Here is a picture of the actual antenna that
@Marcy57 was referring to.
A quick summary of the antenna - it is a "jack of all trades and a master of none" !!
The cost is around $90.00 plus shipping and tax.
If I am scanning VHF Airband frequencies and I use a telescopic antenna set to 24 inches (correct length of VHF air band), the telescopic antenna will be about 20% better than the "all in one antenna".
If I am scanning 145MHz ham or 155MHz police/fire or 160MHz railroads and set the telescopic antenna to 18 inches, the telescopic antenna is about 25% better. Also if I tune in a very strong NOAA Weather tower (162.400) that is 8 miles from my house, the telescopic antenna is still noticeably giving me a stronger signal.
Same relationship seems to follow in the 450MHz and 800MHz bands.
Where this antenna would be better is obviously if you are scanning a wide variety of bands.
The antenna (in my picture) is sitting on a metal pizza pan so I can easily move it around to different places in the house. The antenna has a big magnetic base so you can attach it to the roof of a car but they warn you that the car shouldn't be moving because the base won't hold it to a moving car. The soft drink can is to give you some idea of the size of the antenna, the antenna is not easy to put inside of a car to move it around and it needs something relatively large to set it on.