d2ndkemper

I have an old AM radio in my 1/10 scale touring car (HPI RS4 /2 nitro). It has been working fine since I took it out of storage 4 months ago. Last weekend I was racing in the parking lot with my little brother and the car just takes off. I thought that maybe the batteries went dead or something so I checked them. They were fine, almost new. I put the car on the stand and checked all the radio functions. Everything was fine. I ran the car again and within 2 minutes it did it again.

What is wrong?

Do I need to buy a new radio? The guys at the track tell me I need to get an FM radio. Why are they better? They are more expensive and I never had trouble with my AM until now. Are the FM's more durable?

What should I do?

Your responses are appreciated.

Thanks,
Kemper

dbow

My Feedback: (1)

How are you checking your batteries?

Are you using alkalines with the battery holder that comes with the car?
Sometimes the batteries can shift and slip off a contact inside that holder. Its a hard one to see because the batteries appear to be fine in the holder. This happend to me before I went to a pack, I had to tape them in real good and tight with electrical tape. Dont put to much on though as it wont fit in the slot if the tape is to thick.

Its hard to say without seeing it but I would check the batteries again and check for anything else that could be causing a glitch in your radio.

AM is find for general parking lot bashing, if your in to racing you may want to check out FM. There might be some people that will support AM and bark at me when I say FM is stronger...lol

If I was racing I would certainly run a FM set-up and PCM on top of that for protection.

Dbow

d2ndkemper

I'm running alkalines in the stock battery holder that came with the car. I will check the springs and stuff like that to see what might be causing a problem with connection.

If the receiver goes out does it go completely out or slowly fade away with glitches?

I still don't understand why FM is better than AM. Can you help me to better understand or refer me to a website that compares the two? My AM has enough range to control the car farther away than I can tell what direction it is going.

I do race at the local track in the novice class but plan on moving up as soon as I do some more mods to my car to make it faster.

Thanks for your reply.

d2ndkemper

sorry ,
I forgot to mention I check them with the battery tester that came with the battery kit. It is not the most accurate method but it does show a difference between new and weak. These particular batteries I had in only had a few minutes on them.

Kemper

tbuchta

don't know if you have already found about the differences between the 2, its kinda hard to explain the differences without getting too tecnical but FM does not, I reapet does not have a stronger signal than AM, thats why you can hear a AM broadcast across many states on a road trip and you lose the FM station after getting so far. Also AM bounces their signal off a layer of the atmosphere so you could receive its signal in a valley or other side of a moutain or building, so what does FM have over AM? Signal clarity, an AM signal starts to degrade as soon as it is sent while FM considerably less and because of this FM is less likely to be screwed with by a stray signal like AM would. There is far more info about the 2 modulations but that is the short version, it really depends what you are using them for as to witch is better, the both have good and bad points, but for r/c FM is by far the better of the two modulations. If your looking for a reliable radio system FM is the way to go...for R/C anyway

Midget

i found out that am isent realy good if your running your car/truck fast

tbuchta

Yes that is right, an AM signal would not be as strong or as clear (due to degredation) as an FM would, so you would not get the quick responses you need at a higer speed.

gubbs3

My Feedback: (1)

If you are using the 4 cell AA holder that is most likely your problem. When the receiver batteries start to fade is does not go away slowly but rather you will get glitches. When your servos require that extra amount of power for fast movement they put enough strain on the batteries that their voltage drops below the minimum usefull level and it glitches often sending your servos in extreme directions. Replace your receiver batteries, or better yet buy a rechargable 5 cell pack with an appropriate peak charger. A rechargable pack can last up to twice as long as AA's and give your radio gear premium power right up until the pack dies. I get over two hours of perfect use with two high torque analog servos. I tried AA's before my new receiver pack came in the mail from backorder and they lasted only about 45 minutes before it started glitching.

R/C fan-addict

also with FM there are many different channels and with AM I believe there are only 3

smokingcrater

nope, am and fm use the same frequencies... You might be thinking of radios down on 27mhz, most of which are AM. (but again, they all use the same freq's down there also)

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