Best aerial for scanning

I am not behind the door with CB aerials where I can build to the frequency, but I find it hard to get my head around the frequencies I can cover with the 2 scanners I've got - Uniden UBC360LT and Realistic Pro 2005 shown as .52 to 1300 mhz betwen them, and what sort of aerial(s) can cover such a wide spectrum. I have thrown out a long piece of electrical wire(the live wire from an extension lead) out of the air brick near to my scanner and sloped it down to the 6' fence post about 45' away. In the case of the Uniden it doesn't seem to have improved reception at all and there is minmal improvement on the Realistic. I know they are not the Rolls Royce of scanners but I expected a bit of improvement. I also realise that with the slope there is supposed to be a propogation and if that is the case it would be mainly westward, whereas Manchester Airport is East of my location. Any simple tricks any body knows that actually work please

Back in the early to mid 1990's I had a Discone antenna for scanning. Quite the wide band antenna and worked an absolute treat.
You can still buy them now, I've linked one that was very similar to what I once had: Scanking HF Discone 0.05 To 2000 MHz Antenna (moonrakeronline.com)
It received very well from what I can remember.

Hi  

My discone is in the loft. 
Works great!