Model Boat Mayhem
Technical, Techniques, Hints, and Tips => Radio Equipment => Topic started by: Terry on August 09, 2014, 11:31:50 am
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Hi all, did a stupid thing yesterday. Left the lake with my Tx in it's Aluminium case, Antenna collapsed, and still switched on!! When I took it out of the case approx. 3 hours later it was all very hot. Have recharged the NiMH batteries, they seem OK. The Tx is a Futaba 2 channel 40mhz. I seem to remember reading somewhere that leaving a Tx switched on with the antenna down can do damage to the electronics, does anybody know how this would manifest itself? Would it be a sudden failure, or a slow reduction in operating range? I would hate to see my wifes yacht (it's her Tx) out of control in the middle of the lake.
Cheers, Terry.
P.S. I have just discovered that if I place my Tx antenna close to my PC speakers I hear a tone which changes with movement of the stick, does this indicate a healthy Tx????
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Terry
The noise on your speakers does indicate an output so there's reason for optimism, but I would do a range check before you use it again just to be sure. Hell hath no fury like a woman whose yacht stops working (and guess who'd have to paddle/wade/swim/row out to fetch it)!
Dave M
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P.S. I have just discovered that if I place my Tx antenna close to my PC speakers I hear a tone which changes with movement of the stick, does this indicate a healthy Tx????
That indicates that the insides of the TX still have something working, but, like Dave says, do a proper range check. Running the output stages of a transmitter into the wrong impedance (an effect of the wrong aerial length) can present the output stages with either the wrong voltages or cause too much current to be drawn, either is bad. Make sure that a pukka signal is still being broadcast before losing the boat on the water.
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Hi, I happened to leave my Skysport switched on with the aerial down for quite a while. Result was no range. The model shop asked if I was in the habit of leaving it switched on as I had burnt the circuit board and components where the aerial connects. I did manage to get it repaired by an electronic whizz kid and up to now it is OK. It is surprising how many people do collapse the aerial with the set switched on, the energy has to go somewhere, if not up the spout!! Where, back to the board with the resultant burn. Nemesis
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It does demonstrate very poor circuit design when the output stages are not designed to withstand normal, foreseeable changes in output impedance. Most RF equipment I've ever dealt with is designed to take a total mismatch with 100% power reflected. (including 500W class A RF power amplifiers)
I guess they are intent on shaving another few cents from the ex-works costs.
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Hi guys,
Thank you for the replies. Did a range check, it's kaput. Good news is I now get to do some online shopping for a new Tx. I always find shopping for modelling stuff to be very enjoyable!!
Cheers, Terry.
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Terry
Not that it would be terribly cost-effective for a two channel Tx sent from Austria, but I've used this guy for repairs and servicing before and he is very good indeed http://www.modelradioworkshop.co.uk/servicing (http://www.modelradioworkshop.co.uk/servicing) UK-based Mayhemmers should take note.
Dave M
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Hi Terry
I know this doesn't help but 2.4ghz sets have no extending aerial and will only drain battery, but all bats do not like being fully discharged especially LIPO's
Hope you get it all sorted and I bet you don't do that again in a hurry
Lionel