Save your money. I bought a Nevada Double Discone and a RS Discone works better over a wider frequency range.
Even the name is made up, its not a Double Discone, its a Bicone or Biconical but without the needed matching network at the feedpoint.
I have a couple of real Bicone antennas and they are rated for around a 3 to 1 or 3 to 1 frequency range compared to a Discone which is rated for about 8 to 1 frequency range if properly designed.
My Nevada POS has a good match around 2m but thats about it compared to any other scanner type Discones which have a useable match from around 100 to 800MHz.
For a real Bicone check out the Harris RF-9070 which is rated for about 90 to 470MHz with some slight degradation but in reality it seems to have some gain within its full spec 100 to 400MHz range. Unfortunately it costs a lot of money due to the engineering and complicated matching network in the hub. Here is a link to a spec sheet for the Harris, otherwise there are no good Bicone antennas for a cheap price except for imposters like the Nevada or the rare military surplus find like my Harris RF-7090.
And another thing, the Harris is about 5ft tall and 5ft wide and only covers 90 to 470Mhz at its maximum ratings. I have another military Bicone that covers 30 to 90MHz and its about 18ft tall and 6ft wide where the Nevada is maybe 4ft tall and 2ft wide. How do they get 25 to 1300MHz coverage from something that small? They lie, that's how!