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I don't know if I've heard 'bad' or 'good' MP3 but I find it lacking too. I also find FM can be awful from many prominent stations (mostly top of the pops) but there are some channels that are very good, one French language channel in my area is superb - with the advantage that I can't understand the useless banter but I can enjoy the music.
A discrete transmitter sounds like a fun project, and I could go all-mono with that. Would it be better if made with tubes !?
Sorry ZeroD, no Coronation Street. I gave up on that a looong time ago when my parents dog would howl badly at the theme music. I do have a blu-ray full of Downton Abbey though, does that count ?
A discrete transmitter sounds like a fun project, and I could go all-mono with that. Would it be better if made with tubes !?
Sorry ZeroD, no Coronation Street. I gave up on that a looong time ago when my parents dog would howl badly at the theme music. I do have a blu-ray full of Downton Abbey though, does that count ?
HD Radio is way better then the crap on the regular stations, I can just tolerate regular FM in a vehicle at home, not happening. Like others I can also hear a difference between a 312k MP3 and a 24 bit but only on good systems, in a car, ear buds while mowing the grass or at a party outside 312k is fine.
I would go wifi like other suggested, I have never heard static in my wifi.
I would go wifi like other suggested, I have never heard static in my wifi.
Not that everyone's opinion on the modern state of broadcast FM radio and TV isn't fascinating, but I'm actually interested in the topic. I spend a lot of time with hearing protectors on. I have a version with an FM radio built in. I'd sure be nice to stream my music to them. Does anyone have actual experience with a quality low cost FM transmitter?
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"Does anyone have actual experience with a quality FM transmitter?"
I don't have anything of technical value to add to this thread, but I wanted to quickly state that in all likelihood there is no reason why a "personal" FM stereo transmitter can not be built and used which far exceeds the performance of typical commercial FM stations. FM came out when technology and demanded performance were nothing like it is now. For instance, nobody in their right mind would adhere to a 50Hz to 15kHz bandwidth limit as in traditional FM broadcast format. A lot of kits and commerical FM link products restrict themselves to operation with legacy receivers. If you're designing both the transmitter and receiver yourself, the playing field is wide open. You're not going to have any multipath issues when you're looking to span feet instead of miles. It wouldn't even need to be analog necessarily but even if it were the overall design could probably meet any performance level you require. Depending on the type of transmitting antenna and placement you could also use quite a bit of radiated power without doing anything illegal or bothering anyone. (like in your basement or something.) Why not steer the discussion toward design of a very high performance short range FM system, instead of talking about how old FM radio kinda sucked compared to what's going on now?
I don't have anything of technical value to add to this thread, but I wanted to quickly state that in all likelihood there is no reason why a "personal" FM stereo transmitter can not be built and used which far exceeds the performance of typical commercial FM stations. FM came out when technology and demanded performance were nothing like it is now. For instance, nobody in their right mind would adhere to a 50Hz to 15kHz bandwidth limit as in traditional FM broadcast format. A lot of kits and commerical FM link products restrict themselves to operation with legacy receivers. If you're designing both the transmitter and receiver yourself, the playing field is wide open. You're not going to have any multipath issues when you're looking to span feet instead of miles. It wouldn't even need to be analog necessarily but even if it were the overall design could probably meet any performance level you require. Depending on the type of transmitting antenna and placement you could also use quite a bit of radiated power without doing anything illegal or bothering anyone. (like in your basement or something.) Why not steer the discussion toward design of a very high performance short range FM system, instead of talking about how old FM radio kinda sucked compared to what's going on now?
So anyone who differs from your tolerant opinion is spewing BS , not to metion your deep anti-american shoutout ....
I guess Bigun is getting deported .....
I guess Bigun is getting deported .....
This is a fantastic idea as it would negate two of the main drawbacks of using wifi based streaming, being (1) the source laptop/pc must have the hard drive with the music on it so that the remote controlling device is just controlling the playback software (ie you are not streaming the actual files themselves over the wifi) and (2) if the wifi is down, there's no music.
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Member
Joined 2009
Paid Member
I guess Bigun is getting deported .....
I don't think anybody would have me now, except my mum
+1
I fancy building a pulse-counting tube FM receiver. It's mono, but the whole thing appeals greatly.
I don't really know where I'd start with an FM transmitter but I would vote we start mono and worry about stereo another day (just think, no worries about sweet spot and other nonsense that makes up the pretence of stereo).
OTA digital TV in North America is _less_ compressed than satellite and cable but nowhere NEAR raw uncompressed. Uncompressed 4:2:2 is 1.5 gigabits/second. Best achievable OTA is 19.3 MEGA bit 4:2:0. I was told that satellite converts all formats to 1440x900 for transmission and converted back to 1080i or 720p in the receiver. In LA the highest bitrate is from KCBS and KTTV (Fox) at about 15-16 MBits. NBC is around 12 and ABC below 10 though they are running 2 720p streams plus an SD on their carrier.
BTW the highest bitrate on an HD tape recorder is 440 megabits on the Sony SRW-5000 / 5500 / 5800 VTRs. That's 4:1 compression. Tape is going away as capture and editing. Computers cost a LOT less than a VTR though tape is a backup delivery medium.
G²
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FWIW.......
If anyone in the NE US remembers the legendary "WNEW FM" in the '70s (out of NYC), the sound was truly amazing.. They used top quality equipment and vinyl broadcast live.
Today with digital (mp3?) mostly automated stations (not to mention bass boost) FM sound can range from poor to absolutely horrible..
Also modern FM sections leave much to be desired..
BTW even AM is capable of more fidelity than most realize but AM sections have usually just been included as basically an after thought in most tuners.
If anyone in the NE US remembers the legendary "WNEW FM" in the '70s (out of NYC), the sound was truly amazing.. They used top quality equipment and vinyl broadcast live.
Today with digital (mp3?) mostly automated stations (not to mention bass boost) FM sound can range from poor to absolutely horrible..
Also modern FM sections leave much to be desired..
BTW even AM is capable of more fidelity than most realize but AM sections have usually just been included as basically an after thought in most tuners.
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Greetings everyone. As you can see, I am new to this forum, but electronic, audio, RF and such.
Back to the original question regarding FM transmitters, the CCrane FM transmitter uses a rather sophisticated transmitter chip. It processes the audio signal and generates the signal to drive its RF stage in the digital domain and converts this to analog to drive the RF stage.
I have had several and they work quite well. Even the automatic gain control that is used to prevent over driving the transmitter is digital.
The part number of this chip is Si4712/13-B30. And it can be driven with a digital audio signal with a little work, although it lacks this feature out of the box.
This is what has been being used in their latest version of this transmitter.
It is orders of magnitude better than the BAxxx series of integrated circuits.
I see that it may take several hours for this to post since I am new here and that is fine, I will just sit back and wait and spend some enjoyable time reading previous posts.
Back to the original question regarding FM transmitters, the CCrane FM transmitter uses a rather sophisticated transmitter chip. It processes the audio signal and generates the signal to drive its RF stage in the digital domain and converts this to analog to drive the RF stage.
I have had several and they work quite well. Even the automatic gain control that is used to prevent over driving the transmitter is digital.
The part number of this chip is Si4712/13-B30. And it can be driven with a digital audio signal with a little work, although it lacks this feature out of the box.
This is what has been being used in their latest version of this transmitter.
It is orders of magnitude better than the BAxxx series of integrated circuits.
I see that it may take several hours for this to post since I am new here and that is fine, I will just sit back and wait and spend some enjoyable time reading previous posts.
It may be wide open, but it is still constrained by physics/mathematics. You need to choose a compromise between wide bandwidth (for both baseband and modulation) and linearity and noise. Digital techniques will help, but may bring significant development time/cost. Wider bandwidth requires good linear phase filters, which are harder to design/make.Andrew Eckhardt said:
Perhaps surprisingly to some, the FM broadcast system is actually an excellent compromise. A local sound distribution system might make slightly different choices, but it might not depart too far. As someone who can add technical value to this thread it is my view that in all likelihood you are unlikely to significantly exceed the broadcast spec; most DIY efforts will fall far short of it so the thing to aim at is meeting the standard spec.
The 15kHz limit was introduced with FM stereo, and the whole FM stereo system is a compromise because of the demanded to allow for backwards compatibility with simple mono receivers. A far better stereo system could have eben designed without this limitation.
There are two main problems with FM transmitters, - the first being modulator linearity. This parameter is one of the most important ones in terms of low distortion.This also goes gainst the fact that most modern demodulators are designed to avoid human labour in the control and setup proces, - hence 'modern' demodulators are designed to have no or very limited needs for adjustments. The classical dual slope demodulator is probably one of the best, but requires a lot of trimming and special wobbler oscillators for best performance.
The other problem is transmitter purity and freedom from spurious and out of band mixed harmonics. The FM band is very close to the aircraft NAV band, and almost any kit I have seen over the years have failed on this parameter. Of course this somewhat depends on output power, but nevertheless is a possible problem. The 'Frequency Police' ( read national radio monitoring services) are extremely aware of these problems....
For quite a number of years, I was the tech manager of a community radiostation. We had some severe disputes with one of the neighbours next door, as the second harmonic of our transmitter would knock out ch 10 on her TV. THis was in the mid 80s, before cable or satellite services became common in this corner of the world. Still.... I could never measure this harmonic, and neither could the frequency police, even with their equipment....it was buried in the noise floor of the analyzers, but still anough energy to fiddle with analog TV.
There are two main problems with FM transmitters, - the first being modulator linearity. This parameter is one of the most important ones in terms of low distortion.This also goes gainst the fact that most modern demodulators are designed to avoid human labour in the control and setup proces, - hence 'modern' demodulators are designed to have no or very limited needs for adjustments. The classical dual slope demodulator is probably one of the best, but requires a lot of trimming and special wobbler oscillators for best performance.
The other problem is transmitter purity and freedom from spurious and out of band mixed harmonics. The FM band is very close to the aircraft NAV band, and almost any kit I have seen over the years have failed on this parameter. Of course this somewhat depends on output power, but nevertheless is a possible problem. The 'Frequency Police' ( read national radio monitoring services) are extremely aware of these problems....
For quite a number of years, I was the tech manager of a community radiostation. We had some severe disputes with one of the neighbours next door, as the second harmonic of our transmitter would knock out ch 10 on her TV. THis was in the mid 80s, before cable or satellite services became common in this corner of the world. Still.... I could never measure this harmonic, and neither could the frequency police, even with their equipment....it was buried in the noise floor of the analyzers, but still anough energy to fiddle with analog TV.
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Two carriers might help. You would get less noise and the potential for slightly wider bandwidth. However, you might have problems ensuring that both channels have the same frequency response and phase characteristics in order to maintain good stereo imaging - a multiplexed channel does this almost automatically for you. No such thing as a free lunch.
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