I have the 2.4ghz sektrum radio system. I was wondering why the antenna was so short on the rx??? Anyone know?

An engineer's scale is available for a couple bucks at any office supply store (Office Depot, Office Max, Staples, etc). It's the "triagular" ruler you see there. One of the sides measures inches in tenths.

Also, this ain't rocket science (ok, some of it is...). .6 inches is so close to 5/8" (which is marked on my 6 yo niece's PlayDoh ruler) that the difference (25/1000") should really be insignificant for our purposes. Maybe an issue if you're trying to drive the Mars Explorer, but not for playing with toy cars on the rug (or in the sandbox, or...).

You're right, those engineers are laughing their a$$es off...at those "gay" RC'ers who can't figure out basic measurement. :lol:

Scottrik

Scottrik...

...your insight is incredibly admirable. I'm sure glad you took time out of your busy day to enlighten us with your anal viewpoint.

The manufacturer's direction says "Exactly 3.6 inches", not 'just about' or '3.625"' which also translates to three and five-eights of an inch. With the fear of voiding the warranty, my 10 year old son, who is certainly not as enlightened as you, was worried about cutting his antenna incorrectly.

Please feel free to continue to show all of us your true character (on and off the track, I would guess!).

Regards
Allan

Allan, I'm sorry you've taken offense, but...a fine lesson you're showing your son, indeed, referring in a derogatory manner to people/things you have no knowledge of as "gay". That was my prime objection. I could go on, but it's obvious you see what you wish to see and nothing more.

And if you REALLY think .025" is going to make THAT big of a difference, drop a couple bucks on that engineering scale. Here's a hint...it AIN'T gonna matter, and the "warranty" concern is far greater opening things up and re-routing/re-trimming them than it EVER will be if you're a few thou off when you're trimming it. This warranty concern is a red herring. Your real concern was being shown you were incorrect ("rulers" that measure in tenths are, in fact, readily available) in an, admittedly, facetious manner.

Scottrik

First, higher frequency means shorter wavelength. A very oversimplified explanation is that higher frequencies send the same information at shorter intervals so the antenna can be shorter :-). In truth it has to do with wavelength and antennas work best when they're the same length as (or rather certain multiplies of) the wavelength being sent. It's pretty complicated because you have multistranded wire in the rx antenna and that behaves like lot of side by side antennas, note also the wire thickness has effect on how the signal is received. There is signal strength, then there is signal to noise ratio, the antenna is designed to minimise noise and maximise signal.

Just be assured that the short antenna works.

Well anyway, I measured as close to 3.6" with the ruler I had and recut my arial, and hey presto, my range is back :)

There ya are...sounds like "close enough" was, well, close enough! Great news.

Oh...don't tell Allan, but I'll be nothing is wrong with his radio. I had a similar problem with my JR XS3 Pro and fought with it until I figured out it was caused by how I trimmed my servo to "centered". Same basic radio...

Scottrik

glad to hear that. I will try to find a simple explanation to this phenomena and post it here....

Scottrik
 

Ok, Scottrik,

I concede.

Yes, you are right in that I might have been too harsh in my lack of knowledge regarding the reasonings behind why the manufacturer has their set of guidelines. And, yes, my remark was indeed derogatory. As was my reply to your derogatory post to me. For that, I apologize.

My point; show me any racer at a local club or even at a national event that has an engineering scale in their pit box at the track. There is a tool out there for every instance. I just thought that it shows little thought to the comsumer for a 'toy' manufacturer to expect the median age user to have to purchase yet another item to ensure success in the hobby.

I, in fact, spoke with Spektrum on an unrelated matter and even Tech Support says that it is quite silly to have "3.6" as the "Exact" measurement.

I, for my part, will avoid posting 'derogatory' remarks about and toward anything or anyone. I hope others will follow.

Allan

Alan--no problem. Your appology is accepted and I sincerly hope mine is by you.

My point with the regular ruler was that if someone was going to really measure it out and make the best estimate they could snipping JUST below that 5/8" mark by, like, and X-acto width they would be even less than the 25 thou off. Yeah, engineers get a little "extreme" at times but in this case you can appreciate they took the known amplitude of the signal and made the appropriate division with their calculator. The readout said " 3.6 " so guess what they wrote down in the spec, regardless whether everyone (anyone) was equipped to measure it. What would be funny as heck is if it actually read something like, oh, 3.625 and they did us a favor by rounding to the nearest tenth :lol:

We users tend to complicate the situation by over-thinking the problem. I'm as guilty of being anal about measurements as the WORST case engineer--often measurements that just don't matter if/when one thinks reasonably about it. And no, most people (tool whore me included) don't have an engineers scale in our box. I hadn't even thought that the EASIEST way to do the job would have been with my caliper (set it on 3.6", press one "inside measure" fork against the circuit board and use the other as my cutting guide). I've got a caliper in my race box (actually, one in each), if you don't you can pretty well bet someone at the track does.

Now, your radio and your steering discrepancy. And maybe you've already done it this way--I hadn't. I ended up with the rate dialed WAY up to get enough steering to the "light" side and then used epa to limit the side with too much steering angle. This was NEVER a satisfactory solution as the steering balance had been compromised.

Assuming you installed the servo with the horn as close to centered as you could with the radio at "straight ahead". Be sure you had the steering trim (switch above the wheel) and steering sub-trim (menu item, left and right) set to zero when you do this, and with the radio on and the servo hooked to the receiver. Now, use the sub trim (menu item, L/R) to center the servo as close as you can (why is it I can't buy a servo that is "centered" with the horn pointed straight one way or the other on the case? THERE'S an engineering problem for ya). NOW you should have reasonably equal steering to the left and right. Use your EPA (L/R) to keep from hitting the steering stops, and I use the "rate" to adjust my turning circle. Use the trim switch above the wheel only to adjust if the car pulls one way or the other. It was magic--and I'm embarrassed to say how recently I found this.

hth,

Scottrik

Did this Guy go to the "Borat" school of Math?

ummmm. . . how you mean?

OK here we go, this will settle all arial disputes. This is a reply straight from Spektrum.

But it doesn't explain why when I cut my arial closer to 3.6" that my range came back.

anyone had a runaway with spektrum??
 

Has anyone here experienced a "runaway" with a spektrum system. On 2 seperate occaisions, I installed a charged battery in my car, put the car on the track , grabbed some throttle and the car took off uncontrolled. The car kept going until it went up against a board where my speed control went up in smoke. The first time it happened it was with a Hara Twister and this last time was with a QC2. The first time it happened I figured the speedo just went bad but this time Im starting to think the receiver mmay be the problem. It is the standard spektrum system for a M11 with the module just being updated by Horizon. Has anyone had any similar problems or hear of anything like this??

Coons... The aerial, actually ALL aerials are design to sync into a certain wavelength signal. To do so, they need to be of a certain length. This is why the aerial lengths on different recievers is different. Now, some aerials and systems will have fancy winding patterns, or electronics to mimic the full extended length in a compact package.

In RC, the wavelength is small enough that a full length antenna is best.

The Spektrum even though is is a 2.4GHz system relies on the same principle. In order for the reciever to get the best signal, the antenna length must correspond to a multiple of the transmitted wavelength.

So - it's either full length as it came from the factory, or 3.6inches from the board. Preferrably running the aerial straight up. Hence the specific length.

Running the aerial at any arbitrary length will result in a weak signal being recieved.