Radio equipment iIdentification required.





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  1. #1
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    Default Radio equipment iIdentification required.

    Hi radio hams,

    I came across this thing the other day and was hoping someone could help me id it?

    It looks like some sort of RF filter / duplexer type thing.

    What is its purpose?

    Fluffy and Family Dog, ever seen this thing?
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    Nico Swart

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  2. #2
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    Default Re: Radio equipment iIdentification required.

    Cavity filters, probably diplexer.

    Cavity filters are an awesome technology.

    Think of them like this.

    The walls of the cavity represent the inductor and the end plates represent the capacitor of a resonant circuit.

    Resonant frequency is adjusted by changing the mechanical dimensions of the cavity, usually by having one of the endplates adjustable on a rod or shaft of some kind.
    Last edited by Fluffy; 2019/07/12 at 10:22 AM.
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  3. #3
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    Default Re: Radio equipment iIdentification required.

    Thanks Fluffy, but still way over my head.

    In practical terms, why would one need it on a farm (or a private game reserve in this case)?
    Nico Swart

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  4. #4
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    Default Re: Radio equipment iIdentification required.

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  5. #5
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    Default Re: Radio equipment iIdentification required.

    Quote Originally Posted by Die SwartKat View Post
    Thanks Fluffy, but still way over my head.

    In practical terms, why would one need it on a farm (or a private game reserve in this case)?
    To reduce mutual interference or and in this case to allow a repeater to function.

    What happens in a repeater is that you have separate Tx and Rx frequencies. so for example the your mobile Tx freq is 150.00MHz and your Rx freq I 150.300 MHz.

    The repeater will Rx on 150.00 and retransmit on 150.300. Problem is that because the frequencies are so close the repeaters transmitter will swamp it's own receiver. This is where cavity filters come in. They have incredibly good selectivity and unwanted freq rejection.
    Cheers

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  7. #6
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    Default Re: Radio equipment iIdentification required.

    Quote Originally Posted by Fluffy View Post
    To reduce mutual interference or and in this case to allow a repeater to function.

    What happens in a repeater is that you have separate Tx and Rx frequencies. so for example the your mobile Tx freq is 150.00MHz and your Rx freq I 150.300 MHz.

    The repeater will Rx on 150.00 and retransmit on 150.300. Problem is that because the frequencies are so close the repeaters transmitter will swamp it's own receiver. This is where cavity filters come in. They have incredibly good selectivity and unwanted freq rejection.
    Ok yes, I have a fair idea how repeaters work and this makes some sense.

    But what about ham repeaters where the offset is 0.600. This according to me is still very close to each other, yet I have never seen this cavity filter at ham repeaters.
    Nico Swart

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  8. #7
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    Default Re: Radio equipment iIdentification required.

    ham 100W FM repeater is like pissing against wind if compere to commercial repeaters.

    30 years ago people were complaining about ham interference

    now,hams are complaining about noise pollution from almost everything out there.
    from LED to any cheap electronics.

  9. #8
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    Default Re: Radio equipment iIdentification required.

    If that CF is able to handle your Ham repeater frequencies, it will be the perfect solution and far better than any of the teensy duplexers usually available. Our local Hams also use them.


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