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Radio Check

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Old 03-21-2010, 11:32 AM
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ALO 111
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Default Radio Check

At what distance should a radio still work with antenna in? And should the battery voltage affect this?
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Old 03-21-2010, 11:56 AM
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Default RE: Radio Check

JR says 75 - 100 feet for most of their 72 mHz transmitters. In practice, I can usually go much further. The effect of battery voltage should be negligible assuming the battery is within +/- 10% of normal voltage.
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Old 03-22-2010, 01:42 AM
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Default RE: Radio Check

I am experiencing a massive loss of transmitter power when the battery voltage drops. I have in the past flown with the battery much lower and had no problems. I am using a Jr 2610 and when fully charged it reads about 10.4 volts. The warning comes on under 9 v but only once did this happen while flying and I landed straight away with no problem. Yesterday I flew at about 9.6 volt and nearly lost a plane that was still very close to me. With the battery fully charged my radio check seems fine 100 feet+ but drops to half this when the voltage is around 9.4.
What could be the problem?
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Old 03-22-2010, 01:57 AM
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Default RE: Radio Check

Another strange thing I let the battery run down till the warning came on , about 8,8 volt then put it on the Swallow charger for only ten min.at .6 amp > when I removed it after only ten min. the radio showed 10.6 volt but failed the radio check totally. But after been charged for a long time at the same .6 amp and showing the same voltage it seems fine.
Please help I am going insane!!
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Old 03-22-2010, 07:35 AM
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Default RE: Radio Check

It is not uncommon to see the voltage jump up after only a short time on the charger. That does not mean the battery is charged. If you check the voltage of the battery, under load, you will see the voltage drop sharply after only a minute or two. The load you put on the battery when checking the voltage is supposed to be consistent with the load put on by your Rx or Tx. A typical Tx load would be 200ma. If you just use a Multimeter and do not put the battery under load, you will get inaccurately high readings. Most Expanded Scale Voltmeters (ESV) have a dial that let's you set a load (.5a, 1a, 1.5a). 1a and above is used for LiPos and LithIons.

Depending upon the type of batteries you are charging, a safe charge rate is 1/10 of it's rated capacity. For example, a 1 amp hour battery (1000mah), would be charged at 100mah. Most Wall Chargers that come with your RC Radios charge at 60-150mah for 16 hours. Wall Chargers are good for NiCads and NiMh batteries. Wall Chargers charge at a constant Current rate and do not detect the voltage of the battery so you can overcharge the battery if you are not careful.

If you purchase one of the many Cycling Chargers, you will get more life out of your batteries and better performance. They charge in pulses, rather than constant charging and they anticipate when the battery will reach peak voltage so they do not overcharge. They have many settings to help you set the right charge for your batteries. You can Fast Charge or Slow Charge and you can Cycle the batteries. Cycling allows you to set up the Charge so that once the battery is fully charged, it will discharge the battery at the appropriate rate, recording the capacity of the battery or the time it takes to discharge, then it will charge the battery again. You do not do Cycling often, because it will eventually reduce the life of the battery, but whenever the battery does not seem to be giving you it's rated capacity, a Cycle is in order. It is also good to Cycle the batteries once in the winter time when they are setting on the shelf and not being used.
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Old 03-22-2010, 08:50 AM
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Default RE: Radio Check

Thanx for the advice,it answers a lot of questions. Do you think that it is possible that if lets say my battery( three years old) is falling under load(its a nicad) in other words displaying a high voltage but when put under load that the tx load put out a weak signal? I had it on the swallow charger now for 45 min at .6 amp and the charger indicated that it was full. Tx shows voltage of 10.9v but Tx still fails the test. I am just trying to understand if my Tx is faulty or could the battery cause this?
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Old 03-22-2010, 09:11 AM
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Default RE: Radio Check

When I have had Tx batteries fall below the safe voltage limit I have seen strange things with my servos. They move erratically and slowly, among other things when the voltage drops below 9v. If you are using NiMh batteries, they could be False Peaking the charger. I have seen that many times and had to reduce the charge rate to a much lower level. It is one of the reasons I use Eneloop cells, LiPo cells, or A123 cells instead of NiMh. Eneloop is a form of NiMh that holds it's charge much like LiPos and does not start discharging like conventional NiMh.

If you check your Tx batteries with an ESV set to .5a, you should be able to determine if the batteries are too low.
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Old 03-22-2010, 09:35 AM
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Default RE: Radio Check

3 years old? For the cost of a battery versus the cost of a plane, can I suggest you go ahead and replace the transmitter battery? I do them once a season or two anyways as a maintenance item.
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Old 03-22-2010, 09:51 AM
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Default RE: Radio Check


ORIGINAL: BarracudaHockey

3 years old? For the cost of a battery versus the cost of a plane, can I suggest you go ahead and replace the transmitter battery? I do them once a season or two anyways as a maintenance item.
I ought to be Shot I know its just time goes by so fast. I have had no problems with it so I guess I just forgot.I will replace it tomorrow I promise. Was just still trying to make sure the Tx is fine.
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