The RH77CA performs best in the 450MHz band, and very well in the 150MHz band. But it's not really designed for the 800MHz band, although it works ok.
Likewise, most of the more popular discones are designed for the same bands, and not the best choice for the 800 MHz band, unless you buy a discone designed for that band. Then of course you sacrifice performance in the 150, and 450MHz bands.
If you truly need to cover all three bands, and want to increase performance, you should consider a log periodic antenna. DPD Productions sells one, that I would personally recommend.
118 - 1000MHz Scanner LP Antenna
DPD Productions - Scanner / Radio Antennas for Commercial & Hobbyist Applications