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I am really happy with my Sain Sonic FM Transmitter for my light shows, however I am not very pleased with the antenna performance. I also discovered that the company that makes them gets around the FCC requirements just like the WiFi makers did by using very hard to find RF connectors (RP-TNC with the threads flipped). So, in order to get effective use of the transmitter, I needed to build my own antenna and change the RF connector on the transmitter itself.
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As for building the antenna, you may notice the 50 Ohm indicator on the connector part of the case. This is the Impedance output of the transmitter, so you need to have an antenna with a matching impedance for max efficiency.
You might be able to get away with using a standard FM Dipole Antenna used for FM receivers, but understand that it won't work as well unless you use the 300 Ohm to 75 Ohm transducer.
A DIY Antenna might work better using 50 Ohm coax, and creating a dipole with speaker wire like I did here. Dipole calculators are available online, but here is an example to help you calculate your dipole length for an effective antenna. |  |
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| The RP-TNC with flipped threads |
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| De-solder the RF connector from the board |
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| Panel Mount BNC connector |
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| Short 50 Ohm coax between the connector and the board. |
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***Just a note, a friend of mine used a standard 300 Ohm FM Receiver antenna with his Sain Sonic, using 50 Ohm Coax to the antenna, and he was getting a Half Mile on Low Power.
