How To Questions -FM Transmitter Antenna

N

NavySWO91

New member
I have a FM transmitter for my Kulp board which I am thinking about using. If I decide to use it, I won't need to transmit very far. From what I gather all I need for an antenna is about a 75-76cm wire soldered to the antenna pad. I have briefly toyed around with it on the bench and I do get output, although it is quite finicky, producing quite a bit of static, some of which I attribute to a shoddy test setup.

I have a few questions as I think about packing my enclosure:

1. How well will just a wire work inside an enclosure? Will it be affected by the 600W power supply also in there? or the wifi antenna I may have in there also?
2. How should I route this wire - inside the box or somehow bring it outside the enclosure?
3. Seems like it would be good to have a disconnect somehow instead of the antenna wire soldered to the board. How can I add a connector?
4. Should I consider the dipole antenna I have seen a design for or another type of external antenna attached to the outside of the enclosure? Are those options for this transmitter? In either case, how would I connect an external antenna to this board- center wire to antenna pad and the "shield/grnd" wire to any other GND on the transmitter board?

Appreciate your thoughts.
 
I have similar questions. Did you ever get any answers or do some more experimenting? I have the same setup and am getting a ton of static. Just wondering what you have found to work.
 
Generally speaking, transmitting radio antennae near power supplies is a really, really, really bad idea. For an antenna to be efficient, it should be "tuned" to the frequency you intend to use. This is usually done by altering the length of the wire. If it's not tuned, it may still work somewhat, but it can damage the transmitter if too much RF energy is reflected back to the transmitter's final amplifier circuitry.
 
Yes, what dirknerkle said. Here is a link to building your own "tuned" antenna. The size of the antenna is directly proportional to the frequency you're transmitting.
http://www.doityourselfchristmas.com/wiki/images/a/a7/How_to_make_a_dipole_antenna.pdf
If I remember correctly, antenna's typically have 50ohm impedance, so I used old 50ohm 10Base2 (thin net) networking coaxial cable with BNC connectors to connect my antenna. You could solder a coax w/ a male BNC connector to your board. Make your tuned antenna w/ another male coax connector. Then use coax extension cables in between, which will have female connectors on both ends. My antenna is in the overhang of my front door. In the ceiling of my garage, where my show controllers are, I have an electric box/cover plate that has RJ45 and BNC going to the various connection points through out my house to connect all the show hardware.
 
Just a heads up...make sure you don't have your volume slider all the way up in your controller. Mine was at 100 last year and static was horrible. Dropped it to 70 and all was good.
 
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