I have moved my questions to my topic : My installation and questions - #28 by wiedehopf
Thanks for your answers !
I have not already moved to the Pi4.
Personal preference: power the Uptronics with a separate power supply.
Reasons and/or benefits: less heat generated in the AirSpy. Less chances of problems with the Pi power supply.
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I finally got an antenna installed on the chimney:
It’s made an immediately noticeable difference:
A quick comparison of the day before and the day after shows the maximum range has increased significantly:
I’ll do a proper comparison once I’ve collected some more data.
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Especially your rate “reported positions” is showing a significant improvement
Very nice. I mean, really, very nice 
That’s going to put you right up there in the UK stats, chasing #1
Mine is back to the lower position because I put my new hexbeam up yesterday. I’ve not yet got a full heatmap plot because it’s been up and down over the weekend but should have one tomorrow to compare.
I wasn’t able to get a new aerial mounted on the top of the hexbeam because I’m waiting for it to arrive! It’ll hopefully be here this week sometime and then I just need to schedule lowering the mast, fitting it on top and running coax down to the receiver box. The good news (for me) is that the height of the stub mast and the hexbeam combined means it’ll be about 2ft higher than it was at the start of this thread so around 42ft (just under 13m) AGL.
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It’s a bigger increase than I though it would be - I was expecting it to fill in the areas blocked by parts of the house, but it’s actually increased range in every direction as well so I’m seeing a lot more aircraft over Europe. The much higher proportion of stronger signals shows how much attenuation there is from the roof tiles. I still have a couple shaded areas because there is a large telephone exchange building and a theatre which are both quite tall - measuring with google earth and they line up exactly where the shaded areas are on the elevation plot.
I’ll tidy up the script I used to make the graphs above and put it on github - it uses the data in the files created by the polar script if it’s set to keep data.
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Is that 20 MHz sample rate already?
Yes, using 20MHz on a pi 4 - the only change to the set up is moving the antenna from in the loft to the chimney. Everything else is exactly the same.
I raised my antenna from 14’ to 30’ this morning. Mostly testing atm.
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You can bribe the neighbor that has view of the opposite side of the building to host another antenna and combine the two coax cables at the input of the receiver 
I just took a couple of pvc pipes and some hose clamps and mashed up an extension for my stainless steel mount I made a year ago. It’s clear getting some elevation on your antenna does a lot for reception. I’m actually seeing planes at the 200nm range on the tracker. Not just in the stats.
If I intend on keeping an antenna at this height I’ll have to come up with something more permanent. A good stiff breeze will blow this over!
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Yes, I think that bracket for something as high as that is a bit optimistic. 
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yeah, it’s gonna rip the side of my shop off!!! lol
caius, regarding the photo of your antenna mounted to the chimney, can you advise the material you used for the “white colored” section up to the FA antenna? (ie steel, fiberglass, pvc etc.?)
It’s a 25mm diameter aluminium tube. I got it from the local builders merchant. It’s sold for mounting TV antennas. The chimney bracket came from the same place.
The antenna isn’t an FA one, it’s one of these.
That looks like quite a lever your bracket as well!
Anyway if the mast flexes the wind loads on the brackets are less 
The mast probably won’t flex much, it’s quite stiff. The bracket is rated to hold an antenna of 5kg, and this one is only 0.25kg.
Wind loading isn’t too bad either. A 70 knot wind (36 ms-1) using a conservative Cd of 2.0 to account for the amp, antenna mount and radials (a long cylinder should be about 1.2) puts it in the region of 50N. In practice it will probably be less. That’s not so much considering it’s designed to hold up a multi-element TV antenna.
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That’s 50 N with an arm of maybe 1.2 m?
Still quite some torque, but probably fine
That’s distributed load, so the bending moment at the mount is about 30Nm. I’m not worried about it.