I must admit, CD has done it again. I asked and I received the type of information that will really help. Most of this type of help comes from experience and wisdom directly related to the subject!
Quote:
Originally Posted by Al Skierkiewicz
Mr. Bill,
The kit you bought is intended for very low output and so very short distances. It is a simple design but may be subject to input overload from your audio source. A couple of input pots would easily eliminate that problem. Since the output circuitry is very simple, it is unlikely there will be an efficient coupling to your antenna making the range even shorter....
When you wish to upgrade, take a look here...
http://www.ramseyelectronics.com/hk/....asp?page=amfm
I recently built an FM100B for the radio station here....
I don't have a problem with zener diode circuitry if properly designed. However, in this application, the zener may introduce significant additional noise that will degrade the transmitted audio. |
Agreed, low end kit for first time attempt. I have a feeling I will learn more this way. Additionally, I do have some experience to draw from, I am a EE, that has to count for something.
I looked at the FM10C kit offered on that site Al, it looks as though the circuit is very close to the one in my kit. We will see how it turns out.
I had already planned on adding a couple trim pots on the input if the need arose, so at least we are on the same page there.
Quote:
Originally Posted by Dave Flowerday
Bill, I strongly recommend you do your own research with the FCC who holds the authority for these types of devices....
And, most importantly, you cannot interfere with any licensed broadcaster in the band. If you cause interference for any of your neighbors who are trying to listen to a licensed station, you are violating federal law. The FCC has been known to crack down on offenders too, so don't just assume that no one will notice and you'll get away with it.
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Excellent advice and something I have followed up on. Although, I don't have the proper test equipment to measure the field strength of the signal. So, I will try a couple other tests, such as, if I can't pick up the signal beyond my home, I should be in good shape. If Al's assumption of "Bluetooth range" is true, I will be in good shape.
Quote:
Originally Posted by squirrel
This is the crux of the matter...and whether or not you'll be able to do this depends on how far away your neighbors are. I'm lucky, we live on 4 acres, and the nearest houses are about 500 ft away, so we could probably make an FM transmitter system for our house that would meet the interference requirements, even though it might exceed the allowable field strength. If you're in an apartment or high density housing tract, it might be impossible.
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Middle of town, .25 acre lot, nearest neighbor 50 ft. from where the transmitter will be. Hmmm, that's three strikes.
Quote:
Originally Posted by Don Rotolo
The distance you'll be able to go with an unmodified kit depends on what is between you and the antenna. A bunch of metal, not so far. Nothing but air, a lot further. Antenna in the basement, not so far. In the attic, or on the ground floor (in the linen closet?) better.
Build it, try it, and only if it's not OK do you go further. 200 feet on a few microwatts is easy.
500 mW or 1 Watt is WAY in excess of legal limits. A typical NAL (Notice of Apparent Liability = a fine) for unlicensed FM broadcast exceeds $10,000. Oh, and the FCC can find such a transmitter in perhaps 10 minutes, if it goes looking.
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Don, you and I are on the same page. Honestly, the only changes I plan on making involve audio quality. If the range is good enough to make it to the garage, I'll be happy.