Am I Understanding Antenna Position Properly?

dino9832 · Jul 14, 2020

My Mini has been absolutely AWESOME! With this one small glitch in my fun.

I keep losing signal around 2500'. This is in a rural area with just a few trees around me. So, I did the math for my next attempt.
It seems that at 80' altitude at 2500' my antenna direction should be pointed approximately 1.8 degrees in the air? By "direction" I mean the antennas would by 91.8 degrees (tips just barely facing me).

On a side note, what's odd is that I have full signal bars when the incident occurs. Also, Airdata logs show I'm at 100% signal strength.
Thanks!

old man mavic · Jul 14, 2020

the signal comes from the flat faces of the antennes so its those that need to be pointing towards the drone

Deleted member 103366 · Jul 14, 2020

Your anntennae, aka OMM's flat faces, should be approximately parallel to one another and approximately perpendicular to a line drawn between the drone and the controller.

scro · Jul 14, 2020

maybe the aircraft is getting close to a source of interference, or passing through the 'beam' of a microwave link?

In my experience the signal strength meter often shows full strength until abruptly dropping down to weak signal signal or even losing signal completely.

dino9832 · Jul 14, 2020

There wasn't anything out there but maybe three homes. The log files are from my Android controller, so that might explain why the RTH happened where it did and not where it actually happened.

dino9832 · Jul 14, 2020

FYI, my first post was another similar incident and the last post was today's incident. Didn't want to confuse the issue.

scro · Jul 14, 2020

You don't need to be near a transmission tower to pass through a microwave beam and potentially get interference from it. Think of a microwave transmitter/dish like a light house throwing out a fairly focused beam of radio signal many miles towards a receiving dish. If you fly thru that beam your signal to the drone could easily be drowned out by the high power microwave transmission. The frequencies the mini uses are very close to typical microwave frequencies.

Is the problem happening in the same general area?

dino9832 · Jul 14, 2020

We do have many dish type internet connections out here. No service providers have run (and made available

) any cable service. They just ran some cable and that was that.

But, that's beside the point. Point is there are dishes on many of the homes. Being that internet works both ways, I'd imagine those dishes are transmitting a fair bit of RF energy.

SkyeHigh · Jul 14, 2020

scro said:
You don't need to be near a transmission tower to pass through a microwave beam and potentially get interference from it. Think of a microwave transmitter/dish like a light house throwing out a fairly focused beam of radio signal many miles towards a receiving dish. If you fly thru that beam your signal to the drone could easily be drowned out by the high power microwave transmission. The frequencies the mini uses are very close to typical microwave frequencies.

Is the problem happening in the same general area?

Typical fixed-link microwave communications work at significantly higher frequencies and won’t interfere at 2.4 or 5.8GHz. They aren’t that high powered either, it doesn’t require a lot of power for the short hops that directional communications links use.

scro · Jul 14, 2020

When I say high power, I mean that in a relative sense, compared to the power of the MM controller. I know the absolute power of typical microwave links isn't usually very high. Also, the MM controller antennae are far more omnidirectional than a commercial grade microwave dish so apparent signal strength in line with the dish would seem high.

Acknowledged that the S and C bands are not so common for microwave data links but they are still used widely, and particularly for comms to/from satellites, eg TV and some satellite based Internet. @dino9832 says there are quite a few satellite Internet links in their area.

SkyeHigh · Jul 14, 2020

scro said:
When I say high power, I mean that in a relative sense, compared to the power of the MM controller. I know the absolute power of typical microwave links isn't usually very high. Also, the MM controller antennae are far more omnidirectional than a commercial grade microwave dish so apparent signal strength in line with the dish would seem high.

Acknowledged that the S and C bands are not so common for microwave data links but they are still used widely, and particularly for comms to/from satellites, eg TV and some satellite based Internet. @dino9832 says there are quite a few satellite Internet links in their area.

Satellite downlinks in particular are extremely weak. During my Earth Station days we used an analogy for visitors to describe the signal strength - with a 30-metre dish the received signal strength is similar to the heat you would feel on Earth from a 1KW bar heater on the Moon.

Amplifiers were cooled with liquid helium to reduce the effects of temperature induced noise that would otherwise swamp the required signal. Nowadays you can receive a signal from GPS satellites on a battery-powered handheld device - admittedly in a much lower orbit. The telecoms birds.

scro · Jul 14, 2020

It was the satellite uplinks that I was thinking would pose a bigger concern as you would be much closer to the transmitter. Some satellite internet uses both up and down links via satellite. Some use a terrestrial uplink.

bcfd29 · Jul 15, 2020

One way to test this, albeit not to an exacting degree of certainty would be to install a network analyzer tool on a smart phone and walk/ride/drive the route and measure interference or signal strength at the point where you think that you lost it. There are any number of wifi analyzer apps that can help identify noise in a given area.

dino9832 · Jul 16, 2020

bcfd29 said:
One way to test this, albeit not to an exacting degree of certainty would be to install a network analyzer tool on a smart phone and walk/ride/drive the route and measure interference or signal strength at the point where you think that you lost it. There are any number of wifi analyzer apps that can help identify noise in a given area.

Thanks! That's not a bad idea. The next chance I get I plan to go to the back of my property and fly over unobstructed field. I have a feeling my aim is too high with the antennas.

scro · Jul 16, 2020

Unless you're using reflectors or clip-on yagis the exact angle you face the antennas isn't that critical. The signal spreads out fairly well in most directions other than out the "ends" of the antennas. That's why reflectors and yagis give such a noticable range boost - they focus all that signal into a much more concentrated beam.

Flying overhead is about the only time I adjust the angle of my antennas. Otherwise I keep them approximately vertical so the flat face points towards the drone.

dino9832 · Jul 16, 2020

scro said:
Unless you're using reflectors or clip-on yagis the exact angle you face the antennas isn't that critical. The signal spreads out fairly well in most directions other than out the "ends" of the antennas. That's why reflectors and yagis give such a noticable range boost - they focus all that signal into a much more concentrated beam.

Flying overhead is about the only time I adjust the angle of my antennas. Otherwise I keep them approximately vertical so the flat face points towards the drone.

That's good to know and confirms my mistakenly pointing too high in the sky. I plan to fly the same route with a more vertical facing antenna "| not \". If that doesn't work, I'll try flying further away from the homes where I lost the signal last time.

I really appreciate all the advice. It'd be nice to know if my MM equipment is functioning as it should. I've already verified that it has an FCC ID.

dino9832 · Jul 16, 2020

Today I achieved a bit more distance with vertical antennas instead of angled. Not much, but I did receive some interference errors!
Code: 80015
The issue may be interference.

E	02m 17s	101.0 ft	1,583 ft	Warning	Weak signal. Adjust antennas(Code: 80016)
F	02m 48s	104.3 ft	2,138 ft	Warning	Aircraft in high interference environment. Fly with caution(Code: 80015)
G	02m 51s	104.7 ft	2,188 ft	Warning	Strong wind warning. Aircraft unable to return to home automatically. Lower altitude immediately and return to home manually(Code: 30149)
H	03m 23s	105.3 ft	2,581 ft	Warning	Weak signal. Adjust antennas(Code: 80016)
I	04m 12s	101.0 ft	2,588 ft	Data Loss	Downlink data connection lost for 2 seconds

Deleted member 103366 · Jul 17, 2020

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Am I Understanding Antenna Position Properly?

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