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Duplexer Question

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  • N7DJR
    How far can the frequency spread be for most small internal duplexer s? For example if the notch type 4 cavity duplexer is set to the middle frequency 462.625
    Message 1 of 5 , Jun 18, 2012
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      How far can the frequency spread be for most small internal duplexer's?

      For example if the notch type 4 cavity duplexer is set to the middle frequency 462.625 can I change the frequency to say ch 8 or ch 1 with out retuning the whole duplexer system.

      Another thing I am wondering about is if the RX and RX are inverted with the TX frequency switched with the RX frequency does the duplexer have to be tuned to this two or can you just switch the cables?

      Thanks Dave
    • Jack
      Dave because it all works on assigned splits you would have to retune the whole thing the duplexer is meant to be vary narrow, I have several duplexers one for
      Message 2 of 5 , Jun 18, 2012
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        Dave because it all works on assigned splits you would have to retune the
        whole thing the duplexer is meant to be vary narrow, I have several
        duplexers one for each pair I want to work then I just change the duplexer
        out and set the repeater memory to the correct pair.


        N6UYB

        -----Original Message-----
        From: N7DJR
        Sent: Monday, June 18, 2012 11:23 AM
        To: GMRS@yahoogroups.com
        Subject: [GMRS] Duplexer Question

        How far can the frequency spread be for most small internal duplexer's?

        For example if the notch type 4 cavity duplexer is set to the middle
        frequency 462.625 can I change the frequency to say ch 8 or ch 1 with out
        retuning the whole duplexer system.

        Another thing I am wondering about is if the RX and RX are inverted with the
        TX frequency switched with the RX frequency does the duplexer have to be
        tuned to this two or can you just switch the cables?

        Thanks Dave



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      • Ray
        First, find the spec sheet for the specific duplexer you re working with. But in general, the cheaper the duplexer, the better chance it can do a few adjacent
        Message 3 of 5 , Jun 18, 2012
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          First, find the spec sheet for the specific duplexer you're working with.

          But in general, the cheaper the duplexer, the better chance it can do a few adjacent channels without a retune. Better = sharper, but in your case, you want wide, not sharp, so this a good thing. How wide? That depends on the model and how it was tuned. Only way to know for sure: tune to a middle channel, then check the response on a tracking signal generator across your needed spectrum. Remember that the response may not be the same in each direction, so you may have to change the center to compensate.

          About swapping sides, again, in general, duplexers have a high and a low frequency side. As long as the number of sections is symmetrical, you should be able to swap TX and RX as long as you observe the high and low.

          I would think a cheap mobile type duplexer would be fine for a multichannel GMRS portable repeater, but not a permanent site install.

          Ray

          --- In GMRS@yahoogroups.com, "N7DJR" <dbohmke@...> wrote:
          >
          > How far can the frequency spread be for most small internal duplexer's?
          >
          > For example if the notch type 4 cavity duplexer is set to the middle frequency 462.625 can I change the frequency to say ch 8 or ch 1 with out retuning the whole duplexer system.
          >
          > Another thing I am wondering about is if the RX and RX are inverted with the TX frequency switched with the RX frequency does the duplexer have to be tuned to this two or can you just switch the cables?
          >
          > Thanks Dave
          >
        • n9rhg@comcast.net
          I feel that you would just be better off taking out your duplexer and getting a second antenna. To change frequencies and change your transmit to receive and
          Message 4 of 5 , Jun 18, 2012
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            I feel that you would just be better off taking out your duplexer and getting a second antenna. To change frequencies and change your transmit to receive and back you would have to do a lot of work retuning of the duplexers. Using two antennas makes it much more flexible.

             

            Darren



            ----- Original Message -----




            From: "Ray" <ray@...>
            To: GMRS@yahoogroups.com
            Sent: Monday, June 18, 2012 10:14:58 AM
            Subject: [GMRS] Re: Duplexer Question

             




            First, find the spec sheet for the specific duplexer you're working with.

            But in general, the cheaper the duplexer, the better chance it can do a few adjacent channels without a retune. Better = sharper, but in your case, you want wide, not sharp, so this a good thing. How wide? That depends on the model and how it was tuned. Only way to know for sure: tune to a middle channel, then check the response on a tracking signal generator across your needed spectrum. Remember that the response may not be the same in each direction, so you may have to change the center to compensate.

            About swapping sides, again, in general, duplexers have a high and a low frequency side. As long as the number of sections is symmetrical, you should be able to swap TX and RX as long as you observe the high and low.

            I would think a cheap mobile type duplexer would be fine for a multichannel GMRS portable repeater, but not a permanent site install.

            Ray

            --- In GMRS@yahoogroups.com , "N7DJR" <dbohmke@...> wrote:
            >
            > How far can the frequency spread be for most small internal duplexer's?
            >
            > For example if the notch type 4 cavity duplexer is set to the middle frequency 462.625 can I change the frequency to say ch 8 or ch 1 with out retuning the whole duplexer system.
            >
            > Another thing I am wondering about is if the RX and RX are inverted with the TX frequency switched with the RX frequency does the duplexer have to be tuned to this two or can you just switch the cables?
            >
            > Thanks Dave
            >




            [Non-text portions of this message have been removed]
          • N7DJR
            Thanks guys this is why I subscribed to this group I think I will pick a frequency and stay with it one tune and leave it be. Dave
            Message 5 of 5 , Jun 19, 2012
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              Thanks guys this is why I subscribed to this group I think I will pick a frequency and stay with it one tune and leave it be.

              Dave
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