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RF in the Trees

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Re: RF in the Trees

Hmmm. Interesting theory Vic. I agree that ambient noise probably
doesn't have any particular polarization. My dipoles clearly have less
noise pickup than my verticals. I do have a Cushcraft MV-6 compact
vertical on top of the garage which has a balun as part of its design
and it's noise level seems lower than the ground mounted verticals.
But, it also has negative gain compared to a dipole or a full-size vertical.

I was planning an experiment consisting of a full size vertical radiator
made of aluminum tubing and two horizontal ground planes made of
carefully tuned ham sticks. Now, I'll be sure to feed it through a good
current balun to insure the feedline is fully decoupled.

Another experiment on the summer agenda is a full-wave loop configured
as a vertical rectangle to produce a 50 ohm feed point. I've read that a
full wave loop is much better at rejecting noise and produces a lower
angle of radiation for a given height than a dipole. I'd love to put up
a quad, but $600 is a bit much right now. A full wave loop costs almost
nothing by comparison. I'm wondering if perhaps a delta loop could be
effective as a portable radiator for the KX3. An inverted triangle fed
from the bottom apex seems simple enough.

With summer finally here it is time to pull out the boxes of wire, coax
and insulators and see what sort of interesting things to build.

Doug -- K0DXV

On 6/26/14, 4:07 PM, Vic, K2VCO wrote:

> I have a theory about this.
>
> Compare a vertical to a dipole. One reason for additional noise is
> that a vertical is omnidirectional, and noise comes from all
> directions. The signal is coming from one direction, and if it is the
> right direction, then the 2.2 dB gain from directivity of a dipole
> improves the s/n ratio by that much. But subjectively the difference
> seems greater than this. It's also true that the vertical is better
> for signals off the side of the dipole.
>
> As Brian said, most verticals appear to be far noisier in urban
> environments where there is a lot of manmade noise. I believe that
> this is /not/ because manmade noise tends to be vertically polarized,
> as is often said.
>
> I believe that it is because most verticals are not adequately
> decoupled from the feedline. Therefore, manmade noise is picked up on
> the outside of the feedline and flows directly into the antenna.
>
> This is exactly the same problem that happens with a dipole without a
> balun.
>
> Therefore the solution to the problem may be a good choke 'balun' at
> the vertical's feedpoint.
>
> On 6/26/14 1:38 PM, Brian Hunt wrote:
>> The other thing I have encountered with verticals vs horizontal antennas
>> in an urban environment is that verticals are inherently noisier.
>

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JHRichards

Re: RF in the Trees

In reply to this post by W2RMS

Short wave listeners use kites and baloons to hold up long wire antennas
all the time. I did this long before becoming a ham.

------------------ K8JHR --------------------------

On 6/26/2014 7:24 PM, Slava Baytalskiy wrote:
> I wonder if anyone's ever used a kite in a field to keep a wire "up".
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Phil Hystad-3

Re: RF in the Trees

I remember that Benjamin Franklin was a short wave listener -- his radio used a rusty key as the detector. His resonant circuit included a Leyden Jar capacitor. He quit this hobby though when, during an electrical storm, his lightning protection failed and destroyed his rig. Embarrassed about making such foolish mistakes, he invented an entirely different story to account for his being out in the storm flying a kite.

73, phil, K7PEH

On Jun 26, 2014, at 9:31 PM, K8JHR <[hidden email]> wrote:

> Short wave listeners use kites and baloons to hold up long wire antennas all the time. I did this long before becoming a ham.
>
> ------------------ K8JHR --------------------------
>
> On 6/26/2014 7:24 PM, Slava Baytalskiy wrote:
>> I wonder if anyone's ever used a kite in a field to keep a wire "up".
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David Pratt

Re: RF in the Trees

In reply to this post by JHRichards

There is an excellent video magazine here, all about kite antennas in
Great Britain ....
http://www.txfilms.co.uk/txfactor/txf003.shtml

73 de David G4DMP

In a recent message, K8JHR <[hidden email]> writes
>Short wave listeners use kites and baloons to hold up long wire
>antennas all the time. I did this long before becoming a ham.

--
+ - - - - - - - - - - - - - - - - +
| David M Pratt, Kippax, Leeds. |
| Website: http://www.g4dmp.co.uk |
+ - - - - - - - - - - - - - - - - +

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Gerry leary

Re: RF in the Trees

In reply to this post by Charlie T, K3ICH

Thanks very much for showing me HYpower Anntennas. They look very interesting, and I am going to call them with questions. Gerry

Sent from my iPhone this time

> On Jun 26, 2014, at 9:39 AM, Walter Underwood <[hidden email]> wrote:
>
> For pre-built antennas, HyPower is a good choice. He has lots of options, fan dipoles, loaded dipoles, even combinations. I have a fan dipole made from a full-size 40m element and an element that is full-size for 80 and loaded for 80. He also sells the loading coils if you would rather DIY.
>
> http://www.hypowerantenna.com/
>
> wunder
> K6WRU
>
>> On Jun 26, 2014, at 5:30 AM, "Charlie T, K3ICH" <[hidden email]> wrote:
>>
>> Don't rule out traps.
>>
>> Also, the RF Connection and probably others, sell a nice stranded copperweld wire that has a black polyethylene insulation. If I remember correctly, it is 13 ga and is ideal for antennas. For all practical purposes, it doesn't stretch, is fairly slippery and only a little "springier" than hard drawn copper.
>>
>> I use those double ferrule aluminum crimp on's that are designed for flexible wire cable to hold everything together. I was concerned about them holding through the poly insulation, but the following antenna has been up for about ten years now. It consists of a double (fan) dipole with a pair of 80 meter traps in the top leg for 160 & 80 M coverage and a pair of 40 meter traps in the lower leg for 60 & 40 M coverage. It is fed thru a 1:1 balun with RG-213 and is tuned for resonance. Basically, I operate SSB 99% of the time, so the antenna is tuned for that end of the bands. An MN-2700 tuner in the shack takes care of small excursions from resonance. It's only up about 50 feet, so performance is what you'd expect. It's not straight either and is sort of a lazy Z, being strung between two 55' telephone poles that are 105 feet apart. The ends droop down at about 45 degrees to tie-off points in trees. A compromise? Yes, but it works.
>>
>> 73, Charlie k3ICH
>>
>>
>>
>>
>> ----- Original Message ----- From: "Jim Brown" <[hidden email]>
>> To: <[hidden email]>
>> Sent: Thursday, June 26, 2014 1:55 AM
>> Subject: Re: [Elecraft] RF in the Trees
>>
>>
>>>> On 6/25/2014 5:43 PM, Dauer, Edward wrote:
>>>> So, I've been selecting two of the tallest
>>>> candidates a couple of hundred feet apart and stringing a stout nylon rope
>>>> between them. In the middle of the cord I attach the balun for the Vees,
>>>> thereby allowing the legs to be in the clear, moveable from side to side,
>>>> and tied to smaller (8') trees at their distal ends. In one variation on
>>>> the theme I had a 40 meter dipole as the center section of the supporting
>>>> rope, tied to the same balun as an 80 meter vee. In another I tried a
>>>> linear-loaded 80-meter Vee, about 45' on a leg; it loaded fine but didn't
>>>> perform as well as the full length version.
>>>
>>> If you can suspend a flat antenna between two tall trees, why would you want an inverted vee, which is a less effective radiator?
>>>
>>> Your two trees 200 ft apart could support a full size 80/40 fan and a 20/15/10 fan, in line with each other. A high 80/40 fan is a VERY good antenna, and is easy to build.
>>>
>>> My technique has evolved to starting with #8 bare copper from the big box store, stretch it VERY slowly between a tree and a trailer hitch until it breaks. Do this carefully where there's no one around to get hurt. Now you have #10 hard drawn copper, which is pretty strong, and pre-stretched. Use that for the longest dipole in each fan. Use #12 or #14 THHN (house wire) for the other elements. I make spacers by cutting 1/2-in PVC conduit into lengths of about 16 in for 3-wire fans, and about 12 inches for 2-wire fans. 5-6 ft between spacers is a good rule of thumb. Hold the spacers in place by soldering short lengths of copper around the spacer to the bare copper of the long element.
>>>
>>> The higher your antenna is, the more robust your center insulator should be. A high 80/40 dipole (80 ft or more) will be closer to 75 ohms than 50 ohms. A 20/15/10 fan will be close to 50 ohms. Use RG8 or RG11 depending on the Z at resonance. Don't waste a dB or two with small coax. My 110 ft 80/40 fans are fed with Belden 8213.
>>>
>>> For weights, I fill 6 gallon water jugs with dry sand, and tie one to one end of each span. The other end can be fixed. I have pulleys high my trees. If you don't have a pulley and weight, your antenna WILL end up on the ground, and it won't take a big storm for that to happen.
>>>
>>> My HF antennas are all at the 110-120 ft level in a dense redwood forest that towers 50-75 ft above them. They work. My "seat of the pants" observation is that attenuation increases with frequency, and is greatest with vertical polarization. 432 MHz is a waste of time, 2M sort of works, and 6M works pretty well.
>>>
>>> For an analysis of the value of height, study this. It supports the statement earlier in this thread that a high dipole beats a low tri-bander.
>>>
>>> http://k9yc.com/VertOrHorizontal-Slides.pdf
>>>
>>> When Fred observes that the ends of antennas are "hotter," he means that this is voltage maxima and a current minima, so good insulation is needed to whatever the antenna is attached. I once melted heavy dacron rope that was tied directly to the end of said dipole (well, twice, actually). The extra ingredient was that it was wet. Duh.
>>>
>>> 73, Jim K9YC
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>>
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>
> --
> Walter Underwood
> [hidden email]
>
>
>
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Gerry leary

Re: RF in the Trees

In reply to this post by Edward A. Dauer

I wonder if the tree hurts during key down?

Sent from my iPhone this time

> On Jun 26, 2014, at 6:05 PM, "Dauer, Edward" <[hidden email]> wrote:
>
> Now THAT is what being a ham is about!
>
> OK, my part in this thread is over. Loading a tree can't be topped.
>
> Ted, KN1CBR
>
>
>>
>> We have one member of the ARRL Experimental Group on 600m that has
>> actually loaded a pine tree to act as a vertical antenna, He wrapped
>> a huge amount of wire around the base of the tree as a coupling coil.
>>
>> 73, Ed - KL7UW
>> http://www.kl7uw.com
>> "Kits made by KL7UW"
>> Dubus Mag business:
>> [hidden email]
>
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Dave-5

Re: RF in the Trees

I seem to remember seeing some report about loading trees done for the
military. I'll see if I can find it again.

Cheers - Dave (G0DJA)

----- Original Message -----
From: "Gerry leary" <[hidden email]>
To: "Dauer, Edward" <[hidden email]>
Cc: <[hidden email]>
Sent: Friday, June 27, 2014 10:31 AM
Subject: Re: [Elecraft] RF in the Trees

>I wonder if the tree hurts during key down?
>
> Sent from my iPhone this time
>
>> On Jun 26, 2014, at 6:05 PM, "Dauer, Edward" <[hidden email]> wrote:
>>
>> Now THAT is what being a ham is about!
>>
>> OK, my part in this thread is over. Loading a tree can't be topped.
>>
>> Ted, KN1CBR

Dave-5

Re: RF in the Trees

In reply to this post by Gerry leary

Heres the link to the experiments on 600M to load up trees as antennas and
the page has links to the work done by the military, and other links to
similar experiments.

http://w5jgv.com/tree_antenna/index.htm

Cheers - Dave (G0DJA)
----- Original Message -----
From: "Gerry leary" <[hidden email]>
To: "Dauer, Edward" <[hidden email]>
Cc: <[hidden email]>
Sent: Friday, June 27, 2014 10:31 AM
Subject: Re: [Elecraft] RF in the Trees

Gerry leary

Re: RF in the Trees

In reply to this post by Phil Hystad-3

I do it a little diffeerently. I tie a rock on the end of the Antenna that needs to be in the tree. Then I lay the wire untangled on the ground. Then I tie the other end to myself so I don't throw the wire where I can't find it. I can't get the heighth I would like, But I don't have to try to find the thrown end of the wire later.

Sent from my iPhone this time

> On Jun 26, 2014, at 5:48 PM, Phil Hystad <[hidden email]> wrote:
>
>
>> This may be off topic, but in light of it being Field Day Weekend in the US....
>>
>> The problem with the bow or slingshot is when (if) the projectile comes down.
>>
>> The arrow has an issue because it gets hung up or in branches and doesn't have enough mass to pass through some branches or allow gravity to pull it down. Should it comes later, the risks of impalement can ruin the day.
>>
>> The slingshot can improve over the arrow by increasing mass but can be equally dangerous. Accurate shots are challenging.
>
>
> In my case, the arrows I shoot up into and over trees always land on my property and I am the only one on my property at the time. So, not much chance of hurting anyone. I don't think my bow has enough power to launch an arrow off of my property. Not that my property is that great, more that my bow is not that powerful (30 lb maximum pull). It is just good enough to launch up into and over my trees.
>
> I have never had an arrow get hung up in branches in all of my experience with the bow. I think maybe I am just lucky though.
>
> 73, phil, K7PEH
>
>
>
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Charlie T, K3ICH

Re: RF in the Trees

In reply to this post by k6dgw

The professional "Arborists" use a cloth or leather bag filled with lead
shot and something called "tangle-free" line or similar to throw up in a
tree so that they can pull up a supporting rope for tree trimming etc. From
what I've seen, the bag is about the size of a tear drop shaped golf ball.
The idea of the shot instead of a solid weight is to make the bag less
damaging if it hits your house (or window) on the way down.

I have a neighbor who's son is an arborist, so I've watched him on several
occasions. It DOES take a bit of practice, but the line never seems to get
tangled.

I tried this with a few lead fishing weights on some thin nylon line and it
was a disaster. The secret is to use a thick enough line so that it won't
spin around itself and (mysteriously) tie itself in a knot way up in the
tree.

73, Charlie k3ICH

----- Original Message -----
From: "Fred Jensen" <[hidden email]>
To: <[hidden email]>
Sent: Thursday, June 26, 2014 8:05 PM
Subject: Re: [Elecraft] RF in the Trees

> On 6/26/2014 4:12 PM, Rick Bates, WA6NHC wrote:
>> This may be off topic, but in light of it being Field Day Weekend in
>> the US....
>
> It's radio, Eric will probably see it as relevant, unless we overdo it,
> which we do at times. :-)
>
>> The arrow has an issue because it gets hung up or in branches and
>> doesn't have enough mass to pass through some branches or allow
>> gravity to pull it down. Should it comes later, the risks of
>> impalement can ruin the day.
>
>

JHRichards

Re: RF in the Trees

In reply to this post by Elecraft mailing list

Hmmm.... vertical dipole... vs... end fed half wave vertical "dipole"
- not sure these are equivalent in performance. I know W8JI thinks
the end fed half wave needs some sort of ground system-counterpoise to
keep the feed line from becoming part of the antenna, so I am wondering
- asking not telling - whether these two are really equivalent? (He
said reaching for his ARRL Antenna Book...)

I believe Jim K9YC modeled a true vertical dipole (including the n6BT
end-loaded vertical dipole) - but I would expect it to work out
differently from an end fed half wave vertical. The GAP antennas and
Cuschraft R8 and R9 type are supposed to be loaded vertical dipoles, and
are not, I don't think, end feds... but that is the question... are
these really all equivalent? Certainly feeding at the bottom of an end
fed would be easier from a construction and deployment point of view, so
I can see the obvious appeal therefor, but then does it work as well as,
say, the N6TB vertical dipole fed in the middle?

Again, this is a question not a critique.

-------------------- K8JHR -------------------

On 6/26/2014 10:59 AM, Doug Person via Elecraft wrote:
> The K9YC modelling with EZNEC
> <http://k9yc.com/VertOrHorizontal-Slides.pdf> is quite interesting.
> Certainly has me thinking about vertical dipoles. The half-wave end-fed
> looks like the perfect candidate for a simple vertical dipole.
>
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Don Wilhelm-4

Re: RF in the Trees

Half-wave dipoles are equal no matter how they are fed. With an end-fed
dipole, the short counterpoise advocated by W8JI is merely a method of
accomplishing feed to that high impedance point. There is no difference
in the radiation of any half wave dipole (except as influenced by
ground, surrounding objects, etc.) - if you can couple RF into it, it
will radiate.

73,
Don W3FPR

On 6/27/2014 8:51 AM, K8JHR wrote:
> Hmmm.... vertical dipole... vs... end fed half wave vertical "dipole"
> - not sure these are equivalent in performance. I know W8JI thinks
> the end fed half wave needs some sort of ground system-counterpoise to
> keep the feed line from becoming part of the antenna, so I am
> wondering - asking not telling - whether these two are really
> equivalent? (He said reaching for his ARRL Antenna Book...)
>

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Wes (N7WS)

Re: RF in the Trees

In reply to this post by JHRichards

Why would it matter where it's fed? A half wave dipole has the same current distribution regardless of the feed point.

Wes. N7WS

On Jun 27, 2014, at 5:51 AM, K8JHR <[hidden email]> wrote:

> Hmmm.... vertical dipole... vs... end fed half wave vertical "dipole" - not sure these are equivalent in performance. I know W8JI thinks the end fed half wave needs some sort of ground system-counterpoise to keep the feed line from becoming part of the antenna, so I am wondering - asking not telling - whether these two are really equivalent? (He said reaching for his ARRL Antenna Book...)
>
> I believe Jim K9YC modeled a true vertical dipole (including the n6BT end-loaded vertical dipole) - but I would expect it to work out differently from an end fed half wave vertical. The GAP antennas and Cuschraft R8 and R9 type are supposed to be loaded vertical dipoles, and are not, I don't think, end feds... but that is the question... are these really all equivalent? Certainly feeding at the bottom of an end fed would be easier from a construction and deployment point of view, so I can see the obvious appeal therefor, but then does it work as well as, say, the N6TB vertical dipole fed in the middle?
>
>
>
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Terry Schieler-2

Re: RF in the Trees

In reply to this post by W2RMS

Sal,

The main problem with kites is safety. One doesn't always know when the kite will change directions, dive or loop, with the potential of the kite wire crossing over a very deadly, high voltage utility line. Poof! You are vapor.

73,

Terry, W0FM

-----Original Message-----
From: Slava Baytalskiy [mailto:[hidden email]]
Sent: Thursday, June 26, 2014 6:25 PM
To: Rick Bates, WA6NHC
Cc: Elecraft Reflector
Subject: Re: [Elecraft] RF in the Trees

I wonder if anyone's ever used a kite in a field to keep a wire "up".
I see kites a lot in the summer, along belt parkway here in Brooklyn and they seem to stay in one place for long periods of time.
I'm sure one can use 12 or 14 AWG wire and let a kite carry it pretty high. Of course you need wind for that but being near water (salt water, no less) there's usually wind present.
Hmm.....

Another idea that may be used to place a wire with a lot of precision is one of those RC quadricopters that are becoming wildly popular.
A little servo "claw" to release the wire or just to place it's apex where you want it...
__________________
Slava (Sal) B, W2RMS
[hidden email]

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Eric Swartz - WA6HHQ

Re: RF in the Trees

Administrator

In reply to this post by Charlie T, K3ICH

Good topic, but we're hotting the posting limit for a single topic. Let's wind this one down asap.

Eric
Your friendly jet lagged moderator (at the Freidrichshafen, Germany, Ham Radio show.)
elecraft.com
_..._

> On Jun 27, 2014, at 5:23 PM, Walter Underwood <[hidden email]> wrote:
>
> There is special cord designed to not get stuck in trees. It is called "arborist throw line". It really works, I use it for bear bagging on backpacking trips. You can get the line, a throw weight, and a storage bag as a throw kit.
>
> http://www.wesspur.com/throw-line/zing-it-throw-line.html
>
> wunder
> K6WRU
>
>> On Jun 27, 2014, at 5:27 AM, "Charlie T, K3ICH" <[hidden email]> wrote:
>>
>> The professional "Arborists" use a cloth or leather bag filled with lead shot and something called "tangle-free" line or similar to throw up in a tree so that they can pull up a supporting rope for tree trimming etc. From what I've seen, the bag is about the size of a tear drop shaped golf ball. The idea of the shot instead of a solid weight is to make the bag less damaging if it hits your house (or window) on the way down.
>>
>> I have a neighbor who's son is an arborist, so I've watched him on several occasions. It DOES take a bit of practice, but the line never seems to get tangled.
>>
>> I tried this with a few lead fishing weights on some thin nylon line and it was a disaster. The secret is to use a thick enough line so that it won't spin around itself and (mysteriously) tie itself in a knot way up in the tree.
>>
>> 73, Charlie k3ICH
>>
>>
>> ----- Original Message ----- From: "Fred Jensen" <[hidden email]>
>> To: <[hidden email]>
>> Sent: Thursday, June 26, 2014 8:05 PM
>> Subject: Re: [Elecraft] RF in the Trees
>>
>>
>>>> On 6/26/2014 4:12 PM, Rick Bates, WA6NHC wrote:
>>>> This may be off topic, but in light of it being Field Day Weekend in
>>>> the US....
>>>
>>> It's radio, Eric will probably see it as relevant, unless we overdo it, which we do at times. :-)
>>>
>>>> The arrow has an issue because it gets hung up or in branches and
>>>> doesn't have enough mass to pass through some branches or allow
>>>> gravity to pull it down. Should it comes later, the risks of
>>>> impalement can ruin the day.
>> ______________________________________________________________
>> 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
>> Message delivered to [hidden email]
>
> --
> Walter Underwood
> [hidden email]
>
>
>
> ______________________________________________________________
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Eric Swartz - WA6HHQ

Re: RF in the Trees

Administrator

typo - "hitting" the limit..

Eric
elecraft.com
_..._

> On Jun 27, 2014, at 5:33 PM, Eric Swartz WA6HHQ - Elecraft <[hidden email]> wrote:
>
> Good topic, but we're hotting the posting limit for a single topic. Let's wind this one down asap.
>
> Eric
> Your friendly jet lagged moderator (at the Freidrichshafen, Germany, Ham Radio show.)
> elecraft.com
> _..._
>
>> On Jun 27, 2014, at 5:23 PM, Walter Underwood <[hidden email]> wrote:
>>
>> There is special cord designed to not get stuck in trees. It is called "arborist throw line". It really works, I use it for bear bagging on backpacking trips. You can get the line, a throw weight, and a storage bag as a throw kit.
>>
>> http://www.wesspur.com/throw-line/zing-it-throw-line.html
>>
>> wunder
>> K6WRU
>>
>>> On Jun 27, 2014, at 5:27 AM, "Charlie T, K3ICH" <[hidden email]> wrote:
>>>
>>> The professional "Arborists" use a cloth or leather bag filled with lead shot and something called "tangle-free" line or similar to throw up in a tree so that they can pull up a supporting rope for tree trimming etc. From what I've seen, the bag is about the size of a tear drop shaped golf ball. The idea of the shot instead of a solid weight is to make the bag less damaging if it hits your house (or window) on the way down.
>>>
>>> I have a neighbor who's son is an arborist, so I've watched him on several occasions. It DOES take a bit of practice, but the line never seems to get tangled.
>>>
>>> I tried this with a few lead fishing weights on some thin nylon line and it was a disaster. The secret is to use a thick enough line so that it won't spin around itself and (mysteriously) tie itself in a knot way up in the tree.
>>>
>>> 73, Charlie k3ICH
>>>
>>>
>>> ----- Original Message ----- From: "Fred Jensen" <[hidden email]>
>>> To: <[hidden email]>
>>> Sent: Thursday, June 26, 2014 8:05 PM
>>> Subject: Re: [Elecraft] RF in the Trees
>>>
>>>
>>>>> On 6/26/2014 4:12 PM, Rick Bates, WA6NHC wrote:
>>>>> This may be off topic, but in light of it being Field Day Weekend in
>>>>> the US....
>>>>
>>>> It's radio, Eric will probably see it as relevant, unless we overdo it, which we do at times. :-)
>>>>
>>>>> The arrow has an issue because it gets hung up or in branches and
>>>>> doesn't have enough mass to pass through some branches or allow
>>>>> gravity to pull it down. Should it comes later, the risks of
>>>>> impalement can ruin the day.
>>> ______________________________________________________________
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>>> This list hosted by: http://www.qsl.net
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>>
>> --
>> Walter Underwood
>> [hidden email]
>>
>>
>>
>> ______________________________________________________________
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Jim Brown-10

Re: RF in the Trees

In reply to this post by Gerry leary

On 6/27/2014 3:16 AM, Gerry leary wrote:
> Thanks very much for showing me HYpower Anntennas. They look very interesting, and I am going to call them with questions.

When I was getting back on the air in 2003 in Chicago, I needed a
shortened antenna for 80 and 40. I bought his shortened 80/40 dipole.
It's a full size half wave on 40, with loading coils and more wire on
each side for 80M. It worked fine. When I moved to CA, I bought only the
loading coils for the comparable 160/80 version. I've since used those
coils to build 160/80/40M antennas at two very different sites. I built
the 160/80 per Barry's design, and added a fan element for 40M.

73, Jim K9YC

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Jim Brown-10

Re: RF in the Trees

In reply to this post by Don Wilhelm-4

On 6/27/2014 6:30 AM, Don Wilhelm wrote:
> if you can couple RF into it, it will radiate.

Yes. There are many ways to feed a vertical dipole. I developed a method
that uses the outside of the coax as half of the dipole, and uses a
ferrite choke to form the "end insulator." The choke is positioned a
quarter wave down the coax from the center insulator.

I published this method about six years ago, after seeing a similar
suggestion ftrom Rudy Severns, N6LF. Rudy used a coil of coax, forming
only an inductor. My contribution was the ferrite choke, which makes the
antenna insensitive to feedline length.

The end of a dipole is a high voltage point, so there's considerable
voltage across the choke if you're running much power. I tested this
concept around 2008 on 40M with 1.5kW, and found that I needed two
chokes in series, each of which was 5,000 ohms. A single choke would
work quite well at 100W or less.

Note that electrically, this dipole is center fed -- there's a quarter
wave wire connected to the coax that goes to an end insulator that can
be suspended in a tree, then the coax hangs down, and the choke is a
quarter wave down from the wire. The impedance of a vertical dipole like
this is about 70 ohms at resonance, which makes it a good match for 75
ohm coax. Remember that SWR in a system is determined by the match
between the antenna and the line, so losses will be lower with 75 ohm
coax. Also remember that the velocity factor of coax is for signals
INSIDE the coax. For signals OUTSIDE the coax, the velocity factor is
like any other insulated wire of comparable size, roughly 0.98.

The choke should be wound using the guidelines in my Cookbook.

73, Jim K9YC
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Elecraft mailing list

Re: RF in the Trees

In reply to this post by Charlie T, K3ICH

I don't really understand why traps have gotten such a bad rap. Consider
that most all triband beams use traps as well as many verticals. I have
been using Spi-Ro traps for 20 years and never had a problem and I
certainly don't see any indication that I am suffering some kind of loss
as a result. I have made many comparisons between the trapped dipoles
and single band non-trapped dipoles and the only difference I see is a
reduction in usable bandwidth. The Spi-Ro traps are rated for 600 watts
making them perfect for the KPA500 powered station. Indeed - do not
rule out traps.

I also use a similar wire that to what Charlie mentions. Last order was
for 600 feet. It's great stuff.

Now I'm thinking of what would be the best "all-band" antenna for the K2
which is my secondary operating position in the living room where I can
give demos to visitors. I'm thinking of giving the 88 foot doublet fed
with 300 ohm twinlead a try.

Doug -- K0DXV

On 6/26/14, 6:30 AM, Charlie T, K3ICH wrote:

> Don't rule out traps.
>
> Also, the RF Connection and probably others, sell a nice stranded
> copperweld wire that has a black polyethylene insulation. If I
> remember correctly, it is 13 ga and is ideal for antennas. For all
> practical purposes, it doesn't stretch, is fairly slippery and only a
> little "springier" than hard drawn copper.
>
> I use those double ferrule aluminum crimp on's that are designed for
> flexible wire cable to hold everything together. I was concerned
> about them holding through the poly insulation, but the following
> antenna has been up for about ten years now. It consists of a double
> (fan) dipole with a pair of 80 meter traps in the top leg for 160 & 80
> M coverage and a pair of 40 meter traps in the lower leg for 60 & 40 M
> coverage. It is fed thru a 1:1 balun with RG-213 and is tuned for
> resonance. Basically, I operate SSB 99% of the time, so the antenna
> is tuned for that end of the bands. An MN-2700 tuner in the shack
> takes care of small excursions from resonance. It's only up about 50
> feet, so performance is what you'd expect. It's not straight either
> and is sort of a lazy Z, being strung between two 55' telephone poles
> that are 105 feet apart. The ends droop down at about 45 degrees to
> tie-off points in trees. A compromise? Yes, but it works.
>
> 73, Charlie k3ICH
>
>
>
>
> ----- Original Message ----- From: "Jim Brown"
> <[hidden email]>
> To: <[hidden email]>
> Sent: Thursday, June 26, 2014 1:55 AM
> Subject: Re: [Elecraft] RF in the Trees
>
>
>> On 6/25/2014 5:43 PM, Dauer, Edward wrote:
>>> So, I've been selecting two of the tallest
>>> candidates a couple of hundred feet apart and stringing a stout
>>> nylon rope
>>> between them. In the middle of the cord I attach the balun for the
>>> Vees,
>>> thereby allowing the legs to be in the clear, moveable from side to
>>> side,
>>> and tied to smaller (8') trees at their distal ends. In one
>>> variation on
>>> the theme I had a 40 meter dipole as the center section of the
>>> supporting
>>> rope, tied to the same balun as an 80 meter vee. In another I tried a
>>> linear-loaded 80-meter Vee, about 45' on a leg; it loaded fine but
>>> didn't
>>> perform as well as the full length version.
>>
>> If you can suspend a flat antenna between two tall trees, why would
>> you want an inverted vee, which is a less effective radiator?
>>
>> Your two trees 200 ft apart could support a full size 80/40 fan and a
>> 20/15/10 fan, in line with each other. A high 80/40 fan is a VERY
>> good antenna, and is easy to build.
>>
>> My technique has evolved to starting with #8 bare copper from the big
>> box store, stretch it VERY slowly between a tree and a trailer hitch
>> until it breaks. Do this carefully where there's no one around to get
>> hurt. Now you have #10 hard drawn copper, which is pretty strong, and
>> pre-stretched. Use that for the longest dipole in each fan. Use #12
>> or #14 THHN (house wire) for the other elements. I make spacers by
>> cutting 1/2-in PVC conduit into lengths of about 16 in for 3-wire
>> fans, and about 12 inches for 2-wire fans. 5-6 ft between spacers is
>> a good rule of thumb. Hold the spacers in place by soldering short
>> lengths of copper around the spacer to the bare copper of the long
>> element.
>>
>> The higher your antenna is, the more robust your center insulator
>> should be. A high 80/40 dipole (80 ft or more) will be closer to 75
>> ohms than 50 ohms. A 20/15/10 fan will be close to 50 ohms. Use RG8
>> or RG11 depending on the Z at resonance. Don't waste a dB or two with
>> small coax. My 110 ft 80/40 fans are fed with Belden 8213.
>>
>> For weights, I fill 6 gallon water jugs with dry sand, and tie one to
>> one end of each span. The other end can be fixed. I have pulleys high
>> my trees. If you don't have a pulley and weight, your antenna WILL
>> end up on the ground, and it won't take a big storm for that to happen.
>>
>> My HF antennas are all at the 110-120 ft level in a dense redwood
>> forest that towers 50-75 ft above them. They work. My "seat of the
>> pants" observation is that attenuation increases with frequency, and
>> is greatest with vertical polarization. 432 MHz is a waste of time,
>> 2M sort of works, and 6M works pretty well.
>>
>> For an analysis of the value of height, study this. It supports the
>> statement earlier in this thread that a high dipole beats a low
>> tri-bander.
>>
>> http://k9yc.com/VertOrHorizontal-Slides.pdf
>>
>> When Fred observes that the ends of antennas are "hotter," he means
>> that this is voltage maxima and a current minima, so good insulation
>> is needed to whatever the antenna is attached. I once melted heavy
>> dacron rope that was tied directly to the end of said dipole (well,
>> twice, actually). The extra ingredient was that it was wet. Duh.
>>
>> 73, Jim K9YC
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Edward R Cole

Re: RF in the Trees

In reply to this post by Edward A. Dauer

http://w5jgv.com/tree_antenna/index.htm

Ralph is the ham I was referring to. Now you have as much as I am
aware of. I forgot that Ralph wound a torus around the tree
base. He used an old oak which brings song to mind "tie a yellow
ribbon around that ole oak tree...".

The question about whether the tree feels the electrical field gets
into the whole earth realm of whether flora feel as much a fauna? I
would say, "yes". The tree probably feels "excited with an
electrifying experience!" :-D

Long term effects on the health of a tree is probably
unknown. Mankind generally does not have much empathy for the plant
world. We grow it and we harvest it for food or shelter.

73, Ed - KL7UW
http://www.kl7uw.com
"Kits made by KL7UW"
Dubus Mag business:
[hidden email]

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