I had a 7800 and had good luck with the basic dual band antennas. I had a Larsen NMO-270sh which was a 1/4 wave on VHF. Worked quite well on both 2 meters and 70 centimeters. I used it to monitor a few works things, mostly VHF and 800MHz. Worked just fine for 800MHz, but never really tried anything else.
I later switched to a 1/4 wave VHF whip. A 1/4 wave VHF whip will work on 70CM with a low SWR, however it does have a funny radiation pattern. Was a bit more low profile. 800MHz coverage suffered, but not enough to be a problem for me.
I got rid of the radio a year ago and now just have VHF and 800MHz radios in the truck, ditched the dual band antenna, but I keep it in the garage for testing. Now just have 1/4 wave VHF whip and a 1/4 wave 800MHz whip.