35 ft vs 8 ft RG 6 Coax - worth the effort?


#1

I’ve been procrastinating putting my setup on the garage roof. The major benefit I was planning is the cable run reduction ( 35’ vs. 8’). Same height.

Can cable run make a magnitude difference? Good cable, professionally terminated. Have FA antenna, FA filter, FA Prostick.

flightaware.com/adsb/stats/user/ … tats-22724

I do see the warning about my Pi running at 90% too…Is it better to get a Pi3?

Scott


#2

RG6 is somewhere around 6dB/100ft attenuation so the shorter cable should be about 1.6dB better. Not a huge change.


#3

When I look up RG6 quad shield, at 1000 Mhz it’s 21.5 db per 100 ft.

So every 5ft is 1db. That’s a lot.


#4

Are you sure it’s not 21.5db over 100meters?

http://www.w4rp.com/ref/coax.html agrees that it’s about 6db per 100’


#5

I feel better if its 100 meters. This is what I was looking at since I have a spool of it for TV usage.
http://www.cerroretail.com/assets/517832d28ad7ca0d7d002711/31_cmd_CoaxialCable_6U_QUAD_4_24_2013.pdf

For what it’s worth, I’m installing a 30 foot tower and I’m trying to decide if I will put my RPi at the top with Ethernet cable or use a 30 ft piece of LMR-400.

Thanks for clearing that up, it seemed high for 100 ft.


#6

How often do you expect to physically touch the RPi? The answer to that may influence your decision. :wink:


#7

A problem with putting the RPI in a tower is keeping it cool enough.
I am running into this problem with my RPI3 in my attic. I had to add a fan to the system to keep the CPU cool.
It seems that at around 160F the CPU starts to throttle back. This has caused MLAT to slowly shutdown when I use piaware 3.0~dev.
(This could be also be traffic load related. I get up to 1200 msg/sec and 200 aircraft at a time with my current antenna location).


#8

Well, I have a Universal aluminum tower that can be tilted up and down by hand. The tower will be next to a storage room where my Pi is now. I’m thinking maybe leave the Pi in that room and I could get an old monitor and keyboard to keep on it. That way I only have a 30 ft piece of LMR-400 running up the tower to the antenna. Everything stays out of the weather.

Is there a recommended N type lightning suppressor?

I’m new to this antenna tower business.


#9

@Zeek,

What did you eventually do ?

@FA antenna experts…

Is it worth it to get a “FA cable” pre-made up with N and SMA connectors? I have (as many others do too) a N to F adapter and then a F to SMA adapter on my 30 ft of RG6. I could squeak out 25’ rPi location (if the wife isn’t watching). Have a rPi 3 coming and will be installing 3.03 on that one.

https://www.amazon.com/FlightAware-PiAware-coaxial-Quality-Shipping/dp/B01FFZW44O/ref=sr_1_fkmr2_1?ie=UTF8&qid=1471723778&sr=8-1-fkmr2&keywords=feet+FlightAware+PiAware+Cable

Scott
http://flightaware.com/adsb/stats/user/vannossc#stats-22067


#10

It’s worth it to have your cable and connector impedance match the antenna feedpoint impedance, plus you don’t have changeover loss. So the answer is, yes on the FA cable. On the other hand, if you plan to use any sort of amplifier that doesn’t have either a N for mast mount use, or SMA connector for putting in front of the dongle, then you are back to square one, unless you are using a FA Pro that already has the pre-amp.


#11

My entire installation (including antenna) is strictly indoor, as I live in an apartment with no balconies and cannot install anything projecting outside a window.

During first.2 years of my adsb hobby, I had a run of 50 feet of cheap quality RG6 coax (50 ft coil for can $ 6.99) from antenna to DVB-T receiver, to keep antenna near a large glass window. I got poor results. I then added an 18 dB satellite amplifier located near antenna, and got very good range/plane count.

If you use a ProStick, it has a built-in 20 dB amplifier. The FA filter will eat up about 2 dB, still leaving 18 dB to cover for 2 dB losses for 35 feet RG6 coax, and 16 dB to boost signals, cover connector losses, mismatch loss due to 50 to 75 ohm transitions etc.

Later I purchased RPi and placed near antenna, and now connection between antenna & DVB-T/RPi is by 12 ft of cheap quality RG6 coax (RPi #1) and 4 feet of cheap quality RG6 coax (RPi #2). Both performs very good. Recently I replaced both DVB-T (black) by ProStick+Filter, which further enhanced performance.


#12

Sorry…should have laid out my setup: rPi 3, FA Prostick, FA antenna on roof. I’d like to eliminate all adapters if possible. I also have the FA filter but don;t use it as it seems to impede my data about 10% or so.


#13

It is always better to keep your receiver (ProStick) and Pi indoors, at an easily accessable point. This has following advantages:

(1) You can place your ProStick+Pi in a place which is dry and much cooler than outdoors.

(2) Ease of access to Pi & ProStick. I have to access my Pi several times a month.

(3) No problems of running long length of power feed to Pi.

(4) Pi can be connected to router by wire, no wifi needed. In case you opt for wifi, the wifi signal strength will much better when Pi is indoors, nearer to router.

The only drawback is Coax attenuation. With 35 ft Coax, the coax attenuation is not big even with RG6.

With built-in amplifier of ProStic 35 ft RG6, with two adapters/transitions (N to F ar antenna, F to SMA at ProStick), should be ok. The connector outdoor should be wrapped in self-fusing/self-amalgamating tape to protect ingress of rain water & moisture.

However if you feel uneasy/non-confident about attenuation of RG6 and/or adapters at both ends of coax, go for pre-made LMR240 or LMR400 with N male at one end and SMA male at the other end. This will be somewhat costlier, but will give you peace of mind.


#14

I have done nothing yet except prove that a cantenna is better than a FA 8db antenna at ground level (4ft). It has been raining so often in my area that I have been unable to get concrete in to install my tower. I actually live between Denham Springs and Watson, LA where we had 30 inches of rain in three days last week. The flood water came up under my front porch but we were one of the few houses that escaped without flood damage.


#15

@zeek70706
Your cantenna in your profile picture looks twin of this one I made in August 2014 :slight_smile:
http://forum.flightradar24.com/threads/3831-best-antenna?p=55629&viewfull=1#post55629

Birth of Cantenna, June 2014 (Name at birth: 1/2 λ sleeve dipole)
http://forum.flightradar24.com/threads/3831-best-antenna?p=53094&viewfull=1#post53094

Name Change to Cantenna, Aug 2014
http://forum.flightradar24.com/threads/3831-best-antenna?p=55872&viewfull=1#post55872


#16

Yep, the only real difference is I screwed my coax directly to the bulkhead connector inside of the can.

When my tower goes up, it will spend some time up there for comparison to the 8db FA antenna.