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I have one of these transmitters and am dealing with sound that's too quiet and lackluster compared to other radio stations. I know the problem lies with the transmitter, not breakaway or the sound card because another transmitter we were using on the same system didn't have this issue.
Here is a link to the transmitter:
http://www.fmtron.com/data/50w.php?item_id=85I have used an oscilloscope to verify that the sound card output has no major defect. Tilt is correct, etc
Pre-emphasis has been disabled at the transmitter and is handled solely by Breakaway. Over-modulation isn't occurring, but it happens easily if I try to raise the gain beyond what it is now. I am not using a multiplex output.
Any thoughts on what I can try?
Unless you can run MPX/Composite into the transmitter, it's not going to ever perform very well at all. The Left/Right audio inputs have a high-pass of 50Hz, and probably phase distortion from the filter which will distort the waveform a LOT.
See if you're able to use that RDS/SCA/MPX input for the *entire* MPX/Composite input with audio in it as well. If there's no high-pass filters on that either, then you should be sounding pretty good & loud on air. 🙂
Thanks for the reply. I tried to use that MPX input but I get screeching high sounds with no base or mid range. Am I doing something wrong?
Seeing RCA connectors for audio inputs and a microphone input starts alarm bells ringing straight away with me that this must be a cheap transmitter and most certainly not what most would consider a Professional unit.
It's unlikely that you can disable the internal stereo encoder, my guess is that it's all on the one board with no way to defeat it and connect a MPX signal straight to the exciter. I notice there is an RDS input socket but this is just combined with the already internally generated stereo MPX signal.
If the audio sounds very flat and lacking in high frequency, maybe in BBP, you have pre-emphasis on but if you are using the L/R outputs and not the MPX out, maybe the de-emphasis is selected on, which will mean that the pre-emphasis is not getting passed on, it's being reversed before the output.[quote author=yorkie98 link=topic=5352.msg18939#msg18939 date=1482077955]
Seeing RCA connectors for audio inputs and a microphone input starts alarm bells ringing straight away with me that this must be a cheap transmitter and most certainly not what most would consider a Professional unit.
It's unlikely that you can disable the internal stereo encoder, my guess is that it's all on the one board with no way to defeat it and connect a MPX signal straight to the exciter. I notice there is an RDS input socket but this is just combined with the already internally generated stereo MPX signal.
If the audio sounds very flat and lacking in high frequency, maybe in BBP, you have pre-emphasis on but if you are using the L/R outputs and not the MPX out, maybe the de-emphasis is selected on, which will mean that the pre-emphasis is not getting passed on, it's being reversed before the output.
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Thanks for the reply. The transmitter is a piece of junk. I'd urge anyone to avoid most Chinese transmitters as they lack quality for a number of different reasons. In this case, pre-emphasis is disabled at the transmitter and enabled in breakaway without de-emphasis checked. The sound quality problems are minimal but existent nonetheless. For our small radio station we will be replacing the Chinese junk with a Tugicom transmitter.
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