Message-ID: <4CA0FB40.5060404@telus.net>
Date: Mon, 27 Sep 2010 20:14:56 +0000
From: Scott Tilley <sthed475@telus.net>
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Subject: Re: LF: Loops on TX
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  Hi Roger

My TX loop pretty much works as modeled which I can't say for most 
verticals I've tries as they are highly dependent on the installation 
site, weather and time of year...

My TX loop is a 20m high by 30m long #2 AWG aluminum wire beast.  I find 
that there is little to no noticable difference in the tuning during 
different weather conditions.    The loop is installed inside a line of 
trees and in some cases in direct contact with the foliage/branches.  I 
choose the type of conductor I used as it is tested by CSA to at least 
3KV but rated for 600V with a thick XLPE insulation.  Ie. risk of 
breakdown low and has not been a problem for me at high power and rainy 
conditions...

The loop is mounted about 3m over the rocky ground here.  I would not 
suggest moving the loop base closer to ground and certainly not burying 
it.  Move it the other way if you can as the higher the flowing current 
the higher the ERP.  I^2 x R...  As you move the loop closer to ground 
the losses will go up and the 'I' down...  In fact, I think my poor 
ground may in fact be the reason for my low ground losses.  My Rloss = 
1.21ohms! On high power I can circulate a current approaching 40A all 
night long if need be and not need to worry about the weather...

If someone knows the relationships for how a loop behaves over ground 
I'd love to see them too!

My loop seems to work just fine and produces audible signals nightly at 
over 2000km range and It has almost completed a QSO with JA (7200Km) 
with some nights producing signals in the QRSS10 copible level there.  
QSB on the path and poor RX situations (QRM) in JA being the limiting 
factors...   I can't say that for the vertical tried at this QTH.  Very 
high feed impedance and it produced a very poor radiated signal no 
matter what I did to improve the ground with the reports or lack of to 
prove it...

To summarize

Loop - dependable compromise antenna for certain QTH types where 
verticals won't work well.  Ie.  it will work fairly well pretty much 
anywhere as long as you have supports for it.
Vertical - If you have good ground/soil and lots of clear land it will 
work VERY well.  If you're a normal person with a normal lot, build a loop.

One issue with a loop is as you go QRO the tuner becomes abit more 
'complex' to design.  Voltages and currents can kill caps.  If you need 
more info I can supply off list.

73 Scott
VE7TIL
http://www3.telus.net/sthed/argo/



On 9/27/2010 5:24 PM, Roger Lapthorn wrote:
> Good to see the reflector back again.
>
> For the last week or so I've been running my vertical "fully in the 
> air" TX loop (1mm diameter wire, 80m sq area) on both 137 and 500kHz. 
> Now, the bottom of the loop is laying right on the lawn with no 
> attempt to raise it off the ground. Weather has been mixed and 
> yesterday it rained all day. Results on 500kHz suggest it is every bit 
> as good (actually better) than my top loaded Marconi used last winter 
> with best DX so far with 2mW ERP being LA3EQ last evening (heavy rain 
> all day and evening). Results on 136kHz with <20uW ERP have been 
> encouraging too with 6 different WSPR reports out to 148km. I clearly 
> know that improving the wire diameter will improve the ERP simply as a 
> result of reducing resistive losses. What I'm less clear about is why 
> people say all of the loop should be raised above the ground.
>
> My questions are these:
>
>     * What additional losses, if any, do I suffer having the loop on
>       the ground (even wet ground)? How do these arise?
>     * Could I bury the return part of the loop wire in the ground and
>       maybe gain a few more square metres of area?
>     * Is there anywhere where I can get a simple explanation of loop
>       losses due to ground presence and foliage presence?
>
> In the last year a lot of accepted theory/beliefs, for example on 
> earth electrode antennas, has proved to be questionable and I am 
> wondering if the "loop must be in the air and away from foliage" is 
> another accepted "fact" which needs to be questioned.
>
> 73s
> Roger G3XBM
>
> -- 
> http://g3xbm-qrp.blogspot.com/
> http://www.g3xbm.co.uk
> http://www.youtube.com/user/g3xbm
> G3XBM   GQRP 1678    ISWL G11088

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    Hi Roger<br>
    <br>
    My TX loop pretty much works as modeled which I can't say for most
    verticals I've tries as they are highly dependent on the
    installation site, weather and time of year... <br>
    <br>
    My TX loop is a 20m high by 30m long #2 AWG aluminum wire beast.&nbsp; I
    find that there is little to no noticable difference in the tuning
    during different weather conditions.&nbsp;&nbsp;&nbsp; The loop is installed inside
    a line of trees and in some cases in direct contact with the
    foliage/branches.&nbsp; I choose the type of conductor I used as it is
    tested by CSA to at least 3KV but rated for 600V with a thick XLPE
    insulation.&nbsp; Ie. risk of breakdown low and has not been a problem
    for me at high power and rainy conditions...<br>
    <br>
    The loop is mounted about 3m over the rocky ground here.&nbsp; I would
    not suggest moving the loop base closer to ground and certainly not
    burying it.&nbsp; Move it the other way if you can as the higher the
    flowing current the higher the ERP.&nbsp; I^2 x R...&nbsp; As you move the
    loop closer to ground the losses will go up and the 'I' down...&nbsp; In
    fact, I think my poor ground may in fact be the reason for my low
    ground losses.&nbsp; My Rloss = 1.21ohms! On high power I can circulate a
    current approaching 40A all night long if need be and not need to
    worry about the weather...<br>
    <br>
    If someone knows the relationships for how a loop behaves over
    ground I'd love to see them too!<br>
    <br>
    My loop seems to work just fine and produces audible signals nightly
    at over 2000km range and It has almost completed a QSO with JA
    (7200Km) with some nights producing signals in the QRSS10 copible
    level there.&nbsp; QSB on the path and poor RX situations (QRM) in JA
    being the limiting factors... &nbsp; I can't say that for the vertical
    tried at this QTH.&nbsp; Very high feed impedance and it produced a very
    poor radiated signal no matter what I did to improve the ground with
    the reports or lack of to prove it...<br>
    <br>
    To summarize<br>
    <br>
    Loop - dependable compromise antenna for certain QTH types where
    verticals won't work well.&nbsp; Ie.&nbsp; it will work fairly well pretty
    much anywhere as long as you have supports for it.<br>
    Vertical - If you have good ground/soil and lots of clear land it
    will work VERY well.&nbsp; If you're a normal person with a normal lot,
    build a loop.<br>
    <br>
    One issue with a loop is as you go QRO the tuner becomes abit more
    'complex' to design.&nbsp; Voltages and currents can kill caps.&nbsp; If you
    need more info I can supply off list.<br>
    <br>
    73 Scott<br>
    VE7TIL<br>
    <a class="moz-txt-link-freetext" href="http://www3.telus.net/sthed/argo/">http://www3.telus.net/sthed/argo/</a><br>
    <br>
    <br>
    <br>
    On 9/27/2010 5:24 PM, Roger Lapthorn wrote:
    <blockquote        cite="mid:AANLkTinsoxgfUWU1o-JxrpVn0fcDhbWDMdO0BhD7gpfV@mail.gmail.com"        type="cite">Good to see the reflector back again.<br>
      <br>
      For the last week or so I've been running my vertical "fully in
      the air" TX loop (1mm diameter wire, 80m sq area) on both 137 and
      500kHz. Now, the bottom of the loop is laying right on the lawn
      with no attempt to raise it off the ground. Weather has been mixed
      and yesterday it rained all day. Results on 500kHz suggest it is
      every bit as good (actually better) than my top loaded Marconi
      used last winter with best DX so far with 2mW ERP being LA3EQ last
      evening (heavy rain all day and evening). Results on 136kHz with
      &lt;20uW ERP have been encouraging too with 6 different WSPR
      reports out to 148km. I clearly know that improving the wire
      diameter will improve the ERP simply as a result of reducing
      resistive losses. What I'm less clear about is why people say all
      of the loop should be raised above the ground.<br>
      <br>
      My questions are these:<br>
      <ul>
        <li>What additional losses, if any, do I suffer having the loop
          on the ground (even wet ground)? How do these arise?<br>
        </li>
        <li>Could I bury the return part of the loop wire in the ground
          and maybe gain a few more square metres of area?</li>
        <li>Is there anywhere where I can get a simple explanation of
          loop losses due to ground presence and foliage presence?</li>
      </ul>
      In the last year a lot of accepted theory/beliefs, for example on
      earth electrode antennas, has proved to be questionable and I am
      wondering if the "loop must be in the air and away from foliage"
      is another accepted "fact" which needs to be questioned.<br>
      <br>
      73s<br>
      Roger G3XBM<br>
      <br>
      -- <br>
      <a moz-do-not-send="true" href="http://g3xbm-qrp.blogspot.com/"          target="_blank">http://g3xbm-qrp.blogspot.com/</a><br>
      <a moz-do-not-send="true" href="http://www.g3xbm.co.uk"          target="_blank">http://www.g3xbm.co.uk</a><br>
      <a moz-do-not-send="true" href="http://www.youtube.com/user/g3xbm"          target="_blank">http://www.youtube.com/user/g3xbm</a><br>
      G3XBM&nbsp;&nbsp; GQRP 1678&nbsp;&nbsp;&nbsp; ISWL G11088<br>
    </blockquote>
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