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maverick99
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I'm looking to make/buy an RF(radio frequency) to detect and display the level of an incoming RF signal. This is going to be used on a radio controlled vehicle. Any suggestions and info would be greatly appreciated.
berkeman said:What frequency and what modulation are you trying to detect?
McCormick said:www.mackrackit.com/djm/LF411%20Reciever.html[/URL]
Here is a simpler AM Reciever that might help. It basicly amplifies the incoming RF through that OP amp. If your transmitter isn't AM then you shouldn't use the low pass filter at the output.
I am not sure how you want it to detect, you could place an LED on the output.[/QUOTE]
The problem with that receiver is that it is for the "AM Band" in the US, which is around 1MHz. And even that low, the LF411 opamp they show is running topped out. The RC bands are more like 30-40MHz, I think (I forget exactly), so a vanilla opamp isn't going to help in terms of gain. The amplification will need to be done with higher-speed amps or with discretes or a combination. And again, you will need to be very careful about shielding the input stages from the amplification output stages, and you will need to pay attention to power supply splitting and filtering. Otherwise your amp will sing like a songbird (and ignore the input signal).
berkeman said:The problem with that receiver is that it is for the "AM Band" in the US, which is around 1MHz. And even that low, the LF411 opamp they show is running topped out. The RC bands are more like 30-40MHz, I think (I forget exactly), so a vanilla opamp isn't going to help in terms of gain. The amplification will need to be done with higher-speed amps or with discretes or a combination. And again, you will need to be very careful about shielding the input stages from the amplification output stages, and you will need to pay attention to power supply splitting and filtering. Otherwise your amp will sing like a songbird (and ignore the input signal).
Actually, chroot's suggestion may be the best for you. Do you just want to light an LED when the car is detecting a control signal? As chroot says, just figure out which signal coming out of the car's receiver is a carrier detect indicator, and buffer that to turn on your LED.maverick99 said:Could anyone supply me with a schematic that would work the best for the 30-40Mhz incoming signal? I'm basically wanting to detect the rf signal and light an LED when it detects it.
berkeman said:Actually, chroot's suggestion may be the best for you. Do you just want to light an LED when the car is detecting a control signal? As chroot says, just figure out which signal coming out of the car's receiver is a carrier detect indicator, and buffer that to turn on your LED.
chroot said:maverick,
I doubt that the RC controller actually broadcasts a continuous carrier, even when none of its buttons are being pressed (though I am not sure of this). In that case, the only time your LED would light up is when you're pressing a button on the controller. Of course, when you're pressing a button on the controller, your car will be moving... so it all seems a bit redundant.
- Warren
McCormick said:Actually I build a circuit that would detect an RC controller, and it did brodcast continuously even when the buttons weren't being pushed.
Although I didn't have it tuned to the frequency of the RC contoller
(47MHz)... when I turned it on, my receiver Led would light up.
This is the RF detector that I built:
www.mackrackit.com/djm/LF411%20Reciever.html[/URL]
you just need to change L1 and C1 to tune the circuit, (like using a 1uh coil and a 20 pF capacitor will give you 35 MHz) and omit the low pass filter on the output.
Does this help?[/QUOTE]
I think this will work for what I need. I'm sure I will be back for more questions but thanks for the schematic!
McCormick said:Actually I build a circuit that would detect an RC controller, and it did brodcast continuously even when the buttons weren't being pushed.
chroot said:What the hell, McCormick? We already told you why this receiver won't work -- the LF411 has a gain-bandwidth product of 3 MHz! There's no way this op-amp can amplify a 30-40 MHz signal! Why did you post this again?!
- Warren
chroot said:The frequency in question -- in the 40 MHz ballpark -- won't go through the LF411 op-amp at all.
Do you even know what "gain-bandwidth product" means?
- Warren
maverick99 said:McCormick, on your schematic, is R2 just a resistor in the feedback line? I was just confused on what the wire above the 100k label was.
RF detection for radio-controlled vehicles is the process of detecting and identifying radio frequency signals used to control remote-controlled vehicles.
RF detection works by using a receiver to pick up signals from the transmitter of a radio-controlled vehicle. The receiver then processes the signals and converts them into commands that control the vehicle's movement.
RF detection is important for radio-controlled vehicles because it allows for precise control and communication between the transmitter and receiver, ensuring that the vehicle responds accurately to commands.
Some important factors to consider when choosing an RF detection system for your radio-controlled vehicle include the frequency range, sensitivity, and interference resistance of the system. You may also want to consider the size and weight of the system, as well as its compatibility with your specific vehicle.
While RF detection for radio-controlled vehicles is generally safe, it is important to be aware of any potential interference from other electronic devices that may affect the signal. It is also important to follow the manufacturer's instructions and guidelines for proper use and maintenance of the system.