I have a Marantz 2270, and would like to know if anyone can recommend a good fm antenna?
What will be a good antenna for you depends on your needs. When it comes to selecting an FM broadcast band antenna it is all about the
quality and strength of the signal that is in the air
at your location, for your station(s) of interest. It tends to be a little bit of trial and error and it not necessarily the same for you as for others. Recommendations of " I have antenna XYZ, it works great/pulls in a lot of stations" does not necessarily mean that it will work for you, although it might.
For stations that have moderate to strong signals, just a piece of wire may work okay and or an FM broadcast band dipole may work for you. Rabbit ear type antennas may work better than the dipole antennas because they offer easy adjustability, the length and position of the elements can be adjusted for best reception, especially if your stations of interest lie in different directions.
Get an outdoor old TV antenna
This may not necessarily be good advice. The term "old TV antenna" covers a lot of ground. Not all TV antennas are created equal when it comes FM broadcast band reception.
Since the change over to digital over the air TV it is not uncommon for what one might call an "old TV antenna" to be a VHF high band (174 MHz to 212 Mhz) /UHF (470 MHz to 890 MHz) antenna. This is way above the FM broadcast band and will likely provide poor performance.
Even VHF TV antennas that cover the VHF low band channels may provide less performance than a 30 dollar purpose designed outdoor FM broadcast band antenna. It is not uncommon for their performance to mostly drop off a cliff above about 93 MHz. Of course if your are in a strong signal area, just about any random piece of metal/wire stuck up in the air indoors or out doors may be sufficient
FM Fool and
Radio Locator can give you a rough general idea of the strength and direction of your stations of interest if needed.