Hi Brandon,

This is hard for me to write, because I don't have good news for you.  You can find many receivers and transmitters for 433MHz that are used for remote control, such as wireless doorbells, garage door openers, lost model locators, etc.  These are extremely cheap, a couple of dollars literally.  While this tech can be modified to operate with wildlife tags (around 150MHz), we are talking about hacking RF, not to be approached lightly.

If you really need to DIY, I see 2 options: migrate to 433MHz and build/rebuild all your kit (tags, collars, receivers, locators).  Commercial solutions are cheap and available, the work remaining is not much above handyman level.  But it is work, and not just work but also testing.

The other option is to remain with 150MHz (although you can make your own tags) and modify an aviation receiver (it lets you listen in to aircraft talking to each other or to the airport).  These receivers operate at 130MHz, which puts it in spitting range of 150MHz wildlife tags (this matters).  This is the option I'd go for, just because I know it can be done, and I have less sense than curiosity.

You mention you're working with an engineer, here are a couple of pointers:

• with an SDR (the "digital USB receivers" you mention) you can scan some bandwidth to detect radio pulses. I'm only familiar with the Lotek coded VHF transmitters but they can be received as in the Motus Sensorgnomes. I can point you at the code used there, it does involve a good amount of digital signal filtering/analysis code. One issue with the SDRs is that they're pretty power hungry so you need to plan on more solar panel and battery than you may like, e.g. even rPi Zero + SDR is probably >300mA. Another issue can be interference in that SDRs have a very wideband front-end and so TV, radio, and other stuff can desensitize the front-end.
• there are integrated receivers (ICs) that can be tuned to 150Mhz and can detect VHF transmissions, it's easy for non-coded ones, a bit more involved for coded ones. Specifically, the Semtech sx1231 or sx1276 series are widely available (often called Hope RF69 or RF96, which are modules with those chips). You need someone comfortable writing a customized driver that uses OOK mode or RSSI detection. The other issue is that while there are many suitable boards available for 433/868/915Mhz (e.g. Adafruit, Sparkfun, LilyGo, and many others) you most likely won't find one for 150Mhz. However, for RX-only the matching isn't so super important if you have a good antenna and the signal isn't crazy weak. From a power point of view these can sip power so you can run one on an 18650 for days and a small 1W-5W solar panel is most likely all you need.

Hope this helps...

Have you considered Arduinos?

Hi Tom,

I'm with Akiba, you have to test.  A collaborator has deployed solar-augmented kit in secondary jungle and some of them got enough light, and others didn't, so it can work.  The open circuit voltage of solar panels doesn't change a whole lot in dim light, but the current drops drastically.  So you would choose an oversize panel of the same voltage (or a bit higher).

Thanks

I've been intrigued by this topic. Thinking about ways you could use drones or some kind of launcher to deploy panels above the canopy. Sadly I live in the great white north so I have no way of testing any concepts. Maybe even some kind of solar balloon that could float above the canopy. Interesting design problem.

Hey Tom,
Since the output is dependent on a couple of factors such as the solar irradiance of the place, shading from the canopy, the type of solar panels (mono, poly or amorphous) and orientation of the panels, etc, I'd suggest you use a software to simulate the different parameters to get an almost accurate estimation of the output. You can try PVsyst- it has a free month trial (I haven't used it before but I hear it's great) or any other PV software :)

I'll add -  avoid fast curing resins/epoxies for, at least, two reasons: 

1. The exothermic reaction between the two compounds can cause sensor issues (ie: heat).

2. Air bubbles will form (and cure) more easily in fast curing compounds.

Hi Roland,

This is really amazing, great to hear about your set-up! I'm just wondering what the overall cost was to set up this system? Just thinking in terms of setting up something similar in other parks and what they should expect with regard to price. Would also be great to hear about the overall effort, e.g., hours/team members required. It would be great to have this act as a blueprint for other organizations/research stations wishing to deploy a similar system within their respective national parks/areas/etc.! 

Hi Rolland,

Interested too, but why did you choose SigFox (a private network) rather than LoRa (open network)? 

Sigfox currently has some financial troubles that, don't know what it will become in the long term.