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27MHz carrier signal using a oscillator chip or with few transistors alone

Discussion in 'Radio and Wireless' started by Kovardhani, Jun 4, 2021.

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  1. Kovardhani


    Jun 4, 2021
    I am trying to generate a 27MHz carrier signal to transmit it through a loop antenna, I referred many circuits couldn't able to find the one I need. can anyone guide me on generating it using a few simple transistors or using an oscillator chip with a 3v cell battery? The thing is my design is going to be very small, so I don't want to use transformers to overtone the crystal oscillator. is it even possible?
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    You should at east list the ones you have discarded. Otherwise you'll be presented with exactly those circuits you don't want to use.

    Also more details are required, such as exact frequency, permissible tolerance of the frequency, output power etc.
    Does it have to be based on a crystal or would an LC oscillator be sufficient?

    Please note also: the 27 MHz band can be freely used in many parts of the world. However, regulations as to max. power, max. bandwidth or even a requirement to register your device with local authorities may apply. Are you aware of the applicable regulations in your region?
  3. Kovardhani


    Jun 4, 2021
    Thank you! I am aware of the regulation in my country and it's free, the frequency band extends from 26.957 MHz to 27.283 MHz and the maximum allowed power is 5W.

    As of now I am concentrating on generating frequency from 27MHz to 27.124MHz later I can adjust it to the desired frequency and I am expecting the output power to be few milliWatts say, a 100mW. The circuit must work on a 3V cell Battery and the output is going to be a pulsed one.

    if the circuit is based on the crystal it does need to be overtone by using a transformer from the fundamental frequency right? if so I don't want to prefer that. In that case, LC oscillating would be sufficient.

    1. When I referred to the below circuit problem I faced was the transformer


    2. In the below circuit I thought of removing the MIC, R1, and then by tuning the L1, C4 I would get a frequency of about 27MHZ something and by replacing the battery by 3v( not sure if this circuit will work) and couldn't able to understand the requirement of L2 in the circuit
    F=27.29MHz ( Limit is 27.28MHZ) couldn't able to achieve
    3.This was the simplest circuit I have come across but didn't get the concept completely also the TX3E IC is not available in our country.

    I don't have complete knowledge of building a circuit if you can help me with this please do. Thank you.
    Last edited: Jun 5, 2021
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