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leave Tx on with ant. down..why does this matter??

Old 09-05-2003, 03:12 AM
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bjp
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Default leave Tx on with ant. down..why does this matter??

I've read a couple of posts where people were talking about how they have left there transmitter on and then someone else will ask if the antenna was down. Just curious, but why does this matter?
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Old 09-05-2003, 03:15 AM
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Spaceclam
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Default leave Tx on with ant. down..why does this matter??

It sounds like a range check. you turn on the model and start the engine. you then collapse the antanna fully and walk away from it. you should get at least 100 feet before it starts to jitter, or if you have pcm, you recieve lockout.
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Old 09-05-2003, 03:51 AM
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Steve Guinn
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Default leave Tx on with ant. down..why does this matter??

Leaving the Tx on with the antenna collapsed can fry it.
Sorry for the technical jargon
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Old 09-05-2003, 03:57 AM
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Default leave Tx on with ant. down..why does this matter??

No I think he means when leaving the transmitter on for say burning in the electronics or testing them rather but not by range check.

When you leave a transmitter on for any period of time with the antenna fully collapsed it makes the module in the transmitter become really hot and can damage the radios effective range. Do not ever leave the antenna fully collapsed period when its on, always try to open the antenna as much as you can...

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Old 09-05-2003, 11:13 AM
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Default leave Tx on with ant. down..why does this matter??

The output circuit in the trans puts out the same amount of energy wether the antenna is up or down. when fully extended the antenna is the proper load to the output circuitry, when retracted you have an improper load causing the output transistor ( or fet or whatever) to absorb the energy it is trying to put out, hence the heat. If the transmitter is designed for it, it would not hurt to leave the antenna down, but since you dont really know how the trans was designed it is the safe bet to allways have at least some load on it (1 or 2 sections pulled out) when left on for more than a minute
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Old 09-05-2003, 01:55 PM
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Default leave Tx on with ant. down..why does this matter??

When the antenna is extended, the energy in the output stage is radiated as RF like it was designed to do. When the antenna is retracted, the SWR (standing wave ratio) goes way up and instead of radiating the energy, the energy is converted to heat in the output stage and causes excessive temperature rise and possibly causing failure. At the very least, the added heat will accelerate the failure rate. It is a prudent idea to never run with the antenna retracted more that a minute or two while doing your range test.
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Old 09-06-2003, 04:25 PM
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Default leave Tx on with ant. down..why does this matter??

hmm.. thanks for the insight, I actaully left my radio on for a whole day with antena down and i posted asking if the batteries were damaged, now i am worried that i hurt the tx itself. Is there any way to tell if it is damaged? How much range loss could i have posibly caused?
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Old 09-06-2003, 05:13 PM
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Default leave Tx on with ant. down..why does this matter??

i don't think you damaged anything. the radio stops drawing power at about 6 volts i think, just charge up the batt. as for the tx, there is no reason why low voltage would fry your tx. don't worry about it
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Old 09-06-2003, 08:28 PM
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Default leave Tx on with ant. down..why does this matter??

SpaceClam it's not the voltage, it's the power. It all goes into heat, which will kill an RF transistor. The only way to tell if you damaged it or not is to charge your battery plug it in turn it on and see if it works. Heat will always shorten the life of electrical components, it shouldn't outright kill it, but don't do it often. If it did manage to burn out the RF amplifier then you can have it replaced.
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Old 09-06-2003, 11:36 PM
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Default leave Tx on with ant. down..why does this matter??

Originally posted by bjp
hmm.. thanks for the insight, I actaully left my radio on for a whole day with antena down and i posted asking if the batteries were damaged, now i am worried that i hurt the tx itself. Is there any way to tell if it is damaged? How much range loss could i have posibly caused?
A high SWR will draw more current.
When I do a range check I keep the TX off,walk away to about 150 feet.
Then just do a fast check with the antenna retracted.
All my transmitters are peaked to full output so I try to be more aware of the SWR.
They supply no papers with the radio gear so maybe a phone call to the factory and ask if the TX has any type of SWR protection built into it
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Old 09-06-2003, 11:44 PM
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Default leave Tx on with ant. down..why does this matter??

Originally posted by Lynx
SpaceClam it's not the voltage, it's the power. It all goes into heat, which will kill an RF transistor. The only way to tell if you damaged it or not is to charge your battery plug it in turn it on and see if it works. Heat will always shorten the life of electrical components, it shouldn't outright kill it, but don't do it often. If it did manage to burn out the RF amplifier then you can have it replaced.
If you did some heat damage to the final it's best to replace it.
The driver stage is now not looking into the proper load that the final presents and if you continue to fly the plane you can blow out the driver stages.
Order a new final and the drivers.
If you know a local EE they know what SMT finals can take a beating and keep on going
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