New to this project but could not find anything on installing multiple antennas at different heights to account for surrounding topology and interference. I work in the communication industry and we have been asked to look at installing receivers at various heights on the same tower. We think we can accommodate losses and still mount at a height of over 200’. This would allow us to install one antenna set at 35-50’ and another at 200’. The hope is to allow altitude calculations and better coverage over the great lakes. My question is two fold (1) has anyone ever installed over 100’ on a tower and what was their experience, (2) has anyone ever installed more then 1 set of antennas on a tower with separation of over 50’ that yielded different results?
Wow, 200’ is serious! I’ve installed using ~80’ runs of coax up towers and have not seen any significant decline in SWR values, but I’m not familiar with that height, nor have put two separate sets of antennae on the same structure. I’m not sure how you intend to calculate altitude from these detections, as signal strength is a function of altitude, distance from station, atmospheric conditions and antenna orientation, etc. I think your set of 200’ antennae may better detect trans-lake migrants, but I don’t know what else you can estimate from that
I have done two stations at over 100 feet on towers, but in both cases the computer and cell phone were mounted near the antennas. It is my understanding that there is substantial signal loss on 434 MHz antennas with runs of LMR 400 of 50 feet. Somewhere on this wiki there is a table with data on signal loss.
A quote from Matt Webb on this topic: “with LMR400, at 100 foot, we lose ~30% of signal for 166MHz, and ~45% of signal for 434MHz”
Found the loss calculator: https://timesmicrowave.com/calculator/?productId=52&frequency=166&runLength=150&mode=calculate#form
Yes, signal loss is the main issue! As mentioned above, and using prior signal loss calculators and advice from antenna builders we tend to limit coax runs beyond 50’ as the 434MHz antennas will lose significant amounts of signal at that point, even if you may be able to stretch that to 80’ with 166MHz.
In some situations, you may be able to install your receiver near the antennas above ground. The main issue thereafter pertains to long-term maintenance and update of equipment and if your access to the receiving equipment is difficult (e.g. 100’ as above ground, on a tower). Good luck!
We would be mounting the controller at height with remote reboot initially and hopefully remote control as well down the road to address the signal losses.
I have done tests using a Low Noise Amplifier (LNA) and I would recomend using that at the antenna and power via coax. The LNA I used were less than $10 and provide about 30 dB gain so you can use RG-59 instead of LMR-400 which would be a significant cost savings!
If you are using multiple antennas for different directions they should be butt mounted rather than stacked snicce stacking will compromise the antenna pattern.
I uploaded a report of tests donein 2019 which includes a discussion of using LNAs
Nano_Life Drone tag tests.docx (3.9 MB)