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Old 11-19-2006, 04:07 PM   #31
Scorpion
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Quote:
Originally Posted by HomieG
They're seeing reduction in the sat signal because of other factors. In fact, that's why there is a repeater there, to cover that. But go ahead, believe what you want.
Believe what you want, but you are wrong. Spend a few minutes searching this site and you'll discover others have observed the loss of satellite reception in areas with strong repeater coverage. This can even occur in locations where the antenna has a totally clear view to the satellites. There's nothing unusual about this type of receiver behavior in the presence of a extremely strong signal. Try observing your antenna aiming menu next time you drive withing a few miles of a repeater.

http://www.siriusbackstage.com/forum...ad.php?t=89718
http://www.siriusbackstage.com/forum...ad.php?t=77092
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Old 11-19-2006, 07:29 PM   #32
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Quote:
Originally Posted by Scorpion
Believe what you want, but you are wrong. Spend a few minutes searching this site and you'll discover others have observed the loss of satellite reception in areas with strong repeater coverage. This can even occur in locations where the antenna has a totally clear view to the satellites. There's nothing unusual about this type of receiver behavior in the presence of a extremely strong signal. Try observing your antenna aiming menu next time you drive withing a few miles of a repeater.

You are interpreting the data wrong. And while there are some great and accurate posts at SBS, there are also a lot of misconceptions. Look at some of the SDARS receiver patents and SDARS receiver chips and you'll see the following.

There are dual-AGC's on the down converters in the receiver and their gain are controlled, individually, by the BER of the demodulated (but undecoded) signal. The receiver cannot use a single AGC because the strength of a terrestrial repeaters signal (several million times stronger than the strength of the satellite signal) would reduce the gain of the received satellite so quickly that it would cause cut-outs of the demodulated satellite signal, and the receiver needs to operate so as to minimize that possibility so there aren't interruptions when entering and leaving an area covered by a terrestrial repeater. So there are two, and some patents have even been filed for three (1x terr and 2x sat), AGC loops, each separately controlling the gain of the down converters. Remember, the digital modulation technique is different between the satellite and terrestrial signals as well, and based on several factors, what comes out as demodulated/decoded audio may be from either of the two signals (SAT/TDM or TERR/OFDM).

If the BER is such that one of the downconverters gain must be reduced, or increased, it is. There is a threshold such that the BER needs to be reduced to an acceptable rate. What you are seeing is an increased BER, therefore decrease in gain on the down converter for the sat receiver. I suppose you could consider that a desense, it's a direct, and correct function, of the receiver design. It is done on purpose, in an attempt to get the BER from the demodulted satellite signal into an acceptable range.

What the display shows is a function of the BER, and not the received signal itself, although one is dependent on the other.

It's even possible to see an increase in the sat signal on the display. A strong close-by signal can do that, such as some airport radar, home microwave, 802.11xx wireless signals, and other sources close to the SDARS 2.3GHz spectrum. That doesn't meant the satellite signal is stronger, rather it's an indication that the BER has changed, hence you are seeing what appears to be a stronger satellite or terrestrial repeater signal, when indeed it is not. In fact there have been reports that in the vicinity of an XM terrestrial repeater, the signal display on a Sirius receiver shows excellent strength, but alas no audio is demodulated and heard. Heck, there are postings on SBS that say they are getting excellent signal strength, but no reception. And I can personally attest to the fact that my display shows equal sat and terrestrial strength when passing the airport, yet I know for a fact that I am not receving the satellite. Why? Well the repeater was down for about a month earlier this year. Full sat strength, no audio. High BER, but who knows the cause or the source?

I can see that you and I may be trying to say the same thing. But it's not that the satellite receiver is being incorrectly desensitized because it's being swamped by the terrestrial signal. The receiver is operating exactly the way it is designed...to control the gain of the down-converter in the front end such that there is validation that either a TDM or OFDM can be demodulated/decoded to audio with minimal, and hopefully no, glitches or interruptions to the audio itself.
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Last edited by HomieG; 11-19-2006 at 07:48 PM..
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Old 11-20-2006, 05:04 AM   #33
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Quote:
Originally Posted by HomieG
There are dual-AGC's on the down converters in the receiver and their gain are controlled, individually, by the BER of the demodulated (but undecoded) signal.
That's nonsense. The AGC is set by the measured signal strength, not BER. The goal of the AGC system to keep the the signal level to demodulator relatively constant. BER provides little indication of the actual signal level and is a illogical choice to set receiver gain.

You are correct about the multiple AGCs, but that's a obvious requirement in a system like this. You are also correct the antenna aiming menu is a function of BER. This is a pretty much standard practices with digital communication systems. Something close 0% BER would represent a full scale indication and a higher BER a 1 bar signal. It might be possible for some external interference to produce a signal indication. But the odds of the seeing the correct modulation at the required symbol rate would appear to be slim. By definition interference will increase the BER meaning less bars will be displayed.

I've driven by the Sirius repeater in Phoenix and the antenna aiming menu of my Sirius radio was showing no satellite signal even with a perfect 360 degree view of the sky. The satellite reading slowly recovered as I drove away from the site. I've also parked directly next to a 30KW XM repeater. In that spot the Sirius radio had no reception and the antenna aiming menu had zero bars on both the sat and terr readings. Firing up my 2.4GHz Panasonic phone near the Sirius antenna causes my radio to lose reception and the antenna aiming menu to drop to zero bars. This directly contradicts the behavior you are trying to suggest.

Those cases of people seeing a good signal indication yet not having any audio is a Sirius chipset problem. I've seen this myelf and power cycling the radio often corrected the problem. This is unrelated to any type of interference

Most XM's radios have access to diagnostics menus that directly display the BER and AGC readings of both the SAT and TER channels as well of other useful information. When approaching a XM repeater site, one can first observe the TER AGC reading becoming progressively higher as it adjusts to the stronger signal. Usually the TER BER reading has gone down to 0% average (and often 0 absolute count) well before the AGC starts to increase significantly. As the repeater signal becomes stronger, the SAT BER readings begin to degrade. This first occurs to the satellite transponder adjacent to the repeater frequency but eventually impacts both transponders. With an extremely strong repeater signal, the SAT AGC increases until it pegs out. As that happens, the SAT BER readings will hit max and the satellite channels drop out of lock. However, the radio continues playing without missing a beat due to the terrestrial signal.

You are wrong about the AGC being controlled by BER. You also don't seem to understanstand that the slope of the IF filters aren't infinite. This is precisely why a strong signal from a repeater can impact adjacent band of frequencies, the SAT channels.

BTW, the satellites use QPSK modulation. TDM (Time Division Multiplexing) is the method of how the data is formatted within the bit stream.
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Old 11-20-2006, 10:42 AM   #34
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Well, I think the interference is coming from another terrestrial broadcast unrelated to Sirius. When the interference is present, the Sirius receiver loses lock on the data stream and that's that. Unless the source of the interference is located and corrected, the problem is going to persist.

P.S. XM is fine in that same area.
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Old 11-20-2006, 10:46 AM   #35
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Quote:
Originally Posted by Scorpion
That's nonsense. The AGC is set by the measured signal strength, not BER. The goal of the AGC system to keep the the signal level to demodulator relatively constant. BER provides little indication of the actual signal level and is a illogical choice to set receiver gain.
<snip the rest of the arguments>
Whatever.
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Originally Posted by Andrew-NYC: "...Just make a radio that gets both services, and there will be no need for the merger!"


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Old 11-21-2006, 07:17 AM   #36
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well, whatever the reason - my signal has gone from bad to worse.

from january to end of october, I almost always had 2 bars for satellite and 5 to full for terrestrial on the signal indicator (this is on a starmate replay - it is in my home and radio and antenna have not moved since january)

around the first week of November I started to get a lot of dropouts, and signal indicatow was no bars for satellite and constant fluctuation between 5 and full for terrestrial.

well, now its constant fluctuation between 2 and 5 bars for terrestrial (and of course none for satellite).

I called customer service - not helpful. They told me it MAY be a repeater problem in my area. The operator told me twice that my signal should improved as I drive thru a new area (and I had to remind her twice that my radio is in my house and does not move)


Well, I did enjoy it when I could get a signal - but now the thing is off and I'm done.
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Old 11-21-2006, 08:11 AM   #37
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Quote:
Originally Posted by cagwa
well, whatever the reason - my signal has gone from bad to worse.
And where are you located? That's helpful for readers who might also be in your area.

I hear you about them not listening. I don't know what goes on in that call center that is so distracting but they need to start listening to their customers before they don't have any. I think they need to revamp that entire operation because it's awful. I may not have cancelled if I thought Sirius as a whole was more attentive to my concerns.
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Old 11-21-2006, 09:56 AM   #38
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Angry Poor signal in Los Angeles

So my Sirius radio is in my car. My job is driving in Los Angeles. Right around the 13th of November my radio signal started dropping constantly. This made my radio unlistenable. Dealing with customer service has been a nightmare. Most of them act as if I'm an isolated incident. One of them said it must be a problem with my radio or antenna. As a result I bought a new Sirius One radio, went through the hassle of installing it, and ended up with the same problem. I called Sirius yesterday, fed up with the poor reception and awful customer service and requested to cancel my subscription. They transferred me once again and said the problem was with my radio, “The Sirius One radio is an inferior product”. This doesn’t explain why my old radio has worked fine for the past 11 months. Well their solution is they are sending me a new radio (at no charge) and they say this should solve the problem. I kind of doubt it, but I figure I might as well give it a try. As for the people who are trying to impress themselves posting the most technical arguments they can come up with, I’ve find this annoying and pointless. The point is, many of us seem to be paying for a product that is not working.

Last edited by silenciox3; 11-21-2006 at 10:04 AM..
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Old 11-21-2006, 10:03 AM   #39
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Quote:
Originally Posted by silenciox3
As for the people who are trying to impress themselves posting the most technical arguments they can come up with, I’ve find this annoying and pointless.
Yeah, it's kinda like when dumbasses post the same message twice in the same post. Even though you've since edited that out. Is that what you mean?

If the technical discussion is above your comprehension, maybe you shouldn't read those posts, eh?

The new radio isn't going to fix the problem... I guaranteee it. That's based on technical information I won't annoy you with.
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Old 11-21-2006, 11:02 AM   #40
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Skylooker, I wasn't refering to your post, I understand what you are talking about. I was refering to the arguments between HomieG and Scorpion. It's really too bad you thought I was talking about you when I'm in the same boat that you were in. All I wanted was a straight answer from sirius aknowledging the problem and giving me some info if they plan on doing something about it.
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Old 11-21-2006, 11:03 AM   #41
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hey Skylooker

I'm in the Playa Del Rey area. I have a friend in Venice and one in Eagle Rock experiencing similar issues with their reception.
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Old 11-21-2006, 11:37 AM   #42
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Hey cagwa... it's horrible in Downtown LA (last I checked) over by the 10 & the 110. Where I live near the 210 & the 15, it's not bad at all. That's why I think it's not a repeater issue but rather something on teh ground interfeing with the satellite signal. There's no repeater near the house but the signal is fine. When I get into Downtown LA (under clear skies) the reception is awful. It magically clears up when I get close to work at Wilshire & Hauser on the Miracle Mile. There's a repeater right at that intersection (perhaps on the roof of our really tall building). I think the repeater is powerful enough to step on the interfering carrier and maintain a good Sirius signal.

Anyhoo, if they ever fix it, I'd love to activate my account again... maybe!
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Old 11-21-2006, 04:59 PM   #43
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I have the same problem with downtown LA and the hollywood area. Its really a problem. I am calling them as we speak.
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Old 11-21-2006, 06:10 PM   #44
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Default signal drop outs in L.A.

I'm getting signal drop outs in Koreatown, Silverlake, Hollywood, Beverly Hills, pretty much everywhere I try and use my radio. Hopefully if more people tell Sirius about this problem, they will try and fix what has been going on. I know if the reception remains this way for much longer I will be forced to cancel my subscription. Has there been any problems with XM in L.A.?
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Old 11-21-2006, 07:26 PM   #45
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We are experiencing the same issue here in Denver. Someone called and said that Sirius is aware of the problem and are working on it.

http://www.siriusbackstage.com/forum...ad.php?t=90812
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