Yeah, so for receive only 75 Ohms is not an issue at all. The problem is most hams do transmit and in that case is quite wrong (even damaging the hardware in the process).
Yeah if you are getting good stuff. 
I use RG-6 for my ham transmissions, up to 100 W, no problems at all.
Even on transmit, the difference from 50 to 75 Ohms is negligible.
When 50 ohm is mixed with 75 ohm,
Reflection Coefficient Γ = (75-50)/(75+50) = 0.2
SWR = (1+Γ)/(1-Γ) = (1+0.2)/(1-0.2) = 1.2 / 0.8 = 1.5
With SWR=1.5:
Transferred power = 96%, Reflected Power = 4%
Transferred voltage = 80%, Reflected voltage = 20%
Thanks @abcd567
The little mismatch is easily handled by the transceiver’s auto tuner.
What are the specs for RG6 from a Dollar store?
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UNKOWN SPECS
Dollar Store one is good for short lengths (without LNA).
During 2013-2015, I have successfully used 15 meters (50 feet) of Dollar Store RG6 with Satellite in-line amplifier. The antenna was located near a large window, while DVB-T was plugged into Windows Desktop in another room.
https://forum.planefinder.net/threads/ads-b-diy-antenna.23/post-210
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The only one I know of is the price.
Except as a short jumper for temporary use, I avoid those.
The RG-6 available at Walmart Canada is good. Go with quad shield.
I buy long runs from a satellite dealer on eBay. I use it on my ham station.
We have $2 shops in Australia but most things are more expensive here.
A few years ago i bought a 10 metre RG6 terminated extension from a local $2 shop.
It dropped my 1090 signal by about 30db.
I did not have an inline amplifier.
If i can find it I’ll test it and see what it’s loss actually is at 1090.
I won’t be doing that till the end of next month as we are preparing to go to the Outback to see Lake Eyre which is currently nearly full.
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I’m looking to mount a 1090 antenna on my roof and not be too noticeable. The FlightAware 1090 antenna has the green tube around it. If I remove the green tube, will the antenna still work? Without the covering, how long will the antenna last outside in a hot, humid climate. I’d appreciate any recommended antennas that are made for outdoors without the need for a tube to cover them. The antenna should be at least as good as the FlightAware antenna.
Yes, but only until it rains.
Grey heatshrink perhaps?
I’d be concerned about wind loads mainly.
The base could be sealed with non-acid silicone and while the wire might corrode, that shouldn’t impact performance.
Sealing the base might change the frequency and impact performance somewhat.
Overall i’d rather go with a smaller cheaper antenna and combine it with an LNA, you can get good range with that combination. (New Product: RTL-SDR Blog 1090 MHz ADS-B LNA)
If you can put it directly below an antenna like this one (https://www.ebay.de/itm/1pcs-ADS-B-PCB-Antenna-1090MHz-Antenna-SMA-female-Antenne-CASE/253915016420), the reception should go to 250 nmi in my opinion.
Some good watertight tape around the LNA and antenna base to avoid water ingress into the LNA and connections.
Then tie the antenna to a plastic rod with cable ties. That’s the only point i’m not so sure about, the mounting of such a plastic tube.
It should be less visible than the big FA antenna.
There are also good antennas available in white if the dark green is the problem.