barbed wire fence glitch

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RH
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barbed wire fence glitch

Post by RH »

A barbed wire fence running through the combat engagement zone may have been causing some radio glitching if you flew low enough, directly above the fence. Has anyone else ever experienced this? Is it possible or just my imagination?

I fly over fences quite often and never had it happen before.

rh
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Which_way_is_up
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Post by Which_way_is_up »

Only if there's something already wrong with your RX or if your RX is AM.
RH
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Post by RH »

3 of us, that I know, of were experiencing similar issues and nobody is running AMs. The first time I crossed it to retrieve a bird I touched it very gingerly thinking it might be electrified but it wasn't.

rh
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Post by THend »

[:D]There is a barbed wire fence in Tucson[:D] I was running fast and low with the ole Manta when it just stopped in mid air. The engine liberated from the firewall, and the plane just hung in mid air from where we were standing. When I got there, it was stuck on the wire.[:p]

What I would do.. take the plane, with the engine off, and sit it by or above the fence. Have someone monitor it, while the Tx is taken back to the flight line.

Now, have some friends dive bomb your buddy out by the plane[:p] Aw, just kidding, but it would be good to fly some around the area.

If you see glitching, well odd as it may be, something may be up. I really doubt that the fence has anything to do with it, but this test would kinda divide and conquer the issue.

While your at it, take the plane somewhere else as well and perform the same test.

Now, if you do it with the engine running, you may get different results. The engine running generates tons of vibration, and if you have a marginal crystal, it will cause glitches.

One of the best things you can do if you think you are getting hit is to climb and kill the engine. If it is a true glitch, you don't want to be at power, and if it is vibration induced..killing the engine may very well save the plane.

The maiden flight of the Manta suffered this very fate. I was so nervous about it all, I range checked the plane with the engine off. Upon launch, all seemed well, and then the plane went nuts on me. At first, everyone blamed the design etc.. as soon as I killed the engine, it flew like a dream and I landed a few feet away from where I was standing. Another range check performed with the engine running confirmed that I had a compromised crystal.

The rest of the story is funny, so I'll share it with you since I am on a roll. Well, I was supposed to meet some combat buddies down the road at Palomar. I was out of time at the Fallbrook field, and needed to get down the road to meet my friends.

I now knew that the plane flew better than I had expected, well at least in glided flight. So, I changed the crystal and went to Palomar.

When I got to Palomar, I had so many guys jeering that the Manta would not fly well with that crazy wing. I just said that I guess we will see.

It was launched, flew better than anything those guys have ever seen.

Another thing you can do is to hold your Dremel tool body against your receiver in the shop. If vibration is an issue, the Dremmel will induce enough vibration to bring it out.
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Post by THend »

uhh
thojo
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Post by thojo »

barb wire fence glitch, yep, it could be...[:D]

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Post by Web-Pilot »

A rusty barb wire fence could conceivably cause interference. With the power we are running, I would not think it is probable, but it is certainly possible. A barbed wire fence just in its construction has a joint of two metals, the wire and the barb. Add a little chemical action and you have oxidation, or rust. The rust on the steel make two dissimilar metals touching each other. Two dissimilar metals can cause a diode junction effect. When you have a diode, you can have mixing. Mixing can cause intermodulation interference (Intermod). Normally with the low power and the specs of the FM transmitters and receivers we are running, we do not have to worry about Intermod. But with a rusty barbed wire fence, the possibility is definitely there. We have all even spaced frequencies, which means that any two evenly spaced frequencies can mix and generate a third frequency. S for instance if you have Channels 17, 18, and 19 on at the same time, you could create Intermod on channel 17, 19, 16, and 20. Again, normally this does not happen because the transmitters and receivers are designed to not let Intermod mixes happen in them. When you have an outside influence like a barbed wire fence, it may act as an intermod generator. If you get an intermod signal generated by an outside influence from two evenly spaced transmitters, it falls directly on the receive frequency of the third plane, and there is nothing to keep it from interfering.

So how far from the flight line was the fence? I know that Quad said he was having bad glitching so chose not to fly after that happened. Was the problem only over the fence? How close to the fence did you have to be to experience the problem?

So bottom line, possible but not probable.

George
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Post by RH »

Thanks for the explanation, George. I have to digest all of that and try to understand it.

I would estimate the fence at 75 yards, straight out, I should have paced it off. I only was hit flying low and parallel to the fence. It comes around to the left closer, maybe 40 - 50 yards. We only crossed it to land, usually dead stick or at an idle, with no apparent problems. I was watching jj once when he got hit and I thought he was pretty much perpendicular to the offending section. I thought he was trying to scrape those draggy streamers off his wing at first!

At that distance it is hard to judge if you are right over it or not, but I thought I was pretty close or maybe a bit beyond when it was going googoo.

rh
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Post by Web-Pilot »

Randy,

I would think that at 75 yards, 225 ft that there would not be enough transmitter energy to mix and cause a receiver problem, but it is theoretically possible. Best to go back up there and test the theory! We better do that before the October meet.

Is there and electric fence close to the barb wire fence?

George
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Post by RH »

No electric fence nearby. It may be closer to 50 than 75 yards, guys?

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Post by Air Scharnell »

We will test that theory this week end George.
Quad has some extra xtl's in his box...........
Like Randy was thinking that fence is close .
Best bet would be too contact Marv......for the distance.

Frank
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Post by danpow1973 »

If the fence is proven to cause interference then get a ground stake at the local home imprivment warehouse. Drive it in as deep as possible. Then run some wire to ground each strand to it. Make sure you clean the barb wire and get a good conection. This would elimimnate the possibility of interference.
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Post by RH »

Frank, if you guys test be sure to find a rusty section of fence. It seems to me that the one we fly over at our field has not rusted through the galvanize(or whatever it is) yet.

I fly right next to one out east of town, low passes, very close, with no problems but it is pretty new with no rust.

rh
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Post by Cajun »

I have had considerable problem with interference from fences, but not with slimers. My problems have been with electrics. The HiTec HFS-04 receiver will glitch when flown over a barb wire fence at an altitude up to 10 feet. The Feather receiver will glitch when flown over the fence at up to about 50 ft. But then a Feather receiver can be glitched by a coin toss[B)].

Ground rods are of no use as all of our fences are installed with iron posts.

The fence in the Thojo picture seems to have acted like a magnet for several pilots at Alazan, but I doubt the wire was the problem. If memory serves me correctly, Randy bought it trying to follow me between the two top wires. That trick works every time[:D]The only trick I like better is successfully flying under the bottom wire with a bogey hot on your tail[:p]

Our field had electric fence for a number of years and never was a problem with interference.

I think George probably had the answer in galvanic reaction of dissmilar metals. We flew over a old barm with a rusty metal roof at Alazan and when the wind blew any plane flying within 75' of this barn was at risk. I had to conclude it was the wind flapping that old tin around. This affected almost every receiver in the club.
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Post by RH »

This fence has steel t-posts so the rusty wire is probably jiggling against the rusty posts as well.

rh
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