SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Closed Thread
Thread Tools
Old Dec 10, 2006, 06:18 PM
swede
denial15's Avatar
United States, UT, Vineyard
Joined Aug 2005
3,871 Posts
Discussion
When do receivers go bad?

A couple of months ago I crashed my GWS Spitfire. I was flying at a new field, and shortly after launch the plane seemed to get some sort of interference and nosed into the ground.

I figured at the time it was some sort of radio interference, but I'm beginning to wonder if the RX has just gone bad. I was using a Hitec Feather (-shift). Granted, I know that is not the highest quality RX and I don't expect it to be perfect and last forever.

The crash broke the antenna wire approximately two inches from the RX. The wire was removed from the RX and the remaining length was soldered onto the RX. The plane has been resurrected, but the RX is a no go.

When I do a preflight check, i can only get about 5-6 ft away (antenna down) before the plane is totally irresponsive. I doubt the loss of 2" would have that dramatic of an effect. Within the 5-6 ft there is a lot of twitching, but as soon as I get past the 5-6 ft, it all goes dead. No control from the TX and no twitching. I've tried different xtals and get the same result.

I would think the crash possibly did something, but with the antenna up, it does the same thing as the day it crashed. There was nothing traumatic prior to the crash so I am just wondering if the RX has just decided to give up the ghost.

Forgive me if there is a current discussion, I performed a "search" a couple different ways, and I looked back for the past five pages or so and haven't found any recent or similar discussions.

Any ideas?
denial15 is offline Find More Posts by denial15
Sign up now
to remove ads between posts
Old Dec 10, 2006, 06:22 PM
Registered User
vintage1's Avatar
East Anglia, UK
Joined Sep 2002
29,705 Posts
Something is broken....probably a copper track near the input end of things. Years ago I had a home built RX in a plane and it went out of range at about 30ft..finally found an old ex government surplus capacitor with mucky leads had come loose from the board..fixed it with a 12v or possibly a gas soldering iron. My, we were crude in them days.
vintage1 is offline Find More Posts by vintage1
Old Dec 10, 2006, 06:32 PM
Registered User
Joined Oct 2006
89 Posts
if im reading corectly you soldered your antina back on to the RX after it has borken off correct?

if so then ya your RX is no good as soon as it starts gliching at 5-6 feet then its a goner because you should be able to get 50-60 feet away with the Tx antina down (I have the same Rx)so ya then only thing esle that could be causing it is the crystals but i HIGHLY dought it. What you could do is go to ur local hobby store and test it there but its a waist of time just buy a new RX your old one is done
GWS mustang is offline Find More Posts by GWS mustang
Old Dec 10, 2006, 09:43 PM
Outcast outlaw
As far away from RCGroups and the AMA as possible!
Joined Aug 2004
6,601 Posts
Yes -- the two inches will make a world of difference. Go buy a full length antenna, and put it on your receiver -- I'll bet it works just fine.

Antennas must be the length (or half) of the wavelength of the frequency it is picking up. If you changed your antenna by two inches, you have changed the frequency it picks up.

It's like flying with your RECEIVER antenna down.
Red 61 is offline Find More Posts by Red 61
Old Dec 10, 2006, 09:55 PM
swede
denial15's Avatar
United States, UT, Vineyard
Joined Aug 2005
3,871 Posts
Quote:
Originally Posted by Red 61
Yes -- the two inches will make a world of difference. Go buy a full length antenna, and put it on your receiver -- I'll bet it works just fine.

Antennas must be the length (or half) of the wavelength of the frequency it is picking up. If you changed your antenna by two inches, you have changed the frequency it picks up.

It's like flying with your RECEIVER antenna down.
Well crud. If I had known that, it would have been a lot easier.

You'll have to forgive my ignorance, but what do you mean when you say the length (or half) of the wavelength of the frequency it is picking up?

And if that were so, then why would it bug out on me for no reason when it crashed? I probably had over 30 flights on it with no changes or modifications when all of the sudden my Spitfire wanted to be a lawnmower.
denial15 is offline Find More Posts by denial15
Old Dec 10, 2006, 10:39 PM
I havent decided yet
Indiana
Joined Jun 2006
2,120 Posts
greater antenna length on the rx doesnt mean greater range....the length of the wire is "tuned" to the rx. some of the radio gurus will jump in and elaborate on that...also, reducing the length by 10%doesnt just reduce the range by 10%
dmiller746 is offline Find More Posts by dmiller746
Old Dec 10, 2006, 10:47 PM
Outcast outlaw
As far away from RCGroups and the AMA as possible!
Joined Aug 2004
6,601 Posts
Exactly what dmiller746 said. Knocking off two inches of antenna might knock off 60% (or more) of your reception.

With respect to the wavelength issue... I could draw you a picture, but it's kind of difficult to explain...
Red 61 is offline Find More Posts by Red 61
Old Dec 10, 2006, 10:49 PM
swede
denial15's Avatar
United States, UT, Vineyard
Joined Aug 2005
3,871 Posts
Quote:
Originally Posted by dmiller746
greater antenna length on the rx doesnt mean greater range....the length of the wire is "tuned" to the rx. some of the radio gurus will jump in and elaborate on that...also, reducing the length by 10%doesnt just reduce the range by 10%

I knew specific rx's have specific length and wire types for their own rx. I don't think Red 61 was implying the greater length to be greater distance. I think he was also saying the same thing as you.

I can see how changing the length could change the frequency; I guess I just didn't think such a small amount would make such a big difference. But that still doesn't answer why it went berserk on me in the first place.
denial15 is offline Find More Posts by denial15
Old Dec 10, 2006, 10:59 PM
is it flying time?
Jerry Combs's Avatar
Wyandotte Oklahoma
Joined Oct 2004
2,777 Posts
Quote:
Originally Posted by vintage1
Something is broken....probably a copper track near the input end of things.
I think Vintage has hit the nail on the head, it sounds like a crack in the board someplace. I have a couple of Feather receivers and one cracked for unknown reasons the 2nd time I used it, the other is still going strong 5 years later.

Jerry
Jerry Combs is offline Find More Posts by Jerry Combs
Old Dec 10, 2006, 11:11 PM
swede
denial15's Avatar
United States, UT, Vineyard
Joined Aug 2005
3,871 Posts
Quote:
Originally Posted by Jerry Combs
I think Vintage has hit the nail on the head, it sounds like a crack in the board someplace. I have a couple of Feather receivers and one cracked for unknown reasons the 2nd time I used it, the other is still going strong 5 years later.

Jerry

Is that going to be something you're going to be able to see by eye, or is it going to be burried in something? Or both?
denial15 is offline Find More Posts by denial15
Old Dec 10, 2006, 11:20 PM
Registered User
Joined Oct 2006
89 Posts
I think I have one suggestion to your spit fire going down, if just stopped responding in mid flight then it could be one of your connections. what you could do is plug every thing in on your plane then go to every conection like ESC to battery and grab it in between ur index finger and your thumb and just roll is back and forth and if it cliches some thing is wrong with your conection there, if not then keep trying other spots if every thing is ok then I dont know why ur plane went down mabey just a major clich.
GWS mustang is offline Find More Posts by GWS mustang
Old Dec 10, 2006, 11:26 PM
Outcast outlaw
As far away from RCGroups and the AMA as possible!
Joined Aug 2004
6,601 Posts
Denial -- how do you KNOW the crash broke the antenna? Is it possible the antenna was broken before you launched it?
Red 61 is offline Find More Posts by Red 61
Old Dec 10, 2006, 11:33 PM
Electric Coolhunter
Thomas B's Avatar
United States, TX, Fort Worth
Joined Jun 2000
14,640 Posts
An RX that quits once in a while due to a loose or broken connection can usually be made to show the problem if you strap it to something that vibrates intensely while you watch for the problem.....a skill saw, a jig saw, etc.

I have also seen one RX fail when it got warm (would heal at home that night after a warm day at the field) and one fail in extreme cold.

Usually, if an RX passes the vibration tortue test, the heat torture test and the cold torture test, it has no bad joint issues.
Thomas B is offline Find More Posts by Thomas B
RCG Plus Member
Latest blog entry: 2014 events and travel
Old Dec 11, 2006, 12:52 AM
swede
denial15's Avatar
United States, UT, Vineyard
Joined Aug 2005
3,871 Posts
Quote:
Originally Posted by GWS mustang
I think I have one suggestion to your spit fire going down, if just stopped responding in mid flight then it could be one of your connections. what you could do is plug every thing in on your plane then go to every conection like ESC to battery and grab it in between ur index finger and your thumb and just roll is back and forth and if it cliches some thing is wrong with your conection there, if not then keep trying other spots if every thing is ok then I dont know why ur plane went down mabey just a major clich.
I did all that with the Feather while it was still in the plane. I unplugged and plugged everything in a few times with the same results. On the first post I posted the like to a thread describing the crash. It crashed right after take off. It flew level for a second or two then it acted as if I gave it full down elevator. (Yes I am positive I was on the right model, all linkages were tight, and I did not give it down elev.)

I switched out the rx tonight with a NIB Hitec HFS04MG (same xtal as used in the Feather) and I was able to walk down the street with the antenna down with no glitches and full control of the plane.


Quote:
Originally Posted by Red 61
Denial -- how do you KNOW the crash broke the antenna? Is it possible the antenna was broken before you launched it?
I guess I donít KNOW it wasn't broke before the crash. All prior landings have been smooth and it worked fine on all prior flights. I had the antenna wire strung through some antenna tubing out of the top of the fuse. When the plane crashed, the rx was ripped from the plane. The antenna didn't want to come out of the antenna tubing during the crash. I guess it is possible it was like that.


Quote:
Originally Posted by Thomas B
An RX that quits once in a while due to a loose or broken connection can usually be made to show the problem if you strap it to something that vibrates intensely while you watch for the problem.....a skill saw, a jig saw, etc.

I don't think the vibration is the current issue here. I suppose it is possible it could have received some prior damage due to vibration, but it's schizo while standing still.


Quote:
Originally Posted by Thomas B
I have also seen one RX fail when it got warm (would heal at home that night after a warm day at the field) and one fail in extreme cold.

Usually, if an RX passes the vibration tortue test, the heat torture test and the cold torture test, it has no bad joint issues.
The crash happened in October, so temps were still relatively warm. It is about 35f ish today. I've got the same results since October.

I think the most likely cause is the antenna. I purchased the rx used. The prior owner had a micro antenna on it, and put the normal one on when I purchased it. Red 61's comment about if it was pre-existing is starting to look more feasible. I guess it is likley it could have been loose from the connection since that was where it broke when the plane came apart.

I'm confident it was not broke prior to the flight, but it very likely could have been loose.

Now I'll have to find out the type and length of antenna to solder back on and see if that resolves the issue.

Red 61, does that prop look familiar?
denial15 is offline Find More Posts by denial15
Old Dec 11, 2006, 01:32 AM
resU deretsigeR
PaulVi's Avatar
Dublin Ca
Joined Aug 2004
7,787 Posts
Ch.# / Frequency (MHz)Ch.# / Frequency (MHz)Ch.# / Frequency (MHz)11 / 72.010 28 / 72.350 45 / 72.690 12 / 72.030 29 / 72.370 46 / 72.710 13 / 72.050 30 / 72.390 47 / 72.730 14 / 72.070 31 / 72.410 48 / 72.750 15 / 72.090 32 / 72.430 49 / 72.770 16 / 72.110 33 / 72.450 50 / 72.790 17 / 72.130 34 / 72.470 51 / 72.810 18 / 72.150 35 / 72.490 52 / 72.830 19 / 72.170 36 / 72.510 53 / 72.850 20 / 72.190 37 / 72.530 54 / 72.870 21 / 72.210 38 / 72.550 55 / 72.890 22 / 72.230 39 / 72.570 56 / 72.910 23 / 72.250 40 / 72.590 57 / 72.930 24 / 72.270 41 / 72.610 58 / 72.950 25 / 72.290 42 / 72.630 59 / 72.970 26 / 72.310 43 / 72.650 60 / 72.990 27 / 72.330 44 / 72.670



http://k4far.home.att.net/calc.html


for wire try the wire from the silver phone hook up wire there are 4 or 6 stranded wires in each of those flexable and can be cut to lenght.

and you are shooting for a 1/4 wave length not a 1/2 as mentioned before.

so of the gws use a 1/8th wave length ant at around 19 inches
PaulVi is offline Find More Posts by PaulVi
Closed Thread


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Question How do I know when Lipos go bad? MedcinMn Batteries and Chargers 3 Jan 19, 2007 04:19 PM
Discussion when good children go bad...... dutchydawg1 Slope 6 Jun 05, 2006 03:24 PM
Alert Can receivers go bad??? Puget Sound Flyer Radios 2 Dec 03, 2004 05:04 PM
Where do the planes go when you get bored with them? thunder1 Parkflyers 45 Dec 10, 2003 10:40 PM
Do crystals go bad? freeflight Radios 4 Apr 17, 2003 05:28 AM