VOk, so here’s the thing…The antenna length is calculated based on the frequency. Ive asked Wyze, multiple times, what frequency and protocol (like zwave, zigbee, UHF/VHF, alien tech, etc.) they are using on sense and aside from confirming it’s not zwave - they sort of evaded the question. So - the coil inside is a fairly precise length of wire tuned to the frequency used. Because it’s coiled, it loses some radiated rf energy which = loss of range. It it was uncoiled (I’m assuming of course it was manufactured correctly length wyze (see what I did there)), it would be the correct length for that frequency in 1/4, 1/2 or more or less a division of the frequency - that’s called a quarter wave, half wave or full wave antenna,v It would then be optimum. Adding wire (it doesn’t matter if it’s insulated or not - it would if it was SHIELDED - is only helping because it’s helping the tuned coil to radiate. If you took a 6” VHF rubber ducky walkie-talkie antenna, for instance, and stripped off the rubber you’d find a long pierce of wire coiled up inside. The length would be precise based on frequency - the higher the frequency the shorter the antenna. Without knowing the actual frequency you can’t determine the antenna length. So you’re cheating the system with the added wire which is again, just adding a conductive radiator or to make it easier to visualize a reflector to it, you’ll overcome the downside of rf attenuation realized from the coiling. When I have the time I’ll put a meter (frequency counter) on the thing and get the actual frequency being used and then it’s a simple math problem to get the exact length that’s optimum. The balancing act here was that the sense units had to be super small so that constraint is one of the issues. (RF power output and some other factors all add to antenna/signal performance). This is an industry wide issue known since Marconi. Adding a length of any type of relatively small gushed wire will give all sorts of mixed results but in many cases will improve the signal radiated rf power. If you wanted to get creative, and improve the performance and don’t mind a big ass pierce of wire sticking out of the sensor you could uncoil the antenna and that would be the correct length. Additionally, if you can locate a ground point and attach a (same length as the coil) wire to it, you would have a counter poise which would be more effective and electrically correct for lack of a better word. Like I said, next weekend when I have time, I’ll disassemble the whole thing, figure out what magic is in these inexpensive radios and I can post some numbers but in all honesty, and I’m a big Wyze fan, I don’t see how these cleared qa testing for range in anything other than a straight line of sight situation. If it were (it’s not) zwave for example, then they could inetract to form a mesh which would allow the signal to propagate between devices extending each ones range proportionate the the number of nodes inherent mesh. There’s only so much RF you can get from a tiny radio with a tiny battery and a tiny coil of wire. Like I said, all will be clear once I sacrifice a sensor and a sense base and spend a few minutes on the bench. There are several other ways this could have been engineered - none of which would give you that much product at that price point - it was a trade off and it is what it is. For those interested in the backstory, behold an instructable on antenna length:
“the formula for calculating antenna length was given as “length in meters =300 / frequency in MHz”. The example given was for a Bluetooth antenna with a frequency of 2450MHz. The antenna length was calculated as 300/2450 = 0.1225m = 12cm. The author then divided it by 4 to make a “quarter wave” antenna length of 30mm. Why divide it by 4 and what is the benefit of a “quarter wave” antenna. What is the effect of the conductor leading to the antenna? If the 30mm antenna is soldered to a 4mm lead, does that result in a 34mm antenna? For a fractal antenna, should the 30mm length of wire be folded into a fractal shape or should the total fractal antenna be 30mm in width? I have read somewhere that one of the benefits of a fractal antenna is that they are able to receive signals of different wave lengths.
Everyone confused yet 
good, me too and I know this stuff. My head still hurts 50+ years into it but it’s not magic. It’s science and math (send you kids to STEM classes everyone) calculations and some physical engineering. Before I open it, I can say, the issue is clearly power. It’s a friggin low voltage low amperage power source and it’s supposed to last a long time - 2 things that are diametrically opposed - hence the need for engineering genius to squeeze the most out of the package. Now I need a drink, have fun experimenting.
7 Likes