Thanks, that is what i’m going to monitor indeed. If so it will be replaced shortly thereafter.
It’s 30 ft of cable, I need to get 21 ft in order to reach the intended position on my balcony. 
It it doesnt’ perform the antenna will be moved indoors with a 10 ft CLF200 cable mounted behind a double pane window.
That wil give some loss as well I guess (the windows)
First gonna do a trial run with it prior to drilling the holes to the outside 
The cable loss is likely preferrable over not mounting it with free view in all directions.
The coax you linked not even having a spec sheet though … kinda bad omen.
Something like this here you at least know it’s around 2 to 3 dB attenuation or the 8m run: https://www.amazon.de/Verlustarmes-Verlängerungskabel-GEMEK-Koaxialkabel-Antennenverwendung/dp/B07NZ1416W
You’d be better off leaving it outside and using a better coax. If the thickness is an issue then there are much better alternatives than RG58. Something like M&P Hyperflex 5 only about 2.6dB loss over 10m and Ultraflex 7 only 1.9dB. RG58 will be something like 5-6dB.
If it’s 5 dB … it shouldn’t really be a huge issue with a good SDR with builtin LNA.
But if the coax doesn’t even have a specsheet … you just don’t know what the attenuation is going to be.
Yeah you have to bear in mind the RG58 is the specification for the dimensions of the cable, and says nothing about the construction, materials used or electrical properties. You can get good quality and terrible quality cable with very little copper that have the same number on it.
It’s gonna be used with a Blue Flightaware Prostick Plus and a Flightaware 1090 Mhz (darkblue) filter.
All of my receivers have the same setup, filters are added due to the presence of celltowers within 400 meters of my home.
I already have 2 FA adsb antennas and ordered 2 Vinnant antennas that you advised a few days ago.
They are enroute so then I can decide where to place which antenna.
Free view is an issue, I live on the 3rd floor of a 9 story building.
In front of me are trees almost as high as the buidling itself. Mean range is here around 100 NM peaking to 180 NM
On the other side I have a better view but still highrise buildings on the horizon so some sectors don’t show low traffic. Mean range is 140 NM and peakrange is 200 NM.
Until now I had the antenna’s indoor ( 2 of them) covering both sides of the building ( one overlooking an approach route and the other a departure route of EHAM.
I’ve now doubled the number of recievers to 4 in order to cover the dead spots in my coverage.
Globally they are covering NE. SE, SW and NW.
But as said, I expect some blindspots due the the high rise buildings around me.
If the cable is rubbish then I’ll cut my losses and either move the antenna inward or get another cable if I want to keep it outside. I don’t want to move the reciever outside (as I look at it now), have to get a network cable outside then and a power socket for the Pi (not a big issue).
But I’d rather keep the equipment inside. ( sorry for hijacking this thread btw).
Oh and I really appreciate the feedback on this matter so thank you both 
To check your cable for a short circuit between centre pin and shield, you really need to be using an insulation tester, rather than a multimeter, as an insulation tester sends a high voltage down the cable is and much more able to find short circuits in cables.
A true short-circuit can be detected with a battery and light-globe. A multi-meter is also fine.
An insulation tester (typically a Megger) is better, but unnecessary for a receiving antenna.
Thanks all for the helpful tips. I’ll read a bit more and try some more precise testing once I recharge from all that work! I’m also going to test the swapped out SMA pigtails next time just for sanity.
I suspect connectors. But one thing I remembered, the first couple days of signal decrease were dry but unusually gusty/breezy almost all day for a couple of days. The N connector was still tight, sealed and dry when I swapped antennas while troubleshooting. I’m wondering if there was maybe stress from the wind somewhere in the zip tied cable run 33 feet up the mast.
Anyway, all is well now. My signal first mostly recovered May 19 by connecting the 978MHz antenna and cable while waiting for the new cable for the 1090MHz antennad to arrive on May 22.
BTW - for others, like me, trying to learn more about cables and types, I found this resource useful last week. It’s standard specs, so you still need to look for the manufacturer’s spec sheet as wiedehopf mentioned!
I called the cable supplier this morning, was able to cancel the RG58 cable, it is going to be replaced with this one
Specs can be found here:
I think we’ve all experienced odd problems at times, but there are so many factors to consider - nailing down exactly what’s happening can be very difficult, so you’ve done the right thing by methodically swapping out components.
If there is any cable / connector issues, then the wind will certainly accentuate any damage or stress points.
Yay, good job 
Looks like quality stuff and good specs 
Mine is actually labelled CF400, but looking at the manufacturers spec sheet, the spec matches that of LMR400, as does your CELF400.
1.28dB loss over 10m / 33ft @ 1GHz 
My cable arrived yesterday, it looks quite good and very decently made.
I secured also the permission from the Board of house owners ( living in an appartment building) to mount the antennas on the inside of the balcony’s.
You have to obtain it prior to installing them since they normally don’t allow antennas that will extend outside of the building.Luckily the secretary of the board is a radio amateur so at least they know about antennas and their function
So all I have to do now is wait until the Vinnant antennas arrive from Slovakia and then I can set it up. 
Great news about your cable and getting permission to mount your antenna in a better place - hopefully it will make a big difference for you!
What are the chances the secretary is an amateur radio enthusiast 
P.S. Loving the profile picture 
yep private pilot, owner of 2 doggo’s and 3 catto’s so that was easy
Most SMA connectors are not IP-rated. It is possible to purchase IP67 or IP68 SMA connectors, but they are uncommon and expensive. If you are using SMA connectors outdoors, as it appears in the above photo, moisture ingress is probably responsible for your gradually decreasing range and signal strength.
Yes, I considered this as a possibility. The connectors at the antenna are sealed with sealing tape, but the connectors at the utility box, while in a dry enclosed area, are not sealed. Moisture from humidity in the air could certainly accumulate and degrade connectors and signal. But this particular event happened quickly over a couple days in spite of near record dry weather. It was so dry that I was more worried about dust in the connections that I adjusted.
I’m certain I triggered the problem physically by moving things around just a few days before the signal decrease started. Just need to pinpoint what I broke! Previous moisture decay could be underlying cause indeed, no sign of it though.
Just to let you know, antenna’s arrived yesterday so I’ve set it up.
The cable makes a huge difference in terms of message rate. I’ve got 2 identical antenna’s now , the one with the LMR400 cable is running steadily around 400 messages per second, the other one wit LMR200 cable is running about half of that rate.
Range is comparable, up to 200 NM on both setups. What a difference a cable makes
Next project will be cable replacement I guess 
That’s good news - it would be interesting for you to swap around the connections to your setups, to double check the coax and see if the message rates swap over too, if that makes sense.