SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Feb 02, 2006, 02:13 PM
uhhh....this thing on?
skyking1231's Avatar
Long Island, NY USA
Joined May 2005
1,655 Posts
Discussion
Fact or Fiction ?

Can you damage a transmitter by turning the power on without the antennae in? Obvioulsy you wouldn't fly with out the ant. But just for tesing stuff on the ground. I was told many years ago that you can damage the radio. But want to see if someone here knows.
skyking1231 is offline Find More Posts by skyking1231
Reply With Quote
Sign up now
to remove ads between posts
Old Feb 02, 2006, 02:18 PM
Go Navy!
maverick06's Avatar
USA, PA, Media
Joined Apr 2005
905 Posts
you cannot damage the tansmitter... you could damage the aircraft haha

every transmitter i have opened up (half dozen or so). the antenna is just screwed into a wire. no problems with unscrewing it. If it is glued in place or directly soldered to the board you may be in trouble. I had a pistol transmitter for an rc car and inorder to stow it away in the box you had to take the antenna out.

I cant see a problem with it.

Rick
maverick06 is online now Find More Posts by maverick06
Reply With Quote
Old Feb 02, 2006, 02:18 PM
Registered User
Staffs, UK
Joined Nov 2003
10,561 Posts
You certainly can damage some Txs but only if you have them on for hours with no antenna. It's the same as not extending the antenna. I'm not sure why anyone would go to the trouble of actually removing the antenna rather than just not extending it though.

See the discussion in "Range Check" here : http://www.rcgroups.com/forums/showthread.php?t=472733

It's also been discussed many times in the "Radios" forum.

Steve
slipstick is offline Find More Posts by slipstick
Reply With Quote
Old Feb 02, 2006, 02:22 PM
S.A.D. member
ivanc's Avatar
United States, TX, Round Rock
Joined Dec 2004
9,422 Posts
Steve, some trannies have rather long antennas even when it's fully collapsed - my Hitec Flash 5X for instance - it doesn't fit in my tranny carrying case with the antenna on so I have to remove it every time before putting the tranny in the case. The Eclipse, Optic and Prism have shorter antennas when fully collapsed and fit in the case without having to remove it.

Ivan
ivanc is offline Find More Posts by ivanc
RCG Plus Member
Old Feb 02, 2006, 03:13 PM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
13,406 Posts
I remember seeing an article in a model mag, (quite a few years ago), where it was recommended to do any servo setup tests at home with the aerial removed.

And not to leave the tx on for long with the aerial down, (collapsed), as this could cause the output stage of the tx to overheat, because of something to do with the output stage is tuned to the full aerial length, and a collapsed aerial changes the circuits impedence.

Must admit I don't know much about electronics, BUT, my ederly Futaba tx does get a 'hot spot' on the back of the case if on with the aerial down, but not with the aerial up. It might just be older tx's used transistors output stages that were liable to overheat.
eflightray is offline Find More Posts by eflightray
Last edited by eflightray; Feb 02, 2006 at 03:31 PM.
Reply With Quote
Old Feb 02, 2006, 03:22 PM
Gotta have more cowbell!!
MTwallet's Avatar
Clawson, MI USA
Joined Sep 2002
2,169 Posts
To the best of my knowledge on this subject (which is very little)

YES, you absolutely can damage some Tx's by having them on without the antenna extended or not installed at all.

The Tx's would be those that use a module for the RF transmission like the Futaba 9C, Hitec Eclipse, etc. With these radios, if you need to turn them on for any length of time without an antenna or the antenna collapsed, you should remove the module from the Tx otherwise it could overheat and fail.

If you are setting up a plane, you can usually extend about 12-18 inches of the antenna and this should be enough for the module to stay cool.

If you do not have a Tx with a module, you should still at least remove the crystal to prevent the Tx from transmitting RF. This also saves on the battery if you are using your Tx with a flight sim or something.


MT
MTwallet is offline Find More Posts by MTwallet
Reply With Quote
Old Feb 02, 2006, 04:00 PM
Sponsered By My Wallet!
Minimole's Avatar
Colwyn Bay, North Wales, UK
Joined May 2004
5,559 Posts
What about when youre using a sim?
My spare TX is on for a while at time, and I dont have the antenna screwed in or anything. Dont have the crystal in either...
Minimole is offline Find More Posts by Minimole
Reply With Quote
Old Feb 02, 2006, 04:07 PM
Gotta have more cowbell!!
MTwallet's Avatar
Clawson, MI USA
Joined Sep 2002
2,169 Posts
Quote:
Originally Posted by Minimole
What about when youre using a sim?
My spare TX is on for a while at time, and I dont have the antenna screwed in or anything. Dont have the crystal in either...
Remove the crystal or module and you should be fine.
MTwallet is offline Find More Posts by MTwallet
Reply With Quote
Old Feb 02, 2006, 05:54 PM
FREEDOM IS NOT FREE!!
ronmar1's Avatar
Knoxville Tyson, Tennesse, United States
Joined Feb 2004
564 Posts
I posted this in an earlier thread along the same lines. Since the question is ask again I'll just copy my post here;

Being an old Radio Tech from the Army, let me assure you that operating a TX with the antenna down, can cause serious damage to the final transisters in the radio. Leaving the antenna down causes a build up of standing wave ratio or SWR . Simply put that is when the radio signal does not properly radiate into the atmosphere so it builds up in the final output amplifiers. For a radio whether it be a TX or RX, it must have the proper legnth of it's antenna cut to match the frequency waves of the radio. Ask any Ham radio tech about operating a radio with out an antenna. The damage will be done in seconds.

How ever the build up of heat in the finals of a RC transmitter would be slow and not near the extent of a more powerful CB or Ham radio.

Range checking with the antenna down usually only take a few seconds and there fore doesn't significantly over heat the finals of a RC TX. If you are leaving the radio antenna down during long term opperation it could cause damage.

Ron
ronmar1 is offline Find More Posts by ronmar1
Reply With Quote
Old Feb 03, 2006, 12:01 PM
phillyphly
e-guru's Avatar
United States, PA, Philadelphia
Joined Sep 2005
1,223 Posts
Quote:
Originally Posted by Minimole
What about when youre using a sim?
My spare TX is on for a while at time, and I dont have the antenna screwed in or anything. Dont have the crystal in either...
Typically when you are using a sim, power is not being sent to the antenna. In fact, on my JR radios, you plug sim cable into D.S.C. and just enough power is drawn to recognize stick positions (this plug's original function is to direct test servos on the ground).
e-guru is offline Find More Posts by e-guru
Reply With Quote
Old Feb 03, 2006, 01:45 PM
Registered User
Staffs, UK
Joined Nov 2003
10,561 Posts
Quote:
Originally Posted by e-guru
Typically when you are using a sim, power is not being sent to the antenna.
That's typically only true for JRs. Some others are o.k. *IF* the cable is wired correctly. For most (Futaba/Hitec/Airtronics etc) removing the crystal is the only safe thing to do.

No crystal (or module), no RF, no damage....guaranteed.

Steve
slipstick is offline Find More Posts by slipstick
Reply With Quote
Old Feb 03, 2006, 02:05 PM
Intermediate Multi
Trisquire's Avatar
Columbus, OH
Joined Mar 2005
3,294 Posts
What if I've left the crystal in for a year of simulator flying? If the radio range checks OK, am I good to go?

Regards,
Tom
Trisquire is offline Find More Posts by Trisquire
Reply With Quote
Old Feb 03, 2006, 02:48 PM
Trapped in California
foamflyer's Avatar
United States, CA, Arcadia
Joined Nov 2003
1,857 Posts
Mybe the Mythbusters can tell us.....
foamflyer is offline Find More Posts by foamflyer
Reply With Quote
Old Feb 03, 2006, 04:42 PM
Noob Extraordinaire!
flyinhawaiian968's Avatar
Hillsboro, OR
Joined Nov 2005
183 Posts
I can verify that two separate JR radios (my Max 6 bought in 1990, and my neighbor's new SX600-or something like that) do not transmit while plugged into FMS via the usb sim cable. This was tested with a frequency counter. You also cannot use the sim cable if the power is turned on at the transmitter, same goes for buddy cables between the two radios.

I am more than familiar with transceivers going out due to bad antennas, and having no antenna is even worse. Basically, the power output from the transmitter section has nowhere to go but back into itself, which heats up the final transister (what we call finals in the radio world), but I cannot see this happening in a matter of seconds, or even minutes, with such a low power output from our transmitters. Assuming the radio puts out a maximum power level of 750mW (what's specified as the output power of the JR XP6102). At such a low power level, it would take quite a long time to actually burn the final out, but not impossible.
That said, it clearly states in that same manual to turn the power on WITHOUT THE ANTENNA UP to do a range check! If JR feels this is okay to do to their own equipment, why question it?
As for your question, Tom, I'm sure if it range checks according to the procedure in your manual, it'll be just fine to fly. And, if it's a JR, you haven't done any damage at all since its never actually transmitted during that period!
Most of the players in the r/c industry build quality equipment, and I'm sure they wouldn't allow a unit to be produced without being able to handle this type of abuse. If they did, they would have thousands of units being returned yearly for repairs, and they probably wouldn't be in business too long!

Chris
flyinhawaiian968 is offline Find More Posts by flyinhawaiian968
Reply With Quote
Old Feb 04, 2006, 03:39 AM
Registered User
Staffs, UK
Joined Nov 2003
10,561 Posts
Quote:
Originally Posted by Trisquire
What if I've left the crystal in for a year of simulator flying? If the radio range checks OK, am I good to go?
Yes, in my experience they either stop working completely or are fine. Some transmitters never seem to fail however much you abuse them and others die very quickly.

Steve
slipstick is offline Find More Posts by slipstick
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Idea CBA LiPOly Capacity Decay - fAct or Fiction? everydayflyer Batteries and Chargers 5 Jul 24, 2005 02:07 PM
Stock: Fact or Fiction..... Geoffrey109 Micro Helis 0 Nov 26, 2004 09:26 PM
Razor Fact Or Fiction? mike3976 Power Systems 9 Oct 26, 2003 05:12 PM
LI-PO Fact or Fiction? gbruce Electric Ducted Fan Jet Talk 4 Oct 24, 2002 01:48 PM
Kyosho F16, Fact or Fiction? stuart warne Electric Ducted Fan Jet Talk 20 May 31, 2002 12:49 AM