I have a FlightAware ADS-B fiberglass antenna mounted indoors in a closet.
Will reception improve if a ground wire is fastened to the mounting base?
I don’t need lightning protection.
Try and see.
I dont think anyone has experience of grounding an indoor antenna.
Here is my Flightaware antenna installed indoor, but never grounded.
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What sense does it make to ground an indoor antenna?
Errr … speak for yourself.
Connect an antenna into any bench test gear and it’ll be grounded.
I can’t be the only one to have connected a mobile / HT antenna to a base station radio (grounded).
Connecting / disconnecting a ground wire is an interesting test when either listening or watching the noise floor of the SDR waterfall
I’ve grounded an indoor antenna.
To a water pipe in the attic that goes down to the crawlspace and through the earth.
Also a friend took his flightaware antenna and tied onto the shield and ran it to one of those power outlet static ground plugs for handling electronics, and his reception went up.
Like this
https://www.amazon.com/dp/B071J61CSV/ref=cm_sw_em_r_mt_dp_U_dqGzDb5PNJGXT
If grounding indoor antennas is beneficial, then let us ground cell phones. These also have indoor antennas. 
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Grounding an antenna is done for a number of reasons and, with the exception of lightning protection, the reasons hold true if mounted indoors or outside.
Grounding is often part of the antenna and is also used for other reasons such as static discharge (even indoors) as well as helping to keep RF running down the outside of the coax.
A random piece of wire stuck into the connector on a receiver works in a fashion but does not define the best practices for antenna design.
S.
No, these aerials don’t need a ground connection. At least, not any more than is provided through the coax back to the equipment. They don’t need any specific extra earthing.
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Is an ungrounded mast a problem?
As in my antenna sits on top of a 1 m aluminium tube which isn’t grounded.
(It’s working fine but i’m curious)
Not at all - Collinear type aerials really don’t need any direct grounding. For the last thirty years, all the collinears I’ve used have been on steel or aluminium poles, fixed to T/K brackets that are screwed to the house. They’re effectively grounded back to the equipment via the coax braid but no, you don’t need to earth them in any other way unless you’re worried about lightning protection.
It is “grounded” from the 1090MHz frequency perspective:
- The outside shield of the coax cable goes to the receiver.
- The receiver ground goes to the Pi trough USB cable.
- The Pi ground goes to the power supply.
- In the power supply, like in any switched mode power supply, there is at least a parasite capacity to the 120/230V voltage side (most have a real capacitor) of enough value to act like a conductor for 1090MHz frequency. And that power is connected to the ground (one side directly, the other via parasitic capacity).
On the other hand… there is no actual need for the 1090MHz signal to reach the true Earth ground. Just the ground of first demodulation stage, inside the dongle. From there, the IF or digital signal can be transmitted in any other way. Even via optical cable… it still works.
Grounding is indispensable with outdoor installations, on higher masts, to protect with the static electricity or worse (lightning strikes).
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Which are they?
All devices where an antenna is connected are grounded by the power device. Why not the particular antenna connected to a Pi?
I agree, there are several antennas in house, but how are they grounded?
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What I said was that an antenna that needs a ground will, with the exception of lightning protection, need a ground if it is mounted outdoors or indoors.
I was not talking about any particular antenna.
Several of my Pi are powered over Ethernet and it is definitely NOT grounded by the power device.
S
Not by the power device per se, but they all meet eventually, unless there is a galvanic isolator along the way.
What about battery powered devices like cell phone & tablet?
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Signal ground and earth ground are distinct things.
And you don’t necessarily need earth ground, just signal ground.
Which can be totally fine if it’s floating.
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And then there is the issue of ground loops, but that’s for another discussion.
Signal ground is absolutely necessary. Can be achieved through capacitors that are basically “wires” at those frequencies.
Low frequency AC or DC grounding is different, needs a continuous metallic path.
Lightning protection is different because most of what we think as being insulators will be easily jumped or break-trough by the huge impulse voltage. The pulse has not low frequency and high frequency components, so it needs a metallic path, as straight as possible (no turns or loops to minimize induction).
And the proper gauge, something like 6 AWG, I think.
I haven’t seen a ground loop since taildraggers were the latest from 
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