Saturday, February 13, 2010

600m outdoor loop - The Plumbtenna

Did some cutting and tweaking. This is what is done so far...

The Cutting
Both pipes are cut in half. One of the four pipes is shortened by 4.5cm, this is the approximate width the T-piece will add. Loeki loeki (please ignore the dirty floor, that's my car's room, aka garage):

The Necklace
The sequence of parts is of some importance here. The photo shows the first of the four turns completed. Still lots of slack as one can see. In the process of threading through the rest of the speaker cable, I learned that is helps to stick all pipes into all fittings and just loosen the one I want to thread the wire through. This will result in tighter turns. The cables insulation and the PVC corners create good friction :-( Some petroleum jelly could maybe help here... not willing to have that mess today, I decided to go w/o any lube. Guggsch Du hier:

The Loop
I know, the gray PVC stuff is not the best, electrically - I couldn't find any of the white stuff :-( However, the color makes this thing really look Navy/commercial/military like... OK, maybe the bar-code stickers disturb that impression a bit. Kijk maar:

Conclusions and Future Steps
It is clear that, despite my best efforts, there is still more cable in the pipe than necessary. Well, not much I can do about, should have used petroleum jelly in the first place.
Some measurements:
  • one end of cable is about 60cm long
  • the other end is about 50cm long
  • the minimum inside side length is about 53cm, make that 55cm in average for the individual twin lead
Hence: 55cm × 4 = 2.2m and 2.2m × 4 = 8.8m. With a stretch of 10m cable available, and about 60cm + 50cm = 1.1m outside, just 10cm of cable is distributed wildly about the circumference of the loop. That should not be too bad.

I did not, but the valued reader may, take too much care that the twin-lead is not twisted. Randomly distributed turns and unmotivated twists of the twin-lead will mess with the currents and fields in the loop. Lube may help with one too :-))

Matching and coupling will be done in waterproof box.