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Any RC CAM forum members given thought to, or actualy tried, using a helium (or other lighter than air gas) balloon to raise an antenna to extend area coverage/radius?

Just an idea ....

The first thing that comes to mind regards this idea and the power output restrictions we are all encumbered with when using ISM gear (i.e. 2.4Ghz gear and similar), is the signal loss that is likely to be incurred just getting a signal up to an antenna raised from with balloon at several hundred feet - the dB losses will almost certainly outweigh the benefits of height & improvement in transceiver performance*. A bit of a false economy?

Could use an Ubiquiti Bullet (or similar transceiver using POE)? i.e. locate the transceiver up in the air, fix the antenna directly to the transceiver at balloon altitude and run Cat5 ethernet cable from the ground up to the antenna (Cat5 ethernet max length, according to the standard/s, is around 100m, but I've run Cat5 cable over 200m on occassion with little drop in performance).

There are going to mass and "steering" issues associated with using a directional antenna in this kind of setup (though with careful design & prep it could be done), but use a well designed omni-directional and you stand to realise significant additional range/coverage, through both a clearer signal path, as well as potentially improvements in transceiver performance*.

Anyone have their own ideas to share e.g. suitable antennas/antenna characteristics, suitable transceivers, set-up & system config ideas, balloon hardware ... etc etc ....?

* many 802.11X transceivers run log's in their firmware to monitor the rf enviroment in which they are operating, and will adjust power output (and other Tx/Rx characteristics) to fit in and optimise peformance with "competing" 802.11X transmissions around them.

Edited by Helix1

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In short yes.

I am in the process of using a kite and a tethered hot air balloon to get round some of the rules that block me from doing AP from my normal aircraft and it did cross my mind to use one as a repeater. Not for long range but to give good cover right down to the ground at sub 1 mile sort of distance. I also have interest in wildlife at night and have been toying with the idea of a remote mars rover type thing to creep about and take pics. At the moment a mast is the main plan for such things but my balloon is a possibility.

If I do use it with a directional rx aerial then it will be my auto tracking patch but mounted on a gyro stable platform.


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I've been using tower mounted high gain omni antennas as shown in post #10 of this thread:

After many long distance flights at near ground level, I can offer these notes for those of you trying to fly under these conditions:

1) Video is most always going to be the most difficult because:

  • Bandwidth is more than 1000 times greater than the R/C control link so video starts with more than a 30 dB disadvantage.
  • Currently available (at reasonable cost) video is not spread spectrum so it is very prone to interference.
  • Antenna gain and TX power is most often limited on the air platform

Based on the above, the video should be at a lower frequency than the R/C control link. This will give some additional gain for the video. For example, operating video at 1.28 Ghz instead of 5.8 Ghz will provide about 12 dB improvement. The improvement is much greater when trees and buildings are blocking the path.

2) A 2 watt FASST R/C link operating at 2.4 Ghz with 15 dBi omni antenna will nicely match the low altitude range of a 1.28 Ghz, 1 watt video system using 8 dBi omni antennas with 1dB Noise Figure RX. This comparison might at first appear to be unbalance in favor of the R/C link because there is about a 30 dB advantage for the R/C link. However, the low altitude with trees and buildings blocking the path produces a tremendous loss difference for 2.4 Ghz compared to 1.28 Ghz so that most of the 30 dB R/C link advantage is lost.


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Seems that with my 5.8Ghz video link low level is out of the question , I must admit I break into a cold swet below 100ft :o


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I can’t help but think at times the powers to be deliberately imposed all the restrictions they have regards RF power outputs and frequency options when it comes to video (tongue in cheek).

Of course, as most folk on this and similar forums will know, the higher your transmit frequency the greater the required output [power] needed to cover a given range/radius, and the harder that becomes to implement the more bandwidth one needs to use (as is the case with video content – analogue or digital). Likewise, on the receive side, the harder it becomes technically to realize receive sensitivity the greater the received bandwidth is (which is why we see lower and lower dB sensitivity figures for receiver bandwidths, as the bandwidth figures is increased). We’re stumped either way.

Still, the antenna is the one component in all the components we use as part of an rf link that remains free from any legislated restriction – we are free to adopt whatever antenna design(s) we wish and whatever antenna size we wish to use not forgetting ERP restrictions/Gain limits and the practicalities of mass/size/volume, at least as far as the airborne antenna is concerned. Still, it’s the one component we remain free to experiment with, and excepting also the restrictions imposed on us by way of nature’s laws when it comes to frequency/power/distance, there is a lot that can be done to get the most out of antennas

Old Man Mike raises a few notable points:

1) the comparatively large bandwidth required (versus the small – very small - telemetry bandwidth required). No way round it.

2) conflict with other transmissions

3) antenna setup and practical TX power on flying models

On the “drawing board” at the moment are 2 versions of a single airborne antenna design idea I hope to able to share with members by Xmas:

1) a steerable +/- 7-8dB antenna enclosed in an AWACS type dome that will have multi-turn azimuth.

2) E beam-width will be around 26degrees and the H will be around 65 (yes, this will be horizontally polarized).

3) elevation? – will be nice to have around +/-20degree each side of the horizontal – the idea been to get as close as possible to 90degrees each side of the horizontal (@ 3dB [beam width]). The problem of course is going to be the dome profile: 20degree each side of the horizontal means as large a dome diameter as one is ever likely to be able to have, and even that is going to mean a min model size of around 2m (6’5”) or so wingspan. This of course is for a 1300Mhz – 1600Mhz. Working with a video transmit freq to 2.4Ghz – or in Terry’s case, even 5.8Ghz – makes implementing a design like this much easier as a smaller dome will be required, and therefore will be easier to setup with a smaller model.

I am tackling the design from 2 perspectives to start with – both electronically steerable, and mechanically steerable.

An electronically steerable version is “simple” – the requirement been to interface the antenna element/s design with switching referenced to the ground station GPS Long/Lat position – a reverse of mechanical steering of a ground station antenna based on the models GPS telemetry transmitted down to the ground station. The advantage here is little in the way of mechanical components, and the weight they would add to any design (i.e. servo mass - and power requirements, as well as the bearing and slip-ring requirements).

The 2 tricky aspects are:

- designing a half-decent antenna element layout, essentially a disc shape layout configuration consisting (currently) of half a dozen horizontally polarized yagi’s - one of which is active at any one time depending on the models' location/position in the air in relation to its' ground station (or balloon raised) antenna.

- secondly, balancing the antenna element layout/size against dome diameter and thickness.

The mechanically steerable option does away with the conflicts associated with optimizing multiple antenna element layout in such a confined space and replaces it with the issue of mechanics associated with having to constantly and accurately, rotate what would now be a single antenna element layout (versus 6 layouts) round and round and round as the model flies. The issue of dome thickness still remains though – a balance between antenna size and desired elevation beam-width will remain and still has to be dealt with from an aerodynamic perspective.

At the moment I am working through problems associated with the slip ring design (an essential requirement for the mechanically steered option should one wish to avoid wire & coax wind-up!). It needs to be light and incurr low loss, which means it needs to be small and that conflicts with slip ring design. There is also the issue of maintaining the 50ohm match across the ring track and contact pin. That too is never an easy point to deal with on slip rings. Digital servo’s though, are plenty plenty accurate enough nowadays to be used for both elevation and azimuth – no prob’s there – but the slip-ring is going to mean some mid-night oil burning before it comes right.

An AWACS type dome enclosed steerable directional antenna would be great as well - raised on a balloon. If I can get it to be reliable enough to work on a flying model, then I see little prob’s getting a larger higher gain version it to work from a raised balloon, htoug I have to conceed that overall this side of it is more experimental than actual problem solving (i.e. there may be instances in which it's a viable option, but all round it's hardly ever to be a first choice).

I'm open to all and any ideas .........

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