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How do I do this? (balloon tethered node)

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G0OFY's picture
How do I do this? (balloon tethered node)

Here is your Christmas brain teaser.

1. Deploy a self contained mesh node.
2. Battery life of 5 days.
3. IP67 rated.
4. Tethered to a balloon at around 300 feet. A few square miles of reliable coverage.
5. Got to work without problems.

Looking to create a system to cover a large area for a few days similar to the Rajant system but for a tenth of the price. I have already sussed out the supporting platform but I need a simple (haha) system probably based on a Bullet.
Your input would be greatly appreciated.


kg9dw's picture
some ideas
First, I love your callsign. How creative!

I don't have a complete solution for you, but a couple of ideas...

- you don't really need it to by IP67 rated, just meet the specs, right? and just for the electronics? can the antenna be expendable?
- battery life of 5 days is the hard part, if you want the battery in the air. 
- I bet you're wanting omnidirectional coverage

Let's assume 300mA for the radio in a linked state with some traffic going through. 24 x .300, that's 7.2Ah per day, and then for 5 days would be 36Ah. You're looking at a battery that is 15lbs. A Bullet weights less than half a pound, and you can use just about antenna you want as long as its radiation is down.

What I would do is use outdoor rated CAT5 for your balloon tether. 300' of CAT5 weighs about 10lbs. If you do this, you can have near unlimited power with a battery and solar panel at the base!

How much can your balloon lift?
kg9dw's picture
down the rabbit hole
I just looked up and realized I've spent an hour working on this problem. Thanks for the challenge!

After reading a few papers on helium lift capacity, including some interesting documents from the USFS (Forest Service) from the 70s, I came across this site:

You're looking at a 7 to 8 ft diameter balloon to do this, or multiple smaller balloons. One of the USFS papers showed using a tether and a data wire for power and data. If weight is still a problem, use a tether of paracord (300ft weighs 1.5lbs, breaking strength of 550lbs) and then just run a single twisted pair from CAT5 to power the radio (should weigh no more than 2 lbs). Now you're down to only needing a balloon that can lift 5 lbs which takes you to a 5 ft diameter balloon.

AE6XE's picture
Phosphate light weight battery
There's also lithium Iron Phosphate batteries advertised up to 80% lighter (but more $$).     Found one online for 3.75 lbs with 26-35Ah (should be the higher capacity rating given the low discharge rate expected).   
G0OFY's picture
How do I do this?
Hi All.
Thanks for the comments so far. I intend to use a Helikite (half balloon half kite)as my aerial platform. My max weight is around 5lbs. I was originally going to use a portable repeater,made up of two handies back to back or one radio in crossband repeat. Then I was told that extra facilities were required which scuppered the handies idea. Weight is a major factor as is the total cost. if I cannot get the battery life I need then I might have to visit the site daily to change batteries. That is not a problem and it does let me examine the kit for any damage and to top up the balloon if needed. Feeding power etc from the ground may be OK but a 300 foot run of cable could be a problem for voltage drop supplying the node. On the plus side if I use a non mesh bullet at least it will act as a WiFi extender if fed by Ethernet.
There has to be a lot more experimenting yet before I commit to the Helikite (£600 = $750) plus all the other kit I will be getting up to a grand, serious money.
As for my call sign, yes it is genuine, it took me 6 months of waiting to get it way back in 1990. The only people who acknowledged it on my T shirt, when on holiday in Florida back in '92, was the person in the goofy costume and a guy from the RSGB while I was at the Orlando Hamvention.
kg9dw's picture
voltage drop
The voltage drop will work fine if you're using ubiquiti gear and feeding it with 24V at the end of the 300ft CAT5. The radios work fine with 12V as well, so if you put a radio in the air you only need to give it 12V.  I would recommend doing what the balloon launch amateurs do in buying all of the gear except for the balloon and helium, check everything (including weight) on the bench, and then make the big purchase.

Keep us informed of your progress!
"The radios work fine with
"The radios work fine with 12V as well"

Just to make sure those who come across this in the future, that is 12v AT the RJ45 JACK.  24v feed over 300ft of CAT5 will be fine (its above the 12v marker) but feeding from base at 12v over 300ft wouldn't work over CAT5 (if you had some thicker wire to an injector at the top that is another story)
Just wanted to make sure that is clear to anyone who comes across this in the future.
For the batteries...
For the batteries...
I have been playing around with the 18650 lithium cells(same cells in laptop batteries). These can be recovered from old laptop battery packs. Could use 4 cells(3000mAh) packs in series for 14.8V nominal and add more packs in parallel for the needed runtime. Two high capacity 2S LiPo in series should be easier to implement. Check these links, they included a Loco M2 in the payload.
kj6dzb's picture
The man is right cat5 cable
The man is right cat5 cable is no the propor cable to use. You need to look for cat7a spec. Think a little about the ballist/ teather, a motorized spool, will save you hassel when deploying.
kg9dw's picture

We aren't talking about gigabit speeds here. Why use anything more expensive than CAT5 shielded outdoor rated cable?

AE6XE's picture
Ditto KG9DW...
Ditto KG9DW...

- The maximum length for a cable segment is 100 m per TIA/EIA 568-5-A.[8]
- The cable standard provides performance of up to 100 MHz
- Through the use of power over Ethernet (PoE), up to 25 watts of power can be carried over the cable in addition to Ethernet data.

Success stories:

Cat 5E has a Pulling Tension

Cat 5E has a Pulling Tension of about 35lbs and the weight of the cable is about 5.5lbs for 300'.

A 10' Sphere Helium Balloon can lift about 14lbs. 

I think the question should be what kind of rf power does he need to cover a large area with 2.4 or 5.8? So what is a large area?

Could a Raspberry Pi hotspot work?


KX5DX is your friend

"I think the question should be what kind of rf power does he need to cover a large area with 2.4 or 5.8? So what is a large area?"

With the power of line of sight and clear Fresnel zone, 28dBm from a Bullet (plus antenna gain) is plenty of power. Below is a capture from from my really bad location at the given 300ft. The horizon area is roughly the size of my county, 1000 square miles or so. 


Image Attachments: 
G0OFY's picture
How do I do this?
Thanks again for all your comments.
The location I will be using still has to be confirmed by the event organisers but the main event location is in a valley with hills on either side of over 600 ft. Manned checkpoints, possibly 25, are located on the other side of these hills. On past events in different areas I have deployed a couple of repeaters with handies and mobiles which have been OK but only to 10 or so outstations after using mapping software to check if there was a signal. Since dropping WiFi inton the HQ on this years event the request has come for more. Next years event has now the need for all the outstations to be in contact with the event centre 90% of the time, supply the Internet again the usual voice links are also needed.
As you can imagine placing the node at 300 ft in the event centre still creates a problem so it looks as if I may have to deploy on one of the hills or find the local friendly radio mast operator (if there is one in the right area).
I like the POE option suggested as It call all be powered from the mains power then all I need is a bullet at the kite end with a smallish antenna. The bottom line is the total cost of deploying the dearest item being the balloon.
I am doing another small event next and I will be testing out some of your suggestions.
Thanks again

Another Balloon Project
For a special rural event, we need greater coverage than can be obtained by any portable ground station. All previous efforts have failed, including use of a portable
relay station.  Need live video. So we are considering a balloon approach. Kitoon actually.  It would be tested well in advance, and if it works it works, otherwise we tried.
We only need it for part of a day.  We know it will not work if the weather is bad.The basic idea is to use a Bullet node. 15 dBi TP-Link omni innards hanging down (no heavy PVC cover, I already know what it looks like inside, from its previous failure). Use it as a relay node, so no need to run heavy 8 conductor ethernet cable up there, just a lighter 2 conductor power cable, so no electrical height limitation.   We can maybe reach 300-500 feet.   Are we crazy hams or not?
Maybe a drone?

Just a few observations:
Just a few observations:
A handy rule of thumb: Range-in-miles = 1.23*sqrt(Height-in-feet) so 300 feet buys you a 42 mile diameter coverage circle.
Here's a handy balloon lift calculator:
There is FAA Part 101 that regulates tethered balloon operation.  The height limit is usually 500 ft so that's not an issue.  Weight is - I think it's 12 pounds split between two packages.
Balloon material matters.  Some balloon materials are not intended for long term outdoor use.  Some are intended to be reusable but are very heavy.

If you do go to the 12 pound limit you will need about 250 cu-ft of lift gas.  The price of helium might be a big surprise.  There is also hydrogen that is much cheaper but gives some people the willies.

For some reason balloons rotate about their tether.  This is really a big issue.  I suspect that the constant winding/unwinding would break cat cable.  If you just wanted power you could probably find a split ring swivel.

The balloon and payload has to have enough buoyancy to overcome the strongest winds it will encounter or may be blown down significantly.

73 Martin W6MRR

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