Kite-lifted long wire antenna operation (Part 1)

Equipment Antennas
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our local Karen’s go in to apoplexies if they see anything they don’t like or understand - mind they will believe anything you tell them , i once told one in my best GRU ( despicable me ) "actually i am a spy , but you must not tell anyone " her response was that she would "report " me and wandered off muttering to herself - had another who complained when i was test flying a large Codey kite in the local park - that it might drop on her head and injure her - my response was " so might a jumbo jet dear - and i know which will hurt more "

we have a LOT of very odd folk round here … and amateur radio /kites seem to attract them

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I use carbon as like others its what i have handy and that’s what the first article i read on kite lofted wires said use - so not saying any other type won’t work - so long as they are " non inductive " apparently - they are ok

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Brett,
Why do they have to be non inductive? You are not making a dummy load or a HV RF divider. It is a DC leakage device.

It just has to be a high impedance compared to the antenna. Something with inductance might be better.

73
Ron
VK,3AFW

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44

A 1 Mohm wirewound resistor is likely to use very thin wire, which might make it more prone to failure than a chunk of carbon composite. Especially in field conditions. Over the years, I have found more than one metal oxide film resistor to be open circuit where the end cap has come loose. So, I’m not sure why inductance would be a problem, but given the choice, I’d probably go for carbon…

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Adrian,

Sorry to dissent.

Firstly all good brand companies make good high value resistors.

Have you seen a 1 M ohm wire wound resistor? Not tiny but robust enough if that’s what you need. The ones I used to use were the size of a pint and were expected to be in use for 50 years. The small ones, the size of half a match box are expected to last half that time. I have some that are over 50 years old.

If the end caps come off the film resistor it has been abused. Undue mechanical stress when mounting or severe electrical overload can cause this.

Carbon rod ones have more clay than carbon in them. While they can last for years they are not on top of the list for MIL spec applications for reliability and stability.

Their end connections are not more robust than film type resistors.

I go back to what I said earlier. If you have a 1 W rated 1 M resistor in your parts bin, use it.

73
Ron
VK3AFW

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46

I did this a few months ago on Waun Fach (GW/SW-002) & it worked extremely well. Video on my YouTube channel if anyone is interested.

The kite I used in the video has rigid struts in which means it can’t be folded down. This made it awkward to carry, especially in the wind. I’ve since purchased a kite without the struts which can be folded down & stuffed into a backpack. The weight of the entire setup is probably about the same, if not slightly lighter than my normal setup.

As for grounding to bleed off static, there’s more than one way to skin a cat. Others have already mentioned the option of using a 1 meg resistor.

I used an EFHW on 40m. The 49:1 which I used to feed the antenna has an earth stud for a counterpoise/earth rod. This is a direct path from the antenna wire at DC so I connected this to the ground rod.

I used a dog stake (the type that you screw into the ground & attach the dog lead to) in order to secure the kite to the ground. This also served as the ground rod.

Clearly you need lots of space on a quiet summit which doesn’t see too many other people to do this. You don’t want to strangle any unsuspecting members of the public because I don’t think that would be a particularly good advert for SOTA!

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47

Hi Ron, dissent welcome, especially when it is polite and well reasoned!

Yes, I have two candidates in my junk box, a 1M ohm 2W by Welwyn, and a pair of 500 K ohm 1W by Muirhead. They are 0.5 % and probably pulled from test equipment. They do look rather more rugged than I remembered - especially the fully enclosed Muirhead types. I guess they will have exceeded their design life, but they still test OK.

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The most recent that I recall was the driver stage bias resistor in an FT290. Vertically mounted on the board, so no stretching between holes. No signs of mechanical damage, and no other component faults, so no electrical stress. Just O/C. One end cap came off easily once removed from the board. To be fair, though, it had no doubt exceeded its design life.
(Me finding a fault like this a very few times in 60 odd years is not a statistically valid measure of reliability, of course, I understand that!)

Hi James, I like that idea, especially because the grounding is part of the aerial system, so you would have some indication if it failed. If a bleed resistor failed, you might only find out when it was too late.

I don’t pretend to be an expert in any of this, just enjoying other people’s reports and sharing my thoughts along the way - it is good to have them challenged, that’s how we learn :sunny:

73
Adrian

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Completely agree Adrian. The best part of amateur radio is that (once you get the basic knowledge from passing the exams) you are free to learn whatever you want. You set your own syllabus depending on what interests you & there are always people willing to help.

Like you, I don’t pretend to be an expert but I’m not so sure that it would be noticeable if the ground was disconnected with an EFHW antenna?

An EFHW can run without the counterpoise. I often do this when running an inverted-L or an inverted-V on SOTA summits (I’m sure that many portable operators do this).

With no counterpoise, the shield of the coax will act as a counterpoise.

The point is that if the coax shield acts as a counterpoise then the antenna will still work & you probably won’t notice any drop in performance if the ground becomes disconnected…unless you had a very short piece of coax between the radio & the 49:1 which wasn’t long enough to be an effective counterpoise.

Hence why I’m not sure that I agree with your assessment that “you would have some indication if it failed”

Anyone smarter than I am care to confirm or correct my logic here?

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49

RON - this explanation from SOTAbeams is pretty much what i first read and others have agreed with in various articles on the net - as i said seems to work for me - but theres always another way of course

quote : Kites - static discharge: having a static leakage system on your kite antenna is an essential requirement. This needs to present a high impedance to RF and a relatively low impedance to the static charge. The RF impedance of the leakage system needs to be at least ten times the antenna impedance at the lower end. If you work on an end impedance of 10k Ohms (for an end fed wire) you can see that the impedance needs to be high. RF chokes are possible as are parallel tuned circuits (in some cases). However, best performance across all bands is likely to be achieved with a non-inductive resistor of a value of at least 100k Ohms. I would go for 470k or 1 Meg. Use one rated at 2 Watts or so. Across it I would make a spark gap - but if you are seeing sparks you are in trouble! : end quote ( with thanks to sotabeams )

what we ideally need is some way of measuring static build-up on the wire ?? -

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Touch it on your tongue & see if it tingles. That’s what my electronics teacher at school used to do with 9v batteries!

Disclaimer:- I think most people should be able to pick out the sarcasm in that statement but PLEASE DON’T DO THAT!

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Gentlemen

No you don’t want to be measuring static build up. You want to make sure none occurs. This discussion is veering intro danger. If you don’t know how it would be done do not try. Leave that to the physicists.

I challenge anyone to produce a non inductive 1 Mohm resistor. Not that that matters as It will be capacitive at RF.

The shunt capacitance may be a few pF, say 5 kohms capacitive reactance at 7 MHz.

The ground peg resistance should clearly be smaller than the bleed resistor, so something of 1 k ohm or less would work very well. It is not critical.

Last words. An elevated antenna represents a hazard if there are thunderstorms in the vicinity. No bleed resistor can bypass a lightning strike.

Enjoy your experiments but do take care.

73
Ron
VK3AFW

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:+1:

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where i am now - we get maybe 2 a year ?? - it’s more the odd rumble of thunder with a shower - but i appreciate that others see many more - BUT when we do get one , they tend to be good un’s - fortunately usually at night - so we are not out flying then anyway ( too much aggro to comply with the CAA requirements for lights on kites and strings .lol ) - but yes your caution is well placed as i had a work colleague killed during a storm many years ago - and had a couple of " near misses " myself - so if its about - I’m not !! - nor on the radio period !!

its funny stuff - i used to live on Dartmoor - we had a strike across the road from my place - blew a granite chimney to bits - and several plugs and the telephone line off the wall in my place - my friend , who was on holiday at the time - left his gear unplugged and he thought safe - but on his return called me to see a radio on his bench that a spark from the feeder , which was 2 foot away , had roasted !! - literally !! - nothing else damaged bar the desk top that had a scorch mark on it … lucky it did not catch the house on fire …( i was a serving firefighter back then btw ) … that would have been embarrassing to have come home to

so yes folks treat the stuff with GREAT respect !! …

73

Brett G6URM

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Thanks James,

Your video has shown that it is possible and practical - on some SOTA summits at least - for a solo activator to use a kite antenna - but I probably have to give up the idea of having the ‘vertical’ LW hanging from (just) below the kite independently of the kite string.

I’ve tried it about four times now using the same SOTAbeams sled and drone kite that you have in the video [which is very stable over a wide range of wind speeds] and the problem is the bottom of my vertical LW wants to keep moving around (with the kite) whereas I need it to remain still for connection to the rig.

Without a second person to steer the kite or otherwise constrain the vertical LW, the solution is - as you did - to make the antenna wire be also the kite flying cord. Although inevitably this leads to the antenna being less vertical, that’s no different to the sloper or inverted V configurations I use right now with my telescoping fibreglass pole. Your reports (given and received) testify to the effectiveness of your 20m half-wave long wire used that way.

Re your 49:1 UnUn, I intend to repurpose a 9:1 UnUn from an end-fed LW I used to have at home. I don’t know which ratio would be better when wishing to operate on more than one band. Perhaps others might comment. Either way my KX2 internal ATU should help

It would be interesting to know what the load strength is of Kevlar woven electrical wire to determine whether the backup cord you used is redundant or not.

As a [mainly] CW operator, I find CW QSOs take my full attention and wonder if I could spare any to keep an eye on the kite. Might be better to stick to SSB until confident.

73 Andy

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Hi Andy,

I’ve seen a few diagrams on the internet where people suggest doing it this way. I ultimately came to the same conclusion that you appear to be coming to. I decided that it was just too much hassle & there was too much to go wrong.

That was something that I wondered about. I don’t know what the radiation pattern would look like but given that it is effectively a sloper, I suspect that would make it at least a little bit directional. Obviously this will be affected by the wind strength & will therefore change throughout the activation.

Unfortunately the angle of the sloping wire & the direction it points are two factors which are pretty much outside of our control unless you have a 4g signal & direct phone number for The Anemoi!!!

In practical terms, I don’t think it makes enough difference for me to be concerned about. As you said, the signal reports were good so I won’t worry about something I can’t control.

Either should work. I prefer the 49:1 because EFHW antennas don’t tend to be to fussy about having a counterpoise, whereas it’s a bit more critical on a 9:1.

AS an EFHW, this setup will obviously work on 20m & 10m. Make the wire longer (1/2 wave on 40m) & you should get 40m, 20m, 15m & 10m…might also get 17m with the tuner?

According to the manufacturer of the wire, it breaks at 60kg. I can’t remember what the manufacturers of the kite recommend, so don’t like the idea of not having the kite string as a backup.

I’ve since purchased some DX50 wire from DX Commander which (according to his website) has a breaking strength of 130kg. I’ve also purchased a bigger kite which has more pull but actually packs up smaller because it doesn’t have the rigid supports inside it. The manufacturers of that kite reckon around 100-110kg of pull, so I reckon the DX50 wire should be a good match.

I’ve test flown this locally but not on a SOTA summit (where the wind is likely to be much stronger).

I probably could get away without the kite string as a backup but if you saw my first video on this you will know that I’ve already lost 1 kite. I’m not sure that I want to rely on the wire to take the load without a failsafe!

Good luck, however you decide to do it.

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The bleed resistor (or the antenna side of an UnUn grounded on the ‘cold’ terminal) is there to provide a continuous DC path to ground for charges which would otherwise build up on the antenna wire. This is known as triboelectric charging (due to the loss of electrons between the wire and surrounding air molecules) a problem well known to aircraft designers.

It avoids the potential difference getting large enough to cause a discharge between the antenna and the rig. It shouldn’t be confused with the static build-up in clouds between rising warm air and ice crystals in the clouds, which – if large enough – can cause a lightning strike.

Lightning strikes can explode big trees [the sap boils and the resultant gas creates huge pressure inside the tree]. So, our puny anti-static bleed device is no lightning conductor. As others have said, with even a sniff of thundery conditions we should avoid activating with any kind of antenna (not alone a kite one – What are you, Benjamin Franklin?) and get off the hills ASAP.

73 Andy

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Andy.

A good explanation. Should be mandatory reading.

When I was young and foolish I discovered that the static electric shock from a balloon elevated Gibson Girl antenna was worse then any electric fence or car ignition. Before I was old enough to get a driver’s licence I had experienced all three.

That’s when the “earth wire on first” approach was found to be a good move.

I would expect any kite flyer would connect the earth and static bleed before raising the kite.

73
Ron
VK3AFW
Older and only a little wiser.

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I think it has to be recognised that static charges on a wire can build up even in the apparent absence of lightning, so don’t be misled by apparently benign weather conditions. In the right weather, there is electrical charge in the air whether it makes blue lights or not.

I once disconnected a 2m quarter wave antenna, from a fm transceiver in my shack. After unscrewing the outer ring of the (ugh) PL259 plug, I then pulled out the remaining centre conductor from the SO239 socket. As I drew it away from the socket on the back of the radio, a spark was seen and I felt a mild jolt, as I was holding the chassis of the radio and the outer of the antenna cable. So without needing any kite, there was enough static on the say, 20m of coax cable, part of which was under my house, to create a spark that of course, destroyed the front end amplifier of the radio. I say 20m rather than the quarter wavelength at the top, because once the outer of the cable is disconnected from the earth side of the radio, the grounding effect of the outer ring is no longer present. It would have been wiser to connect a jumper between the outer conductor and the chassis of the radio. Lesson learned.

Andrew VK1DA

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Thank you to all who have contributed to this informative topic which has got me thinking of the total lack of grounding that I have been providing for my antennas during an activation. My 60m linked dipole may not be hanging from a kite, but it’s still a significant length of wire in the wind and rain. I have on occasions heard a click/ tick noises which I suspect was static build up, and alarmed me sufficiently to make me pack up and swiftly make my way off the hill.

Having done a quick search of the reflector for ‘Static Shocks’ and reading through most of the 38 results, I think I will be taking this more seriously.

73 Kevin, MW0KXN

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I’m no antenna expert but I understand symmetric antennas like a dipole do not need a ground / ground plane, though you need a method of coupling the balanced antenna to the (usually) unbalanced rig antenna input.

I use a 80m/60m inverted v linked dipole on a 6m or 9m pole. I don’t think the wires flap around nearly as much as a long wire lifted by a kite.

You say “a click”, so not many. Clicks on AM modes like SSB/CW/AM could - without a detailed description - be caused by lightning strikes, nature’s very-broad-spectrum spark transmitters. Given the energy in the ‘spark’ you can hear them on the radio 100’s of miles away.

The occasional click or two wouldn’t get me packing up prematurely.

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