AM-FM

[tom]

From what I remember the length was calculated based on the fm band wave length.

[BlackoutSteve]

Yeah, fm..

http://www.crompton.com/wa3dsp/hamradio/antcalc.html

[lakeholme]

FYI, the rear antenna works fine with a new repo. AM-FM.  I've got one in my 68 right now.  No problems.
As John says, however, the rear antenna is limited, and even the original AM radio has limited range and a fair share of static here in the NC mountains.

[Pex68]

Another thing to remember is the rating of the speakers.  Stock speakers are 10 Ohm and all aftermarket are 4.  If you run the 4 Ohm with a stock radio you will be pulling over twice the current through the radio and run the risk of burning things up.

Any yes, best antenna reception for any frequency is a ¼, ½, or full match to its wavelength with the full match obviously getting the best reception.