A question for the Audio/Electrical gurus out there:

"If only EssExTee could be so grossly incandescent" (essextee) 11/04/2014 at 09:26 • Filed to: gremlins

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So, I have this FM modulator for my car due to a lack of an Aux jack. It works just as advertised and the sound quality is very good, but when it's hooked up it destroys the rest of my radio reception. Even if it's off, the only station I can get clearly is the one that's broadcast a mile from my house. What's causing this, and is there anything I can do to fix it?

I have a hunch the problem is these antenna adapters I had to buy. In my experience, cheap stuff like this tends to be the problem. Oppoinions?

crowmolly > If only EssExTee could be so grossly incandescent 11/04/2014 at 09:34

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How does it sound with the ignition off?

If only EssExTee could be so grossly incandescent > crowmolly 11/04/2014 at 09:43

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Same thing. The station it's set to and the local station come in fine, all other stations are so bad that the seek function won't land on anything else.

RamblinRover Luxury-Yacht > If only EssExTee could be so grossly incandescent 11/04/2014 at 09:48

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I must confess I don't know much about these, as most FM modulators I've encountered don't interconnect with your antenna at all - just local broadcast with an internal antenna. Remember that to pick up broadcast, the circuit really has to be as clean as possible, because the induced currents in the antenna circuit are so unimaginably tiny. Any of those antenna connections that are at all dirty will kill signal, as will poor quality/conductivity and the box itself. Just not a good idea, IMO.

Mattbob > If only EssExTee could be so grossly incandescent 11/04/2014 at 09:54

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how is the system setup? Does this box go inline with the existing antenna line, and just insert the new audio signal? EE here.

Mattbob > If only EssExTee could be so grossly incandescent 11/04/2014 at 10:00

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I think I have a solution, and it may not be ideal, but yeah.. OK it looks like what you have is the same thing as this: http://www.amazon.com/Scosche-FM-MOD…

it looks like from the comments that with the unit on, FM reception turns to shit.The unit linked solves this by giving you a switch right next to your aux input plug to turn the power to the modulator off. It sounds like you will have to duplicate this by putting a switch in line with the power to the module, and switch it on when you want to listen to your mp3 player. To see if this will work though, first you have to see if you get reception through the device with the power off.

If only EssExTee could be so grossly incandescent > Mattbob 11/04/2014 at 10:02

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Exactly. Radio antenna goes in one end, other end goes into head unit. The box "overrides" a selected frequency and allows you to insert your own audio signal via those stereo cables. Theoretically all stations other than what the box is set to will be untouched but not in my case.

Think one of these things, but hardwired into the head unit:

If only EssExTee could be so grossly incandescent > Mattbob 11/04/2014 at 10:04

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The unit already has an inline switch (at the top of the first picture) and reception is still shit with the box off.

JGrabowMSt > If only EssExTee could be so grossly incandescent 11/04/2014 at 10:16

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Interference.

Long story short (because I worked in radio for a while), the adapter cables to plug it in are either too high or too low in terms of resistance. When your now stupid radio tries to get either quartz lock or however it works on a signal, it's now met with a weaker signal than it's used to, which causes it to continue to seek without luck. Essentially, the fix is to rip out your cheap little FM "transmitter." Fact of the matter is that it's not even actually a transmitter, it's more like an adapter, it doesn't actually "broadcast" anything. It's a lot like the channel 3/4 coax boxes we grew up with for PS2 systems or other consoles that couldn't plug into old TVs any other way. Admitted though, those channel 3/4 boxes worked a whole lot better.

I would find the tape deck that came with the Neons:

It would go in Factory, and look pretty good. What I would then get is one of these:

You'll wonder why you bothered with anything else. I've got one for the SL because sometimes the 6 CD changer isn't what I want, and the radio has nothing good on. Pairs really easily with everything, and just works. Battery life I've gotten is something like 6-10 hours if you turn it off when you aren't using it.

Mattbob > If only EssExTee could be so grossly incandescent 11/04/2014 at 10:27

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what kind of car is it? Depending on the setup of the stereo, there may be an impedance mismatch. Do you know if you have a powered antenna?

If only EssExTee could be so grossly incandescent > JGrabowMSt 11/04/2014 at 10:27

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Yeah but I like my CD player. I don't think there was a radio with both CD and cassette, so I'd have to get both the radio and the separate CD changer and figure out how to wire them up.

If only EssExTee could be so grossly incandescent > Mattbob 11/04/2014 at 10:29

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2002 Dodge Neon. I believe it is unpowered.

Mattbob > If only EssExTee could be so grossly incandescent 11/04/2014 at 10:37

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does the switch disconnect both power lines or just the power? Can you characterize the bad reception? Is it just weaker, or is there unwanted noise on the line(perhaps noise that changes with the RPM)?

Mattbob > If only EssExTee could be so grossly incandescent 11/04/2014 at 10:43

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if it is just weak, I'm thinking there may be a path to ground, and the signal is being attenuated. As a test you could unplug both the positive and negative power leads and try it then. If not, it could be a bad circuit design in the unit itself, maybe some capacitance across the signal in lines that could attenuate it down.

jariten1781 > If only EssExTee could be so grossly incandescent 11/04/2014 at 10:46

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Well, if it's the signal from the box overwhelming the whole band you could do what they did in the tube radio days and build a wave trap centered around that frequency then switch it on when you want radio.

http://www.jaycar.com/images_uploade…

If it's that the box is weakening antenna reception, on the other hand, you could run a straight wire in parallel and switch the box in or out depending on what you wanted. You'd want to make sure you match impedance in both configurations to what the tuner in expecting.

Also, make sure you don't have a ground loop.

uofime > If only EssExTee could be so grossly incandescent 11/04/2014 at 11:17

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find used DIN radio on CL with aux in, use this adaptor kit, http://www.crutchfield.com/p_120996503/Me…

,or similar.

problem solved

JGrabowMSt > If only EssExTee could be so grossly incandescent 11/04/2014 at 11:49

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The radio in the picture has both.