But it is only half of the game!
Good Radio reception is a result of lots of factors working together. A chain can be no stronger than its weakest link...and radio reception can only be as good as the weakest element. Sometimes you can imporve the elements, it just takes money...
Remember that the 160Mhz band in nominally "Line of Sight". That is, if you are in a valley, mot of the signals will pass over you...the radio signals dont bend well at that frequency. So if you are looking for a spot for best reception, find the crest of a hill instead of the valley...
A GOOD antenna is a pre requisite for GOOD reception. As stated previously, longer and higher is better. A second, but less important factor, is number of elements. If you have two elements, stacked on top of each other, it's called a "Co-Linear", and it will work in all directions. If they look a little like an old type TV antenna, it's called a Yagi, and it is Directional...it works best in the direction perpendicular to the shortest element. Short antennas, as stated previously, area design compromise between good reception and easy to use/convience. SOme stubby's are better than others.
Also, the antenna should be sized for your frequency. If you get the right kind, the elements can be trimmed for the exact center of the band you are interested in. That generally means a 2-M ham antenna, which is designed for 144-148MHZ, can be shortened to work at the 161 Mhz band. If you have an antenna designed for the Ham bands, you are losing about half the reception effectiveness at 160Mhz. The "Bandwidth" is typically calculated for a "Half Power Point", so if you have an antenna designed for 144-148 Mhz, that means that usually at 148 Mhz, you get a 3Db loss from the best possible frequency. And that means the further you get from that frequency, the more attenuation (decrease) you get in the signal.
If you know a Ham with an SWR meter or an Antenna Analyizer, have him help you trim your antenna to the correct length. Or, buy one that is already trimmed for that frequency. I am pretty sure the Ham outlets sell Diamond Antennas already shortened to the Public service/Business (160Mhz) band.
NOW, receiver senstivity comes into play. If you have a scanner with poor front end sensitivity, you will get poorer reception. But if you have a good front end, and a lousy antenna system, you will also get poor reception.
