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Topic: Cheap UHF spectrum analyzer (and RC tx rx) using RFM22 module (Read 49 times) previous topic - next topic

Rustie0125

He who does not try ,does not fail ,does not learn not to fail again http://powerduino.blogspot.com/

Rustie0125

just few questions to clarify if what im seing is correct.
below is a picture of a test running currently running on the bench.


if you look at the picture with only the RF22 switched on that is working as the receiver it would appear that there is a very high signal detected in the UHF range where i stay ? or am I seing it wrong ?

also the labeling of the dBs on the left hand side would it not make more sence if it started form -120 at the top and -20 at the bottom? I arleady made the mistake at looking at the spike but in reality if i understand it correct is actually the lowest detected frequency that im looking at , can it be swapped ?

other question is , I have a 17cm antenna on my receiver this would offcourse make a differences for freq. in the 800 or 900 range . what then ? or is this meant to  be used with Rf probes only and not general area scanning ?

thanx for any advice , really keen on useing this more
He who does not try ,does not fail ,does not learn not to fail again http://powerduino.blogspot.com/

Devonian

Hi Z,

I'm also using 0023.

I made a clean install on netbook and copied your RF22 library (from your post above) into the clean libraries folder.
Copied the code (from above) and made a new pde called 'rf22_specan_simple' and veried it.
It compiled OK.

Ran up your RF22SpecScan.exe and it runs fine.

I'll try some more later on my main PC and Laptop as this is where I want to mostly use it.

Nigel.

zitron

#63
Apr 21, 2012, 05:38 pm Last Edit: Apr 21, 2012, 05:42 pm by zitron Reason: 1

Hi Z,

I'm also using 0023.

I made a clean install on netbook and copied your RF22 library (from your post above) into the clean libraries folder.
Copied the code (from above) and made a new pde called 'rf22_specan_simple' and veried it.
It compiled OK.

Ran up your RF22SpecScan.exe and it runs fine.

I'll try some more later on my main PC and Laptop as this is where I want to mostly use it.

Nigel.


OK that's good.


if you look at the picture with only the RF22 switched on that is working as the receiver it would appear that there is a very high signal detected in the UHF range where i stay ? or am I seing it wrong ?

also the labeling of the dBs on the left hand side would it not make more sence if it started form -120 at the top and -20 at the bottom? I arleady made the mistake at looking at the spike but in reality if i understand it correct is actually the lowest detected frequency that im looking at , can it be swapped ?


That looks pretty normal.  The RF22 is not meant to be a spectrum analyzer, it will only work properly for the frequency range the module and antenna is made for. You can force it to whatever frequency you want, but results will not be accurate.

RSSI is a logarithmic scale, you are reading it wrong. See http://en.wikipedia.org/wiki/DBm

I just remembered that that I have made some small improvements to the PC program, I have attached the new version.

Rustie0125

#64
Apr 21, 2012, 06:24 pm Last Edit: Apr 22, 2012, 11:12 am by Rustie0125 Reason: 1
Okay

thanx for confirming that . so for example if the RF22 radio max output is 17-20dBs then if i transmit next the the analyzer i will see a 20 dB jump in the graph but so if it was -120 it will  be -100 or around there.

regarding the Antenna issue , all i really wanna test with these unit is if RF equipments is working or not. for example if i have a 433mhz remote i just want to Tx next to it and see a jump in the graph so Accuracy is not that big of a problem. what i think i would do is make a small Antenna relay board with antenna's made for 900mhz, 433mhz and 600mhz and when i switch between them the reply will latch to the correct antenna Automatically i know its not the best but i think it will be best this setup can do.

are you planning on upgrading the Pc app with more functions ?

like to see if you can set a start line on the average incoming signal and the app will update the max output line at the top of the graph and under the setting just show a tab that updates the dB difference between the two lines.

but thank you for all the advice and info looking forward hearing form you regarding the boards
He who does not try ,does not fail ,does not learn not to fail again http://powerduino.blogspot.com/

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