Same horizon, more loss
The radio horizon does not depend on frequency, so the same height gives the same line-of-sight distance as on 2 m. What changes is the loss: free-space path loss at 435 MHz is 105.2 dB over 10 km, about 9.5 dB more than at 145 MHz for the same distance, and diffraction over a ridge is weaker. A small hill that hardly matters on 2 m can leave a clear shadow on 70 cm.
Cities and buildings
The shorter wavelength, about 69 cm, lets the signal slip through windows and bounce along streets. For this reason UHF handhelds and PMR446 radios are usually preferred inside buildings and in towns, while VHF is preferred on open ground and in valleys. A wall can cost from a few dB for a thin partition to 20 dB or more for reinforced concrete or metal-coated glass: these are indicative values, so use the environment setting of the coverage map as a guide rather than a guarantee.
Antennas and cable
Antennas are small, so a 5 element beam or a collinear is easy to build and gives real gain: 3 dB is a doubling of effective power. Cable loss, however, is serious: thin RG-58 loses about 30 dB per 100 m around 433 MHz, so roughly 9 dB over 30 m, while a low-loss cable such as LMR-400 loses about 9 dB per 100 m at 450 MHz, roughly 3 dB over 30 m. Values vary with brand and batch: check the datasheet of your cable and keep the run short. For the maths, read the link budget guide.
