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10.7 MHz oscillator with transistor

Discussion in 'Radio and Wireless' started by aurelZ, Jul 17, 2019.

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  1. aurelZ


    Jun 10, 2019
    I don't know from where you digg all that observation in a shape like "WallOfText"
    Just to let you know ,i finished my high electronic school somewhere at the end of 1988.
    And from then to now i have build many electronic projects.
    fixing many electronic devices,TV,Receivers etc
    So i am surprised about simple thing as is ceramic filter for 10,7Mhz which you can find
    in almost any analog FM radio receivers ,car radios,satelitte receivers and i really don't get it what kind of data you need.
    Here is the image of ceramic filter i use
    Ginawilson likes this.
  2. Audioguru


    Sep 24, 2016
    The very simple 10.7MHz oscillator you posted in post #15 has an output which is AM and FM combined so it is a poor way to test an FM demodulator that is supposed to reject AM.
    chad786 likes this.
  3. aurelZ


    Jun 10, 2019
    AM and FM combined so it is a poor way to test an FM demodulator that is supposed to reject AM.

    Yes Audioguru , i can agree with that but don't forget that main purpose of
    FM detector to pass only one carrier frequency which is 10.7 and as such this circuit is the
    simpliest soulution.
    In the past you must know there are some electronic kit-s with such a option.
    As far as i can say ,for me this topic is finished.
    all best...
  4. majoco


    Nov 10, 2019
    Never mind connecting the oscillator to an FM IF amplifier - do you have a shortwave receiver, preferably digital, that you can use to search for your oscillator around 10.7MHz? Much better than a frequency counter as when you connect the counter to your oscillator, the frequency will change! I use a cheap Degen 1103 digital receiver for all sorts of things, setting the frequency of a tube signal generator, for example - very quick and easy, just listen for the carrier with the radio set to "SSB" on the frequency you want.
  5. bertus

    bertus Moderator

    Nov 8, 2019
    davenn likes this.
  6. aurelZ


    Jun 10, 2019
    problem is already solved,look lat schematic


    May 20, 2017
    Had a look at your link and cannot find any mention of a ceramic trans-filter. Ceramic filter yes, trans-filter no.
    chad786 likes this.
  8. davenn

    davenn Moderator

    Sep 5, 2009

    yeah, we had that one out earlier in the thread
    Trans-filter seems to be some sort of screwball local definition to the OP
    Everywhere else in the world of electronics they are known as ceramic filters :)
    hevans1944 and chad786 like this.
  9. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    Everything that you need to know about ceramic filters can be found on this web page, along with links to other sources of information. Until these spiffy little devices came along, the filters they implemented were made from discrete quartz crystals, hand tuned to specific frequencies. It was an expensive and time-consuming process, so the filters were not cheap. Collins Radio came along later with their patented mechanically resonant filters, which were inexpensive but restricted to a much lower range of frequencies, typically 455 kHz, which was associated with single-conversion super-heterodyne receivers tuning from the AM broadcast band up to about 30 MHz. More about Collins filters here.

    Above 30 MHz or so (there are no sharp boundaries) 10.7 MHz is a popular super-heterodyne intermediate frequency (IF), especially for broadcast band FM receivers. Communication receivers sometimes use it before down-conversion to a lower IF such as 455 kHz. This makes ceramic filters very much a popular design component for RF signal processing such as band-pass and band-stop filtering. However, I doubt anyone skilled in the art would ever seriously consider using them as a stable frequency-determining element. Better, simpler, more frequency-stable circuits are available. As usual, your mileage (or kilometers) may vary. Use whatever works for you.
    davenn and bertus like this.
  10. majoco


    Nov 10, 2019
    VHF FM IF amplifiers need a bandwidth of about 180kHz (as shown on that MuRata pic) so how do we know where in that 180kHz the thing is oscillating?
    duke37 likes this.
  11. cdm889


    Jun 3, 2021
    Indeed, this circuit works well, thanks!
    I am just curious, why is circuit 9th harmonic (FM signal 96.3 MHz) has two sideband harmonics, one at 95.9 Mhz and another at 96.7Mhz? which plus or minus 0.4 MHz?

  12. aurelZ


    Jun 10, 2019
    Thanks Mike ..i am glad that work for you and for me to,it is simple but do the job.
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