Monday, May 02, 2011

recycled steerable dipole

I rescued an old teevee antenna from Karl before he escaped the state. (he has gone to vk7 land).
it had a number of 'large' elements on it for VHF and lots of small elements on it for UHF. =D

I striped all the elements off the boom and started looking at useful arrangements using the longest ones. did some numbers and worked out that i could use the largest and third largest elements and reuse the 'egg' insulators for a reflector element, then wrap an inductor around the 'egg'.... =)

Did the measurements, rough numbers for the coil, should be good for the middle of 10 meters. \o/
Put it together, then spent the rest of the afternoon cutting firewood. consequently I ache all over! =/

So after the pot-belly stove is fired up and the dinner is on the boil, I test the antenna to see where in the 10 meter band it works ok.

So it fails as a dipole for 10 meters. Rather badly actually the SWR > 5:1 across the whole band =(
Not to be discouraged I tested it on 15 meters. Bingo! The SWR < 1.5:1 across most the band. \o/

So lesson for today, is my modeling/measuring concept is right out. However the consequence is that if I tinker with the coil I should be able to find a tap point suitable for 10 meters. A job for next weekend though.


I've added some images of the process and what the final center and loading coil looks like.
It is not particularly self supporting, as the final elements are much longer than the original teevee antenna.