Well we have all been locked down for some time now and although I have a high noise level at home I decided to try a balloon antenna on the flat garage roof.
The balloon antenna was supported by an initial 30ft telescopic fishing pole and then 170ft of ‘floating lightweight wire’ was connected to the top of the fishing pole.
The balloons were several 12 inch balloons treated with ‘Hi Float’ and filled with helium gas and all the balloons were bound together to provide sufficient lift.
The wire used was simple stranded plastic coated hook up wire as its very light.
At the bottom of the fibreglass fishing pole I used an MFJ Versa Tuner 2 to match the antenna on the various frequencies of operation.
I used a 1 Meg Ohm discharge resistor to eliminate static build up from creating unwanted noise on the 200ft balloon antenna.
I used a coax line feed from the Versa tuner back to the bicycle mobile trailer which was in the back garden… I also had a full sized quarter wave vertical antenna for 20m on the bike trailer to compare the performance of the balloon antenna against, although the location of the trailer meant that the trailers quarter wave vertical antenna was in a very screened position.
I had the facility to use radials if required but as expected with this type of antenna the radials gave no benefit whatsoever.
I used my antenna analyser to roughly set resonance using the Versa tuner to resonate the balloon antenna and any fine adjustments were made on air using a low power carrier.
I had problems with balloons randomly bursting that was not linked to RF transmissions and that did cause a few practical problems.
Simon N Wilton, VA3SII kindly sent me the EZNEC modelling of the 200ft antenna which I have posted on here, including VSWR and resonance points (without any ATU)
Firstly the noise level on 20m was high compared to the quarter wave vertical and the performance difference was not as great as I was expecting, specially seeing that the trailer quarter wave was in a poor position (see video)
On 40m the 200ft antenna was a much better performer with some excellent signal reports, one from the Orkney Islands was 59+45… I did rig up a makeshift 33ft vertical on the bike trailer to compare the balloon antenna against and there was a considerable advantage with the balloon antenna, however no DX was worked on 40m as the noise level on the antenna was anything up to S9!!
Finally I tried 80m speaking with David Roper, M0DAD but again the noise level on the antenna was very high making it almost impossible to receive with, had I not had the west mountain CLR DSP unit on board it would have been impossible to use the antenna to receive on.
Conclusion… The balloon antenna may seem simple but requires financial investment of helium gas, several high quality balloons, Hi float sealer to prevent gas loss, a fishing pole or similar to prevent the balloon from drifting horizontal in the breeze and of course the antenna requires effective base impedance matching.
The time effort and expense in my opinion did not not warrant the performance, which generally was poor and although I have done the same experiment 3 times over the last 40 years I will definitely not be doing it at home again… However as I still have some gas and balloons left I intend to try it over sea water as we can now operate by the sea again after Wednesday as the government have relaxed the restrictions for the moment.