Discussion regarding 72mhz, hits, cell towers, train tracks and other...
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Discussion regarding 72mhz, hits, cell towers, train tracks and other...
We built our flying site around 20 years ago on county leased property, all was good, flew for years when AM was popular and even had some Hams. I got out of the addiction for a few years and when I recently returned, there is now a cell tower a couple to 3 hundred yards behind the field, and train tracks 300 yards in front of the field which were there loooong before us. There are only a couple of us using the field at the moment and all are still on 72mhz so you can save the speech on "upgrading" as that's a well known issue although not affordable at the moment for many reasons for all involved. 2.4 brings up its own questions with the cell tower, so by all means, feel free to address that, though!
Here lately we are all seeing very random lockouts on PCM and weird behavior (hits?) on PPM. One of my planes on PCM (Futaba) was holding commands for about 2 seconds on one flight. You pull a sharp vertical, it would half loop. You roll from knife edge to upright, it might go opposite knife edge. It did this about 3-5 times in a ten minute flight before it went into failsafe (last position hold) in a rolling circle nearly drilling a hole within 50 ft of the exact location another member's plane drilled a deep hole a week before, apparently in failsafe as well - right at the train tracks. Mine recovered. I did find the receiver (freebie) had some corrosion so disabled it and put it aside. Everything else brand new with about 10 flights. Now what lead to the questions was a few days ago the other flier drilled another hole near the runway. PCM again, random response on a quicky 500 so the time from the first "oh darn" to the last part of the wing fluttering down was rather abrupt, but I did see enough of its last moments to see the plane randomly responding to elevator attempts. The clicker to all of this? The first hole a couple weeks previous was dug at 5:50. My lockout as well as the Q500 crash were almost exactly 6:20 about a week apart! That much coincidence just throws me off from corroded receivers and random glitches.
I've done tons of research and have come up nearly empty. One fella working on the railroad does believe there are 72mhz signals in the tracks in our area, but the closest switch is mile or a few miles away. My research on cell towers affecting 72mhz has come up with zip. My research on cell towers swamping random frequencies shows a slim possibility so I can't rule that out. And to add to the problem, would retiring the dinosaurs and upping to 2.4 really be useful with that cell tower looking over our shoulder??
I have no idea about locating a frequency analyzer. Being there are only a few of us, that's hardly doable. I wanted to toss this out there for discussion since I've hit a dead end. What have YOU run across in similar situations? Could this really chalked up to randomness with the clock involved above? Or could some unknown source be sending signals at intervals? The closest house is about 1/4 mile away (the town for that matter). There is a trucking company a similar distance. I don't know what else to suspect. I do know I don't feel it's totally random radio failures.
We did have another recent crash (Futaba) but the receiver crystal was missing. Likely it simply wasn't installed properly, but there's always that slim-to-none possibility it fell out when crashing. Probably not, but just tossing it out there.
Here lately we are all seeing very random lockouts on PCM and weird behavior (hits?) on PPM. One of my planes on PCM (Futaba) was holding commands for about 2 seconds on one flight. You pull a sharp vertical, it would half loop. You roll from knife edge to upright, it might go opposite knife edge. It did this about 3-5 times in a ten minute flight before it went into failsafe (last position hold) in a rolling circle nearly drilling a hole within 50 ft of the exact location another member's plane drilled a deep hole a week before, apparently in failsafe as well - right at the train tracks. Mine recovered. I did find the receiver (freebie) had some corrosion so disabled it and put it aside. Everything else brand new with about 10 flights. Now what lead to the questions was a few days ago the other flier drilled another hole near the runway. PCM again, random response on a quicky 500 so the time from the first "oh darn" to the last part of the wing fluttering down was rather abrupt, but I did see enough of its last moments to see the plane randomly responding to elevator attempts. The clicker to all of this? The first hole a couple weeks previous was dug at 5:50. My lockout as well as the Q500 crash were almost exactly 6:20 about a week apart! That much coincidence just throws me off from corroded receivers and random glitches.
I've done tons of research and have come up nearly empty. One fella working on the railroad does believe there are 72mhz signals in the tracks in our area, but the closest switch is mile or a few miles away. My research on cell towers affecting 72mhz has come up with zip. My research on cell towers swamping random frequencies shows a slim possibility so I can't rule that out. And to add to the problem, would retiring the dinosaurs and upping to 2.4 really be useful with that cell tower looking over our shoulder??
I have no idea about locating a frequency analyzer. Being there are only a few of us, that's hardly doable. I wanted to toss this out there for discussion since I've hit a dead end. What have YOU run across in similar situations? Could this really chalked up to randomness with the clock involved above? Or could some unknown source be sending signals at intervals? The closest house is about 1/4 mile away (the town for that matter). There is a trucking company a similar distance. I don't know what else to suspect. I do know I don't feel it's totally random radio failures.
We did have another recent crash (Futaba) but the receiver crystal was missing. Likely it simply wasn't installed properly, but there's always that slim-to-none possibility it fell out when crashing. Probably not, but just tossing it out there.
Last edited by TexasFlash; 11-04-2016 at 06:28 AM.
#2
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I have flown at a field where the cell tower was at least as close as yours. 72, ppm. No problems. In fact I do not remember anyone in the club having hits or glitches and they still fly there.
I cannot comment on the railroad tracks. I just do not see how they can transmit a 70 MHz signal over rails if that is what your saying.
Paul
I cannot comment on the railroad tracks. I just do not see how they can transmit a 70 MHz signal over rails if that is what your saying.
Paul
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I really don't know if a signal is somehow sent down a rail or some underground wiring or simply sent by the train via radio to each switch. I've heard that some railroads do use 72mhz and an ex RR employee my wife spoke with believes it is still done in my area.
When my plane suffered a recoverable lockout for 2-3
seconds we did have to wait for a train crossing about half a mile down the road from where I was flying about 30 minutes after the lockout. Again, this was a receiver with a bit of corrosion on the soldered side of the servo pins. On one hand it all looks like several flukes. But when you throw in the common time of 6:20 and mostly pcm radios it just makes me second guess things. I have a new to me 30%er I won't fly because of the unknowns.
Just yesterday I had a trainer nearly roll inverted after repeatedly ignoring my left turn inputs. I use it to drop parachutes for the Grandkids. It could have been the 10 mph wind - or was it because it was 5:50 which happened to be the time the first plane mentioned in all of this drilled its hole? This was the same transmitter on ppm which was used during the failsafe above on pcm. All crashes and mishaps involved were with 3 different radios, all Futabas, mostly pcm, channels 32ish and 44 with the 3rd channel unknown to me at the moment. We only fly one at a time as well. Odd stuff happening.
When my plane suffered a recoverable lockout for 2-3
seconds we did have to wait for a train crossing about half a mile down the road from where I was flying about 30 minutes after the lockout. Again, this was a receiver with a bit of corrosion on the soldered side of the servo pins. On one hand it all looks like several flukes. But when you throw in the common time of 6:20 and mostly pcm radios it just makes me second guess things. I have a new to me 30%er I won't fly because of the unknowns.
Just yesterday I had a trainer nearly roll inverted after repeatedly ignoring my left turn inputs. I use it to drop parachutes for the Grandkids. It could have been the 10 mph wind - or was it because it was 5:50 which happened to be the time the first plane mentioned in all of this drilled its hole? This was the same transmitter on ppm which was used during the failsafe above on pcm. All crashes and mishaps involved were with 3 different radios, all Futabas, mostly pcm, channels 32ish and 44 with the 3rd channel unknown to me at the moment. We only fly one at a time as well. Odd stuff happening.
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That's too much money for a hunch. My question is directed to anyone who may know about inteference from the sources mentioned as I suspect there are possiblities but it appears there is little to no history of incidents. So possibly you're right. That's why I'm asking since I can't find much in research. It looks like just odd coincidenses. I won't be going to gambling anytime soon.
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There is a concrete plant 1/4 mile one way which was there long before us with about 4 trucks and a K3 vacuum truck company related to the oil fields 1/4 mile the other way which is a few years old with who-knows-what for radios. No known other fliers in the area. Closest house between 1/4 n 1/2 mile or so.
#8
Your mention of ch-44 perked my ears up. Some time back, our town built a new garage in the same park that I regularly fly at - back in a corner of the park. Once it went operational I noticed a VERY LOCALIZED glitch on my 1967 DeBolt Champ, which flies on ch-44. When I was coming in on final approach, at the same point in the park between 15-25' altitude the plane would suddenly go to full throttle and climb vertically. Didn't matter what I did with the controls - same result every time. Once she made it to above 25' she went right back to what my controller was telling her to do.
I checked with the guys in the garage. They've got a microwave xmtr that's pointed right at the town offices, 1 mile away. Standing in-line between the garage and town offices, holding the plane in my hands as high as I can reach, the controls go NUTS, but always full up elevator, full throttle.
I just avoid that spot in the field now, with that plane, and have no problems.
BTW, I've got planes on something close to a dozen channels - ONLY #44 is effected that way here.
The microwaves might be something to maybe think about.
Pic below: I fly to the right of and below the yellow line, which makes my "inside the fence" flying area 500' wide, 1200' long. I've also got many hundreds of acres of fields outside that. Orange line is the microwave beam. My interference point is about half way between the garage and the parking lot, top center of pic, which still leaves an awful lot of field available, even on that one plane.
I checked with the guys in the garage. They've got a microwave xmtr that's pointed right at the town offices, 1 mile away. Standing in-line between the garage and town offices, holding the plane in my hands as high as I can reach, the controls go NUTS, but always full up elevator, full throttle.
I just avoid that spot in the field now, with that plane, and have no problems.
BTW, I've got planes on something close to a dozen channels - ONLY #44 is effected that way here.
The microwaves might be something to maybe think about.
Pic below: I fly to the right of and below the yellow line, which makes my "inside the fence" flying area 500' wide, 1200' long. I've also got many hundreds of acres of fields outside that. Orange line is the microwave beam. My interference point is about half way between the garage and the parking lot, top center of pic, which still leaves an awful lot of field available, even on that one plane.
Last edited by skylark-flier; 11-05-2016 at 08:16 PM.
#9
The AMA has a "loaner" scanner I believe. I had a friend with a regular scanner that would pick up 72 and I bet you could get the Tower Hobbies channel checker cheap now. Our frequencies are spaced in between the other users or you could look at it the other way around. More likely is that their transmitter or your receivers have slipped tune. Unless you think they installed new equipment, it probably has been there as long as you have. What channels is your group flying? There are some 72 mhz used in hearing equipment for theaters and tours, I found out. I still fly lots of 72.
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In a few hours of research I've found some references to "listening devices" on 71, 73 and some other higher 7x mhz frequencies, but there's just not much listed I could see as interference unless it or we were out of tune. I won't rule that out.
Are microwaves that much of a "focused beam"? I had no idea! Whatta pain! At least it's avoidable as long as it's focused as such.
I may look into AMA options but we're so small I wasn't expecting much help there. I had no luck with any searches on Tower.
For whatever it may be worth, I included some pics showing our layout. The green pin is our flight line and we fly to the right of it on the screen. The rodeo barn is mostly empty usually with no one present during our flying time. I've been all through it and have even been involved in events there and there's little to none to be concerned with there. The concrete plant is of minor concern although it was there before we were. The cell tower and vacuum company are the newest additions added since I was there years ago. Again, I know this is little to go on, but as can be seen, I'm not alone with seeing odd "hits" for whatever reason! Keep the information flowing as it's interesting. What radios might these companies be using that could interfere with our frequencies, either directly or via some harmonic?
Are microwaves that much of a "focused beam"? I had no idea! Whatta pain! At least it's avoidable as long as it's focused as such.
I may look into AMA options but we're so small I wasn't expecting much help there. I had no luck with any searches on Tower.
For whatever it may be worth, I included some pics showing our layout. The green pin is our flight line and we fly to the right of it on the screen. The rodeo barn is mostly empty usually with no one present during our flying time. I've been all through it and have even been involved in events there and there's little to none to be concerned with there. The concrete plant is of minor concern although it was there before we were. The cell tower and vacuum company are the newest additions added since I was there years ago. Again, I know this is little to go on, but as can be seen, I'm not alone with seeing odd "hits" for whatever reason! Keep the information flowing as it's interesting. What radios might these companies be using that could interfere with our frequencies, either directly or via some harmonic?
Last edited by TexasFlash; 11-07-2016 at 07:52 AM.
#11
I know you say that 2.4 is out of the question, but I will ask this. Do you or any of the other fellows know anyone else who flies locally with 2.4? If so, maybe try talking to them about your situation and the happenings and then see if they would be willing to go for a couple of flights there, or letting them install a Rx in one of your planes to possibly see if it would be a 72mHz issue?
#12
It has been enough years that the checker is old stuff;the Tower checker will have to be found used now I guess. https://www.rcgroups.com/forums/showthread.php?t=403734 is what it is.
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Hey, thanks for the input on the freq checker! I just bought one NIB and an antenna so although it has a 15 second cycle time, it's better than tossing a plane in the air to check for hits.
2.4 is on my to do list. I'm in the middle of a disability case going on 4 years with no income. Let's just say I have to plan expenses a bit differently than most of you. I got back into this addiction as an escape. Now I gotta go trash talk my mailman as it's been a good 20 minutes since I ordered this thing and he still hasn't brought it to me...
2.4 is on my to do list. I'm in the middle of a disability case going on 4 years with no income. Let's just say I have to plan expenses a bit differently than most of you. I got back into this addiction as an escape. Now I gotta go trash talk my mailman as it's been a good 20 minutes since I ordered this thing and he still hasn't brought it to me...
#15
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I learned to fly in the middle of a 100 acre soybean field, where the owner had cut a short grass duster strip. Except during crop dusting "season, we had to keep our own little strip's grass cut enough to use. There was a BIG natural gas pipeline (underground) on the northern edge of the field, running west/east. Everything was peachy; until one day, we began losing models on a regular basis. All in the same place, but no repeatable time.
Bottom line, we finally discovered that the gas company had installed a radio controlled valve on the line, in the northwest corner of the field... during the week when nobody was out there to see them working. The company would close and open the valve whenever it was necessary... and of course, it was on 72mHz. This was in the late 80s, so we had no options... except to stay away from that part of the field, which basically solved the issue for us.
Something similar could be what's happening to you guys. The timing is what makes sense of this idea. Also, it doesn't have to be 72mHz. If an electronic signal is strong enough, regardless of the freq, it can most definitely jam up your receivers.
.
Bottom line, we finally discovered that the gas company had installed a radio controlled valve on the line, in the northwest corner of the field... during the week when nobody was out there to see them working. The company would close and open the valve whenever it was necessary... and of course, it was on 72mHz. This was in the late 80s, so we had no options... except to stay away from that part of the field, which basically solved the issue for us.
Something similar could be what's happening to you guys. The timing is what makes sense of this idea. Also, it doesn't have to be 72mHz. If an electronic signal is strong enough, regardless of the freq, it can most definitely jam up your receivers.
.
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Well... mucho garcias for that bit of information! It just so happens we are surrounded by pipelines. Our field gate also happens to have about 5 locks no one can account for. We were required to allow some to come and go when the field was started around 25 or so years ago, but everyone has lost track of the locks. A pond that was on the south end of our site is long gone but a tractor has been there lately mowing the line down the side of the tracks which is a pipeline. Anyway, I'll be heading out today with my new freq tester just to see if anything bites.
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Alrighty... I went to the field with my handy-dandy freq checker and found that interesting. No one else was around nor did I take any planes or gear. My radio is channel 44 just for a refresher. I got a lock on 46 before I got out of the truck good. I had hits on 45 and 46 for over an hour totaling somewhere around 30+ hits. The problem with that is I can get this thing to lock onto 45 for 1 to 2 passes no matter where I am, whether it's at the field, home, work, etc, so I'll call that a bug for now unless something in the phone/electrical lines with all these smart meters and such can affect channel 45. ???
I had approx 10-12 hits on 44 which started closer to 5:15 when the concrete plant starting winding down and employees thinned out. My lockout as well a my buddy's crash were previously "around" 6:20 during the daylight savings time. All but one truck shut down so I drove over to the plant and couldn't get a single hit with the antenna off (300 ft test).
When 1 train came though approx 1/2 mile away the same 45 got extremely active usually locking in for 2-3 passes.
When a train came from the opposite direction about 15 minutes later, when it was about a mile away from us channels 11, 13 and 35 lit up. 37 lit up soon after.
While this isn't conclusive due to the off label use of this device, it is enough for me to go "hmmm"...
I had approx 10-12 hits on 44 which started closer to 5:15 when the concrete plant starting winding down and employees thinned out. My lockout as well a my buddy's crash were previously "around" 6:20 during the daylight savings time. All but one truck shut down so I drove over to the plant and couldn't get a single hit with the antenna off (300 ft test).
When 1 train came though approx 1/2 mile away the same 45 got extremely active usually locking in for 2-3 passes.
When a train came from the opposite direction about 15 minutes later, when it was about a mile away from us channels 11, 13 and 35 lit up. 37 lit up soon after.
While this isn't conclusive due to the off label use of this device, it is enough for me to go "hmmm"...