Clipclop

Yesterday I was flying a Robin Hood with a G26 and JR equipment with a PCM receiver on channel 17. I've flown this channel for six years at three fields with no problems, but yesterday was another story. After three minutes of flying I was making a right turn at half throttle and applying up elevator to maintain altitude. The plane began to lose altitude and did not respond to up elevator. It nosed in at almost vertical. The electronics were pulled, checked, and found to be working properly. The battery was checked under load and was good with a 5.2 volt charge. The transmitter had a charge of 10 volts. The elevator linkage was intact. Only one other flyer was at the field, and he was on channel 38. A Hobbico Frequency Checker showed activity on channel 17 and some intermittently on channels 16 and 18. Last week a flyer had trouble while flying on channel 19 although it is not clear if his problems were channel related. The frequency checker is showing the same aberrant activity on channels 16, 17, and 18 with most on 17 at my home 26 miles from the field. My transmitter is turned off. Any ideas about what might be going on? I've never been shy about admitting to having dumb-thumb moments, but something else seems to be going on.

MinnFlyer

My Feedback: (4)

Ask around if anything new has started recently.. A new Microwave antenna, or some new business in the area, etc.

BasinBum

My Feedback: (2)

The Frequency Checker is a good start but even better is a scanner with audio so you can hear what the Rf sounds like. RC transmitters make a distinct sound when listened to through a handheld radio. Sometimes at our field I will pick up broadcast television audio on 72mhz. Being able to listen in helps differentiate the interference.

grinder-RCU

My Feedback: (1)

Any new construction in your area. Heard of an problem on the east coast of Can. of some interference coming from construction cranes. I'll see if i can find the story and club website.

Grinder.

kamakazie frank

My Feedback: (2)

Have that same problem at our field with channels 17 & 18 and we are located in Southern New Jersey.

Montague

We have 4 pair (total of 8 channels) banned at our field. There are pager systems that put out a rather powerful signal that are licensed to operate between our channels. If you are close enough, they can easily take out an airplane, or at least force a PCM RX in to fail safe.

The thing about the pager systems at our field is that they are usually not broadcasting. They only come on for short, powerful bursts. So you can easily fly on a banned channel 10-20 times or for months or even years and never have a problem because you're getting lucky. Then you get blasted the next time you're flying. Happened here several times before we figured it out.

I'm not sure how to do it, but you can get license info from the FCC about who is able to broadcast on 72Mhz in your area, including short-term licenses and such.

pettit

My Feedback: (23)

It may not be an R/C transmitter on the channels you are using, but may be pager transmitters on legal channels BETWEEN your R/C channels.

Find the frequencies of the R/C channels in question. NOT 18, 42, but 72.450 or whatever.

There's a legal pager frequency between each and every R/C Channel.

Let's say you have a problem on channels 17 (72.130) and 18 (72.150)

The frequency between those is 72.140, a legal pager channel.

Then go to this website, under "Frequencies by Frequency, enter that frequency (72.140) and the state you are in.

http://www.phreak.org/html/radio/database.shtml

This will give you a list of all legal pagers in your state on that frequency. Find any in your area that may be close to your field.

It may be due to an out-of-tune receiver in your plane that just happened to hear a legal pager and lock out, causing you the problem.

We had to stop using several R/C channels because of pagers within 5 miles of one of our fields that may have been causing "mysterious radio glitches".

Clipclop

Thank you all for the possible reasons for the problem I had on channel 17 last weekend. I've sent the receiver to have its accuracy checked and plan to investigate pager interference. I've been planning to upgrade to a newer transmitter, so now I have a valid reason to do so and certainly on a different channel.

toprudder

ClipClop,

I was one of the people that arrived at the field just after your crash. As a result of the conversations that followed, I decided to purchase a Hobbico Frequency Checker.

After purchasing mine, I am not too impressed with it. I will usually have a channel indicated around 26-28, but it goes up as high as 31 and as low as 21, depending on the temperature. I have taken it inside an RF sheilded chamber with the same result, so I am sure it is the checker and not a true signal. Also, even with the optional antenna plugged in, it has difficulty detecting some active channels at the field, with the transmitter(s) only 75 feet away. I'm planning on taking it back for exchange.

There was a review on this product, in which the reviewer had a similar problem that ended up being a defective unit. [link]http://www.rcuniverse.com/magazine/article_display.cfm?article_id=565[/link]

As such, I would not put too much faith in the channel 17 active indication that you may have seen on Jim's scanner. In fact, we had four of these out at the field this past weekend and were getting different results with each of them.

When I get a chance, and if the weather is decent, I'll plan on taking my spectrum analyzer to the field to see if I can detect any real interference.

Bob R.

H. Wayne S

My Feedback: (18)

We have this problem at our field on channel 29,30 and 31 We tracked it down to a silo grinder. Every time they started grinding and storing corn these channels would light up. Something to do with there electric motors OR the belts and chains. The silo is a good 1/2 mile from us.

50+AirYears

There are also a number of non-hobbyist companies on the 72 mHz band who make radio controll systems for things like industrial cranes and other mechanical devices. In fact, when the 50 channels first became available to us, the AMA spent a large amount of time getting the FCC to take control of the situation because several of these companies were putting their higher power systems directly on our frequencies. In fact, at our previous field, we had a manufacturer of pre-fab housing components purchase a couple conversion systems for his operation, and luckily for us, one of our members was working for them at the time, and the owners were very co-operative in checking. They found that one system was legal, but the other one was on one of our frequencies. Since the systems were something like 50 or 75 Watts, it was nice that the owner went as far as having his lawyer draft a letter threatening legal action if the control company didn't replace the illegal unit with a one on a legal (for Them) frequency. He was probably more concerned about having his employees hurt because of our operations a bit more than 1.5 miles away.

Rcpilot

My Feedback: (78)

Dirty Channel?

Isn't that Cinemax between 12am and 5am?[sm=bananahead.gif]

50+AirYears

Cinemax is only one of several.