Antenna on roof, what cable to use?


#1

Since a few weeks I’m feeding a couple of sites with ADS-B data.
I use a Raspberry Pi with DVB-T dongle and stock antenna (didn’t even trim the top part off), placed on the second floor behind a window.
Awesome to see aircraft on your own personal radar and enjoying the joy that are subscriptions from the various sites.:smiley:

However, as most men do; they want to do it better. So I’m think about placing a antenna on the roof, either DIY with some coax-cable or something from Ebay (Ebay seller stanislavpalo130 has an interesting one). But the problem is; I have 2 options to do this:

  1. Put everything on the roof. Raspberry, dongle and antenna. This needs to put in a waterproof box along some DC-DC converter, POE-cables (those cheap ones from Ebay).
    Al this connected with one single ethernetcable to inside.

  2. Place a little as possible on the roof. This means only the antenna and dongle. Placing a active USB-cable between dongle and Raspberry Pi.
    This would nog only be cheaper but more importantly, much more convenient since you can still reach the Raspberry Pi.

Either cable (ethernet or active USB) needs to be about 10-15 meters in length and feed between a window and window frame. Normal ethernetcable doesn’t fit so I would use flat ethernet cable.
A USB cable will probably fit; if not; I could use a very short length of flat USB-cable.

My questions is; would you guys think this would work? Placing the Raspberry inside, get 10 or 15 meters of active USB-cable outside and connect that to the dongle?
My understanding is the usual (blue/black) dongle won’t work (because of voltage drop) but the tiny small one do (has the SGM2019 voltage regulator).
Because it this works it would be much more practical.


#2

My roof setup is like so;

  • 25’ ethernet cable from route to pi (living room to kitchen window)
  • Mounted the pi on the wall with an l-bracket
  • 6 foot usb cable to the FA dongle
  • 25’ coax cable running from the kitchen window up to the roof where the antenna is mounted

amazon.com/gp/product/B01FF … UTF8&psc=1


#3

I would suggest putting as little as possible on the roof, but as high as you can. I started with a Cantenna and 75ohm satellite cable, then replaced it with the FAntenna and some nice thick 50 ohm cable. All the rest is easy accessible and playable with on a shelf. I have 11 metres of Westflex 103 (UK only?) which has a loss of about 1.5db, about half that of RG213 cable, and nothing to worry about.

So invest in the cable and make life easier - and simpler to waterproof.

Changing from the Cantenna to the Flight Aware antenna probably gave me a 10-20% improvement - as did changing to the FA Stick.


#4

How much benefit did you see when you switched from the 75ohm cable to 50ohm?

I’m planning on sticking the FlightAware antenna on the roof this weekend (upgrading to that antenna has already made a massive difference even with it just placed on the side of the building), and it should be an easy task, since whoever installed my satellite dish was kind enough to run dual coax down from the dish, only one of which is used.

Obviously the problem is it’s 75ohm.

If I can avoid the effort of running 50ohm cable down, I want to, but if making the change is going to make a serious difference in range etc. I’ll do it.


#5

A short, 6" or 12" RG174 jumper is about the same thickness as flat USB or flat Ethernet. (not counting that ultra thin 32 AWG stuff that would last about 10 minutes in full sunlight).


#6

That was not done as a single step so cannot say - however the aerial /cable are the main components to consider in improving your counts.
If your cable length is going to be less than 15metres, keep all equipment at the bottom end and within reach.


#7

Thanks for the comments!

So I would be better off if I just keep everything inside and only run a coaxial cable to the antenna on the roof?
Using a very short piece of RG174 cable from the dongle through the window/window frame gap and a thicker, better coaxial cable from there to the roof/antenna?
If using about 10-15 meters of coaxial cable is fine then that’s certainly an option.

Now I’ll just have to figure out what kind of coaxial cable I should use; my knowledge about that is very limited.
Here in the Netherlands 15M RG58CU would cost me about €15-20. RG213 would cost me at least double.
Westflex 103 or similar is not something I can get my hands on here and if I could; it’s a multiple of RG213 in terms of cost.

If I would use the latter I might as well put everything on the roof since the cost issue of that (waterproof box, POE etc.) would still be much lower than the cost of the cable alone. And would probably perform better as well…

One thing to note; the outdoor cable will be on the roof but never subjected to direct sunlight.

Difficult this…


#8

If you have to run long lengths of coax stick to RG6 or RG6 Quad Shield, the cost of 50ohm cable will offset any improvements that you could make. An example is 100ft of RG58 (30m) is 21.5dB loss (10.75dB loss for 15m), whereas 15m of RG6 is only 3dB loss.

RG6 is fantastic for receive applications.

An idea would be (if you have outdoor power outlets) to put a wifi dongle on the raspberry pi and move the pi and receiver closer in a weather resistant box.

My Piaware was in this box for a year before I moved it to another (better) box.


#9

As your coax length is only 15 meters, use RG6, a low cost cable with reasonably good performance for short to moderate lengths.

To cross window, use pre-made flat cable pieces. Some examples are gien below.
https://c3.staticflickr.com/8/7286/27416919002_d500c4576f.jpghttps://c2.staticflickr.com/8/7324/27416918972_a6ca20dc22_o.pnghttps://c4.staticflickr.com/8/7401/26907629363_2b94f241db_n.jpg


#10

@ abcd567; I can’t reply to your questions/post on a ‘certain other site’ about this; I says my post needs to be checked by a mod before posting. About a day later my comment still hasn’t shown up…

Anyway; so basically my setup should be: antenna on roof, RG6 cable between antanna and windows (in my case probably Hirschmann KOKA 9 TS), a short pieces of flat RG6 cable between the windows and window frame and that via an adapter cable to MCX/dongle.

So: Antenne - N connector - RG6 cable - connector - flat RG6 - connector - short pigtail cable - connector - Dongle - Raspberry Pi.

One question though; the impedance of RG6/KOKA 9 TS is 75 ohm. A lot of antennas are 50 ohm as well as a lot of pigtails etc.
For example; a 75 ohm MCX to N/F-connector pigtail is pretty hard to find; most is 50 ohm.

Will these difference create problems?


#11

@Iemand91:

  1. In many cases, it may not be possible or practical to have an “all 75 ohm” or “all 50 ohm” system.

  2. Each transition from 50 to 75 ohm or 75 to 50 ohm results in attenuation of signal by 0.155 dB, a very low ammount of attenuation. Therefore having one or two 50-75 ohm transitions is ok.

  3. The main attenuation comes from the length of coax. In the case of a long coax, it is therefore better to use a low attenuation coax. For short lengths, it does not make any practical difference if the coax is low loss (LMR400) or medium loss (RG6).

However using a good quality cable and connectors gives advantage of lesser failures due to weather.

It is also better if instead of using a piece of flat coax, you can pass the normal cable through the wall. May be an already existing hole or conduit, or drill a new hole? This will avoid two connectors of flat coax - a straight run of coax from antenna to receiver without unnecessary joints/connectors.


#12

Indeed.

  1. Each transition from 50 to 75 ohm or 75 to 50 ohm results in attenuation of signal by 0.155 dB, a very low ammount of attenuation. Therefore having one or two 50-75 ohm transitions is ok.

Great, makes sourcing the stuff much easier.

  1. The main attenuation comes from the length of coax. In the case of a long coax, it is therefore better to use a low attenuation coax. For short lengths, it does not make any practical difference if the coax is low loss (LMR400) or medium loss (RG6).

However using a good quality cable and connectors gives advantage of lesser failures due to weather.

Absolutely. But you’d say 15M of RG6 and a short pigtail of flat cable will not take a big hit on the overall performance in this case?

It is also better if instead of using a piece of flat coax, you can pass the normal cable through the wall. May be an already existing hole or conduit, or drill a new hole? This will avoid two connectors of flat coax - a straight run of coax from antenna to receiver without unnecessary joints/connectors.

It would; but it’s not my own house. So if I would start drilling holes in exterior brick wall; they might not be so happy with me. :blush:

If you say this setup is OK, I’m going to source some RG6 cable and the necessary connectors/pigtails and of course the antenna.


#13

@Iemand91:
With 15 m coax length, the attenuation of RG6 is 3 dB, and attenuation of LMR400 is 2 dB, not a big difference. Most likely with both type of coax, you will need an amplifier. So go ahead with 15 m RG6 coax + flat coax piece to cross the window/door.

If you use generic dvb-t dongle, adding a satellite amplifier + power inserter + power supply will do the job. If you use Flightaware Pro Stick, it has a built in amplifier. You may also need a filter (depends upon strength of cell phone signals in your area).

By the way, which antenna you have decided to use?

.


#14

Great.

If you use generic dvb-t dongle, adding a satellite amplifier + power inserter + power supply will do the job. If you use Flightaware Pro Stick, it has a built in amplifier. You may also need a filter (depends upon strength of cell phone signals in your area).

So you think I will most likely need all that too?

By the way, which antenna you have decided to use?
.

I’m thinking about this one: ebay.nl/itm/Antenna-ads-b-co … Swd0BV7Ykx


#15
  1. If you have generic dvb-t (black/blue), first try without amplifier, then add amplifier later. Adding amplifier in most cases gives an improvement.

  2. If you have Flightaware ProStick, it already has a built-in amplifier. Firts try without filter. You may have to adjust gain setting. I had to use 30 to 35 dB when used ProStick without filter.

Later, you may purchase a Filter, and try it. Use of filter may or may not improve reception. This depends on location.

For the locations having strong cell phone signals, use of filter improves reception. For locations which do not have strong cell phone signals, filter will not give any improvement, and for some it has resulted in reduction in performance.

With filter, the gain is to be adjusted, but it be somewhere between 40 dB &50 dB.

I’m thinking about this one: ebay.nl/itm/Antenna-ads-b-co … Swd0BV7Ykx

Using a commercial antenna gives peace of mind & sure results. The Slovekian model you have selected is used by many, and has positive reports.


#16

I have the blue one. I’ll start withouth amp first then.

  1. If you have Flightaware ProStick, it already has a built-in amplifier. Firts try without filter. You may have to adjust gain setting. I had to use 30 to 35 dB when used ProStick without filter.

Later, you may purchase a Filter, and try it. Use of filter may or may not improve reception. This depends on location.

For the locations having strong cell phone signals, use of filter improves reception. For locations which do not have strong cell phone signals, filter will not give any improvement, and for some it has resulted in reduction in performance.

With filter, the gain is to be adjusted, but it be somewhere between 40 dB &50 dB.

If i get poor results with my current setup; I might as well buy the ProStick; it would cost me about €20 from Amazon.de (I think that’s the cheapest way to get it here in the Netherlands).
Buying a inline amplifier, power inserter and power supply will cost me about as much if not more and looks much more messy.
(And I don’t have to climb up the roof again :unamused: )

Using a commercial antenna gives peace of mind & sure results. The Slovekian model you have selected is used by many, and has positive reports.

Awesome.


#17

I’m sorry I’m still bothering you with this but when I almost ordered the coax-cable and other necessary stuff I found this.

In my (almost) daily browse around several Amazon websites for the next day deals, I found on the German site this 5 meter and on the UK site this 10 meter USB-hub.
First of all; it comes with a long USB-cable. But most importantly; a 5V input on the end. (basically for powering power hungry harddrives).
I immediately thought; I can use that.

Put the antenna on the roof with the dongle and the end of this USB-hub (the 10M version). Run the USB-cable to the window and a flat USB-cable between windows/frame.
Voltage will probably to much if I would power the hub from inside with a 5V power supply so I could run it with a higher voltage power supply and put a buck convertor on the end. (power would run through a seperate cable)

This would give me the best setup I think; having the Raspberry Pi inside for easy access while no losses since the dongle is right next to the antenna.


#18

the only thing i would add is that the DVB dongles are power hungry and that length of cable might cause problems.

but worth getting because if it works awesome if not you have a usb extended port :slight_smile:


#19

How do you plan to enclose the dongle? Will it be actually at the base of the antenna? Otherwise, IMO, you are introducing interesting yet unnecessary complexity vs performance.

By all means, it will be fun to see how this works out. Keep us posted! My main receiver is 6 ft. from the antenna on a rooftop, with everything in an outdoor enclosure powered over Ethernet. Always good to have experimentation. I’m curious how the USB extenders perform over seriously long distance.


#20

That’s where the external 5V power supply steps in (via higher voltage power supply and buck converter at the end)…that’s the plan anyway…

In a waterproof box with the dongle at the base of the antenna.
This way I keep the Raspberry Pi inside (easy access) while I don’t have the potential signal loss over the long coaxial-cable.

By all means, it will be fun to see how this works out. Keep us posted! My main receiver is 6 ft. from the antenna on a rooftop, with everything in an outdoor enclosure powered over Ethernet. Always good to have experimentation. I’m curious how the USB extenders perform over seriously long distance.

Me too.

I was set on the coax but then this popped up. Gonna give it a try and see if it works (both with and without external 5V power). If it works; I’m gonna put it in a waterproof box and I’ll guess I’ll finally have to climb up the roof. :unamused: