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Power Supply Question

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  • Ralph
    Gents, I ve built a 5 square loop, framed in 1 PVC and amplified via a Ramsey AA broadband amplifier. In tests so far, it has provided me very nice, clean
    Message 1 of 3 , Jul 16 4:43 AM
      Gents,

      I've built a 5' square loop, framed in 1" PVC and amplified via a Ramsey AA broadband amplifier. In tests so far, it has provided me very nice, clean signal-to-noise compared to my longwire antenna.

      I have situated the loop about 50 feet from my house, away from any sources of electrical noise (my biggest goal).

      Right now, the amplifier runs off of a 9v battery, so this is not a workable permanent situation. The battery drains down in a few days of use. I certainly don't want to have to be going outside during the winter to change batteries on the amplifier unit!

      Question: If I use a 9v DC power source (hundreds of them are available on Amazon), will (a) this create noise at the loop, defeating the main goal of the remote loop? and (b) can I run the DC power line 50 or 100 feet to the antenna -- will this weak current dissipate over that length of wire?

      I am aware that somehow the Wellbrook loops supply DC power to the remote loop, so I suspect I indeed can feed this with a lonnnnnnng DC power line, but would like confirmation from others' experience.

      Regards,

      Ralph
    • John Popelish
      ... Even wire as small as used for a doorbell would carry this small current for 50 feet with only a fraction of a volt lost to resistance. And that can be
      Message 2 of 3 , Jul 16 7:07 AM
        On 07/16/2012 07:43 AM, Ralph wrote:
        > Gents,
        >
        > I've built a 5' square loop, framed in 1" PVC and
        > amplified via a Ramsey AA broadband amplifier. In tests
        > so far, it has provided me very nice, clean
        > signal-to-noise compared to my longwire antenna.
        >
        > I have situated the loop about 50 feet from my house,
        > away from any sources of electrical noise (my biggest
        > goal).
        >
        > Right now, the amplifier runs off of a 9v battery, so
        > this is not a workable permanent situation. The battery
        > drains down in a few days of use. I certainly don't want
        > to have to be going outside during the winter to change
        > batteries on the amplifier unit!
        >
        > Question: If I use a 9v DC power source (hundreds of
        > them are available on Amazon), will (a) this create noise
        > at the loop, defeating the main goal of the remote loop?
        > and (b) can I run the DC power line 50 or 100 feet to the
        > antenna -- will this weak current dissipate over that
        > length of wire?
        >
        > I am aware that somehow the Wellbrook loops supply DC
        > power to the remote loop, so I suspect I indeed can feed
        > this with a lonnnnnnng DC power line, but would like
        > confirmation from others' experience.

        Even wire as small as used for a doorbell would carry this
        small current for 50 feet with only a fraction of a volt
        lost to resistance. And that can be made up for by starting
        with a slightly higher supply voltage. But most RF
        amplifiers are quite tolerant of small supply voltage
        errors, either way.

        I would find a simple transformer, rectifier, capacitor type
        supply, not a switching regulated type, to keep the RF noise
        low. You may want to add a solid state linear regulator,
        but that would best be placed at the amplifier end of the
        wire. Don't forget to add a capacitor to the input end of
        that regulator (at least twice what the data sheet says is
        minimum), to suppress its tendency to oscillate when fed
        from a long wire (highly inductive source).

        --
        Regards,

        John Popelish
      • Don
        You could run the 9vdc on the coax and block it at both ends with capacitors so it does not enter the RF out of the Amp or the RF input to your radio. Don
        Message 3 of 3 , Jul 16 9:11 AM
          You could run the 9vdc on the coax and block it at both ends with
          capacitors so it does not enter the RF out of the Amp or the RF input to
          your radio.

          Don WPC6NDB
          Upland, CA
          34.10 -117.63 1250ft
          R-75 w/250Hz 2x R-71A w/250Hz R-70
          SDR-IQ SR-AF & LPF DSP599zx
          MFJ-784B HD-1418 AF-1 MSB-1
          PA0RDT Mini-Whip x2 @ 15ft
          LFL1010 ALA100L x2


          On 16-Jul-12 07:07, John Popelish wrote:
          > On 07/16/2012 07:43 AM, Ralph wrote:
          >> Gents,
          >>
          >> I've built a 5' square loop, framed in 1" PVC and
          >> amplified via a Ramsey AA broadband amplifier. In tests
          >> so far, it has provided me very nice, clean
          >> signal-to-noise compared to my longwire antenna.
          >>
          >> I have situated the loop about 50 feet from my house,
          >> away from any sources of electrical noise (my biggest
          >> goal).
          >>
          >> Right now, the amplifier runs off of a 9v battery, so
          >> this is not a workable permanent situation. The battery
          >> drains down in a few days of use. I certainly don't want
          >> to have to be going outside during the winter to change
          >> batteries on the amplifier unit!
          >>
          >> Question: If I use a 9v DC power source (hundreds of
          >> them are available on Amazon), will (a) this create noise
          >> at the loop, defeating the main goal of the remote loop?
          >> and (b) can I run the DC power line 50 or 100 feet to the
          >> antenna -- will this weak current dissipate over that
          >> length of wire?
          >>
          >> I am aware that somehow the Wellbrook loops supply DC
          >> power to the remote loop, so I suspect I indeed can feed
          >> this with a lonnnnnnng DC power line, but would like
          >> confirmation from others' experience.
          >
          > Even wire as small as used for a doorbell would carry this
          > small current for 50 feet with only a fraction of a volt
          > lost to resistance. And that can be made up for by starting
          > with a slightly higher supply voltage. But most RF
          > amplifiers are quite tolerant of small supply voltage
          > errors, either way.
          >
          > I would find a simple transformer, rectifier, capacitor type
          > supply, not a switching regulated type, to keep the RF noise
          > low. You may want to add a solid state linear regulator,
          > but that would best be placed at the amplifier end of the
          > wire. Don't forget to add a capacitor to the input end of
          > that regulator (at least twice what the data sheet says is
          > minimum), to suppress its tendency to oscillate when fed
          > from a long wire (highly inductive source).
          >
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