Thinking about removing the amfm antenna on my gm truck and cutting it down to 3" tall mine has a spiral of wire going up to the tip. I know you can buy shorty antennas but would rather experiment.
For what purpose? To see how crappy you can make your AM/FM reception?
No. I think the truck would look better with a small amfm antenna. I already have three on the roof for VHF that are 20"+/-. The truck antenna is next to the windshield. In the past on other vehicles id buy those typeR 1" antennas but I dont want to pay 20-40$ for a stupid chinese ricer antenna.
~~936/F in Mhz will give pretty close in feet.
300/F in MHz will give pretty close in meters.