Antenna length?
 

I have read somewhere that the antenna wire length on the receiver is an exact size depending on the frequency etc.
Whilst trying to push my antenna wire through some flutes in a coroflute spit-fire I am building, I think I may of broken off the end of the antenna wire. I am not exactly sure as I cannot see down into the flute to see if there is any part of the antenna still in there.
If i did break any off it would only be a small length not more than an inch or so as the antenna wire still seems as long as it should be.
Is this a problem and should I worry about it??

TIA,

Troy.

Antenna length?
 

an inch shouldnt be a problem, although it is not recommended to cut any length from the antenna. its better, but not good to fold it rather than cut it..Rog

Antenna length?
 

Thanks Rog,
An inch was only a rough guess. What if its actually more than an inch, say two or three inches? Would this matter? Is there anyway to tell how long it should be so I can measure it and check?

Troy.

Use the Force, Luke
 

Well, here's the real issue...

(and I am not a radio expert)

Why not just replace the antenna with what you KNOW is right, and avoid any risk to anybody or their property? Then you don't always have it in the back of your mind... "Is the range the same", etc..

I've flown with non-standard antenna lengths myself, and got lucky, but I wouldn't recommend it to anyone else.

Antenna length?
 

Because I do not know what is the right length and I do not know how to replace the antenna. I dont want to go pulling apart the receiver to replace an antenna unless its a straight forward job.

Ok...
 

It's a no-brainer...

Just look at the manufacturer's web site, or call their tech support department and find out.

Antenna length?
 

Yet another reason to avoid Spads. :p (I'M KIDDING! It's a joke, so don't start flaming me.)

Measure your antenna. They are all right around 39" if I remember correctly. (Don't have a Rx handy.)

The length of our antennas is calibrated for 72 MHz. Our individual 'channels' are spread out across that frequency range. I don't think losing up to three inches will make a significant difference, but less is better.

Most importantly, do a range check. With Tx antenna collapsed, you should still have decent control of the control surfaces from 100 feet away. If you do, you should be fine.
Dennis-

Antenna length?
 

Anything from 39 to 41 inches will work fine. You won't be able to tell the difference between those lengths.

Antenna length?
 

As Dennis pointed out, do a range check! That's the #1 and only sure way to know. And do it engine off and then with the engine running. If you see a noticeable difference in range, you've got a problem.

Some RX's are more sensitive to antenna length than others, but in general a couple of inches shouldn't make a difference in the real world. I have an FMA RX with an antenna that's been shorted much more than 3" and it's fine. But FMA RXs are good that way, other makes may not be. And I've used other RX's with slightly shorter antennas with no problems.

Antenna length?
 

Troyp,

Mate, if you haven't got an MAAA recognized R/C radio repairer/certifier in your vicinity to check your gear, e-mail me direct.

Remember also, we use the 36 mhz band in OZ.

Antenna length?
 

Damn! Once again I'm guilty of not looking at the poster's location.

Sorry Troy, but any info given regarding antenna length is probably wrong. :rolleyes:
Dennis-

Antenna length?
 

DBCherry,

I figured you didnt realize that I was from OZ.
As my antenna length is only 36 " I decided to do a range test. I walked around 50 yards from my plane and with the TX antenna collapsed and everything worked fine. Then I did the same at 60, 70 and then 80 yards away. I figured at 80 yards with the antenna collapsed I am still going to get normal range with the antenna up and the plane in the air.
(I could hardly see the plane on the ground at 80 yards away), My conclusion is that the antenna must be the correct length and did not break when I thought it did.

Thanks again for the help,

Troy.

Antenna length?
 

Certainly 80 yards with the tx antenna down is plenty of range. Btw, did you do it with the engine running as well? It's always possible the wire is broken but touching inside, and will only show up a shortened range with the engine vibration.

As I've said, I've had antennas get cut more than once and not noticed any change in range in tests, so I'm not surprised your range checked out so well, regardless of weither the antenna was shortened or not.

Antenna length?
 

Kirk,

No the motor wasn't running whilst I did the range check. I will do it again with the motor running and see how it goes.

thanks,

Troy.

Antenna length?
 

STill, even without the engine running, that's good news Troy. Sounds like you're okay. (But try it with the engine.)
Dennis-

Antenna length?
 

80 yards with the antenna down is incredible....

I can only go about 1/3 of that distance with all these Avistar/Superstar Selects with the Futaba Skysport...They start twitching after 30 steps away... :rolleyes:

I've flown my airplane with the antenna down (Airtronics) and never had a glitch, so I'm thinking there is something going on with all those Futaba's!!

You're good!!

It's not that hard to tell if your antenna broke...It's VERY hard to get a clean cut unless you use a wire cutter. If you broke it or ripped it, the end will be stripped, messed up, or just noticably different.

The original antenna's tip is a very clean smooth cut...

Antenna length?
 

Brian,

I was guessing that the antenna wasnt broken from the beggining as the end of the antenna was a neat straight cut and not ripped.

Antenna length?
 

Troyp,

What will happen if the antenna has been shortened is a loss of range when flying.

Another thing to watch out for is the outer covering of exposed antenna wire perishing and breaking away over time, exposing or taking lengths of the inner wire with it.

Glow Fuel exhaust and UV help this process. They combine to make the outer covering very brittle.

It pays, from time to time, to send your Rx to an authorised repairer and have him renew the antenna wire as well as check the fine tuning out.

I once had problems with a near new Hitec Rx. Kept loosing signal then regaining, even when flying close by. It did not happen with other models I was flying that day, so that ruled out interference or the Tx.

A subsequent calibration test of this particular Rx, found it to be way off frequency tune. Probably had been from the factory.

Antenna length?
 

Just to throw in a mathematical point of view:

Length is determined by frequency i.e. 1/72MHz (frequency is the inverse of time) * the speed of light (186,000 miles per second) * 5280 (ft in a mile) * .25 (if they are using a 1/4 wave, can be .125 for 1/8 wave ant.) *12 (inches per foot) will give you 40.92 inches. If you did it for 73 MHz it would be 40.359 inches.
This is of course if they are not using a "loaded" ant. or something special.

Just food for thought...

-Judson

Antenna length?
 

I think you should just get one of those delta wing antenna's you see on cars and bolt it on that sucka and have at it :)

Or better yet... one of those cell phone enhancer thingies for only $9.95... i'll bet that would work good.