When i totaled my alpha 60 i gutted all of the electronics so i could use them in another Alpha 60. When i was removing the receiver i noticed that the antenna was tied in a tight not at the end of the antenna tube. So i simply cut the not off to remove the antenna. Is this bad? I only cut maybe 2-3 inched off but i'm worried i might have killed it.

Yes, changing the length of an antenna is bad. They are set to a specific length (approximately 39") in order in order to function properly. When you cut off wire you risk radio failure and losing the plane. You should solder the wire that you cut back on to the remaining wire. If you can't resolder the wire that you cut off then you need to purchase new wire and solder it back on. If that's not possible then it should be sent in to a service center to have this done.

Considering that the receiver was in a crash it might be a good idea to send it in anyway to have the receiver checked to make sure that it wasn't damaged in the crash. Any receiver that I have involved with a crash goes in for service before it ever goes back into a plane. Trust me, it's cheap insurance against losing another plane. While the receiver is in they can fix the antenna wire.

Ken

well im going to calgary to buy a new plane and i could probably pick up some extra antenna wire. how difficult is it to replace?

It all depends on your experience soldering small components on PC boards and if you have a proper soldering iron for this job. Excesseve heat will start delamination the PC board and traces. To little heat and you end up with a cold solder joint and the leads to intermentent failures. There is a strain releif on the atenna wire where it enters the case and this will have to be properly reinstallled.

I've 40 years experience repairing electronics. I built my own radio system back in the lat 60's, Receiver, transmitter, and five servos. I soldered every component. Today, I would sent the radio in for repair and checkout as RC Ken said.

Don

HeathKit?

well re-soldering the cut wire is kinda out since the wire that i cut off is probably still at my flying site and long gone. Do some hobby stores check receivers out or do you have to send them in to the company? also how bad will this impact the range if it was only about 2 inches?

It could have tremendous effects on reception. If I where you, I wouldn't even consider the idea of using that receiver at least until it gets a new antenna.

I'll go and buy a new antenna when im in calgary since im going to buy a new plane, but i was wondering if their is any way to check if my receiver was damaged in the crash at home. i heard a range check might work but...

Nope, a Royal Clasic six channel with a Kraft three axis stick. I went the "cheap" route and bought the case, and PC boards instructions from Royal and gathered components where I could. Some from work[sm=red_smile.gif] and a lot more from Allide Radio (sp?)

I built my own Tx charger sans transformer, right into the Tx case. My son, now 43, remembers picking up the Tx while it was charging and getting his toes tingled on the basement floor. I never flew that radio. The plane I built for it was out of a magazine, but I made a fiberglass fuselage and foam wing. I had an old Fox .60 with two needle valves and I picked up a carb and cut the top off the intake stack and mounted the carb in it. I couldnt' get the engine running right, probably under 6000rpm looking back. No tach then. The plane weighed a ton. No field to fly from. The radio was a mess, servos chattering like crazy..

The plane ended in the trash. I think I gave my son the RC stuff after he left home. All and all a dismal experence. That was my last trip into RC until two and an half years back. What a change. I had close to $400 into the Royal in 1969 $$. All of it ending in a trash can. This was at a time when my house payment was $89.00, so it was a major ding to my budget at the time.

Don

Not really. A damaged receiver can still pass a range check and then fail in flight. IMHO it's just not worth saving $15 to risk losing a plane. As I said earlier, I will not put a receiver that has been in a crash back in to any plane before it has been checked by a shop. I have had receiver that seemed to work fine come back from the shop with cracked crystals that could have failed in flight.

Ken

A range check might work. Might!. Might not. It will cost you about $30 including shipping to send the radio in for checkup and repair. Maybe a couple bucks more. You will be out of commision for a couple weeks. You can then fly with the confidance you have an undamaged receiver and do not have to worry about it failing in flight. OR, you can pick up a piece of wire, do a quick patch on the radio. buy a new plane and loose it all on the first flight because the receiver had a broken ceramic filter and just gave up.

I like to gamble, but only to the point it is entertainment. I don't go in and spend the rent payment thinking I'm going to hit it big. I set an amount that I'm willing to spend for entertainment for the night and that is what I gamble. If you are willing to gambel your new plane and equipement against the price of a proper checkup on your crashed receiver with a clipped antenna, be my guest. It is just like the casinos, the odds are against you.

Don

Don't fool around trying to repair it yourself. Send it in and get it thoroughly checked out. You could have problems other than a shortened antenna. After all, it is a piece of electronic equipment and is relatively fragile. Impact with the ground could have cracked a circuit board, broken solder joints and a host of other things.
At the risk of repeating myself and others, send it in for check out and repair.
Regards,
doubledee

The antenna is cut to a specific length based on the operating frequency of the transmitter or receiver. In our case, this is approximately 72 MHz (more specific frequency is based on it's channel, channel 11, for instance, is 72.010 MHz and so on). The antennas are cut to a specific length because that length corresponds to the wavelength, or in this case, the quarter wavelength, of that frequency.

Antennas operate properly when they are cut to a specific length matching the wavelength. But, to cut an antenna to a full wavelength would not be practical. However, they also operate in increments of quarter length, and half length. (there are more multiples, but for our purposes, we can stick to 1/4 wavelength because that's where they are operating).

So, using a simplified formula (the real formula uses velocity of the wave in free space) use 300/Freq in MHz = wavelength. See the below drawing. The result is in Meters. Multiply by 39 then divide by 4 and you will get the approximate 1/4 wavelength in inches. Cut the antenna shorter and you now are not operating in the correct range.

Technically, and simplified, portions of the wave that do not meet the 1/4, 1/2, of full wave length begin to 'cancel' out making the antenna less efficient.

CGr

But this only works if there are NOT some "loading" characteristics built into the RX as well.

Just send it in. Cheap insurance.

Oh, I agree 100%. That was only a basic description of why we should NOT cut antennas regardless of base loading. Even with base loading, there should not be any 'adjustments' to antenna lengths. All the base loading does is make a short antenna 'look' like a typical 1/4 (for example) wavelength antenna.

Don't cut them. Plain and simple. Send it back and have it checked. If the plane involved was in a crash, the receiver could have other issues besides a shortened antenna.

CGr.

so who do i send it into? just horizon or somewhere else

You can send it to the JR service center here:

[link=http://www.jrradios.com/ServiceCenter/Default.aspx]JR Service Center[/link]


Or a very good and reputable 3rd party service center:

[link=http://www.radiosouthrc.com/]Radio South[/link]

Both will do outstanding work for you.

Ken

Look other than you cut the antena wire. Most guys do not send in there recievers everytime they crash an airplane, Heli, whatever. You did cut the antena and I don't know if you can just get the same size wire and solder it back or not. Seems as though you could with no problem. I am not sure
if it is some special type antena wire or not but surely you can find that out here real quick after this post.
You can read alot of posts on here that tells you to do a range check and if it checks out go fly. I do know I have crashed many planes [:@] and never sent a reciever in and I do a range check and go fly, as do most on here. There are some like above that tell you to send it in but I would almost bet that they also have reused a crashed reciever without senidng it in. It is totaly up to U but save the money if you can repair the wire. If not and the plane is not one of your better or a cheap( if such a thing) then see what it does on range check. According to the paperwork that come with them it says it will shorten the distance of recievership (what kind of word is that lol). Does not say it will effect it in anyother way. And unless your flying long distances then it will IMHO work for you. I have one plane that I am positive the wire had been cut before i got the reciever it is only about a foot long and works alright. I don't have it in a high dollar plane though. This is completley up to you, your wallet, and peace of mind. But not anyone I know and I know a few that fly sends there recievers in to have them checked everytime they have a mishap, if so they would not be many at our field flying very much lol we all crash now and then. That is the one good thing about crashing is you can reuse the electronics most times. But you MUST check them out as good as you can.
Or spend 30.00 sending it and whatever they charge you to fix the wire. If it was not a high dollar reciever you can buy a new one almost as cheap.

Everybody but RC KEN he is a sender. Also the moderator a nice guy and a darn good pilot also. If i knew him persoanly I am sure I could mess him up some. rofl.

The wire is different than Typical Radio Shack wire in several ways. The insulation must resist damage from our fuels and oils. It also has a high strand count to give great flexibility. Replacements can be bought at the LHS's if you are really good at soldering. Overheating or sloppy work can kill the RX. And you still won't know if it's 100% OK without testing.

are the ribs done yet CGR

They are in the smoker as we speak!!!

CGr

I am going to play the anti-gambler on this one. Suppose your new trainer with the old RX totally locks out while airborne.
if you are flying a level line at 3/4 throttle, How far will the plane travel before running out of fuel or before the radio takes a stray
hit and the plane goes down. can you whole heartedly say that it doesn't matter if my plane flys away , it will never get to a place
where it can hurt someone. If you can't then maybe you should send the RX in or buy a new one for the sake of others safety.

Just a thought
Chris.