If you happened to get one of those $7 SDR radio dongles from ebay and need to put it to work... here's one thing I tried...
Tune in with the R820T... (Using HDSDR)
This is both radios running on one channel. They are out of tune enough that the channels don't even overlap!
Now I switch them into beacon mode and tune to 925.000 MHz...
Now I tune them up by adjusting the EZRADIOPRO_OSC_CAP_VALUE to get this...
Through the magic of special effects, I can overlay them...
Below are the before and after pics of normal transmissions (non-beacon mode)...
Here are the actual results I measured (warming up and final calibration)...
Ground = +7.3 khz @ OV 204 (cold)
Ground = +6.5 khz @ OV 204 (warm)
Ground = +6.1 khz @ OV 204 (hot)
Ground = +0.1 khz @ OV 208 (warm)
Air = -6.5 khz @ OV 204 (cold)
Air = -6.2 khz @ OV 204 (warm)
Air = -7.1 khz @ OV 204 (warmer)
Air = +0.6 khz @ OV 199 (warmerer)
All the pictures in this post are to the same scale. The FSK signals (wider pictures) are on a different frequency than the beacon signals.
Make any predictions on expected range improvement below...
Done! Files here...
So the basic procedure is to download Jake_Tune_Adjuster_(925 or 434).ihx, and flash it onto your radio using the standard 3dr radio config program.
Then open a terminal window to your rado's com port. I highly suggest using putty for windows users.
You should get back: OK
Type ATJ and you should get back some info.
Now enter ATK and the radio will switch to a 600 hz test signal on 925 or 434 MHz for 30 sec..
After 30 sec. the radio should emit a pulsed tone on it's frequency. Now you can use ATU and ATY to tune the OSC value up and down.
ATK takes ~30 sec. to complete. You cannot enter any commands during this period. ATU and ATK should take ~3 sec. to complete.
Shift the frequency up or down as needed, on one or both radios. Note the correct OSCval, then load the corresponding numbered firmware from:
Now you have tuned radios running the latest firmware.
Note that the 434 version will say some wrong settings in ATJ and ATK. The calculations were for the 915 version. Stuff like this is why I had it output multiple ways of figuring things. Since this is a utility firmware and I don't have 433 modems to check it with I don't plan to fix it.
Next task is a beacon mode firmware. Essentially the firmware already does this perfectly, just want to clean things up. The idea is for the scenario where you have a radio link on a lost vehicle, but aren't getting GPS data. You would then enter "ATB" or some other AT command to switch to beacon mode, which would be easier to track with handheld radios and foxhunting gear.
@Jake, I can test your future 433 compiled firmware for you if it can help.
Point about 915 vs 433... My test firmware "Jake_Tune_Adjuster.ihx" is written for 915 radios only.
It *should* work on 433 radios, BUT it will still set them to 925 MHz. The 3 lines are these...
MyFreq = 925000000UL;
Should just have to change those to a lower frequency. There is no problem setting the 433 radios to 925, but the PA/antenna matching/filter circuitry will probably filter out 99% of the output. Might still be usable for tuning though, we don't need much signal to reach a few feet.
I'll try to make a 433 version today, but I don't have any 433 radios to test it on currently.
Thx Jake. I am using 433Mhz radios. I have a few pairs I will test with RF explorer to determine how much they are detuned.
Thanks Jake for this very interesting topic, that made a nice sunday project :-)
@JB, next time that OutBack Joe goes outdoor , make sure He get his keys so we can go Fox Hunting !!
Raspberry Pi2 running Osmocom Spectrum Browser on 315 Mhz with RTL2838 :Green Peaks are Key Pressed
Darn, lost a post...
Anyhow... SiK firmware compiles in linux. I use the Kali linux VM with VMware. There is also a Kali VM for virtualbox.
I use the 32-bit Kali VM and run it in my normal Win7 x64 environment.
Basically you just have to... download and run the Kali linux VM. Then I run the following commands...
sudo apt-get update # Fetches the list of available updates
sudo apt-get upgrade # Strictly upgrades the current packages
sudo apt-get dist-upgrade # Installs updates (new ones)
apt-get autoremove # Removes junk
sudo apt-get install sdcc # Installs SDCC and dependencies
cd SiK # Enter SiK directory
cd Firmware # Enter Firmware directory
make install~radio~hm_trp # Compiles bootloader and firmware for HM-TRB based radios.
Compilation IS required to change the OSC value, BUT I have already compiled a bunch of them for people. I uploaded them to my fork of the project. I did versions for values from 196-212. This is -8 to +8 relative to the default value.
This should probably cover any value needed. If not drop me a line and I'll make one for you. You can find them here...
Thx Thomas & Gary for the info : I'll get learning this right away !
I have a RF explorer for monitoring frequencies, I guess I could use that instead of a SDR dongle.
Issue is I saw on github for the SIk Firmware it can only be compiled on a MAC/Apple ?; Did I get that right ? Compilation is required to change the OCS-CAP-VALUE, right ?
Nice work Jake. Will be checking the RFD900's now as well to see how good they are.
It's good to see some SDR capabilities trickle through for spectrum analysis.
Is anyone keen on setting the RTLSDR dongle up as a secondary telemetry receiver as well? We could then use the onboard companion computer running linux (Rpi,odroid) as a flying SDR receiver for ADSB or redundant telemetry receiver (either 400-900Mhz) or on the ground PC with some spectrum monitoring to automatically choose and set the best channels to use according to RF conditions.
Even better would be to run a Myriad RF/Hack RF/Blade RF board either end and ditch the telemetry radios all together. ;-)