The interesting part about it is the modulation process takes place in a non-linear mixer.
An audio mixer is a linear device. If faithfully reproduces the signal characteristics while allowing the amplitude to be changed-up to the point of distortion.
An audio mixer can combine or "mix" two or more signals while each signals characteristics are maintained (not counting any EQ or other effects you may employ.)
Unlike AM modulation (Department of Redundancy Department) there are no plus/minus sideband frequencies generated.
When you look at the RF carrier envelope using an ocsilloscope, when modulated the RF carrier appears to change in the positive and negative direction at the same time creating a larger/smaller peak-to-peak value. It appears there is only the carrier changing in amplitude.
When you look at two or more signals combined in an audio mixer using an oscilloscope there is no envelope. Rather a single signal which is the combination of the two or more signals added together. One signal is not impressed on the other or to say one is not modulating the other.
Once the AM carrier is modulated, if you want to boost the power with an amplifier it must be a linear amplifier as you must faithfully reproduce the carrier and sidebands.
I had no intention to post on this thread at this time, I was actually planning to post on the Earth Hour thread. But since I'm here, I can make an appropriate point.
This is a thread about modulation. I am modulating this thread by deviating.
Ahhhhh, but that would be Frequency Modulation.
nerds.
Who started this thread?
Can a nerd be a geek?
So, I went to Wikipedia to find out more
Nerd (adjective: nerdy) is a descriptive term, often used pejoratively, indicating that a person is overly intellectual, obsessive, or socially impaired. They may spend inordinate amounts of time on unpopular, obscure, or non-mainstream activities, which are generally either highly technical or relating to topics of fiction or fantasy, to the exclusion of more mainstream activities. Additionally, many nerds are described as being shy, quirky, and unattractive, and may have difficulty participating in, or even following, sports. Though originally derogatory, "Nerd" is a stereotypical term, but as with other pejoratives, it has been reclaimed and redefined by some as a term of pride and group identity.
The word geek is a slang term originally used to describe eccentric or non-mainstream people, with different connotations ranging from an expert or enthusiast to a person heavily interested in a hobby, with a general pejorative meaning of a peculiar or otherwise dislikable person, especially one who is perceived to be overly intellectual.
Although often considered as a pejorative, the term is also used self-referentially without malice or as a source of pride. Its meaning has evolved to connote "someone who is interested in a subject (usually intellectual or complex) for its own sake."
Wow. Nerds are geeks.
A 100 milliwatt input modulated to 100%, (without asysmetical processing) develops about 400 milliwatts P.E.P. Or more clearly, the output of a Part 15 or any AM transmitter develops P.E.P. output of about 4 times over the the unmodulated carrier. So modulating your transmitter at either 100 or 125% positive peaks is a BIG difference. So those not interested in processing may want to reconsider.
So modulating your transmitter at either 100 or 125% positive peaks is a BIG difference. So those not interested in processing may want to reconsider.
I think most everybody is interested in applying processing to improve their signal, but to clarify my earlier point, when it comes down to spending $500 - $700 to acheive that 125% positive peaks, it makes more sense to me to instead spend that money on an additional transmitter to feed remotely, which would result in doubling your range..
To round things off, lets just suppose 1 Rangemaster provides 1 mile range (as 1/2 mile to the north, and 1/2 mile to the south)..
If you employ an Inovonics 222 processor to that transmitter it should increase your range a few hundred feet..
Therefore, that extra few hundred feet is at least a half grand purchase.
What I'm saying is to instead take that money and install a second transmitter aprox 1 mile away (thus 1/2 mile beyond the first transmitters signal range), the result being that you double your range.
$500-$700 used Inovonics 222 = increase range maybe 15%-25% OR..
$300-$500 for used Rangemaster = increased range around 100%
If given an either/or option, I'd choose the additional transmitter, not only due to the obvious advantage, but also for the lower cost investment.
By all means, if there's something wrong with my reasoning, or a factor I'm not considering, then please point it out.
Mr. Powers, you have described a sensible alternative to costly signal processing.
But imagine that some wealthy part 15er came along and did BOTH!
Whoa.
Double, triple, quadruple the range times seven.
Money in the air, strong and proud.
Doing both would be premo ideal.. I personally would LOVE to get a 222, but when I see one become available, and should I happen to have the funds at the time, I still can't justify the cost, considering that I can spend less for an additional premium transmitter to acheive more..
If there is something faulty with this reasoning, I would like someone to point it out.. as a matter of fact, I keep waiting for someone to! Because surely I'm not the first to weigh these pros and cons of such a purchase.
a way to make an asymetrical circuit at home that can do what a Inovonics 222 can do.
What more could it be than some parts and wires?
What I'm saying is to instead take that money and install a second transmitter aprox 1 mile away (thus 1/2 mile beyond the first transmitters signal range), the result being that you double your range.
This would be a great experiment, but here are some thoughts on it...
For prevention/reduction of mutual interference, units in this approach using the same frequency will need to be separated far enough from each other so that they have useful signals in their separate coverage areas -- despite operation of the other setup(s) in the system.
A radiated field does not drop to zero at some specific distance from the transmit antenna. So the groundwave field at 1/2 mile will be reduced to < 50% of that field at a distance of 1 mile.* This can cause significant changes in the net field received from the two stations at some locations, and distortion in program audio, even if the carrier frequency and modulating waveforms are synchronous at each transmitter.
Inadequate physical separation will lead to some significant signal variation or maybe dead zones between adjacent transmitter sites.
About the only way to overcome this is to physically separate the two transmitters so that their radiated fields have no practical affect on each other.
* depends on frequency and earth conductivity
The Breakaway Broadcast processing software does everything the 222 does (asymmetrical limiting, NRSC pre-emphasis, 10 kHz sharp cutoff filtering) at $200 with a free demo version. Plus, and this is important, it has an elaborate multiband compressor/limiter function that can produce extremely high audio density.
I've played around with the demo version. I found that the asymmetric limiting didn't really produce a very noticeable effect, but high density compression/limiting dramatically increases the loudness at the expense of listenability, in my opinion. Music with absolutely no dynamic range is fatiguing to listen to. All the instruments just muddle together. Hyper compression is the rage now days. I think some dynamic range is necessary to expose individual instruments. I think I saw a recommendation somewhere for at least 8dB or 10dB or so to de-muddle music and help preserve at least some semblance of the dynamic range in older recordings. Many modern pop CDs and MP3s are already recorded with hypercompression, so they're already a lost cause. I don't know. It's all very subjective.
It's a different story for voice. Voice will benefit from both asymmetrical limiting and high density compression. Trouble is, unless you are a talk-only station, you can't fully maximize density for voice without degrading the music.
http://www.claessonedwards.com/index.php?Itemid=1103
After my previous post, I searched YouTube for audio hyper compression. This video is a gem. He clearly demonstrates the effect of compression on perceived loudness, and throws in a measure of dry humor. I particularly liked the end where he suggests that by avoiding hypercompression "you can actually have glass breaking and it will sound like glass instead of farts".
That was an excellent