I've never been a big fan of discone antennas. They're typically zero gain and being wide band is not always a good thing especially if it's collecting unwanted signals and interference.
That being said I recently became interested in wide band antenna now that I'm playing with wide band SDR's. I chose a
SIRIO SD2000 N (also available with the "U" suffix which is supplied with a SO239 coax connector if you don't want the Type N). It's frequency coverage is 100 MHz ~2GHz that appears to be as good as it gets for a dual-band aircraft antenna. It's also a true discone, not a hybrid like the Diamond D220R.
It's physical size is what attracted me first. Height 3.1 ft, Cone radial length 1.8 ft. The top vertical whip can be removed if you don't require 145 MHz. That shortens it by 17 in. This makes it ideal for indoors or attic installations. Until my health improves or I find someone willing to install it on the roof it will reside in my home office mounted on a 9 ft light-stand tripod. I almost convinced the wife it was a new coat rack until she noticed the coat hooks were upside down and her coat fell on the floor!
Construction is top notch like most all Serio antennas (Made in Italy). They claim it will stand up to 93 MPH winds!
A Google search turns up numerous places to buy, even Amazon @ $99
I got it hooked up this morning to my SDRplay RSPdx and the first signal as a commercial airlinger checking in with Selfridge Air National Guard Base it the signal was load and clear, so much so it sounded like FM with full quieting which is odd considering VHF Air is AM.