted by RoadClosed
Quote:
Even if I could get a signal from those elevations it wouldn't matter because almost everything you could imagine would block it.
Makes you wonder why so many buy XM doesn't it? I am curious about this because my antenna locations would block those low elevations yet I get perfect signal all day. Perhaps it is my elevation relative.
The elevation values differ depending on your location in the country. For instance, those living in Oklahoma City would have no idea about what I was talking about in my first post. The reason for this is that both active sats are always high enough in the sky at all times, even when they are way down near the equator. For example, even when the east and west sats are handing off at the equator they are both still at least 35 degrees above the horizon in OKC, which is enough to maintain the signal diversity. Of course at the same time in Bangor, ME it is only a mere 13 degrees for the western sat prior to the hand-off, which as I stated, is not high enough to receive a signal. The flip side of this is Seattle. When the rising eastern sat takes over for the setting western one, the elevation is also a mere 13 degrees just like Bangor.

As Blackstar said, perhaps the Sirius antennas aren't properly designed to provide enough gain at those low angles. That would explain why I can't get a signal even in the wide open. Even still, 13 degrees can easily be blocked by a small tree let alone a mature one at a distance, so I don't think antenna look angle or gain is going to help much.

I know Sirius must know about this problem. After all New England is a summer playground for the folks from New York, and I'm pretty sure Sirius management has visited this area at some point and experienced the same thing I have. Hopefully they will be able to come up with a solution in the near future.
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Old 08-08-2005, 06:38 PM   #9
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NHTracker,

Corporate management visitation does make a huge impact. I was a cell phone interconnect engineer once... seems like wherever the CEOs from several major similar comporations meet, a new cell tower was close behind. Especially when trying to impress "fiends" with their new toys.

Thank you for the detailed information. I am lucky... I am above 6ooo feet. Smack in the middle of America.
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Old 08-09-2005, 11:11 AM   #10
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I've been watching this link, waiting for some other "senior" members to give their pro Sirius views for the sats and how they work for all elevations of the country (I've said the opposite for many months here). But nobody has posted yet.

As I posted back in the early winter months of this year, I'm located on the high Pocono Mountains in PA. Still at the handoff times, my sats go to 1 bar and used to drop out for a few minutes before I got the TERK6 antenna. But still a senior member posted that he could not see why that was happening as if the antenna is on the roof, the sats elevation is good "all over America."

But now we have some members who seem to be more adapt in the technical aspects of this, so we'll see.
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Old 08-10-2005, 12:27 AM   #11
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Nope, you are right Foxcraft. According to Orbitron the Pocono Mountains see an angle of 36 degrees exactly an hour prior to hand-off and it quickly goes down to 19 degrees at hand-off. From my experience anything below 30 degrees your bound to have problems at some point. That is unless you can hold a constant signal from the northern sat during this time. If your in a relatively flat area with few nearby trees you shouldn't have too much trouble doing that. But if your not, and especially if your driving, your going to have problems.

Just prior to hand-off for the western sat, I've placed the 30 degree elevation line roughly from Miami, up through Atlanta, Nashville, southwest Kentucky, Southwest Illinois, central Iowa, northeast South Dakota, and central North Dakota. The further north and east from that line you go your going to have issues if you lose sight of the northern sat even if only for a second or two. As I said, it starts about 1 hour prior to the hand-off and gets progressively worse.

On the flip side, when the eastern sat crosses the equator the 30 degree line is drawn from Tucson, northwest New Mexico, southeast Colorado, central Nebraska, extreme southeast South Dakota, and southwest to northeastern Minnesota. So the further north and west you are from that line, the more problems your going to have up to 1 hour after hand-off.

An hour doesn't seem like much but it happens three times a day, and at least twice during the average person's waking hours. If you just happen to be driving somewhere during these times it can be kind of annoying.

Here are the hand-off times for the rest of the month. If you have any problem with reception near these times it is due to the reasons I've cited. You'll notice that they all roll back 4 minutes each day. The times are Eastern time so just adjust for your time zone.

8/10/05 4:50AM, 12:58PM, 8:56PM
8/11/05 4:46AM, 12:54PM, 8:52PM
8/12/05 4:42AM, 12:50PM, 8:48PM
8/13/05 4:38AM, 12:46PM, 8:44PM
8/14/05 4:34AM, 12:42PM, 8:40PM
8/15/05 4:30AM, 12:38PM, 8:36PM
8/16/05 4:26AM, 12:34PM, 8:32PM
8/17/05 4:22AM, 12:30PM, 8:28PM
8/18/05 4:18AM, 12:26PM, 8:24PM
8/19/05 4:14AM, 12:22PM, 8:20PM
8/20/05 4:10AM, 12:18PM, 8:16PM
8/21/05 4:06AM, 12:14PM, 8:12PM
8/22/05 4:02AM, 12:10PM, 8:08PM
8/23/05 3:58AM, 12:06PM, 8:04PM
8/24/05 3:54AM, 12:02PM, 8:00PM
8/25/05 3:50AM, 11:58AM, 7:56PM
8/26/05 3:46AM, 11:54AM, 7:52PM
8/27/05 3:42AM, 11:50AM, 7:48PM
8/28/05 3:38AM, 11:46AM, 7:44PM
8/29/05 3:34AM, 11:42AM, 7:40PM
8/30/05 3:30AM, 11:38AM, 7:36PM
8/31/05 3:26AM, 11:34AM, 7:32PM
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Old 08-10-2005, 11:47 AM   #12
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NHT:
What you're saying I agree with totally. However the times for me are off by 4 hours. Yesterday (Tuesday) using my other "small box" antenna (comes with boombox) the times that were dropped were:
12:30 AM----8:30AM----4:30 PM.
Today so far the problems were within the same range.

Back a few months ago it was happening around 1:30 PM and so on.

Now looking at Orbitron Sirius S#3 was starting to leave the top oval and S#2 starting to enter it.

Last fall when I first got Sirius (for the NFL) it really bugged me each Sunday when the games would drop late in the afternoon for the 4PM games (I didn't realize what was going on).

So with the info I just said, what's happening?
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Old 08-12-2005, 08:23 PM   #13
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Quote:
Originally Posted by Foxcraft
NHT:
What you're saying I agree with totally. However the times for me are off by 4 hours. Yesterday (Tuesday) using my other "small box" antenna (comes with boombox) the times that were dropped were:
12:30 AM----8:30AM----4:30 PM.
Today so far the problems were within the same range.

Back a few months ago it was happening around 1:30 PM and so on.

Now looking at Orbitron Sirius S#3 was starting to leave the top oval and S#2 starting to enter it.

Last fall when I first got Sirius (for the NFL) it really bugged me each Sunday when the games would drop late in the afternoon for the 4PM games (I didn't realize what was going on).

So with the info I just said, what's happening?
I forgot about that one. Yeah that's also a problem because the sats are practically right next to each other which obviously kills the spatial diversity. That problem doesn't seem to affect me too much in comparison to the other. To be honest the standard home antenna is a P.O.S. It seems better geared toward those who receive a repeater signal. Reception with a car antenna in the home is substantially better.
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