PLEASE NOTE: The very last paragraph of this post sums up everything, and takes less eye strain. You might want to just scroll straight down to it now.
Spinning around in a blind circle again..
It started when I came across this page ( http://www.claessonedwards.com/index.php?option=com_content&view=article&id=54&Itemid=58 ) which states Breakaway Broadcast Processor has built in calibration features to equalize both low and high frequency response of your transmitter, and and proceedes to go into detail with pictures on how to apply it with use of an oscilloscope.
Well, three things to consider here,
1, I don't have an oscilloscope,
2, I've never even experimented with a scope, and
3, I don't use Breakaway Proccessor.
But that didn't stop me from looking into it.
If I can achive the optimum positive and negative peaks for my Rangemaster without gambling $500 or $600 on a used Inovonics 222 which may or may not operate properly when I received it, well, I might consider proccessing with Breakaway software.
But..
I got to thinking.. what are my positive and negative peaks right now, as it is, with the proccesing equipment I already have?
So, apparently the only way to know is with a scope, which I don't have, and dont have a clue how to use, and no present cash to buy one either..
Free Ocilliscope Software!!
- I explore that...
Radio Associates has what looks to be an ideal solution, as it's specifically designed and geared for amplitude modulation, but they want $199 for it (I'd sooner buy a real scope), still pretty cool though. http://www.eham.net/reviews/detail/11257
There's Picoscope that offers a free download, but it will only work demo mode with a simulated signal.. I couldn't find how much it actually cost on their website, so it's probally too much.
Then there's this one http://www.multi-instrument.com/ and you can download it fully functioning and uncrippled for 21 days, which might work.. as that would be 3 weeks for me to maybe figure out what I'm doing with it and set the optimal positive and negative peaks for the Rangemaster.
Or so I assume.
Alas, I found SOUNDCARD SCOPE http://www.zeitnitz.de/Christian/scope_en , which is FREE for non-commercial use (I have no idea what commercial use might be). Interestinally they also offer to create a custom version, where you tell them what features you want and they'll provide a quote on what it will cost you.
Anyway, it too uses your soundcard to operate.
(by the way, also found a similuar one called Zelscope http://www.zelscope.com)
So I get ready to download Souncard Scope - then hesitate.. What am I going to do with this??
Where will I start? Can it even serve my purpose?
What am I doing??
Which brings me back to here to ask this question;.
Would something like 'Soundcard Scope' be of use in providing My Rangemaster optimal modulation peaks?
That's my question, which I now realize I should have simply asked from the start and been done with it. But I don't have the heart to deleate this novel after going through the trouble of writing it..
.......IGNORE ALL OF THE ABOVE CONTENT........
I have a question.
Could a oscilloscope software which utilizes your computers soundcard be of use in modulating the 130% positive and 90% negative peak capabilities of the Rangemaster transmitter?
Thanks for this great post .
I am looking at them right now 🙂
Could a oscilloscope software which utilizes your computers soundcard be of use in modulating the 130% positive and 90% negative peak capabilities of the Rangemaster transmitter?
In order to do that the frequency response of the soundcard would need to include the r-f frequency band having the AM carrier and its upper and lower sidebands. AFAIK no soundcards are available with that performance.
Below is a screen clip showing the audio frequency response of a typical soundcard for sample rates of 32, 48 and 96 kHz (left to right). Its upper frequency limit even at a 96 kHz sample rate is less than 1/10 of that needed to display an AM waveform in the medium wave broadcast band.
A simple diode demodulator circuit (Google) would provide an audio output from an r-f sample of an AM transmitter, which could then be displayed on a PC using its soundcard and the needed software. The display would show gross distortions in that waveform such as flattened peaks when the tx is over-modulated by a sine wave, but it would not permit accurately setting positive and negative modulation peaks. Also diode detectors add distortion to their output signal, for some conditions.
Probably the least expensive way for a Part 15 operator to set +/- AM modulation peaks ~accurately is using an oscilloscope. I looked at EBay, and saw some for under $100. Just look for one with an analog input bandwidth extending to at least 5 MHz.
Here is a clip showing the oscilloscope waveforms for +125/-100% AM, and +100/-100% AM using sine wave modulation.
Ok, so that's a no. I did just popover to ebay and narrowed the search to return only analog scopes under $100.. and there are several, but most descriptions are vaque saying "powers up", or "has one channel dead", "needs work" and "not working".. None that I saw made any referance to "input bandwidth", They simply stated "bandwidth" or "bandwith lower than".. I don't know if that refers to the same thing as "input banwidth".
But I only took a look for the sake of looking.. even if I did find a super bargain, right $50 would be a major investment!.. Wintertime is never good for my cash flow.
A scope, I will eventually have to get. but all I was trying to acomplish right now is to satisfy my curiosity of what my modulation peaks currently are in repect to what they should be -- without spending money to find out.
With a scope, I would still not be willing to spend half a grand for an Inovonics 222 , and without a scope any consideration (it's only a consideration) of using Breakaway software as a means of acheiving the proper peaks would also pointless.
So I guess I'm back where I started. But thanks for your advice.
It was all just a thought.
I keep a 'scope on my RF. It's mainly just an indicator showing I'm on air.
If you'd like to watch goto MY MRAM 1500 'SCOPE to see what the RF looks like. I'll keep the camera on for a few days.
What you are watching is the output of a Talking House II. I have a loop antenna connected directly to the 'scope input.
This is a very old 'scope. The brightness drops from time to time as the HV power supply is probably going but most of the time it's bright enough to view.
As the weather changes you notice the overall amplitude of the signal changes. Most likely tuning of the antenna is being affected by the weather.
Try a web search on "Dso Fft Usa" and you will see a 5 MHz scope in the $80 to $90 range. I know nothing about this other than what I read.
Also, try QRZ.com where they have a for sale section. You need not register to view this.
Luck can be a factor such as when I picked up a dual channel 20 MHz scope at an "antique mall" for $10. It was a gamble since it wasn't working but the switches and connectors were worth this so I bought it. Turns out the detachable power cord (same as used on PCs) was bad and the scope works great.
Be patient and keep your eyes open since you never know what will turn up.
Neil
Lol.. $10, and just a bad power cord! Don't you love it when that happens!.. A few months ago I bought a dirty looking Sony Viao laptop at the local thrift store for $5, The outside had surface gunk stuck on it, and the battery was missing, had no power supply, but when I lifted the lid the screen and keyboard looked shiny new. I gambled a 5 spot on it for the chance it had memory and/or a hard drive inside. Got home to find it had both. - Cleaned the outside case with windex and bought a power supply for $4 on ebay.. Didn't do anything else.. It loaded right into Vista, 2ghz duel core, 2gig memory and 160gb hard drive. still is missing a battery!
Mram,
tried to load your ustream for about 5 minutes without any luck.. will try again a few times later tonight and whenever. I catch a look at it eventually!,
I'm new to UStream so I don't know what their track record is. So far, I've been able to bring it up while at work with no problem.
I'll leave it up for a few days anyway. I could record a segment and leave that on UStream for future generations.
It's coming up fine now Mram.. and it looks preety cool! You never struck me as a rap music fan though!
"As the weather changes you notice the overall amplitude of the signal changes. Most likely tuning of the antenna is being affected by the weather."
I recall discussion a while back concerning weather changes coresponding to signal range changes.. I guess having a scope connected could prove benificial to part15 to compensate when neccessary.. no?
Not so much a "rap" fan but I'm an equal opportunity player. And, someone out there likes it.
My playlist includes most everything.
In Ohio, the weather changes to often to bother going up on the roof everytime the tuning goes awry.
I'm waiting for Lefty's report on his new ground mount install. If good, maybe I'll try a ground mount again which would allow for those frequent tune-ups.
I've not yet been able to let go of this, and would like to bring it up one more time..
Ok, The $199 software occiliscope by REA measures and manages the tx high and low peaks via an interface to the transmitter with a little box which they market..
There are several other free or inexpensive occiliscopes for you pc (as described previously) easily obtainable on the net which use your sound card as a source signal.
Another one not previously mentioned (also free) is "Visual Analyser is a complete professional real time software, transform your PC in a complete set of measurement instruments; no new hardware necessary (you can use the Sound Card of your PC) or you can use a specific external hardware.." http://www.sillanumsoft.org/
They provide information with one example concerning interface of their scope software with an satalite dish (I think it's in french).
So, even though most are setup default to use your comptuter ssoundcard, obviously these free occiliscope softwares also have the capability of reading and managing the modulation signals of our transmitters. -- I can't help but speculate that perhaps it might be something so simple as running a signal through an mic or audio input?? .. No? then what would it take?
In a re-read of this entire thread, something that Rich said jumped out at me:
"..In order to do that the frequency response of the soundcard would need to include the r-f frequency band having the AM carrier and its upper and lower sidebands. AFAIK no soundcards are available with that performance..."
Well, I think they do make radio cards for computers, so I tried looking into that.. Here is an pc card to receive AM/FM radio, perhaps this could be used with software occiliscope? http://www.overstock.com/Electronics/PC-Radio-Card/48200/product.html?SID=skim23176X817180X18d1fa9d5272f43ea8e409470e6144ea&PID=5551177&AID=10712286&cid=47248&fp=F&kid=204396
Other things I came across were these articles..
Radio Frequency Spectrum Analysis With PC Sound Cards http://www.radiomuseum.org/forum/radio_frequency_spectrum_analysis_with_pc_sound_cards.html "Good quality radio frequency (RF) spectrum analyzers are quite expensive pieces of hardware. However, for the purposes of the hobbyist, a much simpler (and cheaper) setup using a frequency converter from radio frequency to audio frequency (AF) combined with PC sound card based AF spectrum analyzer software might suffice... He goes on describingmethods, the problems and work arounds, but I don't comprehend becuase I'm not an engneer, but many of you probally will.
Another one of possible interest: Decoding RF link using a PC soundcard.
This is a video refers to interfacing a home security rf transmitter to your soundcard, not the same thing but perhaps some part of his method might be of use in our application? ..Now you could just hook your oscilloscope up to the transmitter and take a look at the timing of the signals. But most hobbyists don’t have that kind of high-end test equipment in their basement or garage shops. [Ray's] approach uses something we all have available to us: a sound card and some open source software. He connected the data pin from his RF receiver to an audio plug and inserted it in the line-in jack of his computer. Using Audacity he recorded the signal as he pressed buttons on the transmitter. This method not only captures the data, but the time stamps native to the audio editing program let him easily work out the timing for each signal.. http://hackaday.com/2012/07/02/decoding-rf-link-using-a-pc-soundcard/
I'm not clear on what this is at all, but I'm going to menion it.. To connect your radio to the sound card, you'll need an interface consisting of three (3) cables, one each to handle the RX (receiver audio), TX (transmit audio), and PTT (transmit) functions. If you want to use your sound card with 2 radios, you'll need a more complicated interface. http://www.soundcardpacket.org/1cablestart.htm
Just to mention.. although I didn't see what I was looking for here the Links to Ham Radio Sound Card Software has some interesting stuff: http://www.westmountainradio.com/content.php?page=links
I checked out the Visual Analyser program. Very nice compared to some of the PC scope programs I've tried.
However, it appears to be for audio only. The two articles they reference show some type of USB soundcard interface which appears to be for audio frequencies. The op-amp chips, TL082, have a great response for audio but not for RF. They do say the analyser can be used with your PC soundcard which also won't work at frequencies much above the audio range.
They show a sat dish but it doesn't appear to have anything to do with the analyser.
What about using with the PC Radio Card which actaully recieves AM and FM radio signals? http://www.overstock.com/Electronics/PC-Radio-Card/48200/product.html?SID=skim23176X817180X18d1fa9d5272f43ea8e409470e6144ea&PID=5551177&AID=10712286&cid=47248&fp=F&kid=204396