Elecraft

Question about suspending a delta loop...

Classic

List

Threaded

6 messages Options

Rick McClelland, AA5S

Question about suspending a delta loop...

I have a 240' delta loop suspended at three points about my QTH. I've been
pondering adding another 47' but this is quite a challenge given the
dimensions of my suburban lot. One thing I'm considering is to make good
use of two trees located in a common area outside my property lines. Easily
said, but I would not want to hang a 5 kg line ballast at either of these
points because I can imagine a couple of neighborhood youths scaling a tree
with one of them cutting a line causing the 5kg weight to crash down upon
the tender skull of the other youth.

Legal matters notwithstanding, my question is whether I'm inviting certain
mechanical failure if I fix the two endpoints outside my property lines and
make use of only a single 5 kg ballast on the tree located within my
property lines. The advantage of doing this is obvious, if any of the
supporting lines outside my property are cut, the antenna falls onto my
property and there is no possibility of injury to the purpetrators of the
dastardly deed.

As a possibly relevant aside, I don't use a typical insulator at each of
the three suspension points. I use a 4" flat acrylic insulator with two 6"
acrylic insulators attached to the end of the 4" insulator such that the
resulting insulating apparatus appears to be a rather large 8" tuning rod.
In my non-mechanical-engineering mind, I imagine that having the insulator
arranged in such a fashion reduces the peak tension at each apex of the
triangle and also allows the wire to move more freely through the insulator
without binding at that point. I realize that this matter isn't related to
any Elecraft product but there are so many sage OMs here that I feel that
an answer will be quickly forthcoming and without controversy.

--
Rick McClelland, AA5S
Fort Collins, CO
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

Chuck N4XS

Re: Question about suspending a delta loop...

I'm not what you'd call sage, but I have an 80m horizontal loop and don't
bother with suspended weights. I figure there is enough stretch in my
support ropes to handle any normal winds, and a major storm is probably
going to break some tree limbs anyway. So much can happen to tree-supported
antennas in big storms that spending too much effort on a support system
just doesn't appeal to me. I'd rather prepare for a quick replacement should
the need arise. My support ropes run from the corner insulators over the
tree tops and down to points near the ground where I tie them off. I do NOT
climb trees, so I don't have the option of tying them off higher up. (I use
a bow and arrow to launch fishing line over a high limb, then use it to pull
nylon twine over, and then use it to pull my support rope over. Quick and
easy.) I don't have a problem with vandalism where I live, and the antenna
stays up for a long time.

Chuck N4XS

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

Rick McClelland, AA5S

Re: Question about suspending a delta loop...

That sounds encouraging. I use good quality wire and it seems quite
strong, I may just give a try with a single ballast and see if the antenna
survives the winter. I also do the same as you, I use long lines and avoid
climbing trees. I have yet to hear about vandalism in my area but I was a
kid once and I know how kids think, so I wouldn't want to encourage bad
behavior. Thanks for your comment.

On Sat, Sep 15, 2012 at 9:04 PM, Chuck N4XS <[hidden email]> wrote:

> I'm not what you'd call sage, but I have an 80m horizontal loop and don't
> bother with suspended weights. I figure there is enough stretch in my
> support ropes to handle any normal winds, and a major storm is probably
> going to break some tree limbs anyway. So much can happen to tree-supported
> antennas in big storms that spending too much effort on a support system
> just doesn't appeal to me. I'd rather prepare for a quick replacement
> should
> the need arise. My support ropes run from the corner insulators over the
> tree tops and down to points near the ground where I tie them off. I do NOT
> climb trees, so I don't have the option of tying them off higher up. (I use
> a bow and arrow to launch fishing line over a high limb, then use it to
> pull
> nylon twine over, and then use it to pull my support rope over. Quick and
> easy.) I don't have a problem with vandalism where I live, and the antenna
> stays up for a long time.
>
> Chuck N4XS
>
>
>

--
Rick McClelland, AA5S
Fort Collins, CO
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

Geoffrey Mackenzie-Kennedy-3

Re: Question about suspending a delta loop...

In reply to this post by Rick McClelland, AA5S

Rick,

Is your delta loop suspended with its apex up or down, or is it a horizontal
loop? If the apex is down or up it is better to use only one counterweight,
otherwise the antenna will "walk" if the trees sway in the wind. A
supporting catenary will also "walk" if a counterweight is used at each end.

At my last QTH in GM all of my HF wire antennas were supported by tall pines
and exposed to very high winds. So I might be able to offer some
suggestions if you could please tell me about the configuration of your
loop.

73,
Geoff
LX2AO

On September 16, 2012 at 4:37 AM, Rick McClelland, AA5S wrote:

>I have a 240' delta loop suspended at three points about my QTH. I've been
> pondering adding another 47' but this is quite a challenge given the
> dimensions of my suburban lot. One thing I'm considering is to make good
> use of two trees located in a common area outside my property lines.
> Easily
> said, but I would not want to hang a 5 kg line ballast at either of these
> points because I can imagine a couple of neighborhood youths scaling a
> tree
> with one of them cutting a line causing the 5kg weight to crash down upon
> the tender skull of the other youth.
>
> Legal matters notwithstanding, my question is whether I'm inviting certain
> mechanical failure if I fix the two endpoints outside my property lines
> and
> make use of only a single 5 kg ballast on the tree located within my
> property lines. The advantage of doing this is obvious, if any of the
> supporting lines outside my property are cut, the antenna falls onto my
> property and there is no possibility of injury to the purpetrators of the
> dastardly deed.
>
> As a possibly relevant aside, I don't use a typical insulator at each of
> the three suspension points. I use a 4" flat acrylic insulator with two 6"
> acrylic insulators attached to the end of the 4" insulator such that the
> resulting insulating apparatus appears to be a rather large 8" tuning rod.
> In my non-mechanical-engineering mind, I imagine that having the insulator
> arranged in such a fashion reduces the peak tension at each apex of the
> triangle and also allows the wire to move more freely through the
> insulator
> without binding at that point. I realize that this matter isn't related
> to
> any Elecraft product but there are so many sage OMs here that I feel that
> an answer will be quickly forthcoming and without controversy.
>
> --
> Rick McClelland, AA5S
> Fort Collins, CO

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

Rick McClelland, AA5S

Re: Question about suspending a delta loop...

Geoffrey, I did leave out that important point. My delta loop is oriented
horizontally, all three support points are at the same height (about 40')
in three different trees.

On Sun, Sep 16, 2012 at 9:23 AM, Geoffrey Mackenzie-Kennedy <[hidden email]>wrote:

> Rick,
>
> Is your delta loop suspended with its apex up or down, or is it a
> horizontal loop? If the apex is down or up it is better to use only one
> counterweight, otherwise the antenna will "walk" if the trees sway in the
> wind. A supporting catenary will also "walk" if a counterweight is used at
> each end.
>
> At my last QTH in GM all of my HF wire antennas were supported by tall
> pines and exposed to very high winds. So I might be able to offer some
> suggestions if you could please tell me about the configuration of your
> loop.
>
> 73,
> Geoff
> LX2AO
>
>
>
>
> On September 16, 2012 at 4:37 AM, Rick McClelland, AA5S wrote:
>
>
> I have a 240' delta loop suspended at three points about my QTH. I've
>> been
>> pondering adding another 47' but this is quite a challenge given the
>> dimensions of my suburban lot. One thing I'm considering is to make good
>> use of two trees located in a common area outside my property lines.
>> Easily
>> said, but I would not want to hang a 5 kg line ballast at either of these
>> points because I can imagine a couple of neighborhood youths scaling a
>> tree
>> with one of them cutting a line causing the 5kg weight to crash down upon
>> the tender skull of the other youth.
>>
>> Legal matters notwithstanding, my question is whether I'm inviting certain
>> mechanical failure if I fix the two endpoints outside my property lines
>> and
>> make use of only a single 5 kg ballast on the tree located within my
>> property lines. The advantage of doing this is obvious, if any of the
>> supporting lines outside my property are cut, the antenna falls onto my
>> property and there is no possibility of injury to the purpetrators of the
>> dastardly deed.
>>
>> As a possibly relevant aside, I don't use a typical insulator at each of
>> the three suspension points. I use a 4" flat acrylic insulator with two 6"
>> acrylic insulators attached to the end of the 4" insulator such that the
>> resulting insulating apparatus appears to be a rather large 8" tuning rod.
>> In my non-mechanical-engineering mind, I imagine that having the insulator
>> arranged in such a fashion reduces the peak tension at each apex of the
>> triangle and also allows the wire to move more freely through the
>> insulator
>> without binding at that point. I realize that this matter isn't related
>> to
>> any Elecraft product but there are so many sage OMs here that I feel that
>> an answer will be quickly forthcoming and without controversy.
>>
>> --
>> Rick McClelland, AA5S
>> Fort Collins, CO
>>
>
>

Geoffrey Mackenzie-Kennedy-3

Re: Question about suspending a delta loop...

Rick,

Thank you for your reply, and my apology for taking so long to acknowledge
it.

I did at first try using bungee cords in GM land as Gary VE1RGB uses them,
and for the reasons which Gary mentioned, but unfortunately the squirrels
(mostly red) living on the farm there liked to chew bungee cords enough to
render them useless. Thereafter I used UV resistant marine rope and Kevlar
to support my antennas, neither of which squirrels like to chew it seems,
together with "fused" counterweights. For the elements of my 40m wire beams
and for my other antennas I used jacketed Flexweave, the jacketed type to
protect the wire from the claws of the birds who perched on the antennas.

If your antenna's wire can move through the supports which are not on your
property without being damaged, a "fused" counterweight hanging near ground
or a suitable bungee cord at the support on your property might be
sufficient. Of course an antenna's support ropes should always pass through
pulleys and not over branches, unless the antenna is a temporary
installation. Marine pulleys (6mm) as used in small sailing boats have
served me well.

Any rope passing over a branch to support a pulley should be "wiggled" every
eight or nine months to prevent the tree from growing over the rope, which
would make it difficult/ impossible to move the rope later on.

If you cannot find suitable bungee cord and are interested in knowing more
about the "fused" counterweights which I used, please let me know.

73,
Geoff
LX2AO

On September 16, 2012 at 6:07 PM, Rick McClelland, AA5S wrote:

> Geoffrey, I did leave out that important point. My delta loop is oriented
> horizontally, all three support points are at the same height (about 40')
> in
> three different trees.

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html