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Futaba sais don't turn on Tx with antenna collapsed?!?

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Old 11-14-2002, 02:35 AM
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Joe B.
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Default Futaba sais don't turn on Tx with antenna collapsed?!?

Here's a snippet from their website under the 9C FAQ section:

When I am using my radio for programming, setup within my house, experimenting, etc, is there anything special I should do?


You should ALWAYS extend your antenna at least the bottom or first segment when turning the radio on with a module in place. If left in the radio with the radio on at your work area with the antenna collapsed for more than short intervals, the module will be unnecessarily exposed and may shorten the life or even immediately damage the module/transmitter.


I've always kept my antenna down on my other radios, but then again that may by why my Radiant 6P died and I'm now the owner of a 9C. Is there any real-world experience of damage from this?
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Old 11-14-2002, 02:48 AM
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Default Futaba sais don't turn on Tx with antenna collapsed?!?

I don't have any experience with damage, but on my 9C I always pull the bottom section of the antenna out as directed. I'd do what they say. Better safe than not be able to fly.

Mike
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Old 11-14-2002, 03:09 AM
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Ed
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Default Futaba sais don't turn on Tx with antenna collapsed?!?

Sure; It should be common knowledge, that in order for the final RF amplifier in your Tx to be properly "loaded", that the antenna should be extended. A collapsed antenna provides an improper load, and the final amplifier, in time, will self destruct.
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Old 11-14-2002, 03:15 AM
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Default Futaba sais don't turn on Tx with antenna collapsed?!?

I have heard of this problem but have never had it happen to any one I know. I extend mine also better to be safe than sorry.
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Old 11-14-2002, 03:26 AM
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Default Futaba sais don't turn on Tx with antenna collapsed?!?

So does this mean that I have to extend the first segment when I range check my 9C ? Probably have to walk more than 100 feet now as I always range check with the antenna totally collapsed.

Funny that this precaution was not mentioned at all in the 9c manual.........
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Old 11-14-2002, 04:08 AM
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flatfour
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Default Futaba sais don't turn on Tx with antenna collapsed?!?

Well if you are just fooling with the programming the solution is easy. Pop the module out
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Old 11-14-2002, 11:48 AM
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tinman
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Default .

it is my understanding that range checks should always be done with one length of antenna out,,,,,and that is how i range check,,,,,,standby.......will most likely hear more on this
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Old 11-14-2002, 02:41 PM
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rajul
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Default Re: Futaba sais don't turn on Tx with antenna collapsed?!?

Originally posted by Joe B.

You should ALWAYS extend your antenna at least the bottom or first segment when turning the radio on with a module in place
Which is the "first" segment of the antenna ? Is it the segment with the smallest diameter ? Or is it the segment with the second largest diameter ? Thanks for clarifying..................Mike
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Old 11-14-2002, 03:02 PM
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Default Futaba sais don't turn on Tx with antenna collapsed?!?

I posted about this just a couple of days ago in the Futaba section after leaving my TX on for 8 1/2 hours with the antenna fully collapsed http://www.rcuniverse.com/showthread...95&forumid=150 .

It is my understanding that range checks should be performed with the antenna collapsed, anything much longer than that timewise and it should be up at least the length of one segment..
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Old 11-14-2002, 03:27 PM
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Default Futaba sais don't turn on Tx with antenna collapsed?!?

I don't know what the inside of the 9 looks like, but with a warning like you say, it is probable that there is no connection from the RF amp to the antenna until the largest section is pulled up to make contact. This has been done by some manufacturer in the past, but I do not remember which one. With the 8U, there is always connection.

Les
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Old 11-14-2002, 03:47 PM
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Default Futaba sais don't turn on Tx with antenna collapsed?!?

A range check with the antena extended doesn't really serve the purpose very well.
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Old 11-14-2002, 08:06 PM
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Ed
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Default Futaba sais don't turn on Tx with antenna collapsed?!?

Just keep it reasonable guys. When you range check with your antenna collapsed, keep the test brief. If you are going to sit down with your Tx and play programmer for a while, extend it.

Don't read into it a big problem. I'd say, that if you kept your collapsed antenna range checks under 3 minutes, that you would never develop a problem. At least, that's the way that it has turned out for me over the last 42 years.

GeeBeeJim
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Old 11-15-2002, 05:17 AM
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Default Range check

There is nothing mentioned in the Futaba Frequently asked questions website about collapsing the antenna for a range check although that's the way i've always performed it. Now I just simply walk farther out to perform the range check with my antenna extended....hasn't let me down yet.
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Old 11-15-2002, 05:32 AM
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Default Damage

I don't know about the 9CAP, but I have damaged a 9ZAP by leaving the antenna down. It would still transmit just fine but my range was reduced some. Never really noticed anything in flight but it did show up on ground range checks. I sent it to futaba and they fixed the module. The ZAP manual mentions this issue, but it is very brief.

The ZAP (I assume the CAP is similar) uses a leaf spring under tension to make contact to the antenna. I believe contact is always made even if the antenna is fully collapsed, but I could be wrong.

The unmatched impedance of a collapsed antenna causes feedback into the TX output transistor. This will cause the transistors to heat up. If they get too hot they will suffer damage. The damage doesn't happen instantaneously as it takes awhile for the transistors to heat up. Short periods with the antenna down (three minutes mentioned before) should be fine.
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Old 11-15-2002, 06:34 AM
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Default Re: Damage

Originally posted by MonkeyBoy
The ZAP (I assume the CAP is similar) uses a leaf spring under tension to make contact to the antenna. I believe contact is always made even if the antenna is fully collapsed, but I could be wrong.
The 9C doesn't use a leaf spring. I also believe that the 9C module is not as sensitive to damage compared to the 9Z synthesized module. Anyway, I'm still extending my antenna to be on the safe side.
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Old 11-15-2002, 08:41 AM
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Default Re: Re: Damage

Originally posted by rajul
I also believe that the 9C module is not as sensitive to damage compared to the 9Z synthesized module.
And what on Earth would lead you to believe that??
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Old 11-15-2002, 10:52 AM
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Default Futaba sais don't turn on Tx with antenna collapsed?!?

Hi MikeL, I can't say for sure but it is something inferred from the Futaba 9Z FAQ http://www.futabarc.com/faq/faq-9z-q243.html that the FSS module is PARTICULARLY sensitive to this type of damage. But again, I could be wrong............
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Old 11-15-2002, 11:02 AM
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Default Futaba sais don't turn on Tx with antenna collapsed?!?

I fly JR 10X and they also say to us to connect the antenna, as to do with the Transmitter module get to warm and get damage then you get reduce range until you get no range....

So the antenna is used to dissipate the heat, I guess it's similar on the Futaba.

Daniel D.
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Old 11-15-2002, 03:40 PM
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Default Futaba sais don't turn on Tx with antenna collapsed?!?

What Mr. Lynch said about sums it up. Keep the range test with a partial extension to minimum. The radio may or may not have current limiting to the final amp but finals can and do fail and the life can be shortened overall from the increased current dissipated in the final from an unmatched output . Why tempt fate ?
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Old 11-15-2002, 04:58 PM
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Default Futaba sais don't turn on Tx with antenna collapsed?!?

Thank you Sweetie.
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Old 11-16-2002, 04:55 AM
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Kevin Greene
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Default Futaba sais don't turn on Tx with antenna collapsed?!?

The RF amplifier (output transistor) gets too hot without an antenna load on it. With enough abuse you could eventually fry it----It could even give up the ghost while flying if weakened enough. You'll never know when.

Buy a DSC cord and use it!!! The final RF amplifier is bypassed when the DSC cord is being used. TX battery drain is reduced too. Many modelers will have their TX on for hours while setting up a plane. Bob Violett lost a jet due to a faulty TX module with a fried amp. Bob now uses one module for his tinkering in the shop if a DSC cord is not handy and a separate module for flying.

Normal range checks that are completed quickly will not harm the output transistor. It is the prolonged antenna down use that will get you in trouble.

Kevin
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Old 11-16-2002, 11:44 AM
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Default Futaba sais don't turn on Tx with antenna collapsed?!?

I'm guessing if I want to setup a model without the need to trim just yet I can remove the module and go through all the menus? Then when setting up the trims/epa/etc. i can just pull the antenna out?
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