Factory antenna amplifier = fried?

[ignorant1]

OK – lame amateur move on my part. I installed a new HU in my ’98 Mercedes E300 (w210 chassis). It has the FM antenna built into the rear glass & a factory antenna amp. The tuner was getting phenomenally good FM reception (pulling in stations & HD stations that I never got before!).

The radio was still on while I tucked in the rats nest of wires, and the antenna lead came off of the radio input. I put it back on, but now the FM reception S**ks. Badly.

So the bottom line is that the antenna lead was disconnected while the antenna amp was on – could that have been enough to fry the antenna amplifier?

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[CrossoverOre 10+ year member]

double check that you are getting power out from the deck on that line. My guess is you burnt that up and not the ant amp itself. might just have to jump the power ant wire to the acc instead of using the deck for power.

 

[ignorant1]

Good call - always check the basics!

So I just went out and tested the leads, and I am getting voltage, so the antenna amp IS getting juice. //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif

 

[keep_hope_alive Premium Member]

possible the antenna jack/cable is busted, or there is a short in the antenna wire/jack/plug. if just one strand of the shield touches the center conductor - reception drops to near zero.

make sure the antenna cable has the center pin in-tact. make sure nothing is inside the antenna jack. did you need an antenna adapter to change from small to large?

neaten your wires. group wires logically and zip tie them. I use around two dozen zip ties behind a head unit. I group wires, secure wires, and make sure to account for bending. I avoid wires being pinched or smashed. I don't use electrical tape because it gets loose over time with heat/cold. excess wire is bundled and stashed in the dash, above or below the radio. sometimes I remove more trim panels so I can train wires as i'm inserting the head unit. it's time consuming but you'll be happy in the long run.

in the future, don't move electronics around when they are on. pull associated fuses before working on the radio (or disconnect battery negative).

usually, the blue wire on the back of the aftermarket radio is power antenna lead. it can power an antenna directly or through a relay. or the antenna amplifier can be ignition powered so it is on when the car is on.

 

[ignorant1]

Keep-Hope-Alive: Thank you again for the help. I truly & SINCERELY appreciate it!

Although I’m an (old) amateur, I actually try to do things right – I solder the wires & use heat shrink tubing. I try to keep things orderly, but at your suggestion I did group things and used a lot of tiny zip-ties to clean up the install this morning. It looks much nicer!

I also re-confirmed that I am getting voltage out of the HU for the antenna motor lead and there is also another lead for turning on an amplifier. Both work, and I've tried using both as sources of 12v for the antenna amp. (not at the same time - duh! //content.invisioncic.com/y282845/emoticons/eek.gif.771b7a90cf45cabdc554ff1121c21c4a.gif)

I am using an adapter to go from the German (Euro style?) antenna coax plug to the antenna input in the HU. I have two different antenna adapters, and they both produce the same results, so it’s not that – unless they’re both bad, which is unlikely.

I purposely tweaked around at the coax plug trying to see if I could perhaps get a temporary connection (assuming an internal break or short), and nothing changed. At first.

While driving this afternoon, after doing NOTHING, the radio spontaneously started getting tremendous FM reception again. Weird. So something is intermittent; the question is what. I have to question if the factory antenna amp could be intermittent? Or do antenna amps tend to fail in a permanent fashion rather than act flakey & intermittently?

I went to a local car stereo shop today to see if they had a coax splice for the small diameter coax (75-ohm) used in the factory harness, but no such luck. My idea is to take the antenna adapter that has about 10” of coax and cut & graft that onto the factory coax. That would at eliminate using any adapter and get rid of the original plug and the last few inches of coax.

I’m not sure where I can find a splice for this thin coax. I don’t think it’s a good idea for me to try butchering & soldering to splice the coax, unless you have some suggestions on how to do it??? I would lose the shielding along the length where I solder the inner conductors together. Or maybe I could use some tinfoil to connect the outer shielding together after insulating the inner conductor, and then shrink wrap the mickey-mouse tinfoil shielding??? There has to be a better way to do it…..

Thanks Again – looking forward to your thoughts & advice!

 

[CrossoverOre 10+ year member]

I might suggest trying a different head unit. Theres a small chance the radio tuner is dying, or dead.

 

[ignorant1]

I wish I could try an alternate HU, but I don't have one. Plus the tuner isn't going completely dead - it always captures a signal, it's the signal strength that is the problem. That's why I'm looking at the antenna amp as a possible culprit, or the coax connector.

I've determined that the coax is "3C2V". I've searched everywhere, but I can't find any connectors to splice this type of coax together.

EDIT: Duh - I was making it more complicated than necessary. Apparently Radio Shack (ick) carries a "solderless" Motorola-type antenna plug, so I'll go pick that up today...

 

[ignorant1]

Well, it seems that I'm just talking to myself here at this point, but for future referrence by anyone needing help with this same problem - here is the outcome:

I replaced the antenna connector on the factory coax cable with a motorola style male plug. This way, I don't need any adapter for the aftermarket HU.

Ever since doing that, the reception has been excellent - so far. It hasn't done its intermittent loss of signal - yet. So it seems like the antenna amp was NOT at fault, it was apparently a bad connection at or near the original coax connector. BUT... I'll give it another week or two and give a final update.

 

[Side Show 10+ year member]

^^ good stuff. also in most aftermarket decks they have some hidden radio settings in the setup menu, also BSM (best station memory) and LOCAL 1.2.3 ect all makes a difference . pioneer decks do n e ways (and a lot of sonys now days have the mw instead of fm)

 

[ignorant1]

Well, let's put a fork in it - this thread is done.

It's been working perfectly well since replacing the OE plug with the motorola style plug. So it seems that the inner coax conductor connection at the OE plug was the problem.

I hope this info helps someone in the future....

 

[Side Show 10+ year member]

glad ya sorted it

 

[stacyhoffman]

possible the antenna jack/cable is busted, or there is a short in the antenna wire/jack/plug. if just one strand of the shield touches the center conductor - reception drops to near zero.

make sure the antenna cable has the center pin in-tact. make sure nothing is inside the antenna jack. did you need an antenna adapter to change from small to large?

neaten your wires. group wires logically and zip tie them. I use around two dozen zip ties behind a head unit. I group wires, secure wires, and make sure to account for bending. I avoid wires being pinched or smashed. I don't use electrical tape because it gets loose over time with heat/cold. excess wire is bundled and stashed in the dash, above or below the radio. sometimes I remove more trim panels so I can train wires as i'm inserting the head unit. it's time consuming but you'll be happy in the long run.

in the future, don't move electronics around when they are on. pull associated fuses before working on the radio (or disconnect battery negative).

usually, the blue wire on the back of the aftermarket radio is power antenna lead. it can power an antenna directly or through a relay. or the antenna amplifier can be ignition powered so it is on when the car is on.

Hi All.
As I've noted on other threads, I've replaced the factory fitted stereo with a touch screen double DIN unit as my original failed and it was only a little more expensive to upgrade rather than repair.
However, I now need a permanent solution for an antenna. I currently have a cheap windscreen antenna, but this is very much a stop gap.
I want to use the roof antenna. I can probably run a coax to this unit and solder onto the terminals straight off the antenna. But! I understand that the factory unit has an amplifier. Does anyone know if there is an RF take off on this before it goes into the tuner, or is it all one package?

Thanks to this bleeding virus I've been "furloughed" from work for at least a month, so I'll have a bit of time to play with this (if the Mrs lets me! ) but I figured I'd ask before re-inventing the wheel.

 

[hispls 5,000+ posts]

I want to use the roof antenna. I can probably run a coax to this unit and solder onto the terminals straight off the antenna. But! I understand that the factory unit has an amplifier.

If you are using an aftermarket head unit you should probably just purchase a new antenna. I did one many years ago for a gal and it was a pretty simple kit where you just drill a hole wherever and run the coax cable up to the head unit. Kit came with grommets and bolts and everything you'd need. Surely someone still makes something like that.