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Laxdude |
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Wednesday, February 8, 2006 at 8:11 AM Does the volume of the radio signal change for the time of day on purpose? ie louder in the AM, quieter in the PM? I come at this from an odd set up. I listen to KNDD Seattle via cable radio. The signal is picked up by a local cableco antenna (I think) and is then sent down the coaxial at a different frequency. I have a set up that I just turn on, so the volume remains untouched. For some reason, when I listen to TACS in the morning I have to turn down the volume from the nights LL. Then when I listen to LL, I have to turn it up. I am pretty sure this is not me, but I do not exactly have the meters to prove it. Is it me, or the signal? Satellite Radio - local frequencies, Amber Alerts, and EBS I understand that Sat radio uses city-based transmitters to bump up the signal. How do they do this? I would guess that they broadcast on another frequency, and the radio unit goes with the strongest...and they do not broadcast on the same frequency. Does each station have a preset sat and local feed programmed in? Since it has local, city based transmitters, does that then mean they are subject to the EBS and Amber Alerts? And finally, what are the specs of the Satellite radio signal? What part of the spectrum does it fall into. What is the true quality they usually broadcast in? I have heard some people with 'good ears' complain about the quality in the past, is that still the case (comparing it to early low-bitrate mp3s)? Since it is digital, I am sure that it suffers from over compression just like on digital cable. —Laxdude |
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24/7KROQ |
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Wednesday, February 8, 2006 at 1:23 PM Radio stations have equipment to process all the audio to try to keep a constant level amongst voice, music, satellite feed, etc. So the difference between Loveline volume and the morning show volume shouldn’t be that great. It’s still possible. For every Starguide receiver, ISDN audio unit, music channel and microphone there are separate audio processors. And, one last overall mix processor called an Optimod. Optimod is put before the transmitter to protect against over modulation just incase a processor unit before it fails. Now what I am thinking is that since your method of listening comes through your cable provider they may have there own direct connection to KNDD. In that case the Optimods mix wouldn’t be needed, since there is no transmitter to protect against over modulation. So maybe you are hearing the difference between two different units’ settings. Try listening one day and night on a normal radio and see if you can also hear the difference.
Satellite radio is on the S-Band- 2.3GHz. Instead of many transmitters being at ground level a couple are up in space and cover a much wider area. Of course the signal has to travel a good distance to get to the ground so it weakens a bit. A densely populated city with skyscrapers makes it impossible for the signal to penetrate through so they install ground repeaters for that area. Exact same signal just being broadcasted from lower power ground transmitters. No local alert systems can break in to the feed.
The audio is compressed so more channels can fit on each services allotted space. It’s not the same quality for all channels though. To make more music channels available the talk only channels will have a lower bit rate so it takes up less space. It will also likely be in mono instead of stereo. I personally am not too impressed with the audio quality; I have Sirius satellite radio service. They say near CD quality but it’s not as close as it should be. I would say there music sounds like 96kbps using an mp3 pro codec.
Hope I helped and didn’t sound confusing.
—24/7KROQ |
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ZT-In-Exile |
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Wednesday, February 8, 2006 at 1:56 PM Если вы читаете это, то ты поставляете сфинктеры.
You're post is also sexist as you assume there are no "radio girls" out there.
—ZT-In-Exile |
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NYBret |
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Wednesday, February 8, 2006 at 2:28 PM Another possible explanation for the decrease in volume at night... Many broadcast stations are required to "power down" in the evening. RF travels much farther at night; therefore, many stations need to decrease their signal wattage at sunset to prevent interfering with other distant stations broadcasting on the same frequency. This "power down" can result in an audible decrease in volume and increase in white noise (caused by lower signal strength). The station powers up again in the morning, possibly explaining why the morning show sounds louder than Loveline. I work at a 10,000 watt AM station which, due to its location on the Monterey Bay, has a signal that covers as much terrain as a 50,000 watt station (nearly 1/3 of California during the day). At night, we are required to power down to 1,000 watts. If we do not power down at night, our signal can be heard in Austin, TX. There are a limited number of broadcast stations which maintain a signal strength of 50,000 watts day and night; they are known as clear channels (which has nothing to do Clear Channel Communications). —NYBret |
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Dark Laith |
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Wednesday, February 8, 2006 at 3:00 PM RF travels much farther at night —NYBret Whyzat? —Dark Laith |
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NYBret |
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Wednesday, February 8, 2006 at 3:32 PM
Edited Wednesday, February 8, 2006 at 3:34 PM Laith - As I understand it, the ionosphere is at a lower altitude during daytime, meaning that RF must essentially fight through it. The ionosphere is at a much higher altitude at night, and thus does not hinder the strength of an RF signal. Therefore, an RF signal with a constant wattage will travel farther at night than it will during the day. Powerful stations will broadcast at a higher wattage during daytime to power through the ionosphere, and a lower wattage at night to prevent the signal from traveling too far. My station has gotten calls from people who can hear our nighttime (1 kilowatt) signal clearly in Boise, Idaho. This is a phenomenon known as RF harmonics. Our signal bounces off the ionosphere, like a laser-pointer reflecting off a mirror at an oblique angle, and can be clearly received in a very distant, isolated location. —NYBret |
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Laxdude |
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Wednesday, February 8, 2006 at 4:37 PM Thanks for the info...I knew if I asked here, someone would answer. I am pretty sure my cable co just has a big assed directional somewhere. Sometimes it just fades out completely, and other nights you can hear it fall out of tune and go to static over a half hour as it wanders (damn seagull). I doubt they would put any money into radio over cable (hell, most people do not even know you can runt he co-ax into your receiver. Maybe they can get it on microwave...I wonder if anyone is using the old telco microwave corridors? Maybe they can tap into the re-broadcaster feed? I would try to listen by radio, but I am more than 300 miles, and I am pretty sure we have local stations on either side that will blow it out. I just wondered it they might have different levels for different times - or that people might like louder at night, while it might blow people away in the morning.
How is it that the local repeaters can operate on the same frequency, wouldn't there be a processing delay...(but, I am thinking analog) that would interfere with the original sat feed?
My brother-in-law runs the back room for the BBC in London, and he is always complaining about the over compression he is forced to do, and how horrid the quality ends up when it gets to a TV.
I wonder when clear channel is going to go after Sat radio, and force them to carry local stations like they did with Sat TV? —Laxdude |
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MajandraFan |
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Wednesday, February 8, 2006 at 9:05 PM
Edited Wednesday, February 8, 2006 at 9:07 PM Digital short wave radio will dominate the universe!
NHK, leading the way. p.s. that doesn't rhyme in japanese p.p.s. i love the radio series of coupling on the bbc, i want it on dvd audio in 22.2 channel surround sound —MajandraFan |
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Colin |
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Wednesday, February 8, 2006 at 11:06 PM
Edited Wednesday, February 8, 2006 at 11:09 PM I was parked in Mountain Home, ID in the summer of 2004. Here's a graphical representation of the stations I could hear:  I know the San Francisco station has 50,000 watts, but I would bet the others do as well. —Colin |
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Laxdude |
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Wednesday, February 8, 2006 at 11:16 PM I was once shocked when I pulled in a station from the great lakes area, from just outside of Vancouver. I am not sure if it was a water thing, but I was in a parking lot way out on a man made ferry terminal, the causeway out must be near 3/4 a mile. And it was with a stock car antenna. It was also at night, and during an incredible cold snap that had dumped massive amount of snow The signal wasn't great, but you could hear and understand it, no way that will happen when everything goes digital. —Laxdude |
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MajandraFan |
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Wednesday, February 8, 2006 at 11:26 PM Digital signals are much better than analogue for travelling great distances.
Of course it tends to be all or nothing so you'll never get the almost-there signal, but in your situation a digital signal would have given you a strong clear sound. —MajandraFan |
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Laxdude |
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Thursday, February 9, 2006 at 6:51 AM But since digital has a lower power requirement, they usually scale back the signal strength - hey, anything to save a buck. So the coverage area ends up being the same, but since digital is an all or nothing...you end up getting a lower coverage area. I wonder if the FCC is ever going to make radio go all digital...that would surely kill the industry. And the reason I am not sexist for asking advice to a "radio guy"...is because we have, what, 5 females at most who post here...and easily as many guys who happen to work in radio. —Laxdude |
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Brice |
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Thursday, February 9, 2006 at 7:35 AM Living in the South, I've happily listend to stations from Canada, New Orleans [when Katrina Hit] New York (880WCBS comes in clear as a bell,) and from LA. Now, when E-skip occurs on the FM dial, that's a radio geek's party! —Brice |
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bguirk |
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Thursday, February 9, 2006 at 9:32 AM Back in the Wolfman Jack era and before stations would broadcast out of Mexico at high wattage to avoid regulations and be able to reach most of the continental US. —bguirk |
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NJC |
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Thursday, February 9, 2006 at 10:04 AM
Edited Thursday, February 9, 2006 at 10:06 AM You guys (and girls, sorry) should know that the Frequency and Mode (among other things) affect the propogation and receivability of radio signals. I will try not to ramble, but there seems to be an interest in this stuff... Starting with Laxdude's question and Anderson's response (at least I think that's Anderson):
The RF power level of any transmission that is digital, has no effect on the perceived audio volume at the receiver. Either you get the information exactly as it was intended, or you don't get it at all. The volume levels are handled by the electronics at the source and the receiver. They employ AGC circuitry (automatic gain control), which try to keep the levels acceptable. However, these levels are probably adjustable in hardware or software at both ends. If you are experiencing different levels, it's probably the equipment at your cable co. When talking about AM broadcast stations, there are two things to consider: The Frequency (880 KHz, KiloHertz, Thousand cycles per second so 880,000 cycles), and the Mode (AM, or more precisely, double-sideband AM).
These frequencies DO NOT bounce off of the ionosphere, as their frequency is too low. They travel strictly by Ground-Wave Propogation, meaning they travel along the earth. AM stands for Amplitude Modulation, which means we alter the amplitude (or strength) of the signal in order to put information on it. The receiver is able to "detect" these variations in amplitude, thus allowing you to hear your ranchero music (with accordions of course). The problem with AM is that local interference (such as a lawnmower) can mix with signals being received by your radio and cause interference.
[Try it: tune an AM radio to a station, then fire up your garbage disposal, or can opener --anything] This is part of the the reason propogation is so much different at night than during the daytime. During the daytime, the sun is beating down on our portion of the earth with all kinds of radiation. This requires the AM signals to be MUCH stronger so that the receivers can detect your radio station over all of the other junk. This junk is called the "noise floor". It's how much crap is already present before we even think about sending a radio signal. Our signal must be strong enough to rise above this noise floor, or all we will hear is noise. At nighttime, when the sun is gone (and factories shut down, etc) there is a much lower noise floor. This allows us to recieve stations that we don't have a chance hearing during the day. This is also the reason why stations have to switch to low power at night. If they didn't, they could interfere with other stations 100's (or even 1000's) of miles away. What about FM broadcast?
The FM broadcast band ranges from 88-108 MHz. Notice the "M". MHz = MegaHertz or "millions of cycles per second", 88,000,000 cycles. These frequencies also do not bounce off of the ionosphere, they are too high. They also do a much poorer job with Ground-Wave (which is why AM stations tend to have a larger listening range than FM). They are primarily Line Of Sight, meaning you have to see it to receive it. Since the transmitters are so strong, and closeby, you don't actually have to SEE the tower, but you can't go very far before you lose the signal. Typically, the higher in frequency you go, the more tight the line-of-sight rule is (microwaves [10+ GHz]can be blocked by a pine needle).
Try your test with the garbage disposal with an FM radio. You won't hear any interference, or not much). This is because with FM, we don't care about the amplitude (strength) of the signal, we care about the Frequency. Instead of altering the amplitude of the signal to send our ranchero music, we alter the frequency. Local noise sources may still cause distortions to the amplitude, but since we aren't looking at the amplitude, we don't care. This is also the reason for the big spacing between stations on the FM dial (106.7, 106.9, 107.1, etc). Any closer, and they would step on each other. If it were digital however, we could fit A LOT MORE (10 times..100 times?) stations between 88-108. The "skip" that is sometimes reported on the FM broadcast band usually is not skip at all. In fact its something called "tropospheric ducting" or "tropo" for short. During changing weather pattens, "ducts" of warm air can become trapped between colder air above and below. Radio signals can get trapped in these ducts and bounce off the cold air above and below. Depending on the length of this duct, and the difference in temps, you can hear an FM station several hundred miles away. So what does bounce off of the ionosphere?
Usually between 3 - 30 MHz. This is commonly referred to as "shortwave". Depending on things like the sun, cosmic rays etc, the layers of the ionosphere become charged with radiation. Sometimes up to 50MHz will be reflected, but it's rare. The current max is known as the MUF or Maximum Usable Frequency. What about Satellite Radio?
[This is just my theory, as XM and Sirius tend to keep the specifics to themselves]
Yes there is a time delay, but unlike AM and FM, you aren't listening in real-time anyway. There is buffering and processing, demuxing, etc that happens before you hear anything. So your XM/Sirius receiver just has to put all the pieces back together, and it doesn't care whether they came from the sat, or from the ground. As long as the data is good, you'll hear the audio it represents. I do believe the ground and sats are on different frequencies though. The receivers are probably always trying to receive anything they can. Each packet of data is serialized, so the receiver knows which one it needs next. As long as it gets the next one (and the next one...) from somewhere, your ranchero music will play without interruption! OK, I'll leave it at that. If anyone wants to dicuss this more, let me know.
(I feel like I might be boring some of the readers) NJC —NJC |
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NYBret |
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Thursday, February 9, 2006 at 12:49 PM NJC - Thanks so much for that explanation. I stand corrected. Why is water so conducive to AM broadcast? Is it because large bodies of water have far lower "noise floors" than land? This is an aerial pic of my station... Click —NYBret |
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Colin |
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Thursday, February 9, 2006 at 1:21 PM "Calling all nerds!" ;-) —Colin |
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NJC |
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Thursday, February 9, 2006 at 5:31 PM
Edited Thursday, February 9, 2006 at 5:36 PM Good to hear from you too, ZT. NyBret: Water is conducive to radio for a couple of reasons. Firstly, it's flat. There are no terrestrial obstructions. This limits line-of-sight communications only to the curvature of the earth. It also provides for excellent ground-wave propogation. Second, it's conductive, at least partially. When you are on or near water, it acts as a ground plane. A ground plane is a reference for your receiver to detect the signals against. Several types of radio antennas use a metal ground plane to improve performance. Another thing to note is that the size of the radiator (the main part of the antenna, the driven element) and the ground plane are functions of the frequency, or more correctly, wavelength. Wavelength is just speed of light(300,000km/s)/frequency (Hz). It is a measure of the width of the wave. Picture a sine wave (warning ascii art: /\/\/\/). Wavelength is the distance between one point, say a peak, and the same point (next peak) on the next cycle of the wave. The lower your freq, the longer your wavelength. AM broadcast waves are HUGE, about 300m (relative to FM broadcast waves which are about 3m long).
Thirdly, yes, the noise floor would be lower, especially on the ocean. Mostly because there is nothing there. No people, no machines (ok some boats, but compared to land), etc. In your station's case, they are using that river as a natural groundplane. It will actually make the antennas more directional, along the path of the river. Neat idea...it's there, why not! Some AM stations that aren't near water use buried cable to enhance their range. Calling All Nerds! —NJC |
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MajandraFan |
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Thursday, February 9, 2006 at 5:45 PM What do you know about digital shortwave?
I heard it can sound as good as FM but travel the whole earth.
Is it super or myth?
I must know these things.
That stuff is not boring. The nerd call is wrong cuz it's not obsessive minutiae, just stuff that requires a bit of thinking. And everyone knows what type of person calls 'nerd' to avoid having to think, or to distract from not being able to.
Anyway —MajandraFan |
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NJC |
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Thursday, February 9, 2006 at 6:16 PM
Edited Thursday, February 9, 2006 at 6:18 PM Digital shortwave is pretty cool. Transmitting digital signals on HF (high frequency, another name for the shortwave band) has been around for a long time. Usually by means of Frequency Shift Keying, Amplitude Shift Keying, and Phase Shift Keying. These are Modes, like AM and FM. But the difference here is that the changes in frequency, amplitude, or phase are interpreted as 0's and 1's. The inherent problem with these modes on HF is that the data rate is a function of the frequency. Low Freq = Low data rate. This is (part of the reason) why your wireless network card operates on 2.4 GHz.
Digital Radio Mondiale is a digital radio system for shortwave which promises FM quality audio. They can get away with this because they use the HF band as a "broadband" meaning they have several channels which all carry part of the program. The parts are re-assembled at the receiver. Imagine you have an old, crappy, slow-ass 14.4k modem. It sucks right? What if you were able to get 50 phone lines, and connect a 14.4k modem to each one? Assuming you could multiplex them all together, you could send/recv files pretty fast. And multiplexing is exactly what it is called. In this case Frequency Division Multiplexing. That just means dividing your program amongst several frequencies at the same time.
So theoretically, yes. You could have worldwide, quality radio. Shortwave is a bitch though. The propogation changes all the time. From month to month, day to day. Sometimes minute to minute. That DRM page indicates adapability, but I think it would need to be perfected. So it is in fact super, and not a myth! —NJC |
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MajandraFan |
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Thursday, February 9, 2006 at 6:41 PM Cool.
Now lets discuss Ultra High Definition Video.
Personally I would like to film human baby births in UHDV. It would certainly put people off filming births. Adam would approve of that I think. —MajandraFan |
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NJC |
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Thursday, February 9, 2006 at 6:49 PM You think it would stop idiots from having kids?
—NJC |
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MajandraFan |
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Thursday, February 9, 2006 at 7:04 PM No, no, remember that thing where he went off on people filming their kids' births?
And then showing the videos, to Adam? —MajandraFan |
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ZT-In-Exile |
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Thursday, February 9, 2006 at 7:38 PM Your id has tourettes ZT —MajandraFanYOU WILL HAVE MY BABIES!!—ZT-In-Exile |
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justnorthofthebridge |
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Sunday, February 12, 2006 at 12:15 AM OK first off, there's alot of BS in this thread (I have a degree in this stuff). I believe the reason you have to turn down the radcio in the morning is that your ears are more sensitive in the morming since it's quite at night and your ears acclimate to the quieter level. Do a simple experiment. Hook a cassette recorder with meters on the front up to your radio and record both the morning and evening broadcasts. You'll probably see that the levels are equivalent although your ears think the morning show is louder since your hearing is more acute in the morning. I won't even get into the AM / FM / digital stuff here. CHeck out the wikipedia entry for Radio Stations for an accurate synopsis. http://en.wikipedia.org/wiki/Broadcast_band AM stations DO bounce off the ionosphere. All frequencies below 60Mhz will do so. (Even FM & TV stations will bounce in a solar flare.) As I type this, I am in the producers chair for a bog AM station taking calls from over 1000 miles away - far further than ground wave propogation would allow. Also, there is a single company pushing digital broadcast equipment to stations. On FM, its marginally useful, on AM it makes the station sounds like a cell phone and obliterates the station on both sides of it. When you are scanning stations on AM and your radio stops on a channel with just static, you're hearing the digital signal for an AM station instead of another broadcast station that used to be able to be heard on that channel. Thanks for playing. —justnorthofthebridge |
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NJC |
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Sunday, February 12, 2006 at 7:47 AM jnotb: I stand corrected about AM nighttime skywave propagation. I see the minimum usable freq is more like 50KHz, so you can get some skip at 1MHz.
I have an engineering degree too, but we don't have to get into a pissing contest over creds. I also think your comment about "a lot of BS" is unfounded. I like your theory about the ears being more sensitive in the morning, I had just assumed that laxdude had ruled out human perception being a factor. I have a question for you (and anyone else too). Have you used any of the PC receivers, like winradio, RFSpace, or anything else? The software looks cool and they promise much better performance than a standard receiver. —NJC |
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Colin |
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Sunday, February 12, 2006 at 12:33 PM Did someone say pissing contest? It's on like Donkey Kong, motherfuckers! —Colin |
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MajandraFan |
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Monday, February 13, 2006 at 12:32 AM I believe the reason you have to turn down the radcio in the morning is that your ears are more sensitive in the morming since it's quite at night and your ears acclimate to the quieter level. You have it backwards Engineering God.
Have your television or some source, like a CD, that you are sure isn't varying and shit and try the morning/night thing.
In the morning the day's noises start up and you have to turn the television UP to hear it over the ambient noise. At night these all disappear and your ears become aware of how loud your television is or whatever and you turn it DOWN. I have casually performed this experiment thousands of times but beyond that it's simple logic. You have it backwards. I won't even get into the AM / FM / digital stuff here. CHeck out the wikipedia entry for Radio Stations for an accurate synopsis. http://en.wikipedia.org/wiki/Broadcast_band Also, there is a single company pushing digital broadcast equipment to stations. On FM, its marginally useful, on AM it makes the station sounds like a cell phone and obliterates the station on both sides of it. When you are scanning stations on AM and your radio stops on a channel with just static, you're hearing the digital signal for an AM station instead of another broadcast station that used to be able to be heard on that channel. Thanks for playing. —justnorthofthebridge Your wikipedia links didn't say anything useful about digital radio at all. I don't know what you mean by 'single company' but you seem to be saying digital is bad.
And I'm not sure why you're saying it's bad.
But whatever. —MajandraFan |
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Laxdude |
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Monday, February 13, 2006 at 1:08 PM I never said that it couldn't be me that found the morning radio louder - although, the ambient noise levels in my area are higher in the morning, and yet the signal seems louder. I wondered if it was some industry standard, based on old standards and practices that people wanted louder radio at night (or lower in the morning). And I am a freak listening to radio via cable, I am not sure that many people even know you can do that. My follow up question about digital radio was also rather stupid...I was not thinking in 'packets', but in an analog way. Is there any way to tell what source you are picking up (local or satellite)? And if you are buffering, is that to even out dead spots, or just to 'catch up' on the compression? If it is the former, how much redundancy is built into the signal? (ie, how many times is the same packet sent?). It would be great if they could throw in enough memory so that you could have the tivo-like ability to pause the radio (and have it build up in memory). That way you would not miss a song you liked, or would make Stern fans happy. Are their any regional differences when it comes to Satellite radio? I know with TV you get local stations, is their anything similar with radio? For instance, do they offer any stations with spots for local news/weather/traffic to get dropped into? Would it even be possible? Do the radios even have the ability for you to enter your region? I know that the Canadian Sirius units are locked down so we are not tainted with the horror that is Howard Stern. Canadian ears must be protected...not only that, we are accustomed to Nickleback super sets. —Laxdude |
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NJC |
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Monday, February 13, 2006 at 1:55 PM
Edited Monday, February 13, 2006 at 1:59 PM I have given a lot of thought to how the satellite radio works. It is a one-way communication, from the bird (or ground site) to you. Therefore there are no acks, and no requests for missed data, unlike internet streams where it is a two-way comm and missed packets can be resent. I have experimented with XM, and tried to figure it out. There is an area where I know there are no ground stations, because if I park under an underpass, I can't receive shit. The interesting thing is that if I drive under it fast enough, I won't lose it at all. I know that for the 1/2 sec or so that I'm under it I'm missing whatever is beaming down, yet the music still plays on... So I think that each packet from the satellite or ground contains 2 parts; the most recent data, and some data offset by some amount of time. This delta-t is probably chosen to be close to the size of the buffer in the receiver. So if your radio buffers 2sec, the delta-t is probably just shy of that. Remember, there is no recovering lost information because it is a one-way stream. I KNOW that I lose signal at this underpass. If I drive under it quick enough (>40MPH), I won't lose it at all. So the radio must be grabbing it the "second time around". If you factor in the ground stations, they are most likely at different offsets still. This gives you 4 chances to get each packet. Since I'm sure they are serialized, the radio knows which one it needs next, and as long as it gets it from somewhere, it plays without a hitch. Of course it's possible there are more than 2 offsets. The more the better, but there is a bandwidth limitation at some point. I think each radio has multiple tuners (at least 2). One for the bird, and one for the ground station. It would make sense that the 2 sats used by XM are on different frequencies, and the ground stations on different frequencies from those two. If not frequencies, then different spread-spectrum algorithms. The point I'm trying to make is that the radio is capable of tuning in to both sats and multiple ground sites at the same time, without them interfering with each other. Actually quite the contrary, they complement each other.
What do you guys think? For the LOCAL question:
XM has a bunch of channels for local traffic/weather, but anyone can receive them. I'm in MA, but I can tune to the LA channel. They also have the Emergency channel, 247, which is for any kind of major situation. Depending how the receiver works, I guess it could tune into the local ground station which could have some kind of locally-targeted programming... I've thought about the "locking-down" too and the question of "how do they know if you have a subscription?"
There must be a signal that is sent from the satellite telling the receivers what they are allowed to do. Couple this with a timeout in the radio (because your radio isn't on all the time and they can't possibly be sending everyone's radio permissions all the time) and you have a way of controlling subscriptions. Because of this, when they cancel your account, there may be quite a bit of time where your radio still works. —NJC |
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Laxdude |
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Monday, February 13, 2006 at 6:12 PM Here is a thought on the subscription lockdown. I assume you have to call up and register only once, and not every month. So behind the scene they probably have a specific frequency that each radio is set up to listen to, likely they have a couple of dark channels (data, and no audio). When the radio hears it's authorization number over the channel, it unlocks for a fixed time, I will assume for one month, maybe with an extra week. If you do not pay, your units unlock number does not send. if you kept your unit away from the signal, it would lock and you would have to call to get it reauthorized. Each radio could programmed to listen at a certain time (they will have to have an accurate clock to sync the packets) - so even if turned off, it will power up provided it has the juice. I doubt that the individual units have any upstream capabilities, it takes a bit of juice to get up to a satellite, especially with no external antenna - just look at the size of a satphone compared to a cell phone. They could however communicate through the cellphone system - but I think the internerds would have raised a hue and cry if their radio was spying on them. It might be different with cars though, since they have antennas, and a lot of juice - but a handheld certainly would be too low-powered. Using a cell based call back system would help stop cloning though - if more than one radio called back with the same number, they could send a lock down code. They must use a hard wired ID system, unlike the cards that Satellite TV used that were one could pirated, the radios must have a hard wired, non-programable chip. It would be interesting to know how many times they send the same packet down the pipe though. I wonder how long it will be until they 'upgrade' the service so people have to buy all new radios to help stop cracking. I wonder how hard it would be to clone a radio unit. —Laxdude |
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