• 23cm 47-element G3JVL loop-Yagi gain and beamwidth figures

    From Andrew Marshall@21:1/5 to All on Tue Dec 22 13:00:55 2020
    I have a 23cm G3JVL 47-element loop-Yagi at 24ft AGL. I have not so far
    been able to find any gain and beamwidth figures for it by searching
    online. Has anyone got these figures to hand, please?

    TIA.

    --
    Regards,
    Andrew, G8BUR, M0MAA.

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  • From Brian Howie@21:1/5 to news@y-ddraenog-goch.org.uk on Tue Dec 22 14:39:05 2020
    uk!brian
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    In m
    essage <rrsqm7$d9s$1@dont-email.me>, Andrew Marshall <news@y-ddraenog-goch.org.uk> writes
    I have a 23cm G3JVL 47-element loop-Yagi at 24ft AGL. I have not so far
    been able to find any gain and beamwidth figures for it by searching
    online. Has any
    one got these figures to hand, please?

    TIA.


    I've a model of a 38 ele loop yagi. Extending it to 47 elements and
    running the model gives a gain of 21.56dBi and a 3dB beam width of
    between 14 and 16 degrees . The F/B is 24dB.

    There's a com
    mercial 49 ele here claiming 21.3dbi and 15 deg B/W

    http://www.vpa-systems.pl/1296mhz-loop-yagi-49el-213dbi-400cm-p-167.html

    Cheers

    Brian GM4DIJ
    --
    Brian Howie

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  • From Andrew Marshall@21:1/5 to Brian Howie on Wed Dec 23 09:20:25 2020
    On 22/12/2020 14:39, Brian Howie wrote:
    In message <rrsqm7$d9s$1@dont-email.me>, Andrew Marshall
    <news@y-ddraenog-goch.org.uk> writes
    I have a 23cm G3JVL 47-element loop-Yagi at 24ft AGL. I have not so far
    been able to find any gain and beamwidth figures for it by searching
    online. Has any
    one got these figures to hand, please?

    TIA.

    I've a model of a 38 ele loop yagi. Extending it to 47 elements and
    running the model gives a gain of 21.56dBi and a 3dB beam width of
    between 14 and 16 degrees . The F/B is 24dB.

    Excellent - thank you very much. That ought to give me an adequately
    accurate basis for assessing ICNIRP compliance. With 16 degrees 3dB
    beamwidth, then to a person on the ground, there should be very little
    incident field strength - I'll only be running the basic 10W RF out of
    the IC-9700, less the loss of about 7.5m of Pope H100.

    There's a com
    mercial 49 ele here claiming 21.3dbi and 15 deg B/W

    http://www.vpa-systems.pl/1296mhz-loop-yagi-49el-213dbi-400cm-p-167.html

    (looks) That seems to suggest that 21.5dBi would be a good figure to
    work with for now. I'll point it at the 'official' calculator and see
    what 'safe distance' is returned. I only wish that it were not so
    conservative as it is reported to be.

    All my other antennas seem to be compliant, except for the 'random'
    ~130m-long horizontal loop at around 4m AGL running around the garden,
    which wouldn't appear to radiate much at a downwards angle of 20 to 30
    degrees or so to a person on the ground - according to a model of an 80m full-wave loop in the fairly-recent RSGB 'antennas' book, it pretty much
    all goes upwards, which is what I wanted, for 40/80m NVIS working, when
    I put it up many years ago.

    Many thanks for the modelling and the link.

    --
    73,
    Andrew, G8BUR, M0MAA.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jeff@21:1/5 to All on Thu Dec 24 09:31:57 2020
    > (looks) That seems to suggest that 21.5dBi would be a good figure to
    work with for now. I'll point it at the 'official' calculator and see
    what 'safe distance' is returned. I only wish that it were not so conservative as it is reported to be.

    All my other antennas seem to be compliant, except for the 'random' ~130m-long horizontal loop at around 4m AGL running around the garden,
    which wouldn't appear to radiate much at a downwards angle of 20 to 30 degrees or so to a person on the ground - according to a model of an 80m full-wave loop in the fairly-recent RSGB 'antennas' book, it pretty much
    all goes upwards, which is what I wanted, for 40/80m NVIS working, when
    I put it up many years ago.

    Many thanks for the modelling and the link.


    Hi

    For the loop any members of the 'public' are almost certainly going to
    be in the near field of the antenna at HF, so it will be the near field
    E and H fields that you have to consider for ICNIRP compliance; which at
    close distances may well be very different from the resultant radiation pattern.

    The best way to do that would be to simulate it using a program such as
    4NEC2 which will give you those figures (graphically if required).

    Jeff

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  • From Andrew Marshall@21:1/5 to Jeff on Fri Dec 25 09:08:08 2020
    On 24/12/2020 09:31, Jeff wrote:
    ; (looks) That seems to suggest that 21.5dBi would be a good figure to
    work with for now. I'll point it at the 'official' calculator and see
    what 'safe distance' is returned. I only wish that it were not so
    conservative as it is reported to be.

    All my other antennas seem to be compliant, except for the 'random'
    ~130m-long horizontal loop at around 4m AGL running around the garden,
    which wouldn't appear to radiate much at a downwards angle of 20 to 30
    degrees or so to a person on the ground - according to a model of an
    80m full-wave loop in the fairly-recent RSGB 'antennas' book, it
    pretty much all goes upwards, which is what I wanted, for 40/80m NVIS
    working, when I put it up many years ago.

    Many thanks for the modelling and the link.

    For the loop any members of the 'public' are almost certainly going to
    be in the near field of the antenna at HF, so it will be the near field
    E and H fields that you have to consider for ICNIRP compliance; which at close distances may well be very different from the resultant radiation pattern.

    The best way to do that would be to simulate it using a program such as
    4NEC2 which will give you those figures (graphically if required).

    Thank you for that info.

    I hadn't seen any mention of near or far fields on the Ofcom calculator spreadsheet, so I thought that to use it as a compliance demonstrator
    would suffice. If that isn't the case, I will have to suspend use of
    that antenna until I can find a way of demonstrating compliance in the
    near field (unless there is a version of 4NEC2 or other program that
    runs under Linux Mint, I will be in some difficulty).

    I can only imagine that thousands of HF operators will be in the same
    boat as me in this respect.

    --
    73,
    Andrew.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Brian Howie@21:1/5 to news@y-ddraenog-goch.org.uk on Fri Dec 25 14:07:04 2020
    In message <rs4a5p$rhg$1@dont-email.me>, Andrew Marshall <news@y-ddraenog-goch.org.uk> writes
    On 24/12/2020 09:31, Jeff wrote:
    (looks) That seems to suggest that 21.5dBi would be a good figure to
    work with for now. I'll point it at the 'official' calculator and
    see what 'safe distance' is returned. I only wish that it were not
    so conservative as it is reported to be.

    All my other antennas seem to be compliant, except for the 'random' >>>~130m-long horizontal loop at around 4m AGL running around the
    garden, which wouldn't appear to radiate much at a downwards angle
    of 20 to 30 degrees or so to a person on the ground - according to a >>>model of an 80m full-wave loop in the fairly-recent RSGB 'antennas' >>>book, it pretty much all goes upwards, which is what I wanted, for >>>40/80m NVIS working, when I put it up many years ago.

    Many thanks for the modelling and the link.

    For the loop any members of the 'public' are almost certainly going
    to be in the near field of the antenna at HF, so it will be the near
    field E and H fields that you have to consider for ICNIRP compliance; >>which at close distances may well be very different from the resultant >>radiation pattern.
    The best way to do that would be to simulate it using a program such
    as 4NEC2 which will give you those figures (graphically if required).

    Thank you for that info.

    I hadn't seen any mention of near or far fields on the Ofcom calculator >spreadsheet, so I thought that to use it as a compliance demonstrator
    would suffice. If that isn't the case, I will have to suspend use of
    that antenna until I can find a way of demonstrating compliance in the
    near field (unless there is a version of 4NEC2 or other program that
    runs under Linux Mint, I will be in some difficulty).

    I can only imagine that thousands of HF operators will be in the same
    boat as me in this respect.

    4NEC2 will run under Wine on Linux Mint. The Offcom ,model is far-field
    only. It is therefore over pessimistic for short distances for HF
    anyway.

    It also includes ground-gain , which is only relevant in the far-field.
    I tried comparing it with a hand calculation and the VK3UM model and
    discovered this fact. The VK3UM model has a ground gain option.

    Brian GM4DIJ
    --
    Brian Howie

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  • From Andrew Marshall@21:1/5 to Brian Howie on Sat Dec 26 09:08:51 2020
    On 25/12/2020 14:07, Brian Howie wrote:
    In message <rs4a5p$rhg$1@dont-email.me>, Andrew Marshall <news@y-ddraenog-goch.org.uk> writes
    On 24/12/2020 09:31, Jeff wrote:
      > (looks) That seems to suggest that 21.5dBi would be a good figure to >>>> work with for now. I'll point it at the 'official' calculator and
    see  what 'safe distance' is returned. I only wish that it were not
    so  conservative as it is reported to be.

    All my other antennas seem to be compliant, except for the 'random'
    ~130m-long horizontal loop at around 4m AGL running around the
    garden,  which wouldn't appear to radiate much at a downwards angle
    of 20 to 30  degrees or so to a person on the ground - according to
    a model of an  80m full-wave loop in the fairly-recent RSGB
    'antennas' book, it  pretty much all goes upwards, which is what I
    wanted, for 40/80m NVIS  working, when I put it up many years ago.

    Many thanks for the modelling and the link.

    For the loop any members of the 'public' are almost certainly going
    to be in the near field of the antenna at HF, so it will be the near
    field  E and H fields that you have to consider for ICNIRP
    compliance; which at close distances may well be very different from
    the resultant radiation pattern.
     The best way to do that would be to simulate it using a program such
    as  4NEC2 which will give you those figures (graphically if required).

    Thank you for that info.

    I hadn't seen any mention of near or far fields on the Ofcom
    calculator spreadsheet, so I thought that to use it as a compliance
    demonstrator would suffice. If that isn't the case, I will have to
    suspend use of that antenna until I can find a way of demonstrating
    compliance in the near field (unless there is a version of 4NEC2 or
    other program that runs under Linux Mint, I will be in some difficulty).

    I can only imagine that thousands of HF operators will be in the same
    boat as me in this respect.

    4NEC2 will  run under Wine on Linux Mint.

    I have a spare laptop running Linux, though I haven't used it for a year
    or so. If it still works, I may try downloading and installing Wine and
    then 4NEC2 (but see below). I don't want to risk rendering one of my
    main Linux boxes unusable because of some installation disaster,
    especially as their availability is critically important at the moment
    for online food shopping and other important tasks.

    The Offcom ,model is far-field
    only. It is therefore over pessimistic  for short distances for HF anyway.

    Thank you for that info. In that case, it looks as if I may be OK using
    the Ofcom calculator for HF, if I can reasonably use the model of the
    80m full-wave loop in 'HF Antennas for Everyone' (RSGB; p221, fig. 5),
    where radiation at 0 degrees appears to be minimal (according to the
    small graph, apparently somewhere between -10 and -30dB below the peak
    quoted gain of 8.3dBi). Allowing a 50% duty cycle should help, too.

    It also includes ground-gain , which is only relevant in the far-field.
    I tried comparing it with a hand calculation and the VK3UM model and discovered this fact.  The VK3UM model has a ground gain option.

    It'll certainly be an interesting modelling to carry out when
    circumstances permit. If for any reason I do feel it necessary to
    suspend operations using the loop, I will have to do so, but as most of
    my operation is above 30MHz, where it seems that all my power/antenna
    options will be compliant, it will be no great problem.

    I can see a fair few second-hand linear amplifiers coming onto the
    market at keen prices before long, though!

    Thank you for the information.

    --
    73,
    Andrew, G8BUR, M0MAA.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Paul@21:1/5 to Andrew Marshall on Sat Dec 26 13:45:23 2020
    Andrew Marshall wrote:
    On 25/12/2020 14:07, Brian Howie wrote:

    4NEC2 will run under Wine on Linux Mint.

    I have a spare laptop running Linux, though I haven't used it for a year
    or so. If it still works, I may try downloading and installing Wine and
    then 4NEC2 (but see below). I don't want to risk rendering one of my
    main Linux boxes unusable because of some installation disaster,
    especially as their availability is critically important at the moment
    for online food shopping and other important tasks.

    Take a spare hard drive and clone over the working disk drive.

    With a Linux fleet as important as the one you describe, you
    must already be familiar with the drill.

    That's how I ended up with two dozen hard drives in this room.
    Any time I lack confidence in the outcome of a experiment, it
    takes an extra ten minutes to prepare for it. For example, I
    have a terabyte of downloads, and that is backed up on a much
    less frequent basis. The tiny OS partitions can be backed up or
    cloned in ten minutes or so.

    On Linux, there is CloneZilla. Boot a USB stick, then do the
    drive-to-drive transfer. On Windows I use Macrium Reflect Free,
    which handles both NTFS and EXT4 partitions, and is "good enough"
    for the Linux installs I do. The current drive in the Test Machine
    has 23 partitions at the moment (and Macrium can back up the
    whole thing, using just as smart a transfer method as Clonezilla).
    I can't really add any more partitions, because the screen is
    no longer wide enough. GPT allows 128 partitions, but then you'd
    not have a big enough screen to work on them.

    Paul

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Brian Howie@21:1/5 to Andrew Marshall on Sat Dec 26 14:13:08 2020
    On Sat, 26 Dec 2020 09:08:51 +0000, Andrew Marshall wrote:

    On 25/12/2020 14:07, Brian Howie wrote:
    In message <rs4a5p$rhg$1@dont-email.me>, Andrew Marshall
    <news@y-ddraenog-goch.org.uk> writes
    On 24/12/2020 09:31, Jeff wrote:
      > (looks) That seems to suggest that 21.5dBi would be a good
      > figure to
    work with for now. I'll point it at the 'official' calculator and
    see  what 'safe distance' is returned. I only wish that it were not >>>>> so  conservative as it is reported to be.

    All my other antennas seem to be compliant, except for the 'random'
    ~130m-long horizontal loop at around 4m AGL running around the
    garden,  which wouldn't appear to radiate much at a downwards angle >>>>> of 20 to 30  degrees or so to a person on the ground - according to >>>>> a model of an  80m full-wave loop in the fairly-recent RSGB
    'antennas' book, it  pretty much all goes upwards, which is what I
    wanted, for 40/80m NVIS  working, when I put it up many years ago.

    Many thanks for the modelling and the link.

    For the loop any members of the 'public' are almost certainly going
    to be in the near field of the antenna at HF, so it will be the near
    field  E and H fields that you have to consider for ICNIRP
    compliance; which at close distances may well be very different from
    the resultant radiation pattern.
     The best way to do that would be to simulate it using a program
     such
    as  4NEC2 which will give you those figures (graphically if
    required).

    Thank you for that info.

    I hadn't seen any mention of near or far fields on the Ofcom
    calculator spreadsheet, so I thought that to use it as a compliance
    demonstrator would suffice. If that isn't the case, I will have to
    suspend use of that antenna until I can find a way of demonstrating
    compliance in the near field (unless there is a version of 4NEC2 or
    other program that runs under Linux Mint, I will be in some
    difficulty).

    I can only imagine that thousands of HF operators will be in the same
    boat as me in this respect.

    4NEC2 will  run under Wine on Linux Mint.

    I have a spare laptop running Linux, though I haven't used it for a year
    or so. If it still works, I may try downloading and installing Wine and
    then 4NEC2 (but see below). I don't want to risk rendering one of my
    main Linux boxes unusable because of some installation disaster,
    especially as their availability is critically important at the moment
    for online food shopping and other important tasks.

    The Offcom ,model is far-field only. It is therefore over pessimistic 
    for short distances for HF anyway.

    Thank you for that info. In that case, it looks as if I may be OK using
    the Ofcom calculator for HF, if I can reasonably use the model of the
    80m full-wave loop in 'HF Antennas for Everyone' (RSGB; p221, fig. 5),
    where radiation at 0 degrees appears to be minimal (according to the
    small graph, apparently somewhere between -10 and -30dB below the peak
    quoted gain of 8.3dBi). Allowing a 50% duty cycle should help, too.

    It also includes ground-gain , which is only relevant in the far-field.
    I tried comparing it with a hand calculation and the VK3UM model and
    discovered this fact.  The VK3UM model has a ground gain option.

    It'll certainly be an interesting modelling to carry out when
    circumstances permit. If for any reason I do feel it necessary to
    suspend operations using the loop, I will have to do so, but as most of
    my operation is above 30MHz, where it seems that all my power/antenna
    options will be compliant, it will be no great problem.

    I can see a fair few second-hand linear amplifiers coming onto the
    market at keen prices before long, though!

    Thank you for the information.

    It's been a while since I searched for Linux NEC2 programs.

    I found xnec2 which is a native Linux version of nec2.

    https://www.linuxjournal.com/content/antennas-linux

    The debian install command runs fine under Linux Mint. I only got as far
    as running the examples, but it seems to work.


    Brian GM4DIJ



    --
    Brian Howie

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Andrew Marshall@21:1/5 to Paul on Sun Dec 27 08:59:36 2020
    On 26/12/2020 18:45, Paul wrote:
    Andrew Marshall wrote:
    On 25/12/2020 14:07, Brian Howie wrote:

    4NEC2 will  run under Wine on Linux Mint.

    I have a spare laptop running Linux, though I haven't used it for a
    year or so. If it still works, I may try downloading and installing
    Wine and then 4NEC2 (but see below). I don't want to risk rendering
    one of my main Linux boxes unusable because of some installation
    disaster, especially as their availability is critically important at
    the moment for online food shopping and other important tasks.

    Take a spare hard drive and clone over the working disk drive.

    That I can easily do. I have a couple of portable HDDs which ought to be
    big enough.

    With a Linux fleet as important as the one you describe, you
    must already be familiar with the drill.

    Shouldn't be a problem.

    That's how I ended up with two dozen hard drives in this room.
    Any time I lack confidence in the outcome of a experiment, it
    takes an extra ten minutes to prepare for it. For example, I
    have a terabyte of downloads, and that is backed up on a much
    less frequent basis. The tiny OS partitions can be backed up or
    cloned in ten minutes or so.

    I have nothing like that amount so my backups don't take very long.

    On Linux, there is CloneZilla. Boot a USB stick, then do the
    drive-to-drive transfer. On Windows I use Macrium Reflect Free,
    which handles both NTFS and EXT4 partitions, and is "good enough"
    for the Linux installs I do. The current drive in the Test Machine
    has 23 partitions at the moment (and Macrium can back up the
    whole thing, using just as smart a transfer method as Clonezilla).
    I can't really add any more partitions, because the screen is
    no longer wide enough. GPT allows 128 partitions, but then you'd
    not have a big enough screen to work on them.

    Thank you for the above (of which I have taken a copy).

    --
    73,
    Andrew, G8BUR, M0MAA.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Andrew Marshall@21:1/5 to Brian Howie on Sun Dec 27 08:53:45 2020
    On 26/12/2020 14:13, Brian Howie wrote:
    It's been a while since I searched for Linux NEC2 programs.

    I found xnec2 which is a native Linux version of nec2.

    https://www.linuxjournal.com/content/antennas-linux

    The debian install command runs fine under Linux Mint. I only got as far
    as running the examples, but it seems to work.

    Many thanks for the link. I'll dig out the old laptop, and if it works
    I'll download xnec2 and try it out. I suspect that I might wait a bit
    first, until I can track down more info on the radiation patterns of
    NVIS antennas, and perhaps consider whether my installation might
    benefit from a change anyway; NVIS, though interesting, is but a small
    part of my operating, so I'll take things at a measured pace.

    Thank you very much for your help and suggestions.

    --
    73,
    Andrew, G8BUR, M0MAA.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jeff@21:1/5 to All on Sun Dec 27 11:56:47 2020
    The Offcom ,model is far-field only. It is therefore over pessimistic
    for short distances for HF anyway.

    Thank you for that info. In that case, it looks as if I may be OK using
    the Ofcom calculator for HF, if I can reasonably use the model of the
    80m full-wave loop in 'HF Antennas for Everyone' (RSGB; p221, fig. 5),
    where radiation at 0 degrees appears to be minimal (according to the
    small graph, apparently somewhere between -10 and -30dB below the peak
    quoted gain of 8.3dBi). Allowing a 50% duty cycle should help, too.


    I think that is a false assumption; in the near field the patterns can
    be remarkably different from the far field pattern.

    When close to a wire the near E & H fields will look nothing like
    resultant fields at a distance, at 0 degrees there will be strong fields.

    Jeff

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From David Woolley@21:1/5 to Jeff on Sun Dec 27 11:35:44 2020
    On 24/12/2020 09:31, Jeff wrote:
    For the loop any members of the 'public' are almost certainly going to
    be in the near field of the antenna at HF, so it will be the near field
    E and H fields that you have to consider for ICNIRP compliance; which at close distances may well be very different from the resultant radiation pattern.



    It is also going to be dependant on frequency and ground conductivity.
    Unless you have a really good ground mesh, extending well beyond the
    footprint, you are going to need to model for different ground
    conductivities, to allow for unknowns and weather effects, as well as at different frequencies.

    Also, far field polar diagrams are calculated for very large distances,
    where the angle subtended by the antenna will be negligible compared
    with the beam width, and you can assume all the radiation comes from a
    central point. Near field levels may even be higher near the actual
    wire, than in the centre of the antenna.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Andrew Marshall@21:1/5 to Jeff on Sun Dec 27 17:18:46 2020
    On 27/12/2020 11:56, Jeff wrote:

    The Offcom ,model is far-field only. It is therefore over pessimistic
    for short distances for HF anyway.

    Thank you for that info. In that case, it looks as if I may be OK
    using the Ofcom calculator for HF, if I can reasonably use the model
    of the 80m full-wave loop in 'HF Antennas for Everyone' (RSGB; p221,
    fig. 5), where radiation at 0 degrees appears to be minimal (according
    to the small graph, apparently somewhere between -10 and -30dB below
    the peak quoted gain of 8.3dBi). Allowing a 50% duty cycle should
    help, too.


    I think that is a false assumption; in the near field the patterns can
    be remarkably different from the far field pattern.

    When close to a wire the near E & H fields will look nothing like
    resultant fields at a distance, at 0 degrees there will be strong fields.

    I'm thinking more and more that I (and many others) will have to wait
    for more precise information on what analysis of radiation patterns will
    be required to demonstrate compliance when using HF with wire antennas,
    before using them in future.

    --
    73,
    Andrew, G8BUR, M0MAA.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jeff@21:1/5 to Andrew Marshall on Mon Dec 28 09:56:38 2020
    On 27/12/2020 17:18, Andrew Marshall wrote:
    On 27/12/2020 11:56, Jeff wrote:

    The Offcom ,model is far-field only. It is therefore over
    pessimistic for short distances for HF anyway.

    Thank you for that info. In that case, it looks as if I may be OK
    using the Ofcom calculator for HF, if I can reasonably use the model
    of the 80m full-wave loop in 'HF Antennas for Everyone' (RSGB; p221,
    fig. 5), where radiation at 0 degrees appears to be minimal
    (according to the small graph, apparently somewhere between -10 and
    -30dB below the peak quoted gain of 8.3dBi). Allowing a 50% duty
    cycle should help, too.


    I think that is a false assumption; in the near field the patterns can
    be remarkably different from the far field pattern.

    When close to a wire the near E & H fields will look nothing like
    resultant fields at a distance, at 0 degrees there will be strong fields.

    I'm thinking more and more that I (and many others) will have to wait
    for more precise information on what analysis of radiation patterns will
    be required to demonstrate compliance when using HF with wire antennas, before using them in future.



    Don't hold your breath, at least from Ofcom, as all they will say is
    comply with the ICNIRP requirements, just like they do in reply to any
    other question where they are asked for advice.

    HF antennas are a problem as they are so dependant on the actual
    location and installation. The best that you can do is to model them,
    but even then simulation software available to most amateurs cannot
    model buildings etc. So it is always going to be a best approximation.

    However, the saving grace is that from the simulations that I have done
    even taking a worst case scenario of 400W continuous transmission the
    safe distances at HF are pretty small. If you add to that the benefit
    that you get from tx/rx ratios, and the fact that the exposure is
    averaged over 30 minutes, then you probably don't have to worry too
    much. just do some simulations if they look ok put then away and carry
    on as normal. No one will ever ask you for them, and if they do you have evidence that you did you best to comply.

    Jeff

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