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Ok, let me start by saying I’m sure that this is not an optimal method, and that some of the old hands here will probably find it crude and perhaps amusing.
Ok, let me start by saying I’m sure that this is not an optimal method, and that some of the old hands here will probably find it crude and perhaps amusing.
I finally got around to downloading the 1.4.1 version of Zara from MRAM’s support page so I could try it with Sound Solution as a plugin. I’ve used Sound Solution for internet streaming, so it seemed like a good experiment to try.
Sounded fine on the computer speakers, but not nice going out over the air. Most likely the modulation level was overdriving my poor little FM transmitter. Switched over to the cd player I use for “blackout” when streaming, and it sounded good and clean, so yop, overdriving. I fussed with levels a bit and got it sounding decent, but it occurred to me that it’d be nice to come up with a way to do some sort of check on the modulation rather than “by guess or by golly” any time I try new software or settings (or hardware, for that matter).
When streaming, I used to catch the stream with another computer in the house on winamp and use the teeny scope on winamp to check for flat-tops on the waves to get my setting zeroed in for max volume without distortion. Well, duh. Use the same method on the transmitter.
I don’t have an oscope, but I remembered seeing a piece of freeware for using a computer as an audio frequency oscilloscope so I went hunting and found it again..
mywebpages.comcast.net/fel4u/oscope/winscope.htm
Having another computer in the house, I installed winscope on it and took a “boombox” tuned to my station and ran a patchcord between the headphone jack of the boombox and the line-in of the computer running winscope. Eureka, we have waves! (start with the boombox vulume at minimum and creep it up since you wouldn’t want to damage the soundcard).
Ok.. so then I hit the “test tone” on Sound Solution, went back to the computer with winscope. Not even close to a nice smooth looking sine wave. So I went and backed the volume down some more and tinkered until I found the max setting that would give something that looked like a nice smooth waveform. Turn off the test tone and use the ears. Still sounded a bit blurry to me.
So it occurred to me to go and listen to some of the commercial stations and see their waveforms with actual music. A little compare and contrast between my station and a nice sounding commercial station a little ways up the dial and I saw that my waveform when playing music was decidedly larger than theirs.
Ok then, so I watched for a few songs to note how high their peaks went and approximately where their average seemed to be, and adjusted my levels to the transmitter to get something that looked pretty similar. By then it was sounding quite nice, and I spent maybe another touching up the Sound Solution settings a little and trying some other experiments.
I had been using an outboard EQ to cut frequencies 16k and up, but the 15K clip on Sound Solutions worked as well, didn’t make any noticeable change on the ram whether it was on or off and eliminated a little “hiss” from my sound chain. On the other hand Sound Solutions doesn’t run when I use my mixing board for voice and non-computer sources, so I put my “poor man’s brick wall limiter” I’d cobbled together from an old generic casette “walkman” and a few junkbox parts back into the chain.
Then I used the test tone on Sound Solution and winscope again to get the brick wall set a bit better.
Overall, switching over to Zara 1.4.1 with Sound Solutions works well. Still getting used to no fadethroughs, but to be honest, sometimes having the fadethroughs isn’t all that wonderful anyway.
So in summary, if you don’t have a scope, but you do happen to have another computer handy, winscope with some kind of reciever is a nice little toy for at least being able to see your modulation at the reciever end and making some rough and ready adjustments. My little FM rig is a small Cana-kit, and I’m quite sure it doesn’t have anything in it that acts as a modulation limiter, so I feel it helped to at least bring the modulation in to somewhere near a good range. Also it was educational to see what wave amplitude some of the local stations were puttting out in comparison.
Daniel
Total posts : 45366Daniel,
Thanks for sharing the “war story”. Your description illustrates the value of measurements in squeezing the best performance from a station. With software as you mentioned it can be done without a whole rack full of equipment.
I have been playing with part 15 AM and FM for a long time and I have never been comfortable with just operating blind regarding modulation. For those such as I who are not audio software literate there are a couple of hardware set and forget methods that I use here so I thought I would add this to your post. They could also be used with your system in case something sneaks through the software.
For AM I am using the SSTRAN AMT-3000 and have found that the internal audio compressor does a fine job keeping things clean. I check the envelope now and then with a scope.
For FM, I use a Ramsey FM-25A fed from an Alesis Nanocompressor(R). Using a field service monitor I was able to set the peak deviation to 75 kHz. just when the compressor’s audio level red light flickers. Even with the compression off, I still have an indication of the modulation that I trust. As does your setup, this compares very well with broadcast stations quality and volume.
The source is the line output from my PC audio card.
So, monitoring the audio level whether as you do with software or as I do with hardware is a good idea and thanks again for bringing up the subject.
Neil
Total posts : 45366That’s usin’ the ole knoggin Daniel! Learning how to work with what you have is half the battle.
I look at my RF signal using an old 10 mHz O’scope. I use a home-made coil and tuning capacitor coupled to a small sensing loop to pickup the signal. Kind-ol-like a crystal radio without the crystal. The test lead from the o’scope taps the signal off the coil. I can watch the actual RF signal and see if the audio is over or under modulating the signal. I prefer this method as it eliminates any distortion that would be added from the boombox itself, perhaps from overloading the receiver.
Some transmitters have a simple diode detector and low-pass filter at the antenna output which works to provide a point where you can monitor the audio right at the RF output. At that point you can either feed it to an amplifer to listen to it or feed it to your WinScope.
You could use a simple crystal radio and connect your WinScope in place of the earphone if the soundcard input impedance is high enough. The idea is to eliminate any other source of distortion to the signal to be viewed.
Total posts : 45366mram1500,
Nice suggestion for monitoring an AM signal, but I think Daniel’s station is FM. This won’t work for FM.
Neil
Total posts : 45366You are absolutely correct. As you had mentioned how you monitor your AM, I figured folks would notice I’m MRAM 1500 kHz, an AM’er.
Actually, by the time I got to the end of the post, I forgot he was talkin’ FM. I need to get more sleep!
Total posts : 45366Correct, Neil. I’m running FM at this time. But still definitely thanks to MRAM for the pointers on AM, since I *do* plan on eventually adding AM. Also a bit tempted by Lee’s 13.56 Mhz shortwave part15 project, since my wife and I spent plenty of hours SWLing in years gone by.
I figure I’ll add AM when I either find a Talking House going at a nice price on ebay or just decide “heck with it” and build a Wentzel based rig. The Wentzel keeps tantalizing me, since I know I could order the parts fairly inexpensively, hit my junkbox for a good number of them, and I could make that bird sing in a couple weeks. LOL
On the other hand, starting with something commercial that has “FCC approved” on it seems logical, so at this point I’m still watching ebay.
But anyway, back to modulation. I hear what you’re saying, MRAM, I’ve been thinking that for AM there’s a lot of interesting options for monitoring the signal and the modulation. In years gone by I’ve made some crystal radios and also “un-junked” some radios that no loneger worked by just cutting out everything but the tuning section and a diode to make them “sound powered”. Kind of a parlor trick in this day and age, but very handy if there’s a power failure and you didn’t think to have batteries for the portable radio.
I know that the boombox almost certainly adds a bit of distortion, but I figured if I could get the test tone it was recieving to look fairly sinusoidal then I had to be at least getting into the right ballpark. I also got to see how much the “bass boost” button that many people leave on all the time on such devices overcooks a highly compressed signal. So I am tinkering with the settings on Sound Solution rather than just relying on the old “Powerliner FM” I used to like because it sounds so nicely massive on an internet stream. Hunting for the right degree of tweak to not sound wimpy on radios without a bass boost but not sound too badly overdone on ones with it on.
But probably the most educational thing was using the boombox/winscope to look at other stations, and get to see some of why some sound better than others. There’s two local LPFMs that are easy to pick up. One is kind of eclectic music and run by the local Arts Council, and the other is run by a local church. Neither really has an excellent signal. The Arts Council one is pushing a lot of bass and compression and one can def see the distortion on the peaks of some of the waveforms and the church one looks like they’re running no compression at all and just keeping levels set low enough that is doesn’t peak too bad. A case of “way too fat” vs “where’s the beef?” to the ears.
Then listening to stations that sound nice, and also using the little spectrum analyzer in winamp with a line-in plugin to get an idea of their eq settings. Like I said, highly educational on how to get a better sound (without actually running out and buying dedicated hardware).
For anyone wondering whether this jury-rigged make-do sort of scope is worth the trouble, I can tell you that you can see distortion on the peaks of a wave long before your ears can pick it up. And if you run something like an inexpensive FM transmitter, if you’re overdriving the transmitter then it probably isn’t just affecting the sound. It can be making you go way wide on bandwidth or generating “spurs” out of band. Both of which are things that can cause interference which could get complaints and the bad sort of attention for your little station.
Besides, we all want to sound as good as (or better than) any commercial station, now don’t we? LOL
Daniel
Total posts : 45366An oscilloscope is a great way to check things out with. You can assure 100% modulation and see any distortion and even plot your system’s frequency response,then use the eq to spice it up! The Wenzel(not Wentzel as I posted before,geesh,old age again!)works well but is no powerhouse on MW. My SSTrans works better there hands down. On SW,its powerful enough given the antenna we are allowed to use. I get s-9 reports all over town on 13.56 with great audio. I wonder has anyone tried to hear my SW?? Still wanting signal reports. I have been tweaking my program material and Zara,I have a really high quality program airing. FSN Worldnews on the hour and Bulletin at half past,pirate weather at :15 and:45,oldies format with some nice jingles and id’s. American Sunrise Radio runs at 6am m-f. all fully automated. I have resisted streaming for now,my ISP would probably want more money if they caught it running… :~) Regards,Lee
Total posts : 45366Daniel,
Mram1500’s suggestion for monitoring AM modulation with a scope is very good. I use a similar method here, the difference is I don’t use a tuned circuit, just an inductor from tip to ground to kill the 60 Hz. hum. Scopes can be had on auction sites for about $25 but watch out for the S&H charges which can exceed the cost of the scope. (Ask them not to handle it!)
If you use diodes to detect AM modulation, be aware that diodes are non-linear and may introduce distortion. The raw carrier envelope as suggested by mram is a better way to watch things though it won’t work with a PC.
As you consider building a Wenzel transmitter you might be interested to know that the SSTRAN AMT-3000 is essentially this circuit with a slight modification in the biasing which improves the modulation linearity. The SSTRAN also provides a crystal controlled PLL synthesised frequency agile carrier generator and a really nice built in audio compressor. No, I don’t work for SSTRAN, I just wanted to give you this information.
Neil
Total posts : 45366Oh, I don’t figure the Wenzel is any miracle, Lee and Neil.
If it was comparable with the SStran or the Hamilton, I figure it’d be getting talked about a lot more than it is in the forums here. Still, for a non-kit homebrew it seems to be well enough spoken of. The parts for it are easy enough to find sources for (many of them would be in my junkbox), and it would allow some experimentation on AM inexpensively.
The one I’ve given the most thought to has been the improved Wenzel circuit with the high Q pot core autotransformer.
See the problem with part15 FM is you really can’t go for range the way the rules are. So playing with antennas or even really making a simple antenna particularly well just isn’t really worth the bother. Actually it’s beyond “not worth the bother” and into stuff that would just put one throughly in violation of the laws. Not worth the fines and trouble to mess with it. I didn’t tune my antenna other than cutting about 1/4 wave (measured with a yardstick) of heavy copper wire, and the swr could be ridiculous. It’s inside the house on a floor that has aluminum siding. I can literally throw a rock as far as the signal “gets out”. Maybe 45 paces for a stereo with an actual antenna of some sort, less than 30 for a “walkman” type radio or boombox. About 60 paces is my most distant listener and we had to hook up an old roof antenna that was unused on her building and turn it to point at my house and then add a “tv/fm preamp booster” to her antenna line that’s probably 70s or 80s vintage to get a clear and reliable signal. And she’s maybe approx 180 ft away?
But that’s about what you *can* do with FM legally, so far as I understand the rules.
AM on the other hand, some people with top of the line gear apparently get a very good range out of it considering the power and antenna restrictions. I figure with homebrew or a Talking House I’d get considerably less than that, but possibly considerably more than I can do on FM. 1/4 mile radius would easilly cover my few current listeners, plus enough to make it possible to gain some new ones. Even 1/8 mile would be over 3 times my current radius, and as such worth the bother.
Not much point messing with things like innovative antenna experiments on FM. Even if (to make a ridiculous example) I made an FM antenna that was scaled down to be the wavelength equivalent of the 3M limit for AM (that’d be an antenna that’s what, half inch to an inch tall maybe?) and by some miracle of inductors and capacitance or shape stumbled on some theoretically impossibe “holy grail” that managed to get 1/2 mile of range.. It’d be illegal on FM, just like if I just built a transmitter with more power or even put a groundplane or maybe a j-pole antenna up on the roof with my current rig.
Anyway, the talking house in my attic or on the second floor (above the aluminum siding) might work well enough for getting a bit more range. Not that I’d buy one at the brand-new from the manufacturer price to find out, though. But if I eventually find one going on ebay at say 50 or a bit more, what the heck. It’s an fcc approved unit according to the manufacturer claims and I’ve never heard of one getting into trouble. Or if I go the homebrew route and build a Wenzel type, I can measure 10 mA X 10 volts into the final rf easilly enough, unlike the 250 microvolts into a calibrated antenna at 3 meters spec for FM.
The other tempting thought with the Wenzel is that assuming I eventually upgraded to something better for AM BCB, it probably wouldn’t be hard to adapt the Wenzel for the SW Part15 option if I wanted to give that a try at some later point.
But I’m not assuming that either the Wenzel or the TH are the optimal choices, just convenient possibilities for breaking into AM a bit and seeing some of what can be done with it in my neighborhood/area. Not looking for miracles so much as to get my feet wet a bit.
Daniel
Total posts : 45366[quote=WILCOM LABS] I have resisted streaming for now,my ISP would probably want more money if they caught it running… :~) Regards,Lee[/quote]
I would worry more about ASCAP, BMI, SESAC, and most important RIAA getting bent over your stream. I’ve read through pretty much everything I could find on the subject, and have labeled it a mine field, not much fun at all.
Not to get off topic, but here is our stream:
[url]http://supermix.sunyocc.edu:8000/listen.pls[/url] for Winamp/VLC
[url]icyx://supermix.sunyocc.edu:8000[/url] for windows media player with the orban aac+ plug-in [url]http://www.orban.com/plugin[/url]We pay BMI, ASCAP, SESAC and SoundExchange (RIAA) to be able to play music. Of the four, RIAA is the most greedy and has the more difficult process with reporting usage.
Total posts : 45366If you’re looking for stream music licensing check LoudCity (http://www.loudcity.net/). Their rates are very reasonable and you are legit for your streams.
What happens is you become a “LoudCity Broadcaster” by term so you are covered under their blanket licensing.
The only oddity is that your stream listeners *must* launch their listening session from a page on LoudCity’s website (domain). There is a long winded explanation but basically they have licensed their web domain as the broadcasting site. So all connections have to start from there. It’s a breeze to set up and if you get a Pro account, you can customize this page to match your sites theme so it’s pretty seamless.
Total posts : 45366Yes that’s correct, Loud city also requires that your stream include song title and artist info in a particular format. I assume this is so that they can do the paperwork to report usage.
The license for educational institutions generally says on school owned servers, so the links can come from a different place for me. I’m sure RIAA has a different definition, but ASCAP and SESAC are happy with school owned servers (multiple) which is part of why we have a sub listing on our main school domain.
Total posts : 45366Didn’t notice the .edu =)
Total posts : 45366I mention educational because it is different from non-com or comercial. For comercial and non-com, I think you are licensed to the particular website, which means dropping a link that will directly open the media player into a forum like this could be seen as a violation. To really find out, you need to hire a lawyer, as I said it’s full of double talk and legalese.
I’m really thinking of coming up with a form letter and having our students ask all the record companies to allow us to play their music without a fee, then I can get rid of a big hassle, and potential big expense (expense for RIAA will be decided on March 4 as they have asked for a rather large increase from all small webcasters!).
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