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simple rf

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dividebyzero

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I need help building a simple rf transmitter and receiver. I searched google, but nothing I found really explained anything well, or just used a module instead of building it.

So... anyone have any good links for learning this? or simple schematics that could be explained?

Any help would be nice.
 
Perhaps a few more details about your application, Rf is a huge field. I've only play at it a few times, usually requires considerable 'tweaking', which is why ready-made modules are so popular. I've been told it's not that bad, if you have the proper equipment

You should include more details to your post. What sort of signal do you wish to transmit. What kind of range do you hope to obtain? What frequency? Modulation?
 
I don't know what frequency I should use (40KHz?), but I would like it to be able to go throughout my house, and it is for an Rf to IR converter, so all need is a momentary pulse.

The _main_ reason I am doing this is to just learn how to do it, so that I can use it on other projects as well.
 
40kHz is a supersonic frequency, not a radio frequency. The AM broadcast band uses a very low frequency range of from 540kHz to 1600kHz.
 
You told us nothing about the application.
What distance?
How long can the antennas be?
What size is the battery?
How long must the battery last?
 
it is for IR to Rf to IR.
~100' distance through walls.
I don't really have any particular battery in mind, I was going to focus on getting a SIMPLE transmitter/receiver woking first.

edit:
The receiver will be stationary and will use wall power
 
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I have a commercially made IR to RF to IR repeater called a PowerMid **broken link removed** . It receives the IR signal at 40KHz and uses this 40 KHz to directly amplitude modulate a 315 MHz oscillator. The received 40 KHz simply turns the RF oscillator on and off resulting in pulsed RF. The transmitter has a very simple antenna consisting of a large coil. This is similar to the design of many common garage door opener remotes.

The receiver of this repeater system has a metal rod antenna about 8 inches long. I haven't had the the RF receiver apart, but it is likely a very simple TRF AM receiver tuned to 315 MHz that has a comparator output to square up the 40 KHz pulses. These pulses are then fed to an IR emitter to complete the system.
 
You did that? Wow, your like a celebrity:) Very cool...
 
The people who might fit the description "amateur radio operators" have numerous organizations and publications. You might do some research in that area as this group includes people who design, build and operate at low to high power - from VLF to microwaves. Many of the participants do not have electrical engineering degrees and many of the publications are tailored for that group. QRP refers to a segment of that hobby and means low power. CW is a mode that is pretty simple - more or less morse code. Within the amateur radio realm are some very sophisticated voice and data tranmission modes.

You might google on amateur radio qrp as a place to start. Keep in mind (and this applies to more than amateur radio) that a good deal of the information available is covered by copyright laws therefore it may not be freely available to you via the internet. Your local library may have publications or there could be a local club that might allow you to borrow books. For some people, a local organization is just what they need so they can learn from others.

Good luck.
 
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I remember seeing an 'IR extender' on some projects site, long time ago. Spent the last year and half exploring AVR... Keep searching the web, it's out there, just need to try different names for it. Probably a lot more out there, for VCR, cable TV and such. Seems like a handy gadget.
 
Digital window comparator

Greetings, I built an acceptable voltage window comparator (Dave Johnson design) using LM311, and then MAX972CPA comparators for a low, go, high voltage indicator . The acceptable window is only +/- 1% of the nominal voltage (6.6V). For each circuits at both low to nom and nom to high transitions the two indicator leds light up. Since I have not programmed in any hysterisis the two leds are lighting up because of oscillation. I need a sharp transition from state to state to avoid any ambiguity therefore I cant afford a hysterisis window. How can I sharpen up the transitions? Resarch has told me that the best way is to go digital with ADC's. Where do I start ?
 
Where do I start ?
Perhaps your own thread. It is often considered rude to jump in a thread with questions that have absolutly nothing to do with the original post.
 
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