Chaddt
Posts: 29
Joined: 8/29/2006
From: Carlyle, IL, USA
Status: offline
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I am not an RF engineer but I have a degree in electronics and have learned what I have needed to own/run a wireless internet provider bussiness for the last four years. Most of what I know RF wise is related to wireless networking equipment. But the general RF theory is the same as anything else out there. I am by no means an expert but don't mind sharing the little that I know.
I dont know what the power output of the current 2.4 RC systems are. I haven't been able to find this information in any of the documentation online, if you have the FCC ID off one of the transmitters you may be able to find it on the FCC's website. Only other option would be to call them and ask. Also I don't know what the recieve sensitivity of the reciever is, or what the antenna gain is on each end or what type of modulation they are using.
There are a total of 11 channels in 2.4Ghz for 802.11b equipment starting at 2.401Ghz and ending at 2.473Ghz each channel is 20Mhz wide so there are only 3 non overlapping channles these are 1, 6, and 11. Here is a pretty good chart showing frequency and power information for wireless networking equipment, it will show you the center frequency for all the channels.
http://www.demarctech.com/techsupport/ism-info.html
Yes both point to point and point to multipoint use the same channels, so you have to be carefull on channel selection as to not interfere with yourself or others operating in the area.
Yes we have both 2.4Ghz phones and I have a 2.4Ghz network in the house and both work fine for two reasons.
1. I am pretty well directly under our tower so the RF generated from the tower is shooting over the top of our house. This would not be the case if I had an RC plane flying up there.
2. Within the house the furthest a cordless phone gets from its base station or a notebook PC gets from its access point is only a distance of 20-30 feet. So they have really strong signals to the base station and to the access point. Its all about your receive signal level vs your noise floor as long as your signal is better than your noise floor you should be ok. Say if your 2.4Ghz noise floor is -90 and your acctual signal is -70 "less negative is stronger signal" your equipment would operate fine. This is what happens with your neighbors wireless networks, even if you are on the same channel as they are as long as you are recieving a much stronger signal from and to your own access point you would be fine, you may see some service degration from the extra noise in the area but more than likely you would be ok.
Cell phone carriers operate on licenced frequencies. Each carrier has a certain amount of spectrum to operate on that no one else is allowed to use so they don't have to worry about interference issues like you do with 2.4Ghz. The way they are able to have so many users at the same time is based off of the modulation/media access method of the equipment they are using. Thier access point is able to concurrently handle so many calls at the same time and is constantly switching between each persons phone passing data back and fourth.
802.11 network equipment works in the same way I have a single access point with 35 users connected to it at the same time using CSMA/CA "Carrier Sense Multiple Access with Collision Avoidance" it allows all users on the system to have access to the internet at the same time. There are different modulation schemes out there some work better than others in different conditions, some allow more users, some have better overall bandwidth, some have better latency, some are better in noisy areas, there is always a trade off though.
Here is a link that explains CSMA/CA
Hope this helps. Sorry for taking this discussion off topic.
Thanks,
Chadd
quote:
ORIGINAL: Flying Geezer
I assume the output power on the 2.4 RC equipment much less than 1 watt because of the power consumption listed for the Extreme power system modules. Do you know what the power limit is?
Are point to point and point to multi-point units allowed on the same channels? Allowed the same power output? Raw power nor ERP.
How many different channels are there in the 2.4 gHz band? What is the bandwidth per channel?
Do you have a cell phone, if so, how does it work in your home? Do you have 2.4 gHz cordless phones? Do you have a wireless network within your home?
I live in a county of 100,000 people, most of whom have cell phones. Most of them seem to want to talk on them while they run the red light that is green for me. At the mall every little kid over 10 has a cell phone in their mouth instead of a lollipop. My home wireless network picks up 4 of my neighbors. I rarely get a tiny bit of noise on my cell phone and my network runs fine.
I need a more complete explanation of how these things work and I think you can help me.
Thanks in advance,
< Message edited by Chaddt -- 8/1/2007 6:55:59 PM >
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RE: 2.4 GHz - A Broad Market Review - 
