spitfire66

Hello Again! I was recently flying at a local uncontrolled airport (with permission of course) where others have been known to fly and ran into an interference problem. I have a JR sx600 with the slimline 700 receiver on freq. 29. I performed the range check before flying and everything checked out fine, 30 paces away or so. While I was on climb out I noticed that the airplane tried nosing down pretty hard twice in a row and I was able to override it. I landed uneventfully and performed another check on the ground and then noticed the elevator was making full nose down deflections every now and then. With the new interference the only thing I noticed that had changed was some farmers cutting milo and more than likely using CB radios within 300 feet from me. Would this cause the interference? I was 30 miles away from the closest sanctioned airfield and the only other thing was a power plant about 10 miles away. I have no idea what could have caused it and I'm hoping somebody might know.

Other information: The plane had about 6 flights since being charged (about 25 minutes worth of flying) and don't know if this could have caused the problem (not sure how long they can go). Checked out fine at my house with no inadvertant control surface movements.

FLYBOY

My Feedback: (11)

A CB wouldn't do it. I have friends that fly JR and the boards have been known to crack in the Rx and they have had the same symptoms. I would start there.

spitfire66

I am not sure what to think about the cracked tx board. I'm hoping that isn't the problem. I have visually inspected the case and there is no signs of damage at all and I have always been extremely careful when handling it. I have tested the radio at my house two seperate times (5 min each) and have not duplicated the problem. "FLYBOY"...when your friends had problems in the past with the tx boards was the problem at least consistent or noticeable, or can that only be found by sending the unit off?

jetmech05

why not get a freq checker they're pretty cheap...cheaper than the pain it would be to remove your receiver and send in for repair..go to the site where you were flying at with your airplane. keep your airplane on the ground, if you get a glitch check the freq checker to see if your getting interference...if you are, fly somewhere else, if not looks like you wil have to send in the transmitter and receiver.
Batteries were fully charged that night before you flew weren't they?

Lomcevak Duck

My Feedback: (14)

I think that's going to be the smoking gun. Get a volt meter and check your batteries before eery flight. You will save yourself a lot of planes that way.

spiral_72

I would disagree on the CB "wouldn't do it". The CB normally wouldn't do it, but around here we have plenty of rednecks pumping serious power out of thier CB with an amplifier.
My buddy Allen, can do some pretty interesting things with electronics using his CB...... not to mention he washes his truck for free at the coin operated car wash.

Jon Easley

i agree with spiral 72 you can put an amplifier on them and cause alot of problems..

jetmech05

always charge your batteries before each flight day....I charge 15 to 17 hrs with a wall wart, or do a quick charge at the field before every flight day.....

Lomcevak Duck

My Feedback: (14)

Citizen band radios still operate on 27 MHz while we fly on 72 MHz no matter what the signal strength. The only way a CB could affect the 72 MHz band is by changing frequencies, not just increasing output power.

broke_n_bummin

At 4 Watts(Max power output allowed by the FCC for 11M radio) that statement would probably hold true. But, he stated that some of those guys are pushing some serious power. I've been in that situation, and I'm here to tell you that it can and does happen. I was on a base station with a little modulator pushing a linear that I had built. It would dead key almost 100 watts and swing close to 6K when I talked. I heard every complaint in the book about setting off doorbells and microwaves, coming in over cable tv even telephones as far as 9 blocks away. What got me busted was when a complaint came in to the FCC from the local radio station. They claimed that I was causing deadspace in their communications array (FM) by "Bleeding over" and interrupting communications between the radio station and the relay station. The radio station was about 8 miles southwest of my house. The tower was out at the lake about 14 miles west of my location. From the station to the tower, they transmit at 159 MHz FM. Now, my base station was grounded and I was using a directional Moonraker 4 full wave antenna. These antennas are known for their narrow propigation and are very reliable. At the time, my antenna was pointed straight north, and shouldn't have interrupted them at all, but it did.
It would not be uncommon for a mobile unit to have almost the same effect using as little as 200 or 350 watts simply because there is no earth ground and an omnidirectional antenna. I used to go out to the lake in my car, clip a set of jumper cables to the bumper and throw the other end in the water or hook them to a set of guard rails, and had no problem with bleedover.
Another thing you have to look at is that on a lot of smaller mobile antennas (1/4 wave, 1/2 wave), as the power increases, and as the coax heats and cools, the SWR calibration changes. An untuned or improperly tuned antenna will also cause bleedover.
Yes, my friend, bleedover is alive and well, and there's probably nothing you can do about it. A guy once told me that the only way to really idiotproof something was to get rid of the idiots... You're probably going to have to find another place to fly.

Rodney

Yes, 27 MHz signals can interfer with 72 MHz if the relative signal strength is great enough. What happens is that there is enough RF energy picked up by the 72MHz receiver to saturate the AGC/noise filters and reduce the gain to marginal levels. It does take a great deal of difference in power levels but it can and does happen.

Lomcevak Duck

My Feedback: (14)

Fair enough. I'll take more experienced word over normal theory any day.

spitfire66

Thank you all for your posts. I will continue to investigate.

Jon Easley

with enough power you can interfear with cell phones I know had it happen to me driving down the highway I was a trucker I heard his conversation on my phone and I also was that guy with an linear amp on my cb I cold talk at least 12 miles on plains ( line of site ) in the hills a diffrent story so yes a cb radio with an amp can cause problems.

Gary L.

I kicked the guy across the street of his computer with mine a couple of times Give me more power !!!!!!!!!!