2.4GHz Band Saturation

It seems possibly the most misunderstood aspect of 2.4GHz radios is how many can be used at one time and if that saturation point is met, what happens?

1. The number of radios that can be used at 1 time is LIMITED. This exact number of radios that can be used at 1 time varies according to several factors, but indeed it needs to be know that the band can only handle a limited number of radios in-use at 1 time. (more on that a little further down…)

2. IF that saturation point is reached, generally “more” radios will not be able to be “turned on”. They will search for an open frequency, will not be able to find one, and will simply wait until one is available. In “some” conditions, the FHSS systems might turn on, but will be slow (It’s OBVIOUS)…

 Some companies have talked more about this than others, but here’s the scoop…

The high-output portion of the band we use in 2.4GHz (as regulated by the FCC) is split up, somewhat arbitrarily by our systems (each company has their own way of dividing up the frequency band).

 FHSS radios bounce around the band, Spektrum and other DSSS or DSM systems simply chop it up into about 80 frequencies (in the aircraft side of things, they use 2 of those frequencies…)

So, indeed only about 39 DSM/DSSS aircraft systems can be in use at 1 time if Spektrum is the only radio in use. (see a link to Spektrum and a quote from their website at the bottom).

 If you mix all the different brands and their proprietary type of signal/system, generally, the total number of radios that can be on and function 100% reliable without slow down, etc. is about 36 for aircraft (surface gets more because when only surface systems are in use, Spektrum is only using 1 frequency at a time instead of 2).

Now, that 36 number can vary, but in our practical testing, we’ve found it’s right around 36-39.

At that point, the DSSS and DSM systems will no longer find a clear signal and the other brands start to slow down a little.

 What it means: EXCERSIZE frequency control at major events or busy flying fields!

Is 2.4GHz better? SURE, OF COURSE!!!. If too many radios turn on, either they will not find a frequency and will not transmit or they will work but just with a little delay (thus you’ll see it and probably just turn off anyway) unlike 72MHz where if some one just “turns on” without concern, he can knock you out of the sky!

So, 2.4GHz is GREAT but there are still limitations and you and your club/flying field might want to consider those limitations.

I hope this helps.

Mike

Note these quotes from Spektrum brand:

http://www.spektrumrc.com/DSM/FAQ.aspx 

Quote from Spektrum:

What happens if the band is full (80 users for surface or 40 users for aircraft) and I turn on my transmitter?

In the unlikely event that all channels are occupied, the next transmitter will scan the band indefinitely until open channels are available. The transmitter will then acquire the channel(s) and begin transmitting. Only then will the system connect.

Spektrum, DSM, Horizon, are all products copyrighted by Horizon Hobby.

www.horizonhobby.com

 I’m only mentioning them here to help create wider understanding of the hobby.

DSSS, Airtronics, Sanwa, are all copyrighted by Sanwa Japana and used by Global Hobby with permission.

(I’m not trying to step on anyone’s toes here!)

Reasons why I Like Sanwa/Airtronics….

1. When we tested the first RDS8000 2.4GHz test sample, their Executive Director and Senior Engineer were there, in person, in So CA, to work with me testing that radio.

2. They didn’t come until they had tested it themselves repeatedly.

3. When we found ways to improve it, they did it….here’s some examples…

longer range

programmable failsafe

trainer system compatible with vG and RD radios of the non 2.4GHz type

4. They gave us MORE samples to test all over the country. When we found ways to improve it, they researched it, executed the improvements, and airshipped revised samples directly to our pilots.

5. Even though they were still on a deadline to get the radio produced, they delayed production for more testing when I just had a “concern”.

6. Their entire R&D staff put in extra hours to work to get the radio done.

7. They made it for a price that makes it a value. It’s not some overpriced piece of work. It’s got an aggressive price to make sure it’s competitive.

8. They didn’t get greedy on the Receiver but instead made it the most affordable 8 Channel 2.4GHz receiver on the market at 79.99 typical street price. They did this, in part, because our test pilots told them how important receiver pricing is.

9. They added a range test feature not in the original design simply because our pilots asked for it. There was no “I’m an engineer and I know more than a modeler” b.s., there was ONLY “Let’s make it right for the modeler on this first radio as best we can.”

Is the RDS8000 perfect in all ways.. of course not… NO Product is….  There are always improvements to be made when you’re striving for perfection… Is it a great value and a super first step into 2.4GHz for Airtronics? Absolutely. The radio looks great, works great, feels great, and will serve Airtronics pilots well.

10. This is the most important….. THEY CARE.

So, you may not buy an RDS8000 (too bad if you don’t, you’re missing out on a great, easy to use, sport radio!) but just know when you’re considering your next radio purchase or radio accessory purchase that Airtronics and Sanwa engineers care, they listen, and they’re dedicated to making great products.

 Having the RDS8000 finish it’s first production run on Christmas was an awesome Christmas gift for all of us at Global. We’re looking forward to this product and to many new radios, servos, and accessories from Airtronics in 2008!

ModelTech Mini Mach Racer

Russ Greaves and I took out the new Model Tech Mini Mach Racer and put it up for its maiden voyage.

OK, it’s REALLY important that the CG be right on a little plane like this:) Yep, REALLY important… (EDIT: Customer says I’m idiotic because I didn’t post the CG here.  So, here’s the CG: 145mm.. )

When we get prototypes we usually get ZERO documentation from the factory. So, we guessed on this one and got it wrong. The good news is, when it went totally out of control on launch, it was no where near anyone (we always launch well away from ANYONE, pilots included) so there was no danger.

The other bit of good news is that this plane and the prototype motor we flew it with was very durable. We launched, it did the tail low, nose up, wing-tip-stalling dance, before it simply pin-wheeled into the ground, nose first…

NO damage! Got lucky there. So, we moved the battery forward and this time, it flew right out of Russ’s hand, PERFECTO!

Wee the fun we have with prototypes! Anyway, it was AWESOME. 80-90 MPH (based on the speed of the other planes and the speed of which other ‘known’ entities fly at) is my guess.

Lands easy, launches easy, flies very fast, is stable in the entire speed range, and was simply a blast! This is a fun plane to fly.

Now we’re waiting on a new sample with some creature comforts to make it easier to use for the pilot (removable fins and magnet attached canopy hatch so that the plane will easily go back into it’s box and the battery will be easily accessable).

Anyway, cool plane, due in probably May.

Whaddaya all think?

Mike

Merry Christmas

12 Days of Christmas at Hobby People

by: Rick Pike

(Sung by the entire staff while traveling together to our Christmas party last Friday…good thing we have a day-job… all that engine noise has apparently made us tone-deaf!)

 On the 12th day of Christmas,

Hobby People gave to me:

12 Drivers driving

11 Poppers popping

10 Trains a-training

9 Chargers charging

8 Boats a-boating

7 Swoops a-swooping

6 Flits a-flitting

FIVE YO-YO STRINGS LA LA LA….

4 Flying Blimps

3 Rookie Planes

2 MX3s

And an X-T-M-Monster-M-T

 Hope your stocking is filled with killer-stuff that makes the hobby even more fun for you in 2008!

-Enjoy the family, enjoy the kids, enjoy the season, and most of all, I wish you a happy and healthy 2008!

 Happy Landings

Mike Greenshields

Review on Ezone

The BH Models Trojan 60 size ARF has a GREAT review online at ezonemag (RC Groups). It not only shows the plane but a fairly affordable conversion to electric power. Powerful electrics are becoming more attainable without exotic equipment. This article really shows how nice a big power system can be.

http://www.rcgroups.com/forums/showthread.php?t=731144

Mike

Went test flying Monday

One of my job duties that really makes my job not a job is test flying. Monday Russ and I went over to Fairview Park to do a little test flying.

The highlight of the trip was test flying a prototype of the new BH Models twin electric DeHaviland Mosquito. What a cool plane!

Power is a 4 cell (4s1P) 3200mAH (EDIT: I originall stated 40000 mAH…obviously that was wrong! Thanks Farrell!)  y-d to two Casle Creations Thunderbird 36 Amp ESC’s and two 2814 KMS motors. We’re running 9×4 props which only pulls about 36 amps total static (18 amps per motor). These motors are rated to 25 amps continuous with no problem so we’re well under the max power we could put through the system.

With that power system the plane takes off in 20-30 feet, flies along at a very good clip, can pull vertical for a little bit to make a very nice wing-over, stall turn, and square loop. Not exactly scale aerobatics since the Mossie was really a bomber, but wow very very cool.

These new BH Models are simply top-notch. The wing is 2 piece with an aluminum tube joiner, the canopy comes off with two thumb screws, and the nose is the hatch for the battery and this is held on with two self-locating magnets making battery access SUPER EASY.

 The cowls are all factory-fit, the canopy/tophatch has the window installed and detailed, and inside sits two factory painted pilots.

 Another cool feature is that the firewall bulkheads are moveable. This way the modeller can change the dept of the firewall to accomodate different length motors and mounts.

We also flew two new Foamies. One is a Ready – t0 – Fly from WattAge called the Sea Vixen. The full scale Sea Vixen was a English twin boom jet. Our foamie is kinda’ stand-off scale, but it looks nice. Instead of a jet, ours uses a little pusher motor. The power system is a 3 cell lipo on a brushless motor which provides PLENTY of performance. This plane has a nice presence in the air, and since the whole thing bolts together, it’s quick and easy to assemble. Truly a RTF worthy of the name.

The final airplane we flew is a new model from Phase 3. It’s a Radio-Ready P-40. This model will be factory assembled with the brushless motor, 3 cell battery, servos, etc.. but will not come with a radio.

This foamie has a unique feature in a Factory-build plane… It has a retractable landing gear! And it’s all factory assembled so you don’t have to go through the hassle of hooking up all that linkage! (I hate retract linkage!!!)

 Anyway, it was a great day of flying, makes me thankful I have such a cool job! (Yes I’m bragging).