Nuvi 710 poor fm signal

Not sure about that but an FM transmitter can be obtained that will plug into your phone and not only received by your car radio but also any other FM radio or hifi you choose. Some of these also have bluetooth.
Some are a general use transmitter and the majority are for in-car use.

Amazon and ebay have pages of them at just about every price range.

Short range FM media transmitters are a much neglected and underrated solution to miles of connecting cables and poor performance - I have an FM transmitter usb dongle for my computer that allows me to listen to music files on a decent stereo as well as an Mp3 player/transmitter for the car...

An FM transmitter is a portable device, which converts a specific audio output into an FM radio signal. It can be plugged into a CD player, satellite radio system, headphone jack, or a portable media player. One common use of an FM transmitter is to play music from an Mp3 player through the speakers of a car.

you can try a AM/FM antenna booster if you know how to get to the back of the radio. Otherwise the radio ground needs to be checked out and the antenna ground would need to be tested to see if there was corrosion on the antenna base or the connector to the back of the radio. On some cars the antenna is located in bad area and they don't get the signal boost off of the cars ground plane The more reflective surface you have on the car the more radio waves will bounce back and increase signal strength. Also Depending on atmospheric conditions and skip conditions sun spots and other natural occurring things can cause poor reception. The signal booster is about $10.00 at any radio Shack or any auto parts store. Hope this helps.

I didn't think this unit had an included FM transmitter - so I looked around for more info, and everything I've found indicates it does not.

It will however play audio via the built-in speaker or headphone jack. Use of a third party FM transmitter will allow playing audio (navigation, alerts, MP3 or audio books) when connected to the headphone jack and with both the FM transmitter and FM radio set to the same frequency.

The FM transmitter will work best when set to a frequency that is unused and has the least amount of interference from adjacent stations. Check by tuning the car radio across the FM band and note frequencies that have those qualities. Leave the radio on one of the clear frequencies and set the FM transmitter to the same displayed on the radio. You should try several to find the one that works best. Also, be aware that as you travel, you may enter an area where that frequency (or one close by) is in use by a broadcaster. This will require repeating the process as needed to reduce interference.

That has happened to me several times. When it happens I go to Tools > Settings > Language. In my case, the Voice field is empty, so I click on the Voice field and then select American English-Jill (TTS) and it's okay afterwards.

did you add a card?

Check antenna connections at radio and antenna assy.. Poor connections will only receive AM and hardly any FM

Check mounting surfaces at antenna. Corrosion or looseness and the antenna loses its ground to the body.

The radio will work only if the headset or earphones are plugged in.

Try increasing the volume in radio or check whether its in mute condition

Are you tuning in to the correct radio station?is the service available?

How do you use fm radio signal to access speakers, in lieu of cassett adapter?