Vastelec FM02: Difference between revisions
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Revision as of 01:54, 30 September 2011
The FM Transmitter with DIY possibilities
The FM02 is a two board FM transmitter. It accepts a stereo audio source and outputs a stereo FM broadcast signal on the frequency shown on the LED display. It comes just as shown in the picture above.
It is rated at 30mw (that's milli-watts) of transmission power. For most Christmas DIYers this is a nearly perfect amount of power. It will transmit a clear signal for about 2 blocks or 1/4 mile. Why is this good? Because it is illegal in the USA to transmit other then very low amounts of FM radiation without an FCC license.
The FM02 is not a complete unit ready for use. Instead, it bridges the gap between an out-of-the-box solution, and a build-your-own unit that starts with a bare PCB and a bag of parts.
The FM02 is very small, but packs in a nice set of features.
Key to these is the use of PLL (Phase Locked Loop) technology. PLL keeps the transmitter locked into the designated transmitting frequency without it drifting up or down. This frequency drift WILL occur on other FM transmitters without PLL as the temperature around the unit goes up or down.
The second key feature is the fact that the transmitting frequency is maintained even after power is turned off and back on.
The FM02 is a very sophisticated assembly. Building a unit of this capability and size would be nearly impossible for most DIY'ers.
So, to create a usable FM transmitter, the FM02 needs some help. The builder of the transmitter will take the FM02 and use it as the corner stone of a complete transmitter.
You will need the following items added to your FM02:
- Power. A regulated 12v DC power supply is needed. 50ma is enough current.
- An Antenna. Never power your unit without an antenna.
- A mounting enclosure. You will need to mount the FM02 boards somewhere safe and dry.
About VAST Electronics
http://doityourselfchristmas.com/forums/showthread.php?12895-FM02-Transmitter-Setup
Power Requirements
Do NOT power it up without an antenna. You don't need to have your 'real' antenna ready for this. You can put the adapter on and then stick a 12" piece of wire into the center of the BNC connector. This will dissipate the RF energy just fine. Just be sure you don't enlarge the hole inside the BNC.
DO NOT apply anything GREATER then REGULATED 12V DC to your unit. If you aren't sure, then ask for help in the forums. Use a meter to check the voltage first. If all you have is a wall-wart that is labeled 12V, then that is most likely NOT regulated. A simple test of the output voltage with a meter will tell the tale. I use one of the voltage regulators from Sure Electronics with my unit. These are about $5 online.
Many folks will experience some HUM when using a wall wart for power that is then regulated via voltage regulator. This is normal. The good news is that you should be able to eliminate this hum with the use of a Ferrite Bead. (more to come)
Detailed Board Dimensions
Outline of the 'display' board.
The second board has the same physical outline dimensions. It also lines up with the 4 corner mounting holes.
Antenna
The FM02 has an antenna connection that will look a bit unusual to most folks. It is known as an SMA type of connector.
Most DIY'ers will want to convert this to the BNC type of connector because BNC components are easier to find. The converter shown below will correctly hook to the FM02. SMA is the smaller gold connector.
Setup
Where can I get one of these wonderful devices ?
These come up as group buys on the DIYC forum from time to time.
They may also be available at WLC Ventures.
They have also been seen for sale on eBay.