FM Transmitter Troubleshooting & Tips

[amybing1999]

With our first year using a FM Transmitter we thought it maybe helpful to search for any troubleshooting/ tips people have found over the years whilst using them.
In hopes it not only lets us grow but also other people who may be searching for FM tips also.

 

[djgra79]

Not so much the transmitter itself but make sure you check on a couple of different devices the radio frequency you wish to use. Make sure it is not close to an existing station, including smaller local/regional stations with much weaker transmitions, aso you may over-power this in your local area.
I thought I had a clear frequency on the stereo I use to power a speaker out the front, but when I tuned in my car radio the next day when the display ws off, it was a faint signal of an existing station so I had to change it after already advertising the frequency.

 

[Skymaster]

I went through 3 frequencies before I found one that didn't clash. Worked out that one of my cars had as sensitive radio that picked up much more than the other.
Eventually found a blank frequency, then i drove with the radio tuned to this (transmitter off) listening to static for 3 blocks each direction. This made sure that I won't clobber any other station within my broadcast area.

Keep the frequencies to the odd decimal. So 89.3, 102.9 etc, not an even (104.6). In Australia we use 0.2Mhz channel spacing starting at 87.5Mhz. Some radios enforce this and so if you set your transmitter to an even decimal frequency, those people won't be able to tune in.

Don't feed in too high of a signal. You may clip the input of the transmitter, causing distortion, or weird behaviour with the stereo subchannel.

If you're using the CZE05 transmitter that mosy do, make sure you set it to low power mode. This is done by unplugging the unit, pressing and holding the power button, and plugging it in to power. This will then enter a set up mode. Set L for low power, then set the maximum frequency to 108.1Mhz, and the minimum to 87.5Mhz

Keep the transmitter away from other equipment. It has caused issues in the past, especially with Pi's and Soundblaster cards, causing them to lock up and crash mid show.

 

[Indigogyre]

Keep the transmitter away from other equipment. It has caused issues in the past, especially with Pi's and Soundblaster cards, causing them to lock up and crash mid show.

Sure, now you say something. I had my PI in the same case as the transmitter stacked on top of my wifi router all cozy together. Everything worked but I did have more static this year for Halloween then last year. Not sure why. I'm in the process of moving things around for the Christmas show.

Also, I did notice we have more signals on the frequency I used last year so will also have to find a new one this year.

Hmm, something to add to this constructive? If putting your transmitter outside into a case look to swap the antenna out for one that can be mounted to the case without leaving open holes.

 

[Domestos]

Another good idea is to make sure all your audio files are at the same volume level. Assuming you are using MP3 files, a simple free tool you can use is MP3 Gain.

 

[DarkwinX]

Excellent advice all, I was going to be working through this for this year - well timed thread @amybing1999

 

[TerryK]

Another good idea is to make sure all your audio files are at the same volume level. Assuming you are using MP3 files, a simple free tool you can use is MP3 Gain.

Audacity has an Effects "Loudness Normalization" tool that does something similar. It amplifies relative to perceived loudness whereas the Effect "Normalize" tool amplifies to a peak db level. If memory serves, the Loudness Normalization tool amplifies to a RMS LUFS level (Loudness Unit Full Scale I think). In any case, the Audacity Help explains how each normalization effect works.

 

[amybing1999]

This damn transmitter will be the death of me
We have it as perfect as we can get it then the Husband walks away from it and bam it all goes to HoHoHo
Who would have thought this would be the hardest part of my first year hahaha

 

[John_82]

I went through 3 frequencies before I found one that didn't clash. Worked out that one of my cars had as sensitive radio that picked up much more than the other.
Eventually found a blank frequency, then i drove with the radio tuned to this (transmitter off) listening to static for 3 blocks each direction. This made sure that I won't clobber any other station within my broadcast area.

Keep the frequencies to the odd decimal. So 89.3, 102.9 etc, not an even (104.6). In Australia we use 0.2Mhz channel spacing starting at 87.5Mhz. Some radios enforce this and so if you set your transmitter to an even decimal frequency, those people won't be able to tune in.

Don't feed in too high of a signal. You may clip the input of the transmitter, causing distortion, or weird behaviour with the stereo subchannel.

If you're using the CZE05 transmitter that mosy do, make sure you set it to low power mode. This is done by unplugging the unit, pressing and holding the power button, and plugging it in to power. This will then enter a set up mode. Set L for low power, then set the maximum frequency to 108.1Mhz, and the minimum to 87.5Mhz

Keep the transmitter away from other equipment. It has caused issues in the past, especially with Pi's and Soundblaster cards, causing them to lock up and crash mid show.

What distance do you need?
I’ve got a 1W device and it keeps locking up the soundcard and I’ve got it 5meters away

 

[Skymaster]

Can you push the output power down? 1W is a pretty hefty transmitter and overkill. The CZE05's are a 0.5W on high power and 0.1W on low power.

You might find putting the transmitter in a metal box will help attenuate the signal to the point where it doesnt interfere. Or at least a metal sheet (grounded even better) - between the transmitter and the Pi / Soundcard would help too.

 

[John_82]

Can you push the output power down? 1W is a pretty hefty transmitter and overkill. The CZE05's are a 0.5W on high power and 0.1W on low power.

You might find putting the transmitter in a metal box will help attenuate the signal to the point where it doesnt interfere. Or at least a metal sheet (grounded even better) - between the transmitter and the Pi / Soundcard would help too.

Yeah I made the mistake of buying a 1W/7W transmitter, I can run it on low at 1W. But still causing lots of issues, I’ll try a metal box and see if that helps, I think I’ll just look at sourcing a lower power transmitter

 

[Skymaster]

Yeah I made the mistake of buying a 1W/7W transmitter, I can run it on low at 1W. But still causing lots of issues, I’ll try a metal box and see if that helps, I think I’ll just look at sourcing a lower power transmitter

https://www.amazon.com.au/Retekess-Wireless-Broadcast-Transmitter-Station/dp/B088T63LPM/ref=sr_1_2

This is the one I use.

 

[John_82]

Awesome thanks, will give it a go!

 

[TerryK]

Transmitters whether FM or AM almost always are enclosed in a metal enclosure to keep the oscillator frequency and harmonics of the transmitter from leaking 'outside' with the possibility of effecting nearby equipment. Typically the metal enclosure (the transmitter's chassis essentially) is also connected to an earth ground in the attempt to dump any RF on/in the enclosure. Note that earth ground is not the same as the V- or GND terminology used in the pixel string connections.

If the transmitters output is too high, another possibility is to a insert an attenuator between the transmitter's output and antenna.

 

[John_82]

https://www.amazon.com.au/Retekess-Wireless-Broadcast-Transmitter-Station/dp/B088T63LPM/ref=sr_1_2

This is the one I use.

Just wanted to follow up and say thank you ! I ordered one of these on Saturday night and arrived on Monday! FM transmitter is now working again for my show