How to build simple radio beacon?

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beamin

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I'm looking to build a simple from parts I have off hand:
Transistors, resistors, diodes, disk caps hand wound air inductors.
Parts I dont have: Crystals or timer chips. I know this can be done but I'm legally blind and having a very hard time finding a schematic online. I'm going to use an SDR to receive and because I have just plastic package through hole transistors its not going to be high power so I'm not worried about interfering with anyone's radio. Its to place a few of them around in a rural radio quiet area and play hind and go seek, to test different antennas. Higher frequency would be better as it makes both antennas smaller.

I have an arduino that I could use to generate the tone or short morse signal.
 

beamin

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Would the bottom of this schematic work as a stand alone transmitter?

Which type of transistor is that? Its an NPN
I have on hand:
bc547b
bc517
bc337
 

beamin

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I use a UHF CB with the TX locked on, low power on an empty channel.
This just needs to be a small device easy to build and powered off a battery.

I was looking at that second schematic and it doesn't have the value of the inductor and im not sure what 3p3 means for a capacitor. 3pf? 300pf?

Also that seems to be a special rf transistor.
 

beamin

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Here an link that might help you out Build Your Own Radio Beacons
Those are good but I dont have a 555. So what if I use the arduino for putting out a frequency and build a simple transistor amplifier? Would this work to generate a carrier wave? Can that amplifier be built without RF transistors?

This whole project seems doable but its getting really hard to find schematics since I don't know enough electronics to make the circuit.
 

slicerwizard

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I hope your SDR can receive very low frequencies, because without RF transistors, you aren't going to be generating high frequency signals.

You can try putting together a simple multivibrator circuit - it's only a couple of transistors, capacitors and resistors.

But you mentioned smaller antenna sizes, which suggests you want something up around 100 to 400 MHz? Not happening.
 

RFI-EMI-GUY

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For recovering model rockets I made a 433.92 MHz beacon using a long range chip from Lynx and a for generating pulses and telemetry, I used a Microchip 8 pin PIC instead of using a 555 timer. The parts count and assembly was far simpler using the PIC. Microchip makes some PIC's with transmitter built in as does Texas Instruments.
 

beamin

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So whats the highest frequency I can make using regular transistors? Do nonrf transistors just not switch that fast?
Now I understand why my other attempts failed.
That would have saved me alot of time trying to look for signals using my sdr as an oscilloscope.

For recovering model rockets I made a 433.92 MHz beacon using a long range chip from Lynx and a for generating pulses and telemetry, I used a Microchip 8 pin PIC instead of using a 555 timer. The parts count and assembly was far simpler using the PIC. Microchip makes some PIC's with transmitter built in as does Texas Instruments.
Are there any schematics for this?
 

RFI-EMI-GUY

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So whats the highest frequency I can make using regular transistors? Do nonrf transistors just not switch that fast?
Now I understand why my other attempts failed.
That would have saved me alot of time trying to look for signals using my sdr as an oscilloscope.



Are there any schematics for this?
send me a PM with your direct e-mail and I will send what I can.
 

RFI-EMI-GUY

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I'm looking to build a simple from parts I have off hand:
Transistors, resistors, diodes, disk caps hand wound air inductors.
Parts I dont have: Crystals or timer chips. I know this can be done but I'm legally blind and having a very hard time finding a schematic online. I'm going to use an SDR to receive and because I have just plastic package through hole transistors its not going to be high power so I'm not worried about interfering with anyone's radio. Its to place a few of them around in a rural radio quiet area and play hind and go seek, to test different antennas. Higher frequency would be better as it makes both antennas smaller.

I have an arduino that I could use to generate the tone or short morse signal.
See the files I posted to your other post today regarding this project.
 
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