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Author Topic: r/c interfaced with sabretooth 2x25 question  (Read 1701 times)

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Offline rodmo1Topic starter

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r/c interfaced with sabretooth 2x25 question
« on: April 08, 2010, 09:19:43 AM »
I recently finished my RC lawnmower.  Right now it is very simple with a Futaba Attack AM 27 Mhz reciever and transmitter pair wired into the 2x25 motor controller.  I got to mow the lawn a couple times recently but have been very unhappy with the range of the vehicle.  Currently only reliable to about 20 feet.  Earlier today I switched off the failsafe switch #6 and tried it again.  This time the range was just as bad however, when out of range the mower went crazy.  I expected this but was hoping for better results.  This is my second transmitter...the first had only slightly better range.  Anyone have experience with this?  Do I have to buy a high cost transmitter for better results.  Through a Google search I read no other complaints regarding this controller.


Thanks
Rod

Offline waltr

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Re: r/c interfaced with sabretooth 2x25 question
« Reply #1 on: April 08, 2010, 10:10:37 AM »
You have a couple of things in combination working against you.

The transmitter (really the issue is in the receiver not the tranmitter) is AM which is very susceptible to noise and second the lawnmower's ignition produces huge amounts of RF noise. Get a pocket AM broadcast radio and listen while the engine is running.

Try a range test without the lawnmower's engine running. I'll bet the range is at least several hundred feet which is why no complaints on Google.

You could try adding noise suppression to the lawnmower's ignition and also move the receiver and antenna as far from the engine as possible. This should increase the range some what.

Using an FM transmitter/receiver should help as FM is as susceptible to noise. Also a higher quality receiver may help.

Offline rodmo1Topic starter

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Re: r/c interfaced with sabretooth 2x25 question
« Reply #2 on: April 08, 2010, 11:42:04 AM »
Thanks for the reply Waltr.  I have experimented with engine on versus off and there is no difference.  Could I be missing something on this radio package?  Tried all fresh alkaline batteries, various antenna configurations, reciever in enclosure versus out of enclosure and nothing seems to make a difference.  Just realized while typing this that I never tried running reciever off of its own power source so I will give that a try shortly.  It is safe to assume that these radio packages have a greater range then 20-30 feet right?

Rod

Offline waltr

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Re: r/c interfaced with sabretooth 2x25 question
« Reply #3 on: April 08, 2010, 12:10:53 PM »
From the very little I know about those RC systems the 27MHz ones are considered toys and may not have a much greater range than what you are getting. Most of the 75MHz RC systems I have experienced do have good range and can maintain control of an RC car further than it can be easily seen.

Antennas are very important in obtaining range with radio systems.
What antenna are you using on the receiver?
Where is it placed?
I it the proper length, not cut?
Do keep it away from any metal, probably best to go straight up to keep it away from the chassis, engine, motors, etc.

The receiver quality is also very important in obtaining range. It could be out of tune from handling and vibration. Do you have it padded?
Tuning a receiver is difficult without the proper equipment and knowledge so I don't recommend trying.




Offline Soeren

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Re: r/c interfaced with sabretooth 2x25 question
« Reply #4 on: April 09, 2010, 09:45:41 AM »
Hi,

27MHz AM was all there was in DK when I was a teen and there were some serious gear produced then.

I don't really believe that it should be as bad as 20' and with what have been tested, I would consider a slightly defect transmitter or receiver, as I assume you're supposed to control an airplane with it (so I'd guess on at least a 300' to 500' range).


I just found a manual for the 2E and 2F version of their 27MHz AM and here is a passage from that, under the heading "Performance Test and Mounting Precautions":
Quote
Make [transmitter] antenna as short as possible (in the case of FP-T2F, extend one section of the antenna) and extend the receiver antenna [fully] and attempt operation from a distance of 20m~30m [60' to 90']. Operation is normal if all the controls are functioning properly. Perform this test within a maximum of 5 minutes time. Never perform this test when the transmitter antenna is not mounted to the transmitter. Otherwise the transmitter will be adversely affected.
This tells us that even with the antenna down it should have a much larger range than 20', so clearly, either TX or RX is bad.
Bring it back to whoever sold you the set for a replacement.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

 


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