Radio pros, need your help...again.

[Fett]

Ok, the past two head units in my car had horrible reception. The most recent head unit has a built in HD turner...same problem. A few weeks ago I took a different antenna cable, new antenna base, and new antenna. I assembled the three peices in my hand, plugged the end into the radio, and held the antenna outside the car with the cable stretched, simulating it being installed. No change in reception.

Today I decided to see if my radio ground was bad, so I ran a separate ground...no change in reception. So, for no real reason, I took a 2 foot piece of 12 gauge wire, stuck one end in the antenna input in the back of the radio (where the car antenna cable should go), and held the other end of the wire in my hand. Reception was perfect.


Short version: Multiple radios have bad reception in my car. Tried different antenna/cable/base, held it in my hand and it didn't work. But a simple piece of 12 gauge wire in place of the antenna worked perfect.

My thought is that the cable or base in my car is the problem....but that wouldn't explain why a new cable/base didn't fix the problem. Unless the new cable was bad as well.

Any thoughts on why a 2 foot long 12 gauge wire would get better reception than a new cable/base/antenna?

 

[NKau]

That's utterly bizarre....

 

[S&B]

I was going to try to help but all I could think of was, "buy some cd's" or hook up your I pod.

Maybe try to buy a Mercedes attenna Kit, its like a sticker that goes in the back window, Thats whay I use when people want a antenna delete wish I could be of more help

 

[5.0Droptop]

We wish you could be more help to S&B,,, But you have a place here at stangnet and helping is not it.

 

[5.0Droptop]

Humans make great antennas............

 

[Fett]

Ok, so it isn't just me then. I was thinking it was a very odd situation, but figured there was something more to antennas than I knew and someone would make sense of it all.

I'm going to try a different antenna cable tomorrow. My hope is that the other antenna cable I used was also bad....which is a stretch I know. But I can't come up with another reason why two different antenna cables, bases, and antennas would have horrible reception...but a 12 gauge wire would bring everything in crystal clear.

 

[fiveohwblow]

I am no expert but maybe some form of a ground loop isolator? Sounds like maybe a distortion in the grounding of your car chassis as opposed to being a radio problem.

Just a theory though, as I am far less knowledgeable than those who have already replied...

 

[Fett]

I am no expert but maybe some form of a ground loop isolator? Sounds like maybe a distortion in the grounding of your car chassis as opposed to being a radio problem.

Just a theory though, as I am far less knowledgeable than those who have already replied...

I was originally thinking ground, which is why I tried a dedicated ground for the radio. But I keep going back to the fact that a 2 foot piece of 12 gauge wire brought stations in clear as a bell.

 

[Saleen0679]

Take a meter to the center pin of the cable and the metal sleeve around the outside of the cable and see if there's a short.

 

[Tstang90]

I was going to try to help but all I could think of was, "buy some cd's" or hook up your I pod.

Maybe try to buy a Mercedes attenna Kit, its like a sticker that goes in the back window, Thats whay I use when people want a antenna delete wish I could be of more help

have any more info on that antenna or a link?
what kind of results have you had with it?
I have a powered hidden antenna and it kinda sucks.

 

[S&B]

I just remeber ordering them through our old wholesailer, back out 6 years ago> I know they were from a mercedes, I found a link on ebay that resembles what it looks like but mine looks much longer and bigger, so maybe the size has come down.
http://cgi.ebay.com/ebaymotors/Hidd...023QQitemZ360040088285QQrdZ1QQsspagenameZWDVW

it works good, not perfect but good enought to get every station that actually comes in

 

[Fett]

Take a meter to the center pin of the cable and the metal sleeve around the outside of the cable and see if there's a short.

Ok, I took my multimeter and tested my stock cable and the other cable I used. Found some interesting things.

Apparently antenna cables are also grounded...didn't know that. The inside pin and sleeve is the antenna itself, but the metal covering on each end is a ground. I checked ohms across the "new" cable and got a .7 reading inside to inside, a .4 outside to outside, and nothing outside to inside.

On my stock cable and antenna base, I got .5 inside to inside, .6 outside to outside, but .00 (as opposed to OL) inside to outside. Which leads me to believe the cable is broken internally, causing ground to come in contact with "positive".

Another thing about the antenna ground. On the outside of the radio wherethe antenna lead comes out, there is a metal ground to the chassis of the radio. I am not sure if that is supposed to be the ground or not. Plus I figured the antenna base itself is also a ground, seeing as it is bolted to the fender. Making the screws, base, and fender the ground.

Tomorrow I am going to try a new OEM base/cable assy, with a new antenna. I know some new antennas have a small wire that wraps around the outside of the antenna....not sure what that is.

The funny part (ie: sad) is that I rarely listen to the radio, except talk radio....which is the only channel that comes in clear right now. My radio has a USB port and an AUX port for my MP3 player...which is what I mostly listen to. Add to the fact that I normally only take my car to and from work, which is 1.1 miles away. So really I think I am doing all this for no reason other than to find out exactly how antennas work, and to make it work just for the sake of making it work.

 

[backfocus]

Fett, you are correct on the grounding. That is why it wouldn't work well in your hand as the antenna grounds to the fender. Some radios also need an external ground but I have not seen any for a long time. Most new radio are now grounded through the harness.

Edit: Most antennas are also grounded at the radio, except now they are done inside the radio were you can't see it.

My guess is the your base and cable connect is weak, as it happens with many vehicles over time, not just our foxes. The new cable and antenna should fix it.

 

[Saleen0679]

On my stock cable and antenna base, I got .5 inside to inside, .6 outside to outside, but .00 (as opposed to OL) inside to outside. Which leads me to believe the cable is broken internally, causing ground to come in contact with "positive".

Definitely not good.

Another thing about the antenna ground. On the outside of the radio where the antenna lead comes out, there is a metal ground to the chassis of the radio. I am not sure if that is supposed to be the ground or not.

The metal sleeve should be connected to the wire or foil shield inside the cable sheath. When inserted into the radio antenna connector the sleeve makes contact with the radio chassis.

Sometimes there is a metal ring around the cable sheath that is screwed into the radio chassis and it's used as a strain relief.

Tomorrow I am going to try a new OEM base/cable assy, with a new antenna. I know some new antennas have a small wire that wraps around the outside of the antenna....not sure what that is.

I heard that was to break up the wind and keep the antenna from 'whistling'.

 

[Fett]

Ok, so it sounds like I am on the right track then. I figured with one lead on the base and one lead on the inside of the antenna wire, the multimeter should have stayed at OL....which is what happened with the "new" cable I tried. But when I saw .00 on my stock cable, I figured it had to be an internal issue with the cable. Sounds like I guessed right.

How strong of a ground does the antenna base to fender need to be? I was thinking of adding a 12 gauge wire to one of the screws to a bare metal spot behind the fender, just to beef up the ground...but I don't know if I need to do that or if the screws through the base and into the fender will be enough.

 

[Saleen0679]

You don't need a big ground. You just need a good clean ground. You've already seen that you don't even need an an antenna ground to receive a signal, but it does help with the quality of the signal, noise rejection, weak signal reception, and so forth.

I'm not sure why you're still having problems with a different cable/antenna assy. unless something is getting grounded out when it's all put together.

 

[Fett]

Ok, after all this...it was the cable. Today I ran a new cable/base assy, and a nde antenna. Radio comes in great.

Well, I learned a lot about antennas.....which is really all I was looking to do. On to the next project....revisiting building a CCRM with relays to operate my two speed fan how it is supposed to work.