Poor AM reception

I'm hoping all the knowledge on this forum can focus on AM radio for a moment. While the amplified tunes from my FM or CD are really great, all I really want to do (day-in, day-out) is listen to talk radio.

AM reception is my ISSUE.

I'm putting a known-working Pioneer head unit in my 1989 F350 work truck. I connected it to a new out-of-the-box Pioneer speaker and to the antenna. Using the accessory key position (the truck engine isn't even on) the AM radio puts out pure static. So much it drowns out the am radio talk. FM radio is OK. I have the antenna well-grounded.

Can someone point me to a solution? Thanks. Dave

Rule of thumb is if you have FM reception and no or poor AM reception, replace the antenna. If you have AM reception and no FM reception, replace the tuner. My advice is try another antenna.

-------------
the12volt • Support the12volt.com

Maybe look into getting an amplified antenna.

sS

-------------
RTFM

Disconnect the negative battery cable. Use a digital meter to measure the ground of the radio with the antenna unplugged. Measure the ground of the antennas outer shield to ground. Both readings need to be less than 0.5 ohms or you will have a problem. If all tests OK try using a test antenna to see if the reception improves. If it does, replace the antenna. If not you may need a new radio. Even brand new ones sometimes have a problem.

-------------
sparky

I'm pretty sure that almost all aftermarket radios are poor am radio receptors, gues it has something to do w the way they are made, more of the circuitry id dedicated to fancy graphics, reading wma/mp3 files etc. and less of an emphasis on am reception. I was told that by a company rep, and i have seen it repeatedly, am always suffers compared to a factory radio.

Good morning guys, thanks for the responses...I would have replied sooner but I had some trouble with the forum recognizing me. Don't they know a VIP when they see one? Yuck, yuck.

Anyway, thanks again and I'll try the ideas suggested. Here are the questions related to that:

1. spookiestylez....I've read about the "enhanced antenna's...I'm always on the search for newer and better...are these really better? The ones mounted horizontally to the inside of the windshield?
2. sparky....Re: "Use a digital meter to measure the ground of the radio with the antenna unplugged..." Do you mean: is the radio's ground wire actually grounded...how else would I measure the radio's ground's effectiveness? And re: "Measure the ground of the antennas outer shield to ground." Here, do you mean the antenna pole itself, or the shielding on the wiring?

Again...thanks. Dave

FM runs through the mast of the antenna while AM uses the base, or the grounded part of the antenna. check to see if the base of the antenna that is actually touching the fender has rusted or isn't getting a good connection. this is why using a DMM helps. something that can help is if you're sure the antenna is getting good connection to the fender, connect a ground strap from the fender to the negative battery terminal. also, you can strip back a little of the insulation on the antenna coax behind the radio and attach a length of wire around the braided wire on the coax and then connect the other end to chassis ground. this has worked for me in the past.

-------------
Whatever you do, DO NOT let the white smoke leak out of the wires.....

I'm sorry to disagree with you flowgalant, but the antenna mast and ground plain both receive the transmission signals for AM and FM. Antennas are optimized for FM reception because it has better sound. Dave. Use a meter to measure the grounds. First disconnect the antenna cable from the back of the radio. Set your meter for a low resistance scale. Place your black probe on a piece of the vehicle chassis that is bare metal. It must be one the car body and not on a steel bracket in the dash. Bare a small section of the radio's ground wire close the radio. Put your red probe on the bare wire. The meter should read less than 0.5 ohms. Do this test with the ignition off. Next move your red probe to the antenna cable. It has a center pin and a outer metal sleeve on the end where it plugs into the radio. Put your red probe on the outer sleeve. Again your reading should be less than 0.5 ohms. If either the radio or the antenna has a poor ground, you must repair the ground where it terminates and not in the shielding as mentioned elsewhere. The antenna grounds where it is mounted usually. Clean up any metal to insure it has a good ground. The ground of the antenna is vital. The fender which it is grounded to receives half the incoming signal, the other half being received through the mast. A final measurement should also be taken. Place your red probe on the antenna mast and the black on the center pin of the antenna lead at the radio. You should again get a reading of less than 0.5 ohms. Post your results if all checks out OK and I can give you more things to check.

-------------
sparky

really, sparkie? so technically i could wrap a peice of wire around the outside braided wire part of the coax and then insert the other end into the center hole in the receiver and get FM reception? didn't think so. again, the mast, which is the center conductor in the coax, is for FM and the base, which is the braided wire surrounding the center part, is for AM. ever grounded the braided sheilding the chassis ground and got better FM reception? i bet not, but i bet AM was better.

-------------
Whatever you do, DO NOT let the white smoke leak out of the wires.....

You don't understand what I mean. Your antenna is divided into two circuits. One is the center lead of the antenna coax which terminates as the antenna mast. The other part is the shielding of the antenna coax which terminates as the base of the antenna. The base of the antenna must be grounded to the fender or another large portion of metal in the body. The antenna mast receives one half of the radio transmission signal, either AM or FM. The other half of the signal is received by the ground plain of the antenna, which is the fender or large metal part of the body. The properties of AM and FM differ. Most manufacturers only want one antenna on their vehicle, so the antenna was designed to optimize FM reception, because it has a better sound quality and is more popular. Therefore the antennas ability to recieve optimum AM band signals is compromised. This is why the average antenna mast is 31 inches long. If you short out the center antenna lead to the shielding you will still get some FM but no AM. Because the antenna is optimized for FM, any fault in it will affect AM band far worse than FM. As for aftermarket radios not being designed with AM reception in mind, that would only apply to low end equipment. Any quality brand name deck will be able to pull in AM band stations just as well as a factory radio, provided the correct antenna adaptors are used if any are required. Many manufacturers are using unique style antenna lead tips and if sub-standard adaptors are used, you again will compromise the antenna and AM will be affected more than FM.

-------------
sparky

the12volt wrote:

---

Rule of thumb is if you have FM reception and no or poor AM reception, replace the antenna. If you have AM reception and no FM reception, replace the tuner. My advice is try another antenna.

---

Why are you making this difficult for the poor guy. I have done a whole lot of poor AM problems and the above advice is right on the money. Try a new antenna (they are cheap) and see what happens. You can probabally return it if it doesn't end up curing the problem anyway.

I am not in the habit of just throwing parts at a problem. I figure out what the problem is and fix it correctly. If the antenna were replaced without knowing the importance of the connections and a good ground then he may never resolve the AM noise problem.

-------------
sparky

This is why I love this site.  Everytime I come here I learn something new.  Thank you sparkie I never knew that about antennas.

-------------
Cause I'm So white and nerdy...
First Class Certi-fried installer

You are very welcome. Even us old guys still learn something now and then.

-------------
sparky

Gee guys...I didn't realize you cared so much for poor lil' ol' me. Seriously...thanks for the education. Now...more dumb questions to ponder:

1. Re the ground/the coax shielding...if it terminates at the antenna base and becomes one with the fender, etc, then the only wire going into the radio's antenna female receptacle is the coax connected to the antenna mast? Or does the ground make the fender connection then lead on to the radio case?
2. No one's commented on the "enhanced antennas" yet. The ones that are sort of hidden up above the rear view mirror. Are they as good or better than the solid mast? If I end up buying a new antenna, I want to get the best possible choice.
3. Besides what's been said, are there any additional layman enhancements I could do...like if the fender is good, why not just continue that ground wire connection right back to the battery ground as well?

No time for sleep boys, keep those thinking caps on.

Thanks again! Dave

1. Yes, the coax runs from the antenna to the radio. Coax means there's two conductors, the inner, and outer. Since the mount provides a ground, it is referenced back to the radio chassis where it makes contact. That's why you can power up a radio without the ground wire connected with no apparent problems at low volumes.

2. These hideaway antennas can be decent for FM reception as long as there's no metal in the way. However, AM reception is horrible- expect a lot of alternator whine.

3. Yes, there's nothing wrong with this, as you want the mount to be as good a ground as possible.

-------------
My ex once told me I have a perfect face for radio.

i understand what you're saying now, sparkie. the only thing i was saying is that one reception, being either AM or FM, doesn't need the other in order to operate. example, you can take a radio and unplug the antenna completely, no reception, right. ok, take a length of wire and strip back one end and insert it into the center female antenna recepticle on the radio, now there's FM. absolutelt nothing is connected to the AM side or the radio chassis. grounding the braided sheilding on the antenna coax just provides a better ground than relying on the fender itself which could have rust/corrosion on the mounting bolts, etc.

-------------
Whatever you do, DO NOT let the white smoke leak out of the wires.....

I didn't even bother reading any previous replies so if I repeat anything thats why.

First off...AM sux....yes..it SUX....get satellite if you like talk radio....BUT.....

If you want AM you must realize the MAST of the antenna is for FM..the GROUND is for AM. If your AM is not satisfactory..try this..Take a regular mast antenna and plug it into the deck. Ground the BASE of the antenna. If you have AM it is a problem with the antenna or cable in your truck or the mast is shorted or base is open..if you don't have AM..it is a problem with the deck.

No rocket science or hours of technical BS needed..it is elementary....thats it.

If you have anymore to add it falls on deaf ears.

-------------