increasing rc's range

[dayshaddow]

hi all
soz its been a while but ive been very very busy,flying the helis,driving my truck and i also i have returned to sea fishing after a 15 year break.
so its pick ya brains time.my trucks range is kinda limited (2.4ghz) is there a good way to increase its range.thing is its a 1.8 scale truck so its kinda large but find aprox 100ft range sucks as i have some wonderfull off road driving places and being big and kinda fast its easy to let it run away

oh and i got me a new canopy which was clear and i sprayed it up and lackered it what do you guys think of the look

https://www.helifreak.com/attachment...1&d=1368119333

[wulfrun]

Originally Posted by dayshaddow

hi all
soz its been a while but ive been very very busy,flying the helis,driving my truck and i also i have returned to sea fishing after a 15 year break.
so its pick ya brains time.my trucks range is kinda limited (2.4ghz) is there a good way to increase its range.thing is its a 1.8 scale truck so its kinda large but find aprox 100ft range sucks as i have some wonderfull off road driving places and being big and kinda fast its easy to let it run away

oh and i got me a new canopy which was clear and i sprayed it up and lackered it what do you guys think of the look

https://www.helifreak.com/attachment...1&d=1368119333

Increasing the Tx power is unlikely to be an option - you also need to increase it far more than you'd think to make a useful difference (doubling it doesn't double the range). If you can get that antenna higher up though, that's probably going to be the most effective way. Might be easier said than done though!

Realistically, a new radio gear setup is likely to be the only way to make a big difference.

[sutty]

Looks good Antony. Well looks good for a car. As you may or may not know, the key to range is the height of your antenna. That's why TV masts, etc, are tall, or high up at least. My suggestion is that you do a small mod by strapping it to the bottom of a model chinook, which will then be able to get you high in the air, giving you plenty of range.

Out of curiosity, what radio gear is it. I know you said it was 2.4GHz, but is it using your normal radio gear, or a specialist controller? 100 feet sounds poor to me, even for ground hugging equipment. Get about that when I push the low power range test button on my DX7 and put the heli on the ground.

Cheers

Sutty

[dayshaddow]

im back from some proper off road bashing with the truck. ok so its sounds like the small 2.4 ghz rx radio needs a longer antena.so i can easily extend the antena by adding more wire so its out of the top of the t ruck.will this affect the 2.4 ghz rx.im shore i remember in the mhz days the length of the antena affected the the rx due to radio frequency ?? will adding extra length to a 2.4 ghz system be changed with extending the antena

hay sutty
the truck is using a weird rc car tx and rx.sadly i know almost nothing about it but its a very simple design with a spring loaded trigger for the throttle.the spring centers it to mid stick or 0%.pulled towards you is + and away is first break then a double tap is reverse ??? the stearing a controled by a wheele on the side of the tx.works well and is very simple to pick up
this is a pic but not of my tx you get the idea
https://www.helifreak.com/attachment...1&d=1368132296

[sutty]

Ah, one of those specialised controllers. Who knows what power they are set to or have available.

Same thing as with your MHz days, the antennas are tuned to the frequency. With Mhz the whole length was generally in play, and they were always about 1m in length. Don't remember how long exactly, but can check in a minute. Same with Ghz, but now the cable is often coax, which means it is screened along the majority of its length. The bit that sticks out at the end, about 30 or 40mm is the part that is tuned to the frequency. It is the height of the active element, not the length. The length of the active part is the bit that makes it tuned.

The maths is easy, c = f x w. Can't do the proper symbols, but c = the speed of light, in m/s, f is the frequncy in Hz, and w is the wavelength in m.

3x10^8 = 2.4x10^9 x w
w = 3x10^8 / 2.4x10^9
w = 0.125m or 12.5 cm

Now as it happens, and I don't know the maths behind this, but I remember it clearly from my radio days, aerials at 1/4 wavelength are preferred. Practicality reasons play a part, but also for whatever reason, 1/4 wavelength is slightly better.

So, for your 2.4Ghz, 12.5 cm full wavelength, 1/4 wavelength just over 3cm, or 31mm ish, which is what we observe on our systems.

For your 72MHz days.

3x10^8 = 72x10^6 x w
w = 3x10^8 / 72x10^6
w = 4.17m

1/4 wavelength therefore = about a metre.

Cheers

Sutty

[redbird300]

Antony, if I may add this: if you would increase the antenna length on your 2.4 GHz system to half a wavelength (62 mm) or a full wavelength (124 mm), this could slightly improve the range. You have to do that at both sides (RX and TX), and make sure the antennas are perfectly straight at all times. And don't solder an extra piece of antennawire, you would need to replace the whole wire, the solderpoint in the middle of the antenna would cause problems. Not sure if it's worth all the effort though.

[sutty]

My memory is very hazy on this, and you'll know better than I Raf, but I thought I recalled from school that simple antennas are best at 1/2 wavelength, and the 1/4 wavelength versions work because the quarter wavelength also creates a 1/4 wavelength virtual antenna reflection in the ground plane of the equipment, once again making a 1/2 wavelength antenna, at least electronically, or mathematically. Is this not true, or have I forgotten something more in all those years?

Cheers

Sutty

[redbird300]

You are right Andrew, IMHO. Problem is that in our relatively small RC devices, the ground plane is very limited in size, and of poor quality, especially at the receiver side, electrically speaking. That's why is was thinking it might help to stretch the antenna. Should try and measure this once myself one day, would make a nice experiment.

Not that hard, now that I think about it, I still have that small 2.4 GHz analyzer that I used in this thread https://www.helifreak.com/showthread.php?t=347351.



You just gave me an idea in fact. I could try to set up a test measure with a stock antenna and a longer one, given the exact same conditions of course. But I would need a transmitting receiver to measure signal strength, hm...., I think I have a spare TM1000 Spektrum telemetry module laying around, let's think...oh God, please stop me now !

[wulfrun]

Originally Posted by sutty

For your 72MHz days.

What were you doing with 72MHz gear? It isn't legal in the UK

Interesting that the US had 72MHz and UK had 27MHz, followed by 35MHz. So, a half-wave UK 35MHz antenna is pretty close to quarter-wave US 72MHz - handy for the manufacturers.

Antenna design, beyond the basic, is actually far more complex than most people believe and I take my hat off to anyone who designs them. It's especially crucial to the Tx to provide the correct load and most efficient radiation. In the "old days" of 27, 35 etc MHz and (relatively) high-power Txes, a bit of wire of approximate length would work well enough for the Rx. Not so for 2.4GHz. The main improvement that's likely to be possible here is, as pointed out, to raise the height of it but NOT change the length or design.

[redbird300]

http://tighar.org/wiki/Frequency,_wa...antenna_tuning

Quote:
Radio waves are transmitted from the movement of an electromagnetic wave along a conductor--the antenna wire. If we had unlimited resources, it would be best to have an antenna that was at least one wavelength long. This is not too difficult with high frequences (short wavelengths--or "short waves"). Popular HAM radio equipment operates on wavelengths of 2 meters, 6 meters, and 40 meters; it is not too hard to rig full-wave antennas for these wavelengths. A full-wave 2.4 GHz antenna is only 4.92" long.
If one cannot afford the space for a full-wave antenna, the next best thing is to use an antenna that is a half-, quarter-, eighth-, or sixteenth-wavelength.
Tuning coils can compensate to some extent for antennas that are not an even fraction or multiple of a wavelength.

[dayshaddow]

Originally Posted by redbird300

Antony, if I may add this: if you would increase the antenna length on your 2.4 GHz system to half a wavelength (62 mm) or a full wavelength (124 mm), this could slightly improve the range. You have to do that at both sides (RX and TX), and make sure the antennas are perfectly straight at all times. And don't solder an extra piece of antennawire, you would need to replace the whole wire, the solderpoint in the middle of the antenna would cause problems. Not sure if it's worth all the effort though.

i think your right it isnt worth the effort.the guys on my truck forum said to change both tx and rx,and even recomended a radio.it looks great and it can be programed so its got me very interested as i want to soften the bottom of the throttle curve and change thr reverse speed.the stock reversing speed is something like 20% max oh and the stock tx has a stupid delay when switching from full break to reverse