Originally Posted by Infinity
Ok guys here is what you need to know....
The nav radio is different that the one in Porsche and the Becker units sold outside the US and older units.
In the past companies were able to flash the removable rom chip to allow the cd changer port to stay alive (meaining it did not require a data stream to open the input). The crossfire radio and ones developed around the same time nolonger use that design.
the aftermarket and Porsche radios were designed not to need the data stream as the inputs would function as either an aux input or for the cd changer based on the radio menu setting.
The Crossfire radio requires a data stream to keep the input port open. In other words it needs to think there is a cd changer connected to it and a cd is playing. The only company I have seen so far that has developed a product designed to fool the radio is
http://www.solisto.de
The reason FM transmitters are hit and miss are the fact that many companies at the launch of the ipod craze and XM/Sirius developed products with output transmitter power in excess of what the FTC has deemed legal. Over time and with some compaines getting caught, products came into spec failed to deliver a strong signal. OEM systems with twin tuners (ours) and diversity systems (nissan and some german cars) typically have a difficult time with FM since their systems look at two different signals and hand off based on which one is stronger. If your ipod signal is weaker, it is overcome by the other signal and you begin to hear noise.
An FM relay pack inline with the ant, is one way of getting a better signal into the radio and they typically are designed for the product they are sold with or work with. Harman Kardon Drive+Play and Drive+Play II are good examples. You can used an FM modulator in line, these are typically how rear seat aftermarket entertainment systems are done, not perfect but better than the smaller broadcast types.
Thanks for the informed response. Your points validate what I have observed in actual practice. An interesting side note is the behavior of my stereo in my Jeep Commander Overland which has the factory entertainment system with DVD player. When using the RCA inputs, it takes a few seconds for the head unit to "see" program material coming in. It won't allow selection of the AUX channel until it gets signal on those inputs. What's even more interesting is that in between songs, it often "goes away" because no signal is detected. Once the song starts, it takes a second or more to come back in. It's a "better than nothing" solution.
I found the harmann/kardonn Drive+Play inline antenna-connected FM approach was barely better than nothing. The radio still detected outside broadcast sources and was a very noisy solution. The broadcast FM modulation was hopeless - going to your point about the strength of the signal it puts out - probably compliant with FCC regs and weak. My Roady XT XM radio seemed to have a lot better performance rebroadcasting the signal - never had the problems maybe because it was over the power limit specified by the FCC....
So I wonder if plugging into the RCA lines of the CD-changer on the NAV unit would give the same results as my Commander - an input stream that the head unit "sees" as long as it detects a signal? From what you're saying, that would require the additional unit (which was my conclusion). Given that, the cost involved really does suggest a better value proposition is to go with a new head unit (higher end sound, more flexibility, XM, iPod, MP3/AAC etc compatibility)... I rest my case...