UKRA 2000 Meeting at Garlands (Home of THRUST)

(Saturday 3rd June 2000)

UKRA ran from Friday the 2nd to Sunday the 4th of June. Saturday was the only day I could go, and also seemed to be the best day for the weather (at the time). Myself, Sean my son and my friend Geoff arrived early at around 9:15am before flying started. It looked as though quit a few people had arrived and there where a few marquees and other tents including Pete Davy (Pete's Rocket's) and Rockets and Things.

I met up with Hugh Gimmel and signed in for a days flying then unloaded the car and set to work prepping.

I had brought only two rockets. A 2 inch 29mm rocket that has flown for years and my rebiult scale IRIS that had flown at K-LOB last year at Pete's farm but had a failure at deployment. The on-board stills camera was still in a bit of a state a few weeks before UKRA 2000 and I had originally decided to re-build this payload. But after discussions with Pete Davy about his Quantum Leap having a video down link fitted during the recent Altitude attempt I decided to fit a similar system to the IRIS.

I had originally investigated using a digital stills camera with MPEG movie capability, but the price was just too much (£450). So I then looked into putting a full 8mm video camera into the rocket. This was just not that practical. The system would require first surface mirrors (two if you manted to take the ground) and was too heav and low tech!

After further discussions with Pete Davy I discovered that MAPLIN do a video sender unit for domestic applications. The range was only 100M but could be extended with better Antenna. After much discussion on the rocketry newsgroup it was decided to go for a Helical Antenna on the reciever. This would boost the signal to at least get motor burn out and some coast. I could then develop (with lots of help from the newsgroup!!) the system to hopfully get to a mile or two.

With little time to complete the project I kept the system as simple as possible. Below details the system used with a link to the Helical Antenna site.

VIDEO TRANSMITTER PACKAGE

The transmitter was letf as original and connect to the pinhole CCTV camera. Both the camera and transmitter where powered from an 8 cell 12v pack of Duracell's. The power from these is more than sufficient. The camera was fixed to the airframe with an aluminium bracket. A hole was drilled in the side for the camera to look down at the ground.  A wind deflect was fitted also to prevent the camera position shifting in flight due to air pressure. A power switch was all that was needed on the outside of the airframe to power up the system.

VIDEO RECIVER PACKAGE

The Yagi antenna was to be built at first but was dropped due to concerns about polarisation of the signal. So that the antenna would have to be orientaed to the rocket during flight. The Helical antenna did not suffer from the is problem and seemed easy to build after seeing construction details on this site http://www.eisa.net.au/~disco4

The reciver antenna would be altered. I made a helical antenna using a 700mm length of 40mm OD high temp waste pipe from B&Q. I then stripped the earth core out of some twin and earth cable (3M approx). This was then would around the pipe in a helix to the dimensions given below by Steve forr 500mm in length. I then cut  the reflector. This was made out of a piece of copper PCB to 130mm diameter. I then bored a hole in the middle to 40mm and fixed it at the 500mm point on the wate pipe.

A small triangular piece of copper strip was then added between the end of the helix core and the reciver signal core as in the web site above. The PCB copper was mad by removing a piece from a piece of PCB by heating with a blow torch to melt the glue. This was epoxyied into place.

The reciver antenna was removed and the screen soldered to the copper reflector disc. The signal core soldered oto the end of the copper triangle at the end of the helix. The reciver was fixed direct to the back of the reflector. AV (signal and sound) Cables then ran to the video recorder and image displayed on a portable TV. A 12v to 240v invertor would be required for remote field opperation. These can be expensive so I am making my own at present. The TV can be 12V battery powered but the video recorder is 240v but only 24W.

E_MAIL from Steve for the exact dimensions required:- 

With an airspaced helical antenna the spacing between turns should ideally be 0.22 of a wavelength (about 27mm)and the diameter of 0.32. of a wavelength (about 39mm). The design Jason has used has both the diameter and pitch at about 42mm - if you do the maths you find that this spacing is just on the upper limit of the theoretical design of 0.2867 of the circumference of winding (see Jason's web page) - so may not be ideal.

One of the great things about helical antenna is that they are quite broadband so relatively insensitive to construction variations. If the TX antenna is the same as the RX you should think about replacing it with a dipole or something similar - from what you say it definitely sounds directional (which is bad news).

The system was ground range tested with Sean before the event. It looked as if it would get a good range. We got over 800 feet on the ground with good picture and sound. How it would perform in the air we had no idea!!

Many thanks to Darren and Adrian for taking the excellent pictures below ! No way could I get them this good....

By clicking on this link you may see the inflight footage taken (at present there is no sound). It is a large file and will take time to download, but it is worth it !! Many thanks to Chris Eilbeck of the MARS Flight Crew for converting the video footage for me !!

https://www.angelfire.com/on/DATSCOPE/images/rock1.mpg

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