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Tilt Issue!
https://forums.stereotool.com/viewtopic.php?f=6&t=33331		 Page 3 of 4
Author:  TheDaChicken [ Wed Oct 26, 2022 3:57 am ]
Post subject:  Re: Tilt Issue!
Quote:
That is 30 kHz??? Not 30 Hz??? 30 kHz square wave is a sine wave anyway (the sound card doesn't go high enough). And that high frequency stuff is the actual audio I assume??

It could be that very loud 30-60 kHz tones confuse the SDR, to rule that out, try lowering the level.
Oops! Yes, I meant that the overshoot was 30hz. That would be really considering if that was khz. That was a misunderstanding I read the FM Test tone as in khz. :D Worried me for a second.

Ahem knowing that it is in hz, I tried 30,000hz-30,000hz yep, still same issue. I tried lowering the volume to where it said 61% modulation. It still has the same issue except it would only go down 2%. I would assume that is considered fixed?

Also, asking since I am not an FM transmitter expert since I also saw this while testing 30khz, is it normal when testing 30khz sine that I can see on the RF FTT that the goes outside the 200khz bandwidth? That is also occurring.
Author:  KDST [ Fri Oct 28, 2022 5:58 am ]
Post subject:  Re: Tilt Issue!
Quote:
Quote:
That is 30 kHz??? Not 30 Hz??? 30 kHz square wave is a sine wave anyway (the sound card doesn't go high enough). And that high frequency stuff is the actual audio I assume??

It could be that very loud 30-60 kHz tones confuse the SDR, to rule that out, try lowering the level.
Oops! Yes, I meant that the overshoot was 30hz. That would be really considering if that was khz. That was a misunderstanding I read the FM Test tone as in khz. :D Worried me for a second.

Ahem knowing that it is in hz, I tried 30,000hz-30,000hz yep, still same issue. I tried lowering the volume to where it said 61% modulation. It still has the same issue except it would only go down 2%. I would assume that is considered fixed?

Also, asking since I am not an FM transmitter expert since I also saw this while testing 30khz, is it normal when testing 30khz sine that I can see on the RF FTT that the goes outside the 200khz bandwidth? That is also occurring.
The transmitter modulator (probably some analog PLL circuit) is very bad. even a raspberry pi can generate a better signal. try BW Broadcast with DDS modulators. or some old transmitter with crystal based modulator. (they're not very stable at startup but soon they get "warm" you will get perfect modulation. Do not fight against the PLL modulator. Even if you get perfect square wave, it will lose frequency with bass and bottom end sounds. Take a look at the power supply too. Bad eletrical levels on the PLL modulator usually does this type of harm to the sound. specially at 30hz
Author:  TheDaChicken [ Sat Oct 29, 2022 2:19 am ]
Post subject:  Re: Tilt Issue!
Quote:
Quote:
Quote:
That is 30 kHz??? Not 30 Hz??? 30 kHz square wave is a sine wave anyway (the sound card doesn't go high enough). And that high frequency stuff is the actual audio I assume??

It could be that very loud 30-60 kHz tones confuse the SDR, to rule that out, try lowering the level.
Oops! Yes, I meant that the overshoot was 30hz. That would be really considering if that was khz. That was a misunderstanding I read the FM Test tone as in khz. :D Worried me for a second.

Ahem knowing that it is in hz, I tried 30,000hz-30,000hz yep, still same issue. I tried lowering the volume to where it said 61% modulation. It still has the same issue except it would only go down 2%. I would assume that is considered fixed?

Also, asking since I am not an FM transmitter expert since I also saw this while testing 30khz, is it normal when testing 30khz sine that I can see on the RF FTT that the goes outside the 200khz bandwidth? That is also occurring.
The transmitter modulator (probably some analog PLL circuit) is very bad. even a raspberry pi can generate a better signal. try BW Broadcast with DDS modulators. or some old transmitter with crystal based modulator. (they're not very stable at startup but soon they get "warm" you will get perfect modulation. Do not fight against the PLL modulator. Even if you get perfect square wave, it will lose frequency with bass and bottom end sounds. Take a look at the power supply too. Bad eletrical levels on the PLL modulator usually does this type of harm to the sound. specially at 30hz
Though, knowing the crap I have, yes. It is very bad.

Thanks for the recommendation! Though, one of the reasons I chose PC electronics is due to their low power. I'm only really looking for ~100mW - 15W. I have very limited options. ¯\_(ツ)_/¯

I bought the power supply from them and they say "it's a good power supply." I am not using some random power supply I found around the house...
Author:  TheDaChicken [ Tue Nov 29, 2022 1:53 am ]
Post subject:  Re: Tilt Issue!
I hate to bump a dead thread.

What are some good recommendations for a better FM transmitter that's low power? Knowing what I bought and what I got out of it, it is bothersome knowing if I will get something that would be a good FM transmitter. I hope that my doubt is justified

For example, in like this thread: viewtopic.php?t=5828
1) One of the companies recommended is PCS electronics... (ahem the crap I got)
2) Many options from a range of companies.

Really, I don't want anything big. Just something that can work in my car that has MPX input. I don't know what is tested and what's not to provide a good signal.

Plus, I have my dad (let's say he's never been a supportive parent...) saying I should get a new hobby. Oh my lord.
Author:  hvz [ Tue Nov 29, 2022 10:09 pm ]
Post subject:  Re: Tilt Issue!
Something that can work in your car? I've used a small battery powered transmitter that I bought for 15 euro when I originally developed the stereo/RDS encoder; modulation level isn't perfect (it has a few kHz overshoots) but it sounds good enough after (a lot of) calibration, with decent stereo separation etc. But I assume that that's not what you're looking for? If you're testing it in your car, I can tell you from experience (from using an analyzer in my car) that the power supply that you can from the car battery can be very noisy and cause all kinds of problems.
Author:  MrKlorox [ Wed Nov 30, 2022 5:59 pm ]
Post subject:  Re: Tilt Issue!
Quote:
Really, I don't want anything big. Just something that can work in my car that has MPX input.
Excuse me for this suggestion if it's not the end result you're looking for since it does not solve the FM transmission issue. To play processed Stereo Tool audio in my car, I use the built-in streaming engine with Icecast and stream it to AIMP on my phone (for some reason the VLC app won't play it). I control the music with Spotify Connect from my phone and have it play on my home PC. And of course, I adjust the sound via the web interface.

Please ignore this if it's not the approach you need.
Author:  TheDaChicken [ Thu Dec 01, 2022 1:18 am ]
Post subject:  Re: Tilt Issue!
Quote:
Something that can work in your car? I've used a small battery powered transmitter that I bought for 15 euro when I originally developed the stereo/RDS encoder; modulation level isn't perfect (it has a few kHz overshoots) but it sounds good enough after (a lot of) calibration, with decent stereo separation etc. But I assume that that's not what you're looking for? If you're testing it in your car, I can tell you from experience (from using an analyzer in my car) that the power supply that you can from the car battery can be very noisy and cause all kinds of problems.
Well, my idea is to mainly use it in the car but I do also want to keep it running inside my house. I am okay-ish with it being noisy in the car. I've been testing it inside my house and it's all over the place while the FM Transmitter has been in the house. I would say that just using that FM Transmitter in the house is pretty annoying to use. I don't know how I would test to check if it's the power supply? Would a bad power supply cause so much tilt + harmonics? How can I tell if it's the transmitter?

In my personal opinion, it would be so cool to be able to broadcast my own signal (even if it's just at home) that isn't shallow, & very loud.
Quote:
Excuse me for this suggestion if it's not the end result you're looking for since it does not solve the FM transmission issue. To play processed Stereo Tool audio in my car, I use the built-in streaming engine with Icecast and stream it to AIMP on my phone (for some reason the VLC app won't play it). I control the music with Spotify Connect from my phone and have it play on my home PC. And of course, I adjust the sound via the web interface.

Please ignore this if it's not the approach you need.
Well, yeah not necessarily what I really want to do. But that's a good idea. Though I don't really want to use any internet and that will require me to use my data plan.
Author:  TheDaChicken [ Tue Dec 06, 2022 5:34 am ]
Post subject:  Re: Tilt Issue!
Well, update:

I tried buying a power supply instead of the one that was got from PCS electronics to see if it would do anything. Didn't change anything. ¯\_(ツ)_/¯

Same "harmonics" (if you would call that) in the spectrum analyzer... Just still a bunch of weird behavior...
viewtopic.php?p=72401#p72401

Still feeling the same eh feeling because I am like ¯\_(ツ)_/¯

I feel so scammed LMAO
Author:  Greg Strickland [ Wed May 17, 2023 2:45 pm ]
Post subject:  Re: Tilt Issue!
TheDaChicken- I understand your interest in getting things perfect. Are you in the USA? If so you are operating as a Part 15 station, and as a practical matter modulation level is not regulated. Adjust it to sound as you like and have fun broadcasting to nearby radios.
Author:  mm1980 [ Fri Aug 04, 2023 11:48 pm ]
Post subject:  Re: Tilt Issue!
Older generations of PCS transmitters had a tilt problem, but nothing like the one in the pictures.
Let's go to find solution:

1. if you already have a sound card capable of generating 192KHz, make a simulation of what comes out of it. So connect the "mpx output" of the sound card directly to the line in (which must also be set to 192khz). I see that you are using the MPX tool, select the line in sound card as the source.

Now test the square, sine in the band 20Hz-57KHz and inspect the purity of the spectrum. If everything is ok, let's move on! Maximum frequency deviations across the spectrum may be 5% (sine test).

2. If it turns out that what comes out of the card is OK, disconnect from the pcs8000 board all the cables except the display.
Improvise a cable that you will connect to the "audio input" pins on the transmitter board. Check if the preemphasis jumper is in the 0 position

3. The transmitter MUST be either on dummy load or on an adequate antenna for VHFII during operation. Otherwise, you will have nasty parasitic interference on the equipment and in the RF spectrum.

3. Generate on the stereotool 400Hz frequency, and adjust the audio level on the transmitter board until you read 100% modulation on the MPXtool analyzer.

4. Now test first the sine at 50Hz. In this test, normally the maximum deviations may be 5%. If the readings are higher (10-15%), the transmitter does not have a flat response, but this can be corrected if there is a sinusoidal shape on the reading. If you read irregular shapes, it means that the problem is with the transmitter modulator, and there is nothing you can do about it.

5. Test the square. If the response has gentler slopes, this can also be corrected.

6. I see that you have a problem with the frequency deviation on the SDR. It doesn't necessarily have to be a problem in the transmitter. If you use a dongle without a TCXO reference crystal, then the dongle itself has reception error in the range of a few kilohertz on VHFII (depending on the ambient temperature)

7. If you're still looking for a good little fm exciter, hit nrg shop or duchrfshop with DIY kits.

Good luck!

PS
You mention that you have a compressor in the chain. You have to throw out everything on the way from the output of the sound card to the MPX input of the transmitter!
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