I have RF in my Attic (I used to have bats)
|Ladder line fed Dipole in attic|
Update 30-03-2016: Since I wrote this article I updated my outside Windom to an 80m OCF Dipole. So I'm no longer using this attic antenna for 80m but it's working great for 40m and above.
I thought if I could install a 40m doublet in my attic I might be able to load it more efficiently (due to less loss into a balanced line) for 80m. I pieced together wire, laid out on my driveway, from a number of other projects to get me 68ft. I still had some ladder line from years ago.
There's no better time to work on a project in the attic of your house than a hot summer day in August.After crawling under and around duct work in my very, hot and dusty attic I had to go back into the breach to adjust wire lengths a couple of times until it tuned properly. That involved a sort of overweight gymnast routine on the balance beam... um I mean rafters... above one of the bedrooms. At the time I was thinking through the excuses I might have if I fell through the ceiling (it wouldn't be the first time I've fallen through a ceiling but that's another story).
I have another qualified success. It's rather more of an inverted "U" than a I'd like but poking fishing poles out the sides of the house with wire attached wouldn't have gone over well with the wife.
Here I've used my finely honed artistic skills to superimpose a drawing of the attic antenna on my house:
|Blue is wire. Red is ladder line. Green is Operator|
|Ladder line winding its way to the operating position|
|Ladder line passing through the wall|
|Ladder line adding it's beauty to the station|
Addendum (9-18-2015): The Attic 40m Doublet actually outperforms my 40m Carolina Windom to the West (both receive and transmit) It's about 12db down on receive compared to the Windom to the North and South even though it equals it in transmit performance (according to a few reports where I've asked for A/B comparisons). With the next outdoor antenna I put up I will do my utmost to get ladder line all the way back to the radio. I'm becoming a believer in ladder line efficiency, which is especially important for lower power operations.
It also introduces just enough RFI in the house at 5 watts to let my teenage son know when I'm having a QSO via his gaming headphones. He's super excited about that as you may guess.
So lower your power and raise your expectations
N4PBQ (now AA4OO)
So I've had the Doublet in the Attic for over a year now and it continues to amaze me. I've also learned a couple of things about Doublet antennas since then... I noted in my blog that I'd measured the doublet to be a total length of 68 feet. I've learned since that the length of a doublet is more dependent on total length including the ladder line than simply the horizontal bits and absolute length isn't that important because you don't want it resonant on any band. I ended up adding a few feet on both ends to improve the tuning across all bands from 40-10.