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Independent tests prove lack of frequency hopping with XPS - Page 51 - FlyingGiants Forums
Three days of stuffing around with the systems and new toys and now I am making head way.
First off a disclaimer. I am not an electronics engineer. I like this hobby immensely and have never and will never set out to make enemies in it. What I have been able to come up with here maybe totally up the shoot bonza. I have been wrong many times before and I consider of part of the learning process. What I say here are my own findings and I think they are based on sound ideas and practices.
It is not my intention to flame Extreme Power Systems or any other brand or supplier of radio equipment in this test. If I have an issue it is my issue that I have chosen to share in the search for an answer or a better way to repeat the test. The equipment I have for testing has not been given to me for free. It has been supplied by FG members and suppliers who are open to fair suggestion and comment.
I dont get a cent for doing this and dont want one. This is fun, it is interesting and its not a competition to find the best. I will leave that judgement up to you. I will try to stick to the facts as I see them and nothing else.
OK I have a set of slides here to show the sequence of the test and events. I will do a seperate post for each one so there is no problem identifying the graph with the activity.
Step 1: Simple stuff. Here is a graph of the environment I done the test in. I shutdown all my wireless systems to make the place was as clean as possible.
Step 2:
Because I wanted XPS off Ch1 I setup some noise to force it away from the left side of the graph. To do that I cranked up the wireless video cam.
Step 3:
Then to be sure I had Ch1 fully loaded up I turned on the signal generator to leave no gaps and be sure to force XPS off that first channel
If you look at the upper graph you will see the yellow line showing the duration and the spread. With the signal gen on it really covers about three channels.
Step 4:
Turn the Rx on and lets see what it does to try and find the Transmitter.
In this graph again on the upper panel you can see there six yellow and red dashes followed below by a scattered pattern of dots as the Receiver hunts for an answer. Note that there are no transmits from the Rx in the occupied channels are shown in solid yellow.
Step 5.
Turn on the Transmitter and get a link.
Here you can very clearly see the red and yellow signal being recorded in this case on Channel 11.
Step 6
Now its time to get things moving or hopping with a little bit of luck. What I done here was place the sig gen in traverse and set it running. As this moves across the channels one at a time in a sequential motion slowly sneaks up on the XPS signal. I really figured if anything was going to make XPS move this would as its a rising noise floor and moving slowly, thus giving XPS lots of time to call for a channel change and out run the danger.
Nothing happened. It rode out the interference and never moved.
Step 7.
Try another way. This time I set up the sig gen to pulse on the same frequency as XPS was locked into. I figured seeing as slowly raising the noise floor did not have any impact I would hit the actual channel with pulses. Again these were set to 5 seconds on and 5 seconds off. Here my thoughts were it has to move under this scenario as it has thousands of milliseconds and lots of gaps to escape from that demon interference I was firing at it.
The yellow bands clearly show the whacks of interference I was firing at the XPS.
Again it just stubbornly refused to move to a clean channel. It stayed stuck in the mud so to speak.
Step 8.
Well there was only one more way to jolt this thing onto another channel and that was hit it with everything. Full on burst on the same channel, no rising floor. I knew this had not worked for others but if I did not try it then it left a gap and room for debate.
So full strength 2.4 on Ch 11 and still it did not move.
Well that about does me on XPS folks. I will not say it does not hop channels as there may be a way that it can. But so far I have:
Raised the noise floor slowly
Pulsed on the same channel
Drowned it with interference
And none of those scenarios causes XPS to swap to a cleaner channel.
SO what's my verdict.
If XPS hops channels then please someone show us on this site and in this thread how, why when and where because I cannot force it to do so, no one else has been successful in doing so. I'm buggered if I know how. I'm out of ideas and scenarios.
I personally would not use this system until its proven.
XPS cannot be made to HOP under reasonable test conditions and circumstances that should force a frequency change.
So after all that I turned off the sig gen and yes sir. XPS was still happily firing away on channel 11.
No thank you.
