Radio interference any solutions?

Unfortunately you have elected to engage in a hobby that ripe with human participation. Because of that there have been, are now and will continue to be human errors. You've had the misfortune to have paid dearly for what seems to be one of those errors. Only sure way to protect from this is to fly where you are positive no one else within ten miles is flying.

Barring that there is nothing you can do but be attentive to your surroundings, aware of what else is going on, know who is doing what with what equipment and on what frequencies. And assuming the disappearing couple were the culprits, learn to associate with a better class of people! Not always possible, I know.

Chuck

I would also suggest checking the automobiles for rooftop "ham radio" antennas as I have seen this shoot down one plane. ONe has to assume that the rest of the world is crossing the T and dotting the I when it comes to keeping their signals clean. The only time I was able to sucessfully run two systems on the same frequency was when one was on FM and the other on AM . It was a ground test. Each worked well up to a point. Never went any further. End of test. We have had problems with one flying and one n hte pits on the same channel causing problems. That is people problems.

You might argue this, but it is my personal experience that those with synthesized frequency selectable transmitters are MORE sensitive to this issue. As a group, we synth owners are VERY aware of proper control and how others can be affected by our actions. It's kind of like how you would expect a police officer to handly a firearm more safely than a casual target shooter in that using the system more often, we have developed a greater respect for it's risks and act accordingly.

Not a good idea because Ham bands are even less protected than R/C bands. You could get hit by someone not even doing R/C but messing with the Ham frequency in the near area at much greater power levels (and don't bother explaining the "legalities" to me, I'm a Ham. I'm talking about the "practicalities").

MJC

| The only time I was able to sucessfully run two systems on the same | frequency was when one was on FM and the other on AM . It was a | ground test. Each worked well up to a point. Never went any | further.

Just in case anybody gets the idea that you can do this in practice ... you cannot.

FM and AM signals will tend to ignore each other (FM especially will ignore AM), so you might have a little luck using both on the same frequency at the same time, but I guarantee that it won't work well.

I've even heard some misguided people claim that their spiffy new radio was so good that two people could use the same channel at the same time! Which is complete and utter bunk. The only way this could possibly work is if the transmitters and receivers were designed to each use half of the channel -- but I know of nobody doing this.

ever heard of upper and lower sideband?

Doug McLaren wrote:

Shoot downs at our field are infrequent, but they do happen. With one exception, when it does happen, the shooter has owned up. One guy was showing another guy a transmitter, switched it on and shot down a plane. If it wasn't for the fact that the guy he was showing the transmitter to insisted that he own up, he wouldn't have said anything. We had one guy who flew big scale planes. He made it a point to ask everyone what frequency radios they had with them. Some people took issue with this because his inquiries were a little "in your face" third degree. He told me he lost a 110" scale Jenny to a shoot down that the guy didn't own up to and had no intention of having it happen again. I would see if someone knew the persons who had the other plane and find out what frequency they were on. I would make it a point to learn everything I could about these people. If they shot you down and didn't say anything, in our group they would be former members. I fly at a private site with a club where pretty much everyone knows everyone else's equipment. Sorry for your loss, Good Luck Bill

I have said it before and I will say it again. I make it a point to know, at any given time, who is on the same frequency as myself. This point is one of the field safety "biggies" yet overlooked by so many. There is a strong need at any field for fliers to simply keep an eye on one another. I would be willing to bet that if another TX with your freq was turned on while you were flying, another impartial pilot may have suspected it but said nothing and let it happen.

rick markel

| ever heard of upper and lower sideband?

Certainly. Now you'll need to explain which one our R/C systems use. (And yes, it IS a trick question.)

And even if you are talking about USB and LSB, do keep in mind that you still can't use the same bit of spectrum with both at the same time. The carrier frequency may be the same, but you're still using different chunks of bandwidth for each modulation type. If you're trying to use the same chunk of bandwidth for both, it's not going to work.

If you've got a RC transmitter on channel 40, and I've got a RC transmitter on channel 40, and we're within a mile or so of each other, they're going to conflict, be it AM vs AM, AM vs FM, or FM vs FM.

If it's AM vs FM, my guess would be that the AM plane would suffer more than the FM plane, everything else being equal, but either way, both planes are going to have problems.

| > In article , | > jim breeeyar wrote: | > | > | The only time I was able to sucessfully run two systems on the same | > | frequency was when one was on FM and the other on AM . It was a | > | ground test. Each worked well up to a point. Never went any | > | further. | > | > Just in case anybody gets the idea that you can do this in practice | > ... you cannot. | > | > FM and AM signals will tend to ignore each other (FM especially will | > ignore AM), so you might have a little luck using both on the same | > frequency at the same time, but I guarantee that it won't work well. | > | > I've even heard some misguided people claim that their spiffy new | > radio was so good that two people could use the same channel at the | > same time! Which is complete and utter bunk. The only way this could | > possibly work is if the transmitters and receivers were designed to | > each use half of the channel -- but I know of nobody doing this.

... for RC anyways.

| We had one guy who flew big scale planes. He made it a point to ask everyone | what frequency radios they had with them. Some people took issue with this | because his inquiries were a little "in your face" third degree. He told me | he lost a 110" scale Jenny to a shoot down that the guy didn't own up to

To be fair, it's hard to prove a shoot-down unless somebody saw the offending radio being turned on, or found it turned on. Other than that, it's a `my word vs. his word' thing.

I've seen a lot of problems blamed on interference. More than half, I suspect that it wasn't interference at all :) And even if it is interference, the interference can come from several locations -- the transmitter owned by that other pilot is only one possiblity.

| > Autopilots are not a current option due to not being accepted by | > the mainstream of flyers yet.

They wouldn't save you anyways. They typically only activate if the stick is in the middle, and in the case of a shoot down, the plane probably sees the stick at an extreme, or bouncing all over the place.

| > In addition, I experienced one as a | > spotter; on a low battery fly a motorized (does 0.15 count as a | > motor?) glider straight down nose first for about 80'. This | > Glider ("Ladybird?") could not be flown straight down if we wanted | > it to. The autopilot was an active horizon type.

The autopilot can't make the plane do something that you can't make it do. It sounds like there was more going on than just an autopilot malfunction if it really did something the plane can't normally do.

| > Program PCM for low power, and near neutral surfaces except for | > some up elevator. (PCM "Programmed Crash Mode" aka Pulse Code | > Modulated - Plan is lowest energy possible over a reasonable | > (walk-able range) decent and stalling sequence.) Lost radio | > contact is always a gamble PCM at least lets me place my bet. | > And, I have heard of but not experienced PCM lockout of | > re-establishing control when the interference was known to be | > removed.

Since most people have plain FM radios rather than PCM, if somebody shoots you down, it's likely to cause your receiver to go into failsafe mode. So do get that set up properly.

| > Also, I am considering Ham Bands for the larger models. (I purchased the | > Ham University CD for preparation)

The technician ham test is easy, and made easier because you have access to the entire test bank. Skim over your study guide, then go to

and take the practice test. Once you can consistently get over 80% on the test there, you're ready to take the real test (where you only need 70%.) There's no need to learn *everything* -- you can miss 30% of the questions and still pass -- so if there's a section that's hard for you, don't worry about it.

(Actually, the general and extra tests are pretty easy too. It's the morse code part that's given me trouble. But you don't need morse code to use the 50/53 mhz ham bands.)

That said, I don't think the ham bands are a magic bullet against interference. Sure, you're not likely to interfere with somebody flying at the field, but a guy down the street transmitting at 100 watts could crash your plane quite easily ...

Couldn't agree more. I have flown on 39 for ten years. The only time anyone has been on the same frequency was an out of towner guest. Yesterday (Which, by the way, was a 50 degree, no wind beautiful day in Central Washington State) a new local guy showed up on 39. So much for having that channel all to myself. We had one guy who lost a giant scale Cub due to being shot down. When it happened, he walked over to the guy in a blind fury and started to read him the riot act. The guy who shot him down said nothing, calmly unclipped and held up the frequency pin that he had just removed from the board and attached to his transmitter. Argument came to an abrupt halt followed by an apology. If it can happen, it will. Bill

With proper filtering, BOTH sidebands can be used simultaneously. DSB systems have been around for over 40 years at least. I trained on DSB intercept receiver systems in the Army in 1969. These systems trransmitted different data on each sideband.

David

One thing I always do is look at the other flyers when I turn my radio on. If anything happens I would immediately turn mine off and investigate. Could save a plane. I've seen the time where it would have several times at our field. Eddie Fulmer

Thanks and I agree exactly as you stated Efulmer. Frequency pin or not, Look first for trouble being caused prior to turning to your airplane at radio start.

To another's response, yes, at my club I know who uses my frequencies. And I go one better, I share this information, see below. And at small Eddie Fulmer

| With proper filtering, BOTH sidebands can be used simultaneously. DSB | systems have been around for over 40 years at least. I trained on DSB | intercept receiver systems in the Army in 1969. These systems | trransmitted different data on each sideband.

Yes, but each sideband is using a different bit of spectrum. The carrier may be at the same frequency for both, but each sideband takes it's own bit of bandwidth. SSB is just a way of using bandwidth more efficiently than AM does, that's all.

And it's moot anyways. I'm not aware of any generally available RC gear that uses SSB. It could be done, but it's not.

Certainly, any fool who thinks that he can use AM and FM transmitters on the same frequency is going to get what he deserves. Hopefully it's just his plane that he crashes, and not some other poor guy's.

| On Mon, 23 Feb 2004 20:21:16 GMT, snipped-for-privacy@frenzy.com (Doug McLaren) | wrote: | | >In article , | >jim breeeyar wrote: | >

| >| ever heard of upper and lower sideband? | >

| >Certainly. Now you'll need to explain which one our R/C systems use. | >(And yes, it IS a trick question.) | >

| >And even if you are talking about USB and LSB, do keep in mind that | >you still can't use the same bit of spectrum with both at the same | >time. The carrier frequency may be the same, but you're still using | >different chunks of bandwidth for each modulation type. If you're | >trying to use the same chunk of bandwidth for both, it's not going to | >work. | >

| >If you've got a RC transmitter on channel 40, and I've got a RC | >transmitter on channel 40, and we're within a mile or so of each | >other, they're going to conflict, be it AM vs AM, AM vs FM, or FM vs | >FM. | >

| >If it's AM vs FM, my guess would be that the AM plane would suffer | >more than the FM plane, everything else being equal, but either way, | >both planes are going to have problems. | >

| >| > In article , | >| > jim breeeyar wrote: | >| > | >| > | The only time I was able to sucessfully run two systems on the same | >| > | frequency was when one was on FM and the other on AM . It was a | >| > | ground test. Each worked well up to a point. Never went any | >| > | further. | >| > | >| > Just in case anybody gets the idea that you can do this in practice | >| > ... you cannot. | >| > | >| > FM and AM signals will tend to ignore each other (FM especially will | >| > ignore AM), so you might have a little luck using both on the same | >| > frequency at the same time, but I guarantee that it won't work well. | >| > | >| > I've even heard some misguided people claim that their spiffy new | >| > radio was so good that two people could use the same channel at the | >| > same time! Which is complete and utter bunk. The only way this could | >| > possibly work is if the transmitters and receivers were designed to | >| > each use half of the channel -- but I know of nobody doing this. | >

| >... for RC anyways.

Normal AM radio is DSB, but the same info is present in both sidebands, and half the transmitter goes into the useless carrier. SSB is AM with the carrier supressed, so ALL the power goes into the selected sideband. AM is prone to natural interference - lightning is the main culprit. That's why FM is used - amplify the heck out of the signal, whack off the top and bottom where the noise is, and have a clean signal left.

David

I dont ever fly during a lightning storm even if I DO have FM. You think I am some kind of nut?? Natural selection will take care of them.

Doug McLaren, I love your last line.

AM is pr>>Doug McLaren, snipped-for-privacy@frenzy.com

A bolt of lightning 100 miles away will trash an AM or SSB signal with a 20/9 or 30/9 static crash !

David

Greetings warlockg,

Well I think the responses so far have been pathetic. You have provided a huge amount of detail on your problem and demonstrated that you are prepared to put in a lot of time and expense to field a first class model yet you have been told that nothing else can be done to protect yourself from idiots. Well if you are prepared to work as hard as you have to get a

1/4 scale into the air, you are entitled to look for and develop the innovative solution.

Now my ideas won't all be appealing, many are illegal or way too hard but perhaps there's something here to brainstorm into best practice.

_Going out of band_

1. Already suggested, the Ham bands.
2. The RC band from another country, yes obviously illegal but at least the equipment can be had without modification.
3. Purchase a license in another band. Just like a taxi company. You pay your money and get exclusive use of a carrier in your area. Then pay a sparky to modify your Rx and Tx circuits.
4. How about the latest bleeding edge spread spectrum technology.
5. Convert your gear to transmit and receive through a pair of mobile phones.
6. Convert your gear to work over WiFi, Bluetooth etc. Put a compact computer in the air and get a down-link for free.
7. Get some crystals cut to a frequency between two channels, every time you fly reserve two channels, with a little luck the idiot will be outside discriminator range of your receiver.

_Power Wars_

1. Fit a linear amplifier to your Tx. It doesn't need to be as rude as those 100W jobs that Hams and CBers favour, heck, just a couple of watts more than the standard RC Tx.
2. Same concept, hang a higher power Tx from your belt connected to the buddy cable from your hand-held Tx. Just key it on the odd occasion that you need to blow away the idiot. May need to shutdown the hand-held Tx without stopping its encoder in order to avoid cross modulation.

_Panic Detector_

1. Obtain a second Tx module and another Rx. Operate the Tx on your belt or back pack, as above feed it from the buddy port. The aircraft will need some smart electronics to change over to the secondary Rx - a circuit to monitor the pulse width from an unused channel, if interference causes that pulse to drop out then it would change to the other Rx.
2. The same monitor circuit as above (forget the second transmitter) interface the panic detector to co-pilot, a gyro or similar.
3. This one should be good for a few laughs. A receiver somewhere in your field kit on the flight line. Same monitor circuit as above. This time when the signal is compromised the clever electronics activates:

12a. Automotive air horn, the louder the better, or 12b. An amp, speaker, recorded message: "GET OUT OF CHANNEL 99 (YOU JERK)"

1. The fail safe PCM business but in some way interfaced to co-pilot, a gyro or similar to overcome the objections in your original posting.

Food for thought,