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 Post subject: Tilt Issue!
PostPosted: Tue Sep 27, 2022 6:33 am 
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Joined: Sun Mar 06, 2022 3:41 am
Posts: 54
I (not recently because it's been too long due to me being busy) got an FM transmitter. I wanted to broadcast loud and with a very good signal! I mean, of course, I am a perfectionist. Haha

When I tried to broadcast, I got a huge amount of tilt up & down showing up on my RTLSDR on the MPX. Including a lot going out of bounds of the 200khz bandwidth. If I used a highpass filter on stereotool and removed all the bass to 150hz it would fix it.

I tried using the Tilt Correction on Stereo Tool. I wasn't able to fix the tilt (or not enough for me to notice).
Using that, I would be able to make square waves straight at around ~100khz when testing those but it wouldn't be able to fix the issue. Plus, adding more tilt correction would just end up increasing the modulation level and making the square waves not straight.
I then got the HiFiberry sound card as it was recommended as a cheaper way but provides a good signal. I was thinking it would be better but it wasn't. It still had the same problem as a Realtek ALC892 I have on my PC and as another Realtek from an old PC I had laying around.

The FM transmitter is from PCS Electronics which said it would produce a good signal. I even tried contacting them about this issue and they told me it wasn't an issue with the FM Transmitter.

My setup:
Yeah, I do not have the proper equipment for looking at modulation levels. That may also be an added problem. I am using RTLSDR and outputting MPX to a virtual audio cable. I am using MPXTool to look at the output.
Currently, I am outputting from HiFiberry on the raspberry pi. Stereotool is running on the raspberry pi 4b. I have RCA cables connected to the Fm transmitter from the hifiberry. I have the FM Transmitter set to MONO.

This is what the tilt looks like:
Image
Image

I could send an MPX recording if you helpful.
Any feedback would seriously be so helpful on how to fix this!


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 Post subject: Re: Tilt Issue!
PostPosted: Tue Sep 27, 2022 12:26 pm 

Joined: Fri Aug 07, 2020 7:24 pm
Posts: 65
Quote:
I (not recently because it's been too long due to me being busy) got an FM transmitter. I wanted to broadcast loud and with a very good signal! I mean, of course, I am a perfectionist. Haha

When I tried to broadcast, I got a huge amount of tilt up & down showing up on my RTLSDR on the MPX. Including a lot going out of bounds of the 200khz bandwidth. If I used a highpass filter on stereotool and removed all the bass to 150hz it would fix it.

I tried using the Tilt Correction on Stereo Tool. I wasn't able to fix the tilt (or not enough for me to notice).
Using that, I would be able to make square waves straight at around ~100khz when testing those but it wouldn't be able to fix the issue. Plus, adding more tilt correction would just end up increasing the modulation level and making the square waves not straight.
I then got the HiFiberry sound card as it was recommended as a cheaper way but provides a good signal. I was thinking it would be better but it wasn't. It still had the same problem as a Realtek ALC892 I have on my PC and as another Realtek from an old PC I had laying around.

The FM transmitter is from PCS Electronics which said it would produce a good signal. I even tried contacting them about this issue and they told me it wasn't an issue with the FM Transmitter.

My setup:
Yeah, I do not have the proper equipment for looking at modulation levels. That may also be an added problem. I am using RTLSDR and outputting MPX to a virtual audio cable. I am using MPXTool to look at the output.
Currently, I am outputting from HiFiberry on the raspberry pi. Stereotool is running on the raspberry pi 4b. I have RCA cables connected to the Fm transmitter from the hifiberry. I have the FM Transmitter set to MONO.

This is what the tilt looks like:
Image
Image

I could send an MPX recording if you helpful.
Any feedback would seriously be so helpful on how to fix this!
1)dont use mpxtool with vbaudio cable. just enable the mpxtool's rf reciever
2)your transmitter might have some tilt
3)so as your sound card

fix number 1 and then you will easily fix the tilt issue


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 Post subject: Re: Tilt Issue!
PostPosted: Tue Sep 27, 2022 3:02 pm 
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Joined: Tue Mar 17, 2009 2:56 pm
Posts: 4151
How it looks if you measure other stations?

To me it looks your transmitter is very bad, i saw similar - very sensitive to very low bass, or you are not passing good signal to MPX tool.

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 Post subject: Re: Tilt Issue!
PostPosted: Tue Sep 27, 2022 9:39 pm 

Joined: Mon Dec 12, 2011 5:02 pm
Posts: 123
Quote:
I (not recently because it's been too long due to me being busy) got an FM transmitter. I wanted to broadcast loud and with a very good signal! I mean, of course, I am a perfectionist. Haha

When I tried to broadcast, I got a huge amount of tilt up & down showing up on my RTLSDR on the MPX. Including a lot going out of bounds of the 200khz bandwidth. If I used a highpass filter on stereotool and removed all the bass to 150hz it would fix it.

I tried using the Tilt Correction on Stereo Tool. I wasn't able to fix the tilt (or not enough for me to notice).
Using that, I would be able to make square waves straight at around ~100khz when testing those but it wouldn't be able to fix the issue. Plus, adding more tilt correction would just end up increasing the modulation level and making the square waves not straight.
I then got the HiFiberry sound card as it was recommended as a cheaper way but provides a good signal. I was thinking it would be better but it wasn't. It still had the same problem as a Realtek ALC892 I have on my PC and as another Realtek from an old PC I had laying around.

The FM transmitter is from PCS Electronics which said it would produce a good signal. I even tried contacting them about this issue and they told me it wasn't an issue with the FM Transmitter.

My setup:
Yeah, I do not have the proper equipment for looking at modulation levels. That may also be an added problem. I am using RTLSDR and outputting MPX to a virtual audio cable. I am using MPXTool to look at the output.
Currently, I am outputting from HiFiberry on the raspberry pi. Stereotool is running on the raspberry pi 4b. I have RCA cables connected to the Fm transmitter from the hifiberry. I have the FM Transmitter set to MONO.

This is what the tilt looks like:
Image
Image

I could send an MPX recording if you helpful.
Any feedback would seriously be so helpful on how to fix this!
Input of PCS electronics exciters are not flat and this looks like it might be it.
We had one and it didn't performed with tight MPX as Siel's, RVR's or even Suono Telecom's. Some spikes went through no matter what I was doing with tilt...

Also after 2 output transistor failure, we decided that we will use it only for backup.


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 Post subject: Re: Tilt Issue!
PostPosted: Tue Sep 27, 2022 11:00 pm 
User avatar

Joined: Sun Mar 06, 2022 3:41 am
Posts: 54
Quote:
1)dont use mpxtool with vbaudio cable. just enable the mpxtool's rf reciever
2)your transmitter might have some tilt
3)so as your sound card
fix number 1 and then you will easily fix the tilt issue
I've seen many versions of MPXTool online. I have no clue what the history of all the versions is. I do not have any MPXTool program that reads directly from an RTLSDR. I don't think the vbaudio cable has any issues with this.
Quote:
How it looks if you measure other stations?

To me it looks your transmitter is very bad, i saw similar - very sensitive to very low bass, or you are not passing good signal to MPX tool.
Other stations look great through the vbcables to MPXTool! No tilting.

Here is an example of another station:
Image
Quote:
Input of PCS electronics exciters are not flat and this looks like it might be it.
We had one and it didn't performed with tight MPX as Siel's, RVR's or even Suono Telecom's. Some spikes went through no matter what I was doing with tilt...

Also after 2 output transistor failure, we decided that we will use it only for backup.
Most likely is the FM Transmitter...

This is actually my second transmitter from PCS Electronics. The first one I bought, they said the first one I bought wasn't great. They said it was the specific transmitter. I bought a new different one from them because they provided a way to fix the previous one that wasn't available for me and still the same issue.
The CEO of the company is just blaming my setup. They told me I cannot return it to get a refund because I am in the United States and it might not arrive.

The reason I went from PCS Electronics is that their transmitters can go low watts. Plus, I am not very familiar with any other options.

I don't know what else I could do. They weren't providing the greatest support that I wanted out of them. I really don't want to spend more money on another FM transmitter. I just want this issue to be fixed!


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 Post subject: Re: Tilt Issue!
PostPosted: Wed Sep 28, 2022 1:21 am 
User avatar

Joined: Tue Mar 17, 2009 2:56 pm
Posts: 4151
Ok so big chance that transmitter is bad. Try calibration in ST.
Before calibration turn OFF RDS and set pilot to ON but at 0%. You will start from 10240 tone. Read that number (ideally should be 71kHz) and then start from 20Hz and up. You must tune to that number.
When you done, try 34Hz squere from ST to adjust tilt.

_________________
control point
control point2


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 Post subject: Re: Tilt Issue!
PostPosted: Wed Sep 28, 2022 2:21 am 
User avatar

Joined: Sun Mar 06, 2022 3:41 am
Posts: 54
Quote:
Ok so big chance that transmitter is bad. Try calibration in ST.
Before calibration turn OFF RDS and set pilot to ON but at 0%. You will start from 10240 tone. Read that number (ideally should be 71kHz) and then start from 20Hz and up. You must tune to that number.
When you done, try 34Hz squere from ST to adjust tilt.
You talking about the extreme calibration, right?
Well, currently I cannot use the extreme calibration due to the new stereo tool web interface. When I enable it on the new stereo tool web interface, it doesn't really "enable" all the options are grayed out. I guess time to write a reply on the web interface forum page.
Should I tune only using the volume slider in extreme calibration and then use the low tilt option?

EDIT: The enable options are grayed out due to don't process high freqs being enabled. it wasn't telling me why


Last edited by TheDaChicken on Sun Oct 16, 2022 8:05 am, edited 1 time in total.

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 Post subject: Re: Tilt Issue!
PostPosted: Wed Sep 28, 2022 3:19 am 
User avatar

Joined: Tue Mar 17, 2009 2:56 pm
Posts: 4151
Quote:
Quote:
Ok so big chance that transmitter is bad. Try calibration in ST.
Before calibration turn OFF RDS and set pilot to ON but at 0%. You will start from 10240 tone. Read that number (ideally should be 71kHz) and then start from 20Hz and up. You must tune to that number.
When you done, try 34Hz squere from ST to adjust tilt.
You talking about the extreme calibration, right?
Well, currently I cannot use the extreme calibration due to the new stereo tool web interface. When I enable it on the new stereo tool web interface, it doesn't really "enable" all the options are grayed out. I guess time to write a reply on the web interface forum page.
Should I tune only using the volume slider in extreme calibration and then use the low tilt option?
Idk what is Extreme calibration. It's FM "Calibration" just under FM Output. Also use version where it works.

_________________
control point
control point2


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 Post subject: Re: Tilt Issue!
PostPosted: Wed Sep 28, 2022 3:28 am 
User avatar

Joined: Sun Mar 06, 2022 3:41 am
Posts: 54
Quote:
Idk what is Extreme calibration. It's FM "Calibration" just under FM Output. Also use version where it works.
Extreme calibration is just how it is labeled in the new web interface:
Image

but alright!


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 Post subject: Re: Tilt Issue!
PostPosted: Wed Sep 28, 2022 3:41 am 
User avatar

Joined: Tue Mar 17, 2009 2:56 pm
Posts: 4151
Don't use that crap, can you use old gui stuff where everything working fine?
There is like 5 sliders just for tilt. wich i don't see there. Also you can easily get lost in there.

_________________
control point
control point2


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