Cheap UHF spectrum analyzer (and RC tx rx) using RFM22 module

This is and excellent project! :slight_smile:
I really want to try it out in my FPV quads.

Does anyone has PCB's to sell?
Unfortunately I have no way to make them.
(well I could but I'd probably ended up sleeping in the balcony)

Thanks!

This is exactly what this is - a DIY project.

It would be nearly the same cost to make a few by hand and sell to you as it would be to buy commercially.

Have you seen this?
http://flytron.com/16-openlrs

Forum support as well
http://forum.flytron.com/viewforum.php?f=7&sid=5794eb0b6f028f25cacb8b980bba52fa

HTH

Nigel.

Rustie0125:
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.

You will only see a 20dB jump if you were perviously transmitting at 0dB! Theoretically, if you are transmitting at 0dBm (1mW), and connect the tx directly to the rx with a coax cable (do not do this!) you will see 0dBm on the receiver. However in real life and if you are using antennas, you will see the rx RSSI change from about -20 (the RF22 will not report RSSI higher than -20) to -100 as you move the rx away from the tx.

Rustie0125:
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.

That will probably work ok, but you will need to write your own code. I might add more to the PC program, but it's not really a priority. You can do your own data processing by collecting the serial data and plotting them in MS Excel or MatLab or even do it on the arduino chip.

Nandox7:
This is and excellent project! :slight_smile:
I really want to try it out in my FPV quads.

Does anyone has PCB's to sell?
Unfortunately I have no way to make them.
(well I could but I'd probably ended up sleeping in the balcony)

Thanks!

Basically what Devonian said. If you want one or two boards that work right out of the box, you are better off getting the openlrs. I only have the bare pcbs.

BTW, Nigel did you get the thing working on your main PC? If your boards are working properly I'll put together some RC PPM code this weekend for you to test. I've not really been motivated to do much this past week because of the terrible weather!

Hi Z,

My first board works just fine as a spec analyser.
I've yet to build my other boards.

I'm a bit like you, no big motivation for UHF at the moment (I have OpenLRS for UHF R/C), plus I have a couple other projects - including weather monitoring, maybe with an RFM22B and an Arduino :wink:
With the British weather, you should get on it !

Nigel.

zitron:
Basically what Devonian said. If you want one or two boards that work right out of the box, you are better off getting the openlrs. I only have the bare pcbs.

My problem sorry, I wasn't that clear.
I'm more of the soldering station type, I prefer to assembly my own gear. :slight_smile:

I know about Flytron gear I actually bought some other parts from them, but yes my intention is to get bare PCB's.
I have all the remaining parts just the PCB that is missing.

I got some time ago some similar RFM boards (RFM21 I believe) to do a telemetry project but got sidetracked and ended
going for BlueTooth and developing an app for it. And the the boards are still here getting dust.

But what you share here is on a another level (special in what concerns range) and rather interests me, so I eager to try it
and put my hands on the code as well. :slight_smile:

PS: I got you guys on the weather (Ireland here)

Hi zitron,

Where did you get your RFM22B? The only that I can find seem to have the emitting power locked and can't do the 100mW.

Thanks

Nandox7:
Hi zitron,

Where did you get your RFM22B? The only that I can find seem to have the emitting power locked and can't do the 100mW.

Thanks

Nandox7:
I know about Flytron gear I actually bought some other parts from them, but yes my intention is to get bare PCB's.
I have all the remaining parts just the PCB that is missing.

I got some time ago some similar RFM boards (RFM21 I believe) to do a telemetry project but got sidetracked and ended
going for BlueTooth and developing an app for it. And the the boards are still here getting dust.

But what you share here is on a another level (special in what concerns range) and rather interests me, so I eager to try it
and put my hands on the code as well. :slight_smile:

Oh, does that mean you can help with the code?? I have 4 boards left, Rustie0125 wants 1, so you can have the last 3. PM me your address, email and how many you want.

Devonian:
My first board works just fine as a spec analyser.
I've yet to build my other boards.

I'm a bit like you, no big motivation for UHF at the moment (I have OpenLRS for UHF R/C), plus I have a couple other projects - including weather monitoring, maybe with an RFM22B and an Arduino :wink:

Cool. I can help you with the code if your weather telemetry project is something simple, like tx/rx of serial data or something.

Hi Z,

I'm gathering together some bits as the data is apparantly sent over 433.92MHz AM radio by OOK (On-Off-Keying) and there is some info on the 'tinterweb about the protocols used.

I may just get another weather station with serial out on the receiving consol and do it that way.

I also have a Raspberry Pi on order (for ages now), maybe a low power web server and automatic weather station??!!

Too many projects and not enough time...!

Nigel.

Thanks zitron, I'll send you a PM.
Yes I do plan to help with the code. :slight_smile:

In regards to the RFM22B I've talked to someone that is trying to get some as well and the only ones he could find
available were the RFM22B-868-D, will those work?
Does it need to be the 433 model or it's possible to change the frequency.

Okay one thing iv noticed between the different in graph that you postted and the one i posted yours seems to be a lot cleaner and not as jagged spiked like mine . but that said mine is set to max output.

once i get my board from you i would like to use it to test home made 433 radios . what would be the best set of settings for use with RF probes and not antennas? i would image i would set the Tx/Rx power right down to minimum ?

Devonian:
Hi Z,

I'm gathering together some bits as the data is apparantly sent over 433.92MHz AM radio by OOK (On-Off-Keying) and there is some info on the 'tinterweb about the protocols used.

I may just get another weather station with serial out on the receiving consol and do it that way.

I also have a Raspberry Pi on order (for ages now), maybe a low power web server and automatic weather station??!!

Too many projects and not enough time...!

Nigel.

The RF22 can certainly do OOK, but it will not be trivial to do the software to read whatever protocol they use... Maybe it's possible to intercept the data before it gets to the transmitter on the weather station, and use your own tx rx? I also want a Raspberry!

Nandox7:
In regards to the RFM22B I've talked to someone that is trying to get some as well and the only ones he could find
available were the RFM22B-868-D, will those work?
Does it need to be the 433 model or it's possible to change the frequency.

The 868MHz version should work just fine. I can even change my 434 module to 960MHz, but obviously it won't work very well. You might need to make sure that 868MHz is a legal frequency in Ireland!

Rustie0125:
Okay one thing iv noticed between the different in graph that you postted and the one i posted yours seems to be a lot cleaner and not as jagged spiked like mine . but that said mine is set to max output.

once i get my board from you i would like to use it to test home made 433 radios . what would be the best set of settings for use with RF probes and not antennas? i would image i would set the Tx/Rx power right down to minimum ?

Did you leave it alone to gather data for long enough? The peak value should smooth out over time.

I think the best way to test radio output would be to connect the tx to rx directly with an attenuator, so you don't have to worry about antenna weirdness. Then again, I am definitely not qualified to answer any RF related questions!

Here is the code for a standard 10 channel PPM RC tx+rx for my boards. You must use my modified version of the RF22 library!

On the TX you need to connect 5V PPM to header D3. You can put a switch or jumper on the header next to the RF22 (GPIO2) to switch between low power (1dBm, 1.3mW) and high power (20dBm, 100mW, red LED on). You can easily change the frequency in the code (remember to change rx as well!).

On the RX the LEDs indicate RSSI values: Green > -70dBm, Green+Red > -85dBm, Red > -100dBm, else/no signal = no LED.

Be careful not to connect servos the wrong way around. I didn't use current limiting resistors on the arduino pins to save having to solder 10 more SMD resistors, so it is possible to damage the output pins if they somehow get stuck on and end up powering your servo!

rf22_RC_TXRX.zip (4.08 KB)

Great improvements!!! Very nice Zitron :wink:

For the ones that ordered the RFM22 from RF-store how long did it took to arrive?
I have all the parts to build the boards (except some solder paste) but I'm still waiting for the RFM22.
I made the order on the 4th of this month. :frowning:

Mine took less than 1 week from Germany to England - not bad for just a few Euro's postage.
You should be able to log in to your account and check your order status.

Nigel.

I've sent them an email.
They replying saying that it got out of stock in the mean time... and haven't sent it yet.
Maybe still during this week they'll received more.

As I got the order stuck there, I was wondering about this: rf-store - rf-store
If I can build the same frequency scanner with it as well for 2.4Ghz. From the specs it seems so as the frequency can be selected up to
a 1Mhz interval.

Nandox7:
As I got the order stuck there, I was wondering about this: rf-store - rf-store
If I can build the same frequency scanner with it as well for 2.4Ghz. From the specs it seems so as the frequency can be selected up to
a 1Mhz interval.

That is pretty cheap, but I don't see a register for the RSSI value anywhere.

It's register 05 for the RSSI.

Btw, after almost a month I got an email saying that my RFM22 were shipped...
I had asked to include one of these cheap 2.4Ghz... but got no reply. :S

We'll I'm going to start assembling the boards as yesterday I got the solder paste and I expect the RFM's to arrive during next week.

Nandox7:
It's register 05 for the RSSI.

Btw, after almost a month I got an email saying that my RFM22 were shipped...
I had asked to include one of these cheap 2.4Ghz... but got no reply. :S

We'll I'm going to start assembling the boards as yesterday I got the solder paste and I expect the RFM's to arrive during next week.

That's a long time to wait! I have been flying my plane with the RFM22, it's working great so far.

Register 05 is write-only, it's "RSSI Threshold for CD detect". You can't read the RSSI value from it.

zitron:
That's a long time to wait! I have been flying my plane with the RFM22, it's working great so far.

Register 05 is write-only, it's "RSSI Threshold for CD detect". You can't read the RSSI value from it.

Yes it is.. :frowning:
And if I hadn't contacted them I wouldn't even knew what was going on.

That's right, I totally ignored the 'W'. :slight_smile:
But if it allows to seat RSSI report or not, it must have a way to read it.

Seems more are looking for it. :slight_smile: