I’m going to sell my MM

[Lionfish]

Thanks for the lesson Skyehigh .
You obviously know your electronics very well ,
It’s good to learn from people that have a greater understanding of the technology and are willing to write it in a way that us “”normal “” people can grasp.
That’s one of things I enjoy about this forum .
So thanks to you and all the other people that are willing to share their expertise here and keep it coming .

Ps I don’t have any areas of expertise on anything , unless it’s getting in the way , oh I’m good at listening to my wife !!, not that I remember anything she said .

 

[PanX]

Impedance being the resistive load presented to an alternating current. It is very similar to that of voice coil of a loudspeaker using a 4-ohm coil connected to an amplifier designed for an 8-ohm speaker.

To get maximum power transfer the impedance of the load should match that of the device driving it.

Video devices have a standard of 75-ohms, Radio (radio frequency) is 50-ohms.

yes but you can "loose" say.. 2db from mismatching and gain 4db from directivity. Actually we have no idea how controler deals with SWR and we should take in consideration that it is a "portable" device which means high toleranse on impedance missmatch.

 

[SkyeHigh]

The ‘apparent’ gain is very misleading. All that is happening is the energy is being formed into a narrower beam than the existing antennas. It means a greater signal strength in the direction of the beam but that increase comes from the energy that would have radiated over a wider area.

The SWR can be very precisely controlled as the length of the coax, the type of connectors and the PCB etched antenna are known in advance and manufactured to a tight tolerance. By contrast a portable transceiver such as used in amateur radio, for example, is sold without an antenna and the end user is providing the cabling, connectors and antenna. In this case SWR is very important to match precisely the impedance of the transmitter and minimise loses, cable length being one of the many causes.

 

[SkyeHigh]

Thanks for the lesson Skyehigh .
You obviously know your electronics very well ,
It’s good to learn from people that have a greater understanding of the technology and are willing to write it in a way that us “”normal “” people can grasp.
That’s one of things I enjoy about this forum .
So thanks to you and all the other people that are willing to share their expertise here and keep it coming .

Ps I don’t have any areas of expertise on anything , unless it’s getting in the way , oh I’m good at listening to my wife !!, not that I remember anything she said .

Don’t put yourself down. Everyone has an area of expertise or experience. Strangely my hearing seems to follow the same pattern!

There are a great many people on this forum who are always happy to help in this great hobby/profession of ours. It’s rare for so many areas of technology to merge into one device but with it brings a whole load of opportunities for all of us to understand how these things work.

 

[Deleted member 103366]

Ooooo SWR takes me back to CB days and films like Convoy uuuum 40ish years ago.

SkyeHigh so is the length of cable connecting 'antennae' to controller 'mother boards' a matter of concern? I am just wondering about the antennae kits that are sold for the likes of the phantom 3 GL300* controllers where the old antennae etc. are replaced by antennae from the kit.

 

[PanX]

It means a greater signal strength in the direction of the beam but that increase comes from the energy that would have radiated over a wider area.

only for clarity i want to point out that flying a drone we dont care for the "energy radiated over a wider area" but, in contrast, for the energy radiated to the drone, so i must say again if we loose (say) 2db for impedance mismatch and gain 4db (say) to the direction of drone that is 2db GAIN on the overall signal. Thats the principle. 73, de SV1COX

 

[SkyeHigh]

only for clarity i want to point out that flying a drone we dont care for the "energy radiated over a wider area" but, in contrast, for the energy radiated to the drone, so i must say again if we loose (say) 2db for impedance mismatch and gain 4db (say) to the direction of drone that is 2db GAIN on the overall signal. Thats the principle. 73, de SV1COX

I’m not disagreeing, I’d say it’s a matter of wording. It is an apparent gain. The signal arriving at the drone’s receiver antenna will be higher by comparison to the standard dipole antenna with its wider radiating pattern.

But we should also remember we’re working here at microwave frequencies, which by their very nature, are already directional.

 

[SkyeHigh]

Ooooo SWR takes me back to CB days and films like Convoy uuuum 40ish years ago.

SkyeHigh so is the length of cable connecting 'antennae' to controller 'mother boards' a matter of concern? I am just wondering about the antennae kits that are sold for the likes of the phantom 3 GL300* controllers where the old antennae etc. are replaced by antennae from the kit.

At microwave frequencies cable length does come into play but the cables are so short the difference is negligible. As the controllers use dual antennas it is more important that the cables to each antenna are the same length.

 

[Deleted member 103366]

Ta

 

[dnmrt]

I don’t like to fly the MM when it’s windy, and due to this I took off only one time over the last 2 months (the most calm period is around midday, but unfortunately I have to work).
I simply think it’s too risky and not fun at this point.
I knew U.K. was a windy country but I didn’t really pay attention on how many days a year were suitable to fly until I bought a drone.
In the meanwhile I have used my FPV on a daily basis, even with strong wind: I think that’s the way to go for me.

Getting back to the topic of the post:
I am exactly the same, got to a point that I just HAD to buy a mini and I didn't even stop to think "Hey, I live in Blackpool, on the Irish Sea, a TINY drone is not a good idea for me". I've completed 57 flights so far and I only had 1 crash due to wind (which was actually a bit more in land, in Preston). I hit a large stone wall at 20mph, battery popped out and gimbal was slightly out of place which was easily fixed. I bought DJI care refresh the next day, it definitely helped with my nervousness.
This week isn't looking great for flying, 40mph wind at 30m altitude all day today, annoying but doesn't make me want to sell it.

 

[Grasscutter]

It was over my own land, and yes I could see it all the way. At half a mile I had to swerve to avoid a wasp.

LMAO, not jokin but, my mini chopped a poor grasshopper in half on its first proper RTH landing - attitude that, took it clean in half and dropped it dead to the floor from about 30 feet up - I have fight data'neveryfin.

 

[Grasscutter]

I understand perfectly what you are saying, what I was trying get at is that it might not be wise to publish the fact that you are breaking the law. It's like videoing youself doing wheelies at 100mph on the M1 and then sticking the video on you tube, it's asking for trouble.

err brb just popping over to youtube.

 

[PanX]

As the controllers use dual antennas it is more important that the cables to each antenna are the same length.

just for reference, this is not a fact for mavic mini, on CE models only the left antenna sends and receives signals the right only receives. On FCC models is vice versa (right is the TX/RX). The info is directly from DJI and is somewhere in this forum.

 

[SkyeHigh]

just for reference, this is not a fact for mavic mini, on CE models only the left antenna sends and receives signals the right only receives. On FCC models is vice versa (right is the TX/RX). The info is directly from DJI and is somewhere in this forum.

The Mini is likely the exception here if it is only transmitting on one frequency, which I believe is the case for the FCC version. I’m more than happy to be corrected but the 2.4 & 5.8GHz versions would require two antenna dipoles, one for each band.

 

[PanX]

The Mini is likely the exception here if it is only transmitting on one frequency, which I believe is the case for the FCC version. I’m more than happy to be corrected but the 2.4 & 5.8GHz versions would require two antenna dipoles, one for each band.

i dont know if it is right to post the picture without the author's name but i can not search now, i have only the screenshot, my apologies in advance. See :

 

[BlackMac]

I don't think I would ever sell my mini, but now the bug has bitten, I definitely want to get a MA2at least I would double my flying time ....It is windy in the UK , and I don't have that confidence that I won't lose it in the wind...the MM will always be a nice drone to take away as you will avoid most of the restrictions and we all know the shots are worth it...