459MHz UHF legal Tx and Rx - Arduino based programability.

[Devonian]

Well, if you want to change the little bit of code before Mihai releases his 'fix' - then just find & change the one line of code in both the Tx and Rx pde, upload to the Tx & Rx and you're good to go.

All's well that ends well and nobody lost anything, thankfully.

Dennis has just realesed v3 of his spec an' software - looks pretty clean and sharp now...
http://forum.flytron.com/viewtopic.php?f=7&t=335&sid=8897d1094050de89667488556e818c7b&p=2545#p2545

I still have the RFM22B hardware I modded and will check the output if I can find the little RF head I built (I think I robbed it for the coax?).
It was such a s*** to mod the board, I wouldn't risk doing another, it really tested my soldering ability to the limit.

Nigel.

[Splashy]

Nigel,

So when you changed the rf circuit component values and experienced an 8mw drop in power output, it was still running on 433mhz (that would now make sense!)

Wonder if you still have that modified vtx ? and if so, I wonder what difference in power output there is when actually on 459 ?

Using my newly acquired OpenLRS spectrum analyzer it shows a peak value of 121 for running at 439 Mhz and 157 for running at 459.

This is of course not definitive but the antenna I used on the spectrum analyzer RX was a 433 antenna whilst the TX antenna was tuned to 459. Distance from TX to RX was a couple of meters but I would not say that any decrease in output power is experienced and if anything there may be a power increase.

[thundead]

anyway, new thUndeadMod fw will be out tomorrow with the 459Mhz band fixed (again lol) hopefully for good this time + some extra goodies in the config app :D

Cheers for everyone who tested out the fw and pointed out the bug.

Mihai out :D

[Coyote]

Nice one Nigel :) My kinda graph :)






After closer analysis it still appears to be transmitting on two channels not 5, 459.05 and 459.35mhz

[Dennis Frie]

The default firmware only have around 18-20% active send-time. With 5 channel hopping, that makes it 4 % of the time, the signal on the single channel is actually present. With around 50 hz update-rate, each channel will be seen as 10 hz. That means you actually have to stay at the same channel for around 100 ms to see the channel - and only 4 % of the samples will actually be taken while the signal is present (that's the reason why it's just barely visible on the average readings, while it's clearly visible on max).

So in short, if you want to get a good picture of the channels, you should increse "Nr avg" to something like 250-500, and if you have a little patience you can also set step-size to 2 or something like that. Unfortunatly, fast scans will/can miss frequency-hopping devices, at the signal is only present rarely.

[Coyote]

Hi Dennis, welcome to Fpvuk.  Loving your work man :)

I tried the test at Nr. Avg 500 Step size  1



And Nr. Avg 1000 Step size 2

[phibin]

wow alot seems to have happened since last time i looked at this thread....

well done on your work guys! :)

so... will the v3.3 FW work @ 459mhz now?

im itching to have a test now but i have 459 antennas and dont really want to use it on 433...
really want to get the best out of it...

thanks,

simon.

[Coyote]

Yes Simon, my pictures above show V3.4 FW loaded and running on 459mhz

[phibin]

yes :)

just found the 3.4 on the google thing..

thanks!

simon.

[Dennis Frie]

I have just done a bit of testing to see how well the RFM22B module performed when used outside the normal 433 mhz frequency band, and figured it might be of interest to you guys, since you use 459 mhz.

Test was done with OpenLRS configured to frequency-hopping between 23 channels, and a receiver as frequency-analyzer. I'm sending at 245 mhz, 255 mhz..... 465 mhz.

First test with the modules connected directly with a cable and 60 dB attenauter:



- and with stock antennas:


In relation to the frequency-response of the module, the test with cable is the interesting part. I have the XML-file if you want the data, but this is the key-data:
Freq RSSI:
245 162
255 166
265 166
275 166
285 166
295 165
305 164
315 164
325 165
335 163
345 162
355 161
365 154
375 158
385 169
395 175
405 176
415 180
425 188
435 192
445 192
455 189
465 182

Now for you guys, the interesting is around 459 mhz. It's clearly that the RSSI value has dropped a bit.
A quick plot in excel gives this around 459 mhz:


My guess is something like 186 RSSI value compared to 192 around 435 mhz. The difference is 6 rssi value ~= 3 dB. That should be about 50% of the power available at 435 mhz.

[thundead]

so that concludes that the olrs operates optimally at 435 mhz right ?

[Dennis Frie]

so that concludes that the olrs operates optimally at 435 mhz right ?

It was a quick test, but it seems so yes. I have just tested your new firmware, will post a quick scan in a moment  :)

[Dennis Frie]

thUndeadMod V3.4.

The frequency is now at 459 MHz as expected  :P

I just chekced, the frequency-spacing have been set to 10 khz, and the default channels (with 6 channels jumping) are 0-45, meaning 459 mhz - 459.32 mhz. A pretty narrow frequency-span.

The seperate channels can't be seen, as they are simply too close to each other. The channels are:
0,5,10,35,40,45
You can see a tiny seperation between channel 10 and 35.

[thundead]

haha that's indeed barely noticeable. We'll have to repeat the range tests to see how bad that 3db drop affects the range... (lets hope its not cutting the range right in half).

Cheers for your tests Dennis :) I'll drop u a PM.

Mihai.

[Dennis Frie]

Just tested with a RF-meter:

On top, thUndead software:
Bottom, default firmware.

The interesting thing is the refresh-rate and send-time.

Do you use packets a lot larger than default firmware? And what about refresh-rate? From what I can see it seems to be 25 hz compared to the default 50 hz.
If so, I suppose the frequency-hopping is 25 hz as well. Isn't that gonna give more "dead-time", if a channel is missed?