I’m a retired Electrical / Computer Engineer and 30+ year avid birder and former NSWO bander. I’m also a 40+ year ham radio operator. I do a log of RPi/arduino tinkering and recently acquired an RTL-SDR.
I’d like to combine the hobbies and potentially setup a Motus reception station to report back any passing tagged creatures.
I see most of the resources here are geared towards purchasing one of a few SDR setups. Is there a resource for starting from scratch and/or Github resources?
If this has been answered and my search failed to find it, I apologize in advance!
Note that this just gets you up and running with the V2 SensorGnome software on a Raspberry Pi. You’ll still need to register a station and add your receiver deployment to it in order for data to flow to the Motus database. There is lots of information about project management docs.motus.org (though some of it is outdated at the moment). There is also some information here about station installation, though I suspect with your HAM background you won’t need any help in this area, and quite likely already have your own tower to use!
Thanks for the quick start. I think I may make one modification to this recommended hardware and go with an SDRPlay RSP1A, instead of the RTL-SDR. The RSP has a 14-bit A/D instead of the 8-bit and that should provide a bit better low-noise performance. Anyone else using any of the SDRPlay SDRs?
My other question is whether it is possible to acquire an example tag of each of the two main types, strictly for testing purposes, to verify that I’m actually setup properly.
No-one has used an SDRPlay to my knowledge. For it to work you have to do the “wiring” so it ends up looking like a 2-channel audio device sampling I/Q at 48kHz that you can feed into vamp-alsa-host. It’s going to take some software wrangling…
Most of the stations use 3x 7 to 9 element yagis per frequency, sometimes 4x. The range on 166 is determined by the background noise floor. I’m in SoCal about 12mi outside of town and my antennas are ~10dB more noisy than ones in the back-country. The result is ~1/4 the range. I get better results with an RTL-SDR + LNA + SAW filter than the FUNcubes, which have a 12-bit ADC. I haven’t been able to test in a spot that has the lower noise floor. So whether 14-bit ADC matters depends on the environment. Also good Q where to spend the $$…
I acquired a LOTEk tag for testing I will warn you it is rather pricey.
$150 for the device that turns the tag on and off
$300 for a tag
$50 registration fee
then there is a large shipping charge $100 if I recall correctly.
My understanding is that CTT is a little cheaper but it is not much better.
If you want to verify your system from antenna to RPI you can make a Motus Test Tag Simulater from an Adafruit Feather M0 RFM96 LoRa Radio - 433MHz - RadioFruit Product ID: 3179 and a small dual band antenna for about $50. The tag will not be processed by MOTUS.ORG but it will show up on the radio page of the sensorgnome
the code can be found on github GitHub - wdittmann/Motus-test-tag.
It would be nice if MOTUS would create a universal test tag for each tag type so that this can be used universally to test a station all the way through.
There are a couple of threads in this forum discussing lotek tag range. IIRC with a 9el yagi and a noise floor around -70dB as reported by a FUNcube I can get 1km-2km. So with noise below -80dB 10km can be extrapolated. There are cases of detections 20km out but I’m skeptical that they are stable/reproducible.
With CTT tags and a 7el yagi I have been able to go 9km without heroics and some headroom left.
When testing the tag mount is very critical. If you hold it in your hand you provide a much better counterpoise to the monopole wire than an actual small bird does. The typ test mount on a wooden or PVC stick is a flask&sponge with saline solution or a piece of hotdog…
@user1163 - I’m also a ham and more recently birder. Over the holidays, I set up a SensorGnome-based station using a recent RTLSDR (v4) + Raspberry Pi Zero 2W. I’m using an old discone antenna, but will probably build a couple of yagis when I have the chance.
I came here today looking for some help with a few minor issues. I’d be happy to discuss what is/isn’t working for me.
Ultimately, I’m looking to set up a few more stations in my region as a local ornithologist I know was remarking on the lack of any coverage nearby.
I have been researching antenna on my MOTUS Journey and I would like the opportunity to ask a question of a HAM. I was originally planning to build a yaggi but based on my research I concluded that Yagis are not that great of an idea because all of the antenna director structure is for transmit purpose to shape the xmit propagation. In a MOTUS system there is no xmit. my current plan is to build an antenna that is essentially a quad reflector element and a quad drive element.
With the disclaimer that I’m not an electrical engineer, just an amateur radio enthusiast who read about this stuff:
With a yagi, the number of elements and their spacing can make a lot of difference in the antenna’s pattern, which applies for both transmitting and receiving. I have seen plans for yagis used for radio direction finding that instead of being optimized for transmission, adjust the spacing to increase “front-to-back” ratio to create a bigger null to reject signals to the rear. I don’t know if “quad” style antennas would get results substantially different than a yagi, and are generally more work to construct.