Originally Posted by rick dazzler

Yikes! I started readiong these threads lately and am a little scared. I was one of the guys who switched from futaba fasst to this .. I have had no issues in 3 years what so ever nor has any of our club members.. I will keep my fingers crossed..

Nothing to be scared of!! Just don't go fixin' something that aint broke!!!

Hi,
today a knew that another crash with A9 and new versions.
http://www.e-voo.com/forum/viewtopic.php?t=120367
http://www.rcgroups.com/forums/showthread.php?t=1506908

here is a good article
http://www.modelairplanenews.com/blo...he-discussion/

Great reading. Maybe 2.4 aint so bullet proof. I know for a fact that we have saw interference using JR radios in a certain location. One of the places we fly is over a natural gas pipeline. When you go over a certain spot the plane will make abrupt moves on its on, even a couple of time totally loosing link. It has been noticed with 72mhz also. I know there is a box located on the pipeline that has something to do with a charge sent down it for electrolysis. If you walk over the pipeline with a compass it will go crazy. I dont know how it works but it most def interferes with TX and RXs.

Yes it is interesting, but I flew for two summers in the same place, always the same, without any problem, and after the software upgrade I lost three models, all flying in a straight line. I am not a beginner, fly R / C of almost 10 years and I never lost a model when I flew in a straight line.

Regards

After crashing with the same receiver 3 times, I think I would be trying another receiver.

Greg

Originally Posted by MUGUREL

Hi,
today a knew that another crash with A9 and new versions.
http://www.e-voo.com/forum/viewtopic.php?t=120367
http://www.rcgroups.com/forums/showthread.php?t=1506908

Originally Posted by YAKMAN76

When they get it resolved they sure will be hurting alot of Futaba and Jr feelings once again....

nope not at all. it will just mean we can get out of the cars when the hitec radios take to the air

I am looking for an Optima 9 receiver.. Anybody here selling one?

Originally Posted by oldrookie

After crashing with the same receiver 3 times, I think I would be trying another receiver.

Greg

I use 2 receivers Optima 7 in 3 times.

Regards
Mugurel

Originally Posted by 2.4ghz

here is a good article
http://www.modelairplanenews.com/blo...he-discussion/

As an engineer, I find this article painful. There is little that is actually wrong, but much that is not completely correct, or is misleading.

The best and easiest examples of what is wrong come in the section on latency. He is right about human latency of 200 msec being dominant for all 2.4 GHz systems. The comments about the speed of light are correct, but irrelevant. He doesn't even mention things which do affect the radio systems latency, such as channel bandwidth, frame rate and processor loop times.

Hey all....
I just wanted to tell you great Hitec service is...
I burned my board on my A9 when I mistakingly soldered the lipo adapter reverse polarity...

within 1-week Hitec fixed it, and sent it back...
They didn't charge me ANYTHING....
I even admitted it was my fault!....
I had the radio for a year... But have only flown planes 2 times with it...

When I sent them my Futaba 9cap, and told them the reason my front case was messed up, due to the fake brass metal flaking off... (since day one) they charged me for everything.....160$ later.....And I will get it back.... good as new! Probly could have purchased a used/newone for that...///

Anyway.... I am not sue if I want to purchase the futaba 18mz now...'
I love my hitec A9, as no issues... I just wanted more channels...

I am not an engineer and it scared the he>< out of me.

Originally Posted by CatalinaWOW

As an engineer, I find this article painful. There is little that is actually wrong, but much that is not completely correct, or is misleading.

The best and easiest examples of what is wrong come in the section on latency. He is right about human latency of 200 msec being dominant for all 2.4 GHz systems. The comments about the speed of light are correct, but irrelevant. He doesn't even mention things which do affect the radio systems latency, such as channel bandwidth, frame rate and processor loop times.

There are MANY types of Engineers...what kind are you?

Originally Posted by CatalinaWOW

As an engineer, I find this article painful. There is little that is actually wrong, but much that is not completely correct, or is misleading.

The best and easiest examples of what is wrong come in the section on latency. He is right about human latency of 200 msec being dominant for all 2.4 GHz systems. The comments about the speed of light are correct, but irrelevant. He doesn't even mention things which do affect the radio systems latency, such as channel bandwidth, frame rate and processor loop times.

Well, holding personally a master degree and a PhD in engineering I would say latency is not the substantial point of Dave Horvath's message.

And btw it is not so easy to give a description of something being relatively complex so that every dummy can understand it. But it is the essence of communication that everybody can understand the message.
Think, Dave has done a great job to convey his message.

Juergen

OK, I'll fess up. Electrical engineer. Too much time with Plonsey and Collins and Ramo, Whinnery and Van Duzer. 40 years of hobby and industrial experience with frequencies from a couple of MHz up through and including ultraviolet light.

More examples of my issues with the article.

Yes, 2.4 GHz is more lightlike than 72MHz, as it is 30 times higher in frequency. But light is 100,000 times higher in frequency than 2.4 GHz, so the two RC frequencies are really pretty close neighbors. When I was a puppy engineer it was common to treat 2.4 GHz differently than "real" radio because components to do "real" radio things like amplifiers, superhetodyne conversion and so on were at best research items. Nowdays the components are cheap and widely available, while "real" radio things are starting to be done at near optical and even optical frequencies. This wide availability (along with relatively low regulatory controls on this band) is why 2.4 GHz RC exists, along with routers, Blue Tooth, Zigbee, telephones and all the other things that are increasing the base noise in this band.

Yes, 2.4 GHz penetrates foliage less well than 72 MHz. Both do better than my Mark I eyeball. If you are flying behind trees and buildings you have higher priority problems than selection of RF band. The smaller antennas of 2.4 GHz are easier to mask with aircraft structure, but the flip side of that is that it is easier to place them away from masking and interfering elements.

I haven't come up a simple way of explaining my thoughts on reflections and Fresnel zone comments. Suffice it to say that I could use the same physics and come up with reasons to question why you would ever select a lower frequency. A short start is that reflections can be either specular or diffuse. Specular is the sun shining off a still body of water. Diffuse is the sun shining off a cornfield or other rough surface. Obviously there can be mixes. Reflections tend to be specular when the surface has roughness or variations that are small with respect to the wavelength of the light in question. So 2.4 GHz will be roughly 30 times less likely to see specular reflection than 72 Mhz. Is that good? Depends. Too many factors for easy analysis.