Independent tests prove lack of frequency hopping with XPS

[klhoard]

Wow, both of my HEROES in ONE video!! I think I'm going to make it my screen saver!!

[KrisW]

	Quote: Originally Posted by wizard
	As an answer to the question about frequency allocation. The problem is trying to find an open area of the radio spectrum. Here is the US frequency allocation chart.

Who else uses 72 mhz?

Just boot them off and give it solely to RC usage.

Are we the "mobile". . or the "Fixed" guys? I'd HATE to think I ever got "Fixed".........

There are lots of dedicated, or semi-dedicated "Amateur' bands that we could use...50-54 mhz, 145, 2.3g, etc.

I guess there are power or encryption standards that kind of make them problematic for us, though.

[RH1N0]

As far as the testing goes, It looks like we have the test items (the 2.4 receivers) and we have the measurement device (Metageek Wi-Spy) but what devices/signals will be used to create the potential interference? The origins of the thread suggest a 2.4GHz video transmitter but there are many different video transmitters on the market and also many other sources of 2.4GHz signals.

I was at my local hobby/consumer electronics store the other day and I had a good look at the specifications on the various video transmitters, wireless cameras, baby monitors etc. It was interesting to note that none of the 2.4GHz items seemed to specify if they were narrow band vs. spread spectrum or direct sequence vs. frequency hopping. Some said that they had four selectable channels and I think that these are probably direct sequence but I think it is important to understand what's out there and which interference sources pose the most risk.

There are also test parameters such as near field vs. far field, electric vs. magnetic, primary vs. spurious etc which should probably be considered. There are probably others but I will need to drag out some text books and refresh my memory.

Just curious to know what the plan is.

[erichevy]

For sure these jammer for cell phones should be tested where Kiwi was talking about.

Eric.

[KrisW]

	Quote: Originally Posted by RH1N0
	FYI... but not intended to derail this thread. http://www.rcgroups.com/forums/showa...mentid=1660908

HHHHHHHHHHHHHHHMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM . . . . . . . . . . . . . . . . . . . . . .interesting. . . . . . . . . . . .

[3ddd]

would the cell phone jammer be enough coverage to give it a good test,even if it didn't cover all of the spectrum it should cover most of it.

[klhoard]

	Quote: Originally Posted by KrisW
	HHHHHHHHHHHHHHHMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM . . . . . . . . . . . . . . . . . . . . . .interesting. . . . . . . . . . . .

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Yeeeeaaaaahhhhhhh, more products from JD. . . .
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[aviti]

	Quote: Originally Posted by hillmanr2
	This is a very easy situation to control on 72mhz. All that would be required is for every 72 mhz radio sold from now on, to scan for unused channels the way 2.4 does and polk hobby radios( no I don't use one) and not transmit on used channels and bind the same way 2.4 does, on 2 free channels although this is not necessary. This would allow 30 users at a time. Don't bother with the GUID thing, it would not matter as 72mhz is a controlled freq and it is a software program not a radio necessity. Rc'ers would then still have a dedicated, shoot down free, frequency tag less, environment, not subject to the increasingly noisy environment of 2.4. which I bet will be to screwed up to use by most within 2 years

How would this solve it? You make all the current 72 stuff that doesn't do this illegal? That would take time like it did with narrow band a few years back. Imagine the outrage from people that still have perfectly good stuff on 72 that would then be useless. Even after phasing all the old stuff out, you could still be shot down by the park flyer that picks up a synthesized module at a garage sale for 5 bucks.

It's a good idea in theory but difficult in practice....

[XJet]

	Quote: Originally Posted by RH1N0
	As far as the testing goes, It looks like we have the test items (the 2.4 receivers) and we have the measurement device (Metageek Wi-Spy) but what devices/signals will be used to create the potential interference? The origins of the thread suggest a 2.4GHz video transmitter but there are many different video transmitters on the market and also many other sources of 2.4GHz signals.

There are *many* different sources of 2.4GHz signals in the "real world"(tm) and they have wildly varying characteristics.

This is why I'm building a flexible signal source for the testing I'm doing. Getting an array of every type of different potential problem device would be a daunting task indeed so the signal source I'm building should be capable of simulating most of them while also providing a way to accurately set power levels, bandwidths, etc in a consistent and reproducable manner.

In effect I'll be able to set the center-frequency, width, chip-rate, power and duty-cycle/rate of the signal(s) being generated so I can emulate most analog or DSS or FHDSS scenarios. The siggen actually has three RF sources so I can create a noise spectrum with holes to check frequency agility under very adverse conditions.

	Quote:
	I was at my local hobby/consumer electronics store the other day and I had a good look at the specifications on the various video transmitters, wireless cameras, baby monitors etc. It was interesting to note that none of the 2.4GHz items seemed to specify if they were narrow band vs. spread spectrum or direct sequence vs. frequency hopping.

In my experience, anything costing less than $1K will be purely analog -- simply modulating a 2.4GHz carrier with and video and audio subcarrier. Depending on the quality of design, this will produce a bandwidth that varies according to the video standard used (NTSC/PAL/SECAM/etc) and content being broadcast. The poor ones are also rich in splatter caused by intermod and other modulation artifacts.

[RH1N0]

	Quote: Originally Posted by XJet
	There are *many* different sources of 2.4GHz signals in the "real world"(tm) and they have wildly varying characteristics. This is why I'm building a flexible signal source for the testing I'm doing. Getting an array of every type of different potential problem device would be a daunting task indeed so the signal source I'm building should be capable of simulating most of them while also providing a way to accurately set power levels, bandwidths, etc in a consistent and reproducable manner. In effect I'll be able to set the center-frequency, width, chip-rate, power and duty-cycle/rate of the signal(s) being generated so I can emulate most analog or DSS or FHDSS scenarios. The siggen actually has three RF sources so I can create a noise spectrum with holes to check frequency agility under very adverse conditions. In my experience, anything costing less than $1K will be purely analog -- simply modulating a 2.4GHz carrier with and video and audio subcarrier. Depending on the quality of design, this will produce a bandwidth that varies according to the video standard used (NTSC/PAL/SECAM/etc) and content being broadcast. The poor ones are also rich in splatter caused by intermod and other modulation artifacts.

Your flexible signal source sounds cool. Should be interesting to see the types of signals you can generate and which ones the 2.4 receivers don't like. I assume the other testers will probably just use a range of consumer devices and see which ones interfere. This is good as well and could help identify the best video transmitter to use if you want on board video on your plane or heli.

Just checked a video transmitter module I had lying around and the spec's say it has 4 seperate channels and PLL freq stability so I guess it's a narrow band transmitter since you wouldn't advertise PLL if you could boast about SS. This particular module was recalled by the supplier because it can transmit beyond the legal power limits.

An example on Wi-Spy web site shows a frequency hopping signal from a Graco baby monitor and a before and after view of a wi-fi network when the baby monitor was switched on. The Graco baby monitor I found on the web retails for $199USD at Target. During my search, it was interesting to read some of the consumer reviews of different video transmitters as there were some interesting comments such as "my wireless router causes fuzzy lines on the video when i click a web link" and "If I select channel 3 on the baby monitor it interferes with my internet".

http://www.metageek.net/docs/sample-...o-baby-monitor
http://www.shopping.com/xPC-Graco-Gr...-Video-Monitor

[acrorc]

	Quote: Originally Posted by RH1N0
	was at my local hobby/consumer electronics store the other day and I had a good look at the specifications on the various video transmitters, wireless cameras, baby monitors etc. It was interesting to note that none of the 2.4GHz items seemed to specify if they were narrow band vs. spread spectrum or direct sequence vs. frequency hopping. Some said that they had four selectable channels and I think that these are probably direct sequence but I think it is important to understand what's out there and which interference sources pose the most risk.

Most consumer type video transmitters are wideband FM (4 to 10 mhz wide). Digital video transmitters are rare and expensive)

John W

[RH1N0]

	Quote: Originally Posted by acrorc
	Most consumer type video transmitters are wideband FM (4 to 10 mhz wide). Digital video transmitters are rare and expensive) John W

Thanks! These ones seem to be very common:http://www.airwave.com.tw/24GHz-Anal...AV-sender.html

The AWM630TX (10mW output power) is the module sold at the local store and the one that was recalled is an AWM612TX which has 500mW output power.