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Re: Beginner question - Varactor tuning diodes references

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  • Lee
    ... that 18V would be across the potentiometer. Heh heh...it may sound right to you, but not to me!! :) lol. The batteries in series sounds ok but 18 volts
    Message 1 of 26 , Mar 1, 2012
      --- In loopantennas@yahoogroups.com, "Mvs" <mvs_sarma@...> wrote:
      >
      > I think that sentense with a "," there ....9V batteries in series, across a 20 turn pot......was perfectly alright. it clearly sounds
      that 18V would be across the potentiometer.

      Heh heh...it may sound right to you, but not to me!! :) lol.

      The batteries in series sounds ok but 18 volts ACROSS the pot ...
      think about it..maybe I`m wrong, at my age I wouldn`t be suprised.

      Anyways...I have followed your directions and put them to paper
      (not too difficult after kickstarting my brain) and made a cicuit
      board, using a hobby knife on a copper clad board and soldered the
      main components in place but in the absence of a varactor am using
      (read :- experimenting) leds and diodes out of my junk box...and
      getting some results with leds, not sure what but varying the pot
      alters the `S` readings...

      Hope you see the funny side of my assertions :)

      Regards.

      Lee...G6ZSG.



      > I dont know why any confusion!!
      >
      > --- In loopantennas@yahoogroups.com, "Lee" <leo1949uk@> wrote:
      > >
      > >
      > >
      > > --- In loopantennas@yahoogroups.com, "Bruce Carter" <rbrucecarter@> wrote:
      > > >
      > > > > 1/ Two 9V batteries in series, ACROSS (??) a 20 turn pot.
      > >
      > > Across?? in series with the circuit, surely??..must be a typo.
      > >
      > > > 9V + 9V = 18V. A lot easier than putting a bunch of AA's in series to make 10.5. The varactor needs about 1.5 to 9.5 to tune the AM band.
      > > >
      > > > > Could you draw a curcuit layout please??
      > >
      > > Circuit even ...Duh..
      > >
      > > > Eventually. I suck at ASCII schematics - which suck anyway. Draw it yourself from the node I described, there are only 4 connections in the whole schematic.
      > >
      > > Yes, but you srung a sensor winding on me ..the rest was clear, what
      > > sensor winding?? my old brain aint so fast nowadays, sorry...
      > >
      > > Regards.
      > >
      > > Lee...G6ZSG.
      > >
      >
    • Lee
      ... Hi Rick. Been searching the web and found about 8 suitable varactors that would do the job including the NTE618, but have a local ham rally where a local
      Message 2 of 26 , Mar 1, 2012
        > >
        > > Thankyou for the url Rick...very interesting reading.
        > >
        > > As I have an ant(untuned inverted L) which is adequate for AM
        > > using a 9:1 transformer for impedance matching...I am looking
        > > more for 17m to 6m and general coverage shortwavebands and am
        > > using a homebrew magloop with air spaced variable cap electro-
        > > mechanically tuned...(would love a vacuum cap but can`t afford
        > > one) but do like the varicap methods described in this thread
        > > and your url looks the best start to experimenting, the varicaps
        > > mentioned are for 50khz - 200khz...which ones would be suitable
        > > for 17 - 6 metres??, never had dealings with varicaps ... lol.
        > > I thought they were capacitance rather than frequency operated,
        > > shows how much I know.
        > >
        > > Regards.
        > >
        > > Lee...G6ZSG.
        >
        > The NTE618 varactor is specifically for the AM BCB 500 kHz to 1700
        > kHz. For shortwave, you need much less capacitance, and lots
        > of diodes are available in those lower values. There would
        > be nothing in principle to prevent you from scaling the
        > loop design in the NCJ article to higher frequencies. Varactors
        > have a capacitance inversely proportional to the bias voltage
        > raised to a power between .5 and 2. Why would you want a
        > vacuum variable capacitor in a receiving loop?
        >
        > Rick N6RK
        >
        Hi Rick.

        Been searching the web and found about 8 suitable varactors that
        would do the job including the NTE618, but have a local ham rally
        where a local mail order business has a stock of BB112 9volt diodes
        will be attending, so I can collect quicker than delivery..and browse
        various stalls at the same time, nice day out.
        Why would I want vacuum cap? because my 3 foot dia magloop is for tx
        and only covers 28Mhz to 16Mhz...

        Regards.

        Lee...G6ZSG.
      • Mvs
        I found http://partsandkits.com/parts.php have motorola make MVAM109 varicaps that are reasonably cheap. Perhaps it could help few American members, even
        Message 3 of 26 , Mar 1, 2012
          I found http://partsandkits.com/parts.php have motorola make MVAM109 varicaps that are reasonably cheap.

          Perhaps it could help few American members, even though they dispatch across world,

          --- In loopantennas@yahoogroups.com, "Lee" <leo1949uk@...> wrote:
          >
          >
          > > >
          > > > Thankyou for the url Rick...very interesting reading.
          > > >
          > > > As I have an ant(untuned inverted L) which is adequate for AM
          > > > using a 9:1 transformer for impedance matching...I am looking
          > > > more for 17m to 6m and general coverage shortwavebands and am
          > > > using a homebrew magloop with air spaced variable cap electro-
          > > > mechanically tuned...(would love a vacuum cap but can`t afford
          > > > one) but do like the varicap methods described in this thread
          > > > and your url looks the best start to experimenting, the varicaps
          > > > mentioned are for 50khz - 200khz...which ones would be suitable
          > > > for 17 - 6 metres??, never had dealings with varicaps ... lol.
          > > > I thought they were capacitance rather than frequency operated,
          > > > shows how much I know.
          > > >
          > > > Regards.
          > > >
          > > > Lee...G6ZSG.
          > >
          > > The NTE618 varactor is specifically for the AM BCB 500 kHz to 1700
          > > kHz. For shortwave, you need much less capacitance, and lots
          > > of diodes are available in those lower values. There would
          > > be nothing in principle to prevent you from scaling the
          > > loop design in the NCJ article to higher frequencies. Varactors
          > > have a capacitance inversely proportional to the bias voltage
          > > raised to a power between .5 and 2. Why would you want a
          > > vacuum variable capacitor in a receiving loop?
          > >
          > > Rick N6RK
          > >
          > Hi Rick.
          >
          > Been searching the web and found about 8 suitable varactors that
          > would do the job including the NTE618, but have a local ham rally
          > where a local mail order business has a stock of BB112 9volt diodes
          > will be attending, so I can collect quicker than delivery..and browse
          > various stalls at the same time, nice day out.
          > Why would I want vacuum cap? because my 3 foot dia magloop is for tx
          > and only covers 28Mhz to 16Mhz...
          >
          > Regards.
          >
          > Lee...G6ZSG.
          >
        • Lee
          ... Well, had a nice day out and came home with a pair of varactors and a nice clean Yaesu FT 790R 2 metre a multimode electric handbag that after a bit of
          Message 4 of 26 , Mar 17, 2012
            > > The NTE618 varactor is specifically for the AM BCB 500 kHz to 1700
            > > kHz. For shortwave, you need much less capacitance, and lots
            > > of diodes are available in those lower values. There would
            > > be nothing in principle to prevent you from scaling the
            > > loop design in the NCJ article to higher frequencies. Varactors
            > > have a capacitance inversely proportional to the bias voltage
            > > raised to a power between .5 and 2. Why would you want a
            > > vacuum variable capacitor in a receiving loop?
            > >
            > > Rick N6RK
            > >
            > Hi Rick.
            >
            > Been searching the web and found about 8 suitable varactors that
            > would do the job including the NTE618, but have a local ham rally
            > where a local mail order business has a stock of BB112 9volt diodes
            > will be attending, so I can collect quicker than delivery..and browse
            > various stalls at the same time, nice day out.
            > Why would I want vacuum cap? because my 3 foot dia magloop is for tx
            > and only covers 28Mhz to 16Mhz...
            >
            > Regards.
            >
            > Lee...G6ZSG.
            >

            Well, had a nice day out and came home with a pair of varactors and
            a nice clean Yaesu FT 790R 2 metre a multimode electric handbag that
            after a bit of furtling works extremely well (Kerching)...thankyou.

            Had a look at these varactors ( 36z-w80 ) which I had been assured
            runs up to 540Khz at 9 volts.. and set about sorting out the bits and
            pieces from my junk box to build the Trask indoor loop antenna as was
            posted earlier in this thread and laid out except for building the
            loop for 28Mhz to 10Mhz at 10 feet circumference...but could not get
            it to work!!

            Finally discovered it works from 9Khz (lowest freq on my Winradio
            G305i SDR) to around 1700Khz ...RESULT YAY... verified it was tuning
            by shorting across the loop input...

            Problem - I want to work around the HF bands and am not sure how
            to convert to the HF broadcast bands I need.. Can any kind person
            advise please..

            Thanks.

            Lee...G6ZSG.
          • Bill McGraw
            Lee, Re the Winradio G305i SDR, I understand it tunes to 1800 mHz or higher and the quote was 1700 kHz. Was that in error? The kit comes with a short antenna,
            Message 5 of 26 , Mar 17, 2012
              Lee,
              Re the Winradio G305i SDR, I understand it tunes to 1800 mHz or higher and the quote was 1700 kHz. Was that in error? The kit comes with a short antenna, wire, not loop? What am I missing with this plug-in card for a laptop?
               
              I do not understand the varactor tuning necessary because I'm weak on electronics for loops. My simple inside office wall loops plug into my receiver with an outside ground and work well enough to satisfy me on SW, no BCB. My Kenwood 2000 and a half wave dipole has super receiving (compared to my Radio Shack DX 398) but weak transmitting ability, something I'll work on later.

              Bill McGraw, KF5FJZ, NRA Life
              "Somewhere South of Chicago"
              Greenville, Mississippi




               




              Well, had a nice day out and came home with a pair of varactors and
              a nice clean Yaesu FT 790R 2 metre a multimode electric handbag that
              after a bit of furtling works extremely well (Kerching)...thankyou.

              Had a look at these varactors ( 36z-w80 ) which I had been assured
              runs up to 540Khz at 9 volts.. and set about sorting out the bits and
              pieces from my junk box to build the Trask indoor loop antenna as was
              posted earlier in this thread and laid out except for building the
              loop for 28Mhz to 10Mhz at 10 feet circumference...but could not get
              it to work!!

              Finally discovered it works from 9Khz (lowest freq on my Winradio
              G305i SDR) to around 1700Khz ...RESULT YAY... verified it was tuning
              by shorting across the loop input...

              Problem - I want to work around the HF bands and am not sure how
              to convert to the HF broadcast bands I need.. Can any kind person
              advise please..

              Thanks.

              Lee...G6ZSG.




               

              [Non-text portions of this message have been removed]
            • Lee
              Hi Bill .. No, 1700Khz was not in error and yes, the 305i tunes to around 1800Mhz...9Khz to 1700Khz was the apparent bandwidth of the antenna that I have just
              Message 6 of 26 , Mar 18, 2012
                Hi Bill .. No, 1700Khz was not in error and yes, the 305i tunes to
                around 1800Mhz...9Khz to 1700Khz was the apparent bandwidth of the
                antenna that I have just built, also, the 305i does not plug into a
                laptop,,it plugs into the ide slot of a desktop computor..The whole
                point?? and IF you DID notice another error..I DID commit a typo...

                The radio I bought is a Yaesu FT 290R not a Yaesu FT 790R. the 790R
                covers 70 centimetres, NOT 2 metres :)

                Bill... I am also at a loss when it comes to tuning antennae using
                varactors but, if you google `magloops` and the way they operate,
                then maybe you will understand the why and how to tune a loop
                antenna..

                I do hope this has been of use to you Bill... maybe someone more
                knowledgable than me regarding loop antenna tuning using varactors
                will be along to advise us both.

                Regards.

                Lee...G6ZSG.


                --- In loopantennas@yahoogroups.com, Bill McGraw <mcgr3799@...> wrote:
                >
                > Lee,
                > Re the Winradio G305i SDR, I understand it tunes to 1800 mHz or higher and the quote was 1700 kHz. Was that in error? The kit comes with a short antenna, wire, not loop? What am I missing with this plug-in card for a laptop?
                >  
                > I do not understand the varactor tuning necessary because I'm weak on electronics for loops. My simple inside office wall loops plug into my receiver with an outside ground and work well enough to satisfy me on SW, no BCB. My Kenwood 2000 and a half wave dipole has super receiving (compared to my Radio Shack DX 398) but weak transmitting ability, something I'll work on later.
                >
                > Bill McGraw, KF5FJZ, NRA Life
                > "Somewhere South of Chicago"
                > Greenville, Mississippi
                >
                >
                >
                >
                >  
                >
                >
                >
                >
                > Well, had a nice day out and came home with a pair of varactors and
                > a nice clean Yaesu FT 790R 2 metre a multimode electric handbag that
                > after a bit of furtling works extremely well (Kerching)...thankyou.
                >
                > Had a look at these varactors ( 36z-w80 ) which I had been assured
                > runs up to 540Khz at 9 volts.. and set about sorting out the bits and
                > pieces from my junk box to build the Trask indoor loop antenna as was
                > posted earlier in this thread and laid out except for building the
                > loop for 28Mhz to 10Mhz at 10 feet circumference...but could not get
                > it to work!!
                >
                > Finally discovered it works from 9Khz (lowest freq on my Winradio
                > G305i SDR) to around 1700Khz ...RESULT YAY... verified it was tuning
                > by shorting across the loop input...
                >
                > Problem - I want to work around the HF bands and am not sure how
                > to convert to the HF broadcast bands I need.. Can any kind person
                > advise please..
                >
                > Thanks.
                >
                > Lee...G6ZSG.
                >
                >
                >
                >
                >  
                >
                > [Non-text portions of this message have been removed]
                >
              • Bill McGraw
                Thanks, Lee. I am relatively new learning and studying loops for Tx, really need a better antenna than my shoddy dipole.   I looked up your radios on iHam,
                Message 7 of 26 , Mar 18, 2012
                  Thanks, Lee. I am relatively new learning and studying loops for Tx, really need a better antenna than my shoddy dipole.
                   
                  I looked up your radios on iHam, didn't know they worked on 2M/70cm as well as HF if that is correct what I read. I'm relatively new at Ham radio, everything seems to lead me to a tangent subject and forget where I started with a question.
                   
                  Again, thanks and I will pursue loops as you suggest.

                  Bill McGraw, KF5FJZ, NRA Life
                  "Somewhere South of Chicago"
                  Greenville, Mississippi

                  --- On Sun, 3/18/12, Lee <leo1949uk@...> wrote:




                   




                  Hi Bill .. No, 1700Khz was not in error and yes, the 305i tunes to
                  around 1800Mhz...9Khz to 1700Khz was the apparent bandwidth of the
                  antenna that I have just built, also, the 305i does not plug into a
                  laptop,,it plugs into the ide slot of a desktop computor..The whole
                  point?? and IF you DID notice another error..I DID commit a typo...

                  The radio I bought is a Yaesu FT 290R not a Yaesu FT 790R. the 790R
                  covers 70 centimetres, NOT 2 metres :)

                  Bill... I am also at a loss when it comes to tuning antennae using
                  varactors but, if you google `magloops` and the way they operate,
                  then maybe you will understand the why and how to tune a loop
                  antenna..

                  I do hope this has been of use to you Bill... maybe someone more
                  knowledgable than me regarding loop antenna tuning using varactors
                  will be along to advise us both.

                  Regards.

                  Lee...G6ZSG.



                  [Non-text portions of this message have been removed]
                • Mvs
                  @bill, I fear that we should NOT resort to varicap tuning of TX antennae. the High power coming from PA of the TX rig would just burn off the varicap diode.
                  Message 8 of 26 , Mar 18, 2012
                    @bill,
                    I fear that we should NOT resort to varicap tuning of TX antennae.
                    the High power coming from PA of the TX rig would just burn off the varicap diode. No lighhtening is need. Let us not waste the costly resource experimenting across the TX antennae.

                    The concept of use of varicaps for tuning loops is valid only for Rx antennae.

                    --- In loopantennas@yahoogroups.com, Bill McGraw <mcgr3799@...> wrote:
                    >
                    > Thanks, Lee. I am relatively new learning and studying loops for Tx, really need a better antenna than my shoddy dipole.
                    >  
                    > I looked up your radios on iHam, didn't know they worked on 2M/70cm as well as HF if that is correct what I read. I'm relatively new at Ham radio, everything seems to lead me to a tangent subject and forget where I started with a question.
                    >  
                    > Again, thanks and I will pursue loops as you suggest.
                    >
                    > Bill McGraw, KF5FJZ, NRA Life
                    > "Somewhere South of Chicago"
                    > Greenville, Mississippi
                    >
                    > --- On Sun, 3/18/12, Lee <leo1949uk@...> wrote:
                    >
                    >
                    >
                    >
                    >  
                    >
                    >
                    >
                    >
                    > Hi Bill .. No, 1700Khz was not in error and yes, the 305i tunes to
                    > around 1800Mhz...9Khz to 1700Khz was the apparent bandwidth of the
                    > antenna that I have just built, also, the 305i does not plug into a
                    > laptop,,it plugs into the ide slot of a desktop computor..The whole
                    > point?? and IF you DID notice another error..I DID commit a typo...
                    >
                    > The radio I bought is a Yaesu FT 290R not a Yaesu FT 790R. the 790R
                    > covers 70 centimetres, NOT 2 metres :)
                    >
                    > Bill... I am also at a loss when it comes to tuning antennae using
                    > varactors but, if you google `magloops` and the way they operate,
                    > then maybe you will understand the why and how to tune a loop
                    > antenna..
                    >
                    > I do hope this has been of use to you Bill... maybe someone more
                    > knowledgable than me regarding loop antenna tuning using varactors
                    > will be along to advise us both.
                    >
                    > Regards.
                    >
                    > Lee...G6ZSG.
                    >
                    >
                    >
                    > [Non-text portions of this message have been removed]
                    >
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