ISM band: 2.4 GHZ is a sweet number

dissymmetry · Nov 04, 2009, 08:18 AM

The base resonant frequency of H2O, microwave ovens (because it's the res of water, it boils it), radar, and all of my favorite electronic toys. Im new to heli's, but my last big electronic love affair was 802.11 wireless networking, so these new 2.4ghz radios are just perfectly suited to what I've perfected, lately. Now as an old "HAM" fan, I already knew the basics going in, and I still like the old HAM expression of radio frequency, not as actual frequency count, but in terms of wavelength, that being the actual length of the radio wave at any given frequency. The reason is that to make an antenna, the trick to "tuning", is that the antenna MUST be measured in fractions of the wavelength. One of the reasons I like this band so much is that the wavelength is about 12cm, which makes some really cute scaled antennas. I made a yagi beam, once, for the 11m "CB" band, that thing was 32 feet across. I made one for this band, out of a popsicle stick!
This is good stuff to know, that your 2.4 ghz antennas are always going to be cut to 3, 6, or 9cm, to tune out, but more importantly, that things like AMPLIFIERS that are made for 802.11b/g, will work, as wil the antennas. I nice plus, too, is that r/c apps need only work in one direction, therefore an amp or high gain antena on your transmiter will multiply it's effective range many times.
Im waiting for my first real heli, now, but I can promise you, related equiptment I already have around IS GOING to be put to the acid test, and I'l let you all know how it turns out. I've connected to public "hotspots", and conected for free internet, at out to a mile, so it stands to reason I can expect the same resaults for my heli. I know that this is extremely overkill, but depending on what you have in your toy, KNOWING that there is no range that you can see the thing that could outreach the radio connection seems comforting to me, at least. And you could probably go way out farther than you could see, if you wanted to. It is a really, dirty, band, after all, with every microwave oven making like 2000 watts of white noise, and such, you cant have too much transmit power, I think.
Any thoughts on that, anyone?
This one watt, fixed gain amp is a bargain, and should do nicely. It's 5vdc, and I have one to exparament with.
http://www.ayagroup.com/product.php?...&cat=24&page=1

hb888 · Nov 04, 2009, 08:54 AM

Quote:

Originally Posted by dissymmetry

The base resonant frequency of H2O, microwave ovens (because it's the res of water, it boils it), radar, and all of my favorite electronic toys. Im new to heli's, but my last big electronic love affair was 802.11 wireless networking, so these new 2.4ghz radios are just perfectly suited to what I've perfected, lately. Now as an old "HAM" fan, I already knew the basics going in, and I still like the old HAM expression of radio frequency, not as actual frequency count, but in terms of wavelength, that being the actual length of the radio wave at any given frequency. The reason is that to make an antenna, the trick to "tuning", is that the antenna MUST be measured in fractions of the wavelength. One of the reasons I like this band so much is that the wavelength is about 12cm, which makes some really cute scaled antennas. I made a yagi beam, once, for the 11m "CB" band, that thing was 32 feet across. I made one for this band, out of a popsicle stick!
This is good stuff to know, that your 2.4 ghz antennas are always going to be cut to 3, 6, or 9cm, to tune out, but more importantly, that things like AMPLIFIERS that are made for 802.11b/g, will work, as wil the antennas. I nice plus, too, is that r/c apps need only work in one direction, therefore an amp or high gain antena on your transmiter will multiply it's effective range many times.
Im waiting for my first real heli, now, but I can promise you, related equiptment I already have around IS GOING to be put to the acid test, and I'l let you all know how it turns out. I've connected to public "hotspots", and conected for free internet, at out to a mile, so it stands to reason I can expect the same resaults for my heli. I know that this is extremely overkill, but depending on what you have in your toy, KNOWING that there is no range that you can see the thing that could outreach the radio connection seems comforting to me, at least. And you could probably go way out farther than you could see, if you wanted to. It is a really, dirty, band, after all, with every microwave oven making like 2000 watts of white noise, and such, you cant have too much transmit power, I think.
Any thoughts on that, anyone?
This one watt, fixed gain amp is a bargain, and should do nicely. It's 5vdc, and I have one to exparament with.
http://www.ayagroup.com/product.php?...&cat=24&page=1

I wouldn't worry too much about sticking an amp on your Tx. I've flown a EDF jet too far to be controlled without lossing RF link with a AR6100 park flyer Rx. You are more likely to suffer from poor reception due to on board intra interference rather than lack of signal strength, or shadowing by CF parts.

I also beleive the USA versions of the Specktrum Tx are more powerful (at around 250mW, you can search FCC's database) compared with the European versions because FCC allows for up to 1W on 2.4GHz. I recall Europe version is like 150mW.

Another reason to avoid sticking 1W on your Tx is that you may saturate your Rx when your Tx is close by, so unless you get some to plug in the RX for you at some distance there will be a risk.

My 2 cents.

If I was to design a Tx/Rx system from scratch I would probably base it around a CDMA system which would be noise immune completely.

One final point. Do you really want to be holding 1W at 2.4GHz in your hands?

RC Man · Nov 04, 2009, 07:09 PM

The current transmitters sold in the US (like Futaba FASST) have a 5 mile range and that’s plenty for most of us. I suppose that it you need more range you could just go to a fractal antenna.

Andrew McGregor · Nov 05, 2009, 06:26 AM

Don't bother with amps... RC receivers have about 30dB better sensitivity than wifi (because they run a lot slower), so you don't need amplification to get a really decent range.

Better receive antennas can be useful... but again, there's no need to go there for most cases.

Remember that you're modifying a tried and tested system in a safety-critical application. So, unless you have a compelling reason, don't.

Also remember that U.Fl connectors (on the TX RF board, for example) are only rated for 15 cycles, and only when used with the correct insertion and extraction tools... don't go fiddling with them, they fail.

Nov 04, 2009, 08:18 AM	#1
dissymmetry Senior Crash Expert Join Date: Nov 2009 Posts: 2	ISM band: 2.4 GHZ is a sweet number The base resonant frequency of H2O, microwave ovens (because it's the res of water, it boils it), radar, and all of my favorite electronic toys. Im new to heli's, but my last big electronic love affair was 802.11 wireless networking, so these new 2.4ghz radios are just perfectly suited to what I've perfected, lately. Now as an old "HAM" fan, I already knew the basics going in, and I still like the old HAM expression of radio frequency, not as actual frequency count, but in terms of wavelength, that being the actual length of the radio wave at any given frequency. The reason is that to make an antenna, the trick to "tuning", is that the antenna MUST be measured in fractions of the wavelength. One of the reasons I like this band so much is that the wavelength is about 12cm, which makes some really cute scaled antennas. I made a yagi beam, once, for the 11m "CB" band, that thing was 32 feet across. I made one for this band, out of a popsicle stick! This is good stuff to know, that your 2.4 ghz antennas are always going to be cut to 3, 6, or 9cm, to tune out, but more importantly, that things like AMPLIFIERS that are made for 802.11b/g, will work, as wil the antennas. I nice plus, too, is that r/c apps need only work in one direction, therefore an amp or high gain antena on your transmiter will multiply it's effective range many times. Im waiting for my first real heli, now, but I can promise you, related equiptment I already have around IS GOING to be put to the acid test, and I'l let you all know how it turns out. I've connected to public "hotspots", and conected for free internet, at out to a mile, so it stands to reason I can expect the same resaults for my heli. I know that this is extremely overkill, but depending on what you have in your toy, KNOWING that there is no range that you can see the thing that could outreach the radio connection seems comforting to me, at least. And you could probably go way out farther than you could see, if you wanted to. It is a really, dirty, band, after all, with every microwave oven making like 2000 watts of white noise, and such, you cant have too much transmit power, I think. Any thoughts on that, anyone? This one watt, fixed gain amp is a bargain, and should do nicely. It's 5vdc, and I have one to exparament with. http://www.ayagroup.com/product.php?...&cat=24&page=1

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Nov 04, 2009, 07:09 PM	#3
RC Man A man with too many helicopter Join Date: Feb 2001 Location: Illinois Posts: 10,713	The current transmitters sold in the US (like Futaba FASST) have a 5 mile range and that’s plenty for most of us. I suppose that it you need more range you could just go to a fractal antenna.

Nov 05, 2009, 06:26 AM	#4
Andrew McGregor Registered User Join Date: Jun 2006 Location: Christchurch, New Zealand Posts: 6,489	Don't bother with amps... RC receivers have about 30dB better sensitivity than wifi (because they run a lot slower), so you don't need amplification to get a really decent range. Better receive antennas can be useful... but again, there's no need to go there for most cases. Remember that you're modifying a tried and tested system in a safety-critical application. So, unless you have a compelling reason, don't. Also remember that U.Fl connectors (on the TX RF board, for example) are only rated for 15 cycles, and only when used with the correct insertion and extraction tools... don't go fiddling with them, they fail.