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NEW FM PROCESSOR

I haven't tried it but here's the link.
I am even now waiting for a smoke-shade screen for the CRT to dry, as I think even at the lowest possible brightness the
resolution was overloaded, and I'm gonna do better next time.

http://www.youtube.com/watch?v=46cVYa50nGA
 
Try turning on some lights enough to make the camera "gain down" the CCD. (unless of course you have full manual over shutter/f/exposure/gain...)
 
Nice vid! I like! :)

However, I must admit I don't understand what the scope is showing. I'm familiar with the X/Y trapezoid display, but not this type. What are you displaying on the X and Y axis?

///Leif
 
It's mono, x axis sampled RF output directly, Y axis same sample, but through a 500pf for a 90 degree phase shift.

There's a nice ring with no audio, which widens with modulation. -100 should be a closed circle. and the extent of the growth
of the ring in modulation peaks show how much asymmetry and positive mod is happening.

I'll try to turn down the video gain on the cam if possible.
 
Could we have a trapezoid instead? Makes for easier interpretation - least wise it's what I'm more familiar with. And - 100 is real easy to spot.
 
littlejohn said:
Could we have a trapezoid instead? Makes for easier interpretation - least wise it's what I'm more familiar with. And - 100 is real easy to spot.
Click to expand...

I won't have time for a few days. Had to deal with real life responsibilities, dealing with my dad's estate, seeing a real estate agent,
moving out some of my dad's tools, etc. Anyone need some hand-built chipmunk traps? I have 3 free to good homes.
And in the morning I'm off to darkest Wisconsin.

In order to have true trapezoid, I guess I'll sample the audio without reverb (easy) and just turn the side channel input with reverb off
during the capture. Otherwise, there is no easy point to pick up an "exact" true audio feed, with the reverb going into a second
modulator input with its own fader. To tap a true audio feed, I'd have to go off the air, and that hasn't happened for more than
a minute or two in 10 years. I need a backup transmitter, even though this has had only 1 part failure in 15 years, an electrolytic cap.

If the audio for the y axis is not exactly the same as that fed to the transmitter (minus reverb) would I expect to see some waver on the
trapezoid? It's only about 3-4 % mod by itself (the reverb). It barely widens or wiggles the circle Lissajous.

I like the circle pattern, and the last time I checked this a few months ago, I was able to get a better phase shift or x/y ratio somehow
and had an almost perfect open circle rather than the somewhat 60 degree-ish pattern on the video.

The Georgio Moroder (sp?) clip I picked was almost totally smashed, and the vid was so "hot", it's not possible to see
the true center point that occurs on -100. It's quite easily seen live, that's why I'm griping about the video overload and
made a filter for the scope screen. Too bad the Du Mont scope needs some work, it had an amazingly sharp display.
 
Hey guys,

Anyone interested in:

LOWER CPU USAGE? ;D ;D

I've reworked the back-end clipper, and the results are in:

Same great audio quality, slightly better peak control, AND lower cpu usage.

As measured on a Celeron 420 machine (1.6 GHz, single core) with 512mb ram and Windows XP:

BBP, 0.90.64 and older:

cpu optimized mode: 65% cpu load
maximum quality mode: 86% cpu load


BBP 0.90.66 and forward:

cpu optimized mode: 50% cpu load
maximum quality mode: 65% cpu load


I don't have one handy to test with, but it SHOULD work on most Pentium 4 computers now!


Download the latest version from:

http://www.claessonedwards.com/beta/breakaway_broadcast_setup_0.90.66_beta.exe


///Leif
 
Hey, Bigrig!

Bigrig said:
hi Leif,

It's an Asus P5KPL-AM motherboard, i'm not sure how the S/PDIF works but I'm just choosing HD audio with a setting of 192khz in the breakaway control panel for the MPX output and the pilot light is coming on but seperation is very bad.

Regards
Click to expand...

Guess what!

I have a computer with this exact motherboard now. I saw the problem.. and I have a solution!

  • Open regedit.
  • Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\
  • Search for: ExternalSpdifReceiverSupportedSampleRates192000
  • Set that value to 01,00,00,00
  • Restart the computer.

That's it! Glorious 192 kHz output, with very little tilt and hf rolloff -- perfect channel separation.

Now, why VIA makes a 192 kHz capable sound chip, advertises it as such, and then makes it impossible to use the feature without hacking the registry, now that's another (and a very good) question.

Best,
///Leif
 
Do the newer versions seamlessly overlay onto the purchased version?

Got a fairly good trapezoid display, very helpful for all adjustments indeed.
In live audio I see the phase shift through the audio frequency range, but overall the slope is pretty good.
I'll try post a video soon.

How does that +150% modulation look?
The natural "peak" in the trapezoid that would be drawn to a point at 100 doesn't "happen" as the entire trapezoid grows
on the positive peaks so that I wonder if in fact I'm seeing 200% or more modulation while not clipping.
If I am to trust the Tektronix, it is so.
With 100 % test tone set to trapezoid height= 1/2 scope display (bottom half), music audio with punch has been full screen on peaks
without yet displaying the pointy point of -100% indication particularly on bass punch info. Very impressive.
 
Hmmm. Their graphs do run thatta way. I was just making mine look like those I saw in ARRL handbooks and texts long ago.
I certainly could swap leads x-y and run it that way while filming upside down, but I'd still need to run the "baseline" trace along the side to show the full growth that happens on the plus 100 stuff.

The trace does go to a point at half-scale on test tones at 100%. You just don't see it happen very much in music.
Watch during the sibilants in Islands in the Stream.

I've never played with any modern test gear, so I hope someone can tell us what the heck this looks like to them.
 
When the pattern comes to a point, that's negative 100% modulation, right?

The way I understand it, you connect the RF sample to the Y axis (so that the trace keeps wiggling up and down, filling in the trapezoid), and the audio to the X axis (so that when the audio is negative, it'll pull the trace to the left, and when the audio is positive, it'll pull the trace to the right).

This way, a negative DC input signal would cause a point at the left side of the screen (since there's almost no carrier then), and positive DC input signal would cause a vertical line at the right side of the screen (since there'll be plenty of carrier).

Did I get it right? :)

///Leif
 
Re: NEW FM PROCESSOR scope audio trapezoid Lissajous

OK, here is the more standard horizontal trapezoid pattern as seen in the reference material.
Sorry about the glitching that occured on the upload, but it doesn't affect the ability to show the extent of the
positive modulation over 100%.

RF is on the Y axis, rectified audio on the x axis. If the audio were not rectified the trapezoid would try to turn into a "diamond".
Both pos and neg audio extend the trapezoid to the left, -100% brings it to a point, +100% and beyond extends the trapezoid
as far as conditions and parameters will permit.

http://www.youtube.com/watch?v=Gow02d4Mock
 
konbaasiang said:
Tom, I still can't make heads or tails of your video!

Isn't it supposed to look like this?

///Leif
Click to expand...
That would be the pattern I get when I put unrectified audio into the x input.
I'll make another video of that. It is not as easy to compare the +/- when they are at opposite ends of the display.
When both pos and neg audio run the trace the same way, it is easy to see that the positve peaks go way beyond the negative.

I'm trying to figure out now what a SHARC is. http://www.youtube.com/watch?v=A1aOwvM7l0s

What are we looking at here?
 
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