Car-Audio FM receivers and their reception . . .

[BonzaiDuck]

Perhaps I could've asked the question in the Title line.

As per another thread about car-audio "upgrades", I have an older pre-2000 OEM audio system -- 4-channel, 12-CD changer that I want to continue using. It has a cassette player!!! -- which offers to be a solution for upgrading the system to two-channel-stereo Bluetooth. Sound quality is great.

And -- I have my own purposes: Not only do I want to retain the old system with some peripheral upgrades, I want to use the FM-receiver so that it only functions with short-range reception. That is, I want to attenuate the reception where most people would want to make it more powerful.

The first thing I can think of doing is to simply remove the antenna connection to the car's external antenna. I see the possibility of then adding an auxiliary tuner which will replace the OEM's function for listening to FM radio. I can connect the antenna-coax to this auxiliary tuner.

Somehow, I'm under the impression that FM receivers disconnected from their spec antennae still function to receive very short-range transmissions. Is this true? If it isn't, I'd need to explore some simple method of attenuating the reception of the connected antenna.

ADDENDUM and UPDATE: I'm still interested in the answer to my question here -- What sort of short-range reception does an FM-receiver get with an unconnected antenna? But the reason I'm asking the question no longer has a compelling motive. Use of empty FM channels to get sound from an add-on Bluetooth-enabled FM-transmitter and MP3 player -- is not likely going to "degrade" sound quality, and with careful choices, not likely to have interference from stations nearby on the frequency spectrum. You might expect something like that on "long trips". So? Switch to the Bluetooth receiver!

As I said on another thread, I've seen a demonstration of this FM-transmitter feature, and it does a good job.

 

[Paperdoc]

Yes, to use an external signal source (like an MP3 player or something) that can send its output as a FM radio signal to your car radio for actual playback, you really need only two things you normally would have, anyway. One is that the source device should have some way of selecting what FM frequency it sends out. And then you simply need to select a frequency that is NOT close to all your other local radio signals. That way your normal FM radio will be able to hone in on that frequency cleanly. It does not matter that other stations also are available for normal radio use.

I did that with a system I had in a 2004 Mazda with built-in CD but no tape player. This was for a hands-free cell phone system device I bought from Motorola. It was battery powered and clipped onto my sun visor. It communicated with my cell phone using Bluetooth, so when it was turned on it took over handling all cell phone activity and I did not need to use hands for much. It had its own speaker and mike, so it could be used stand-alone. But it also had the abiloty to route its sound output to the FM radio instead of its own speaker. For that it had about 15 or 20 pre-programmed frequencies and a way to set which of those to use. I used 107.7 MHz becasue there is no local station there. Then I set one of the radio's pre-set freuqncy buttons to that, so all I had to do was tell the hands-free device to output via FM radio, turn on the radio and push the right station button. Worked like a charm any time I wanted to have everyone in the car hear the phone conversation clearly.

 

[BonzaiDuck]

Well, all my wonderful shee-it came yesterday. I was careful to discard the Amazon boxes at the trash can, even handling it with nitrile glove. I picked up all the retail boxes and came in the house. Then it dawned on me that this stuff is not made in Japan anymore, no longer comes from S. Korea, nor from Taiwan.

It's Chinese. I grabbed my bottle of Isopropanol and looked up "Wuhan industry" on the web. They make a lot of electronics there, as well as surgical PPE and masks!

I've got to test the items, and before I begin, I want to compile my very tiny stub of a 32GB USB drive with the folders from my MP3 collection. I'm going to cut off one of the two 6' wire pairs from a cigar-lighter two-way-splitter, run the wire out the back of the console panel, and use a fuse power tap to connect the hot wire to the fuse box and an appropriate ACC fuse -- like the cigar-lighter fuse, which is about 20 Amps. These items could probably be fused at 5 Amps with the alternative add-a-fuse alternative to the fuse-tap. Just need to find the load and draw sides of the fuse with a voltmeter..

I chose the units to all have on/off switches of their own. It's getting likely that I'll select the unit that fills an extra "head-unit" space in the dash, and has a push-button switch on the left knob. But I need to determine the units with the best sound quality and reliability.

I can try dicking around with the BT-to-cellphone connection, but the primary reason I'm doing this is to give myself a "Library-of-Congress" music collection over and above the 12-CD changer. As I've said many times, the car's head-unit is the OEM 1995 system for the Isuzu Trooper. I can also stick another Bluetooth device in the cassette slot, although it only gives me two-track basic stereo.

But it's nice to hear in this forum from someone who's actually tried such a device, Paperdoc. Someone else was telling me to get a whole new head-unit and lose the CD-changer, which still works. I think I have two front speakers with loose mounts -- something else that can be easily fixed, although I could replace them if I wanted for chump change. I think a screwdriver and some rubber-adhesive weatherstrip will do just fine.

What else to do, until we start feeling hot or have chills, and then start coughing up bloody sputum and find it hard to breathe? But I've already started keeping my bio-hazard suit with the 3M respirator in the car. It's easier to breathe through than the bandana, anyway. Of course, thinking of the COVID/COFEFE symptoms, perhaps my next project should be installation of a spittoon that flushes stuff onto the pavement . . . like a little miniature terlit with the president's picture inside the bowl . . .