Spektrum Spektrum DX7 - DSM2 - Should I be worried?

[mooserider]

So I was out at the field this weekend and some of the guys mentioned that I should be worried about using an older DX7 (not 7s), which uses DSM2. They claim that there are folks around our field that use some special beaming technology that beams info from place X to place Y (these places they told me are like 30 miles apart at least). And that there are 'dead spots' in the sky for your radio if they happen to be doing this beaming stuff at the time.

I'm a very skeptical person. Is this reasonably feasible? They claim it happens about once or twice a week. One of the guys was trying to show me at the time I was out there... literally, "here, watch if I fly over here my throttle will go full without me doing it." I asked him, why would you fly over there then?? I mean, someone reading this might think they were playing a joke on me, but believe me, these folks were serious about it.

But, I put so much work into this plane I'm working on, I don't want to end up crashing because of something like this. Do I really need a new system here to be safe? I've never had any issues with using it for my Trex or other planes, but I don't fly them at the club air field much until just recently.

Thanks.

 

[Smoggie]

I think they are probably being honest but they are most likely 'misguided'. Myths and superstitions can grow from a few people crashing in the same part of the field and all of a sudden that part of the field gets a reputation for being a 'interference zone'. So did the guy's plane go to full throttle when he flew there without him doing anything?... I'll bet not.

 

[mooserider]

Well, he claimed it did while I was flying... "did you hear that?" But I was focused on other stuff.. so then I started pacing his plane and listening, and he said it didn't happen at point. But I try to give the benefit of the doubt... especially in these cases. But I had to wonder why, if it was worrisome, was he still using the same transmitter/reciever. And it was only one of the 2 folks that seemed to talk a lot about it.

I have not spent a lot of time at this field yet. But from my experience, each has its own issues. It was guns we had to worry about back when I was learning... hunters would take out our planes on very rare occassions. Here it's microwave beaming or some such. ; )

 

[Tony]

DSM2 locks on to one channel and keeps that channel until you bind the Tx and Rx again by turning on the two getting ready to fly. DSMX actually locks onto multiple frequencies and can hop between them if the one it's on gets crowded.

The towers they are talking about are likely microwave towers. The ones that look like they have large drums on the top of them. Can these signals cause issues, yes they can if everything is right. Will it "only" cause a plane to go full throttle, no it will not. It will cause what is called a "brown out" which is a complete and total loss of control. You can verify a brown out by the Rx flashing when you get back to the ground. If it's flashing, that means you have lost signal with your plane at one point or another.

 

[Smoggie]

For info...

The Brown out' flashing with DSM2 only occurs if the receiver has lost power and 'rebooted''. It doesnt indicate a loss of reception.

DSM2 actually locks onto two frequencies and stays on them, so if one frequency suffers interference it can use the other. DSMX uses frequency hopping which means that it continuously 'hops' at very high speed between multiple frequencies in a predetermined pattern. So if one or even several of the frequencies suffer interference you dont notice because it hops to the next before any noticable loss of reception occurs.

I'd be pretty much convinced that those guys were 'dreaming it'.

 

[murankar]

Brown out is a signal loss due to low power. I think what your looking for is a lock out. The TX or sat will not show a lock out. Now the other issue that has not Ben addressed is fail safe. If this guy has a poor fail safe the. Yes his throttle can increase on loss of radio communication .

Specktrum sets fail safe at bind. If your throttle is maxed out during bind then that's your fail safe. Most folks will set a slightly nose down attitude with a slight bank to keep the plane is a turn, then set the throttle to something like 15 or 20%. This would cause the plane to come down gradually while in a turn. The goal here is to keep the plane in the general area while trying to land or light crash.

 

[Smoggie]

FWIW the standard/recommended throttle setting for failsafe on planes (and helis) is fully closed throttle. The biggest reason being that if you were to inadvertently turn off the Tx first or otherwise lose signal while on the ground and in the pits you dont want the motor powering itself up. Also if the plane/heli were to crash due to loss of signal you dont want the motor to keep running.

But Uri is correct, if the guy had set failsafe wrong so as to give full throttle then loss of signal would cause throttle to go open, this is a very dangerous situation because it could easily happen on the ground if the Tx were to be switched off.