$31 fm alignment signal generator

[Carbsandcaps]

So i put together this very inexpensive fm alignment setup. The signal generator from alibaba ($15) and the fm transmitter from Mercari ($16). The signal generator is very very nice for its price and size. You can set the frequency and control the amplitude from a dial. There a different patterns to chose, sine, square, triangle, sawtooth, sawtooth reversed, and ECG (not sure why but it looks cool on the scope). The fm transmitter allows you to choose the frequency to find an empty spot on the dial and has a nice long antenna for good reception.

I’ve got the output of the tuner hooked up to a speaker so I can hear it along with my scope so I can see the amplitude. I’m also going to test the output with a dmm and a vtmm for comparison for people without a scope. I’ve decided in my personal setup that a 500mhz signal sent to fm 106.5mhz sounds the clearest.

The goal is to get a stereo MPX signal out of my Harmon kardon tuner that through a stroke of genius, or just a stroke, I decided to align by ear. It works and sounds fine as it is but doesn’t send a strong enough signal to activate my MPX adapter.

I admittedly don’t know what I’m doing so any input is appreciated.

 

[Punker X]

Having yoru transmitter so close to the unit it will be hard to "peak out" your signal. You may need to move it farther away, did it give you how much power it it transmitting at. Some Chinese one put out quite a bit of power. More than enough to get into trouble with the FCC.

 

[Carbsandcaps]

Having yoru transmitter so close to the unit it will be hard to "peak out" your signal. You may need to move it farther away, did it give you how much power it it transmitting at. Some Chinese one put out quite a bit of power. More than enough to get into trouble with the FCC.

No it came in a cardboard box with no instructions. I wouldn’t be surprised if it was above the limits. It took out every station no matter what it was tuned to. Kind of like the super powerful and super illegal green diode laser pointers you can get on eBay.

 

[Bob@FM]

I would put at least 40-60 dB of attenuation on the "antenna out" connector, before the antenna. Be careful - with it that close to you, those kind of unknown RF radiation levels can have adverse health effects. Agreed, these can put out way more power than you want, or need - and in this case, too much is bad thing .. If you can hear it on your car radio more than 50-100 ft away, it's way too much.

RF Safety FAQ

Frequently asked questions about the safety of radiofrequency (RF) and microwave emissions from transmitters and facilities regulated by the FCC For further information contact the FCC's RF Safety Program at rfsafety@fcc.gov or 1-888-225-5322 Index (click on topic below)

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