15-09-2024, 04:32 PM
Well, there's some lessons learnt!
I had been planning to use some 13mm polypipe as spreaders. The pipe comes in rolls and needs to be laid out in the sun to straighten. I slipped it over some bamboo garden stakes and put the pieces in the sun, then I realised I should just use the bamboo, so construction recommenced.
The fan dipole went aloft just before lunch. I was blowing a gale but I figured it would be a good shakedown.
I had cut the wires long and folded them back on themselves.
On the nanoVNA the 12m VSWR lowest point was below the target frequency, the 15m lowest point was above.
So shortened the 15m it moved down and the 12 moved up. Lengthened the 12m legs. Still going in the right direction.
Then the reading started to go all over the shop. Ended up adding wire here, removing it there. After a couple of hours of lowering the wires, adjusting and raising again, the whole thing started to hang oddly. The tension was all wrong.
It was then I realised that my adjustments totalled more than the difference between a quarter wavelength on each band.
The dipoles had swapped roles...
Needless to say, the whole contraption is back in the shed where I will reconfigure it to the starting point, then reassess whether I need 12 and 15m on the same antenna...
I had been planning to use some 13mm polypipe as spreaders. The pipe comes in rolls and needs to be laid out in the sun to straighten. I slipped it over some bamboo garden stakes and put the pieces in the sun, then I realised I should just use the bamboo, so construction recommenced.
The fan dipole went aloft just before lunch. I was blowing a gale but I figured it would be a good shakedown.
I had cut the wires long and folded them back on themselves.
On the nanoVNA the 12m VSWR lowest point was below the target frequency, the 15m lowest point was above.
So shortened the 15m it moved down and the 12 moved up. Lengthened the 12m legs. Still going in the right direction.
Then the reading started to go all over the shop. Ended up adding wire here, removing it there. After a couple of hours of lowering the wires, adjusting and raising again, the whole thing started to hang oddly. The tension was all wrong.
It was then I realised that my adjustments totalled more than the difference between a quarter wavelength on each band.
The dipoles had swapped roles...
Needless to say, the whole contraption is back in the shed where I will reconfigure it to the starting point, then reassess whether I need 12 and 15m on the same antenna...
Colin
Barossa Valley, SAP. PF95ln
(aka VK5CSW)
Barossa Valley, SAP. PF95ln
(aka VK5CSW)