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  • Been lurking and learning here for a few months.
    To keep the feed line short but still keep the antenna away from the noisy computer room, I've had good luck with the 10 meter (32 ft) USB active repeater extension cable by Bluerigger - available through Amazon. Even tried two of them end-to-end for a total of 64 feet and still had success, getting good results from an rtl dongle.

    I also tried several of the USB over CAT5 extensions, but found that they were limited to an earlier USB standard and didn't work with the dongle.

    From an indoor 8 element collinear antenna leaning against the wall on the second floor of my house, my best distance yet is 420km, with 300-350km being the norm. Hope to get the antenna outside onto the roof for better results, before the snow flies.

    Comment


    • Originally posted by T-KJAN4 View Post
      The longest USB extension cable that I have seen WITHOUT an active repeater is 25ft.
      The longest I have seen WITH an active repeater is 48ft.

      Active repeater gets power supplied from the USB port on the computer as well as the port on the device. (i.e printer for example)
      Originally posted by abcd567 View Post
      Thanks for the information. The stores in my neighborhood do not have USB cable longer than 15 ft. Maybe if I tried on-line stores like ebay or amazon, I could get 25ft long USB cable. I solved length problem by combining 4 short lengths to get 48ft (15+15+12+6). If I had found 25ft, I would join 2 lengths to get 50ft.

      The real issue is loss of signal with length, which imposes a limit on maximum length of usb cable (about 30 ft). Active repeater is a good solution to overcome long length issue. I am sure many forum members are using it. I vaguely remember member peterhr (or maybe someone else) once mentioned something like this for his setup.
      The USB active repeater extension cable achieves the same goal as the Coax Cable+Amplifier, i.e. both systems make it possible for antenna & desktop to be tens of feet apart.

      However the Amplifier, having Gain much more than needed to cover attenuation of long Coax Cable, utilizes this Surplus Gain to perform following two extra functions which active USB extension does not:

      (1) The pre-amp of the Dongle is not so good as that of the FR24 supplied receivers & other costly receivers like Beast. The in-Line Amplifier boosts weak signals from far away planes, to a value above the cut-off level of Receiver (DVB-T USB) BEFORE these are fed to the receiver. This substantially increases the Maximum Range
      (2) The Amplifier covers for the low gain/high SWR of not professionally made DIY antenna. This substantially increases the Maximum Range.

      In view of these two additional advantages of an in-Line Amplifier, I prefer it over the active usb extension.
      Last edited by abcd567; 2014-09-14, 08:40.

      Comment


      • A question? I have home built ground plane antenna about 8m in the air running on my pi(see pics)
        Any ideas what I can place round/over to keep weatherproof without affecting signal? I am close to the ocean and have noticed oxidisation of copper radials and main element. Its waterproof from base of ground plane down coax to dongle but wondering if "greening" of copper radials and main element can cause distortion of signals. I was thinking of chinese takeaway container to keep the weather off the elements. Any ideas appreciated.4.jpg1.jpg3.jpg

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        • abcd567 has some pictures where a coke bottle of suitable size was used cut it off where it starts to taper in (maybe cut a slot in the neck section to slide it over the feed cable, pop the bottle bottom over the antenna and the neck (so the neck is inside the bottle a little, cable tie on (needs holes)

          or, could use something like clear nail varnish on the elements maybe (somewhat easier than doing construction)

          Comment


          • Some guys over here who use similar antennas, we call them "Spidertennas", use a clear lacquor spray (spelling?!) to cover it, usually applying multiple layers. Similar to your DIY aerosol spray paint cans, but just a clear varnish-like spray. As the sun in Auz is rather nasty, I presume you will have to give it a touch-up every few months.

            Comment


            • Originally posted by Stephen P View Post
              A question? I have home built ground plane antenna about 8m in the air running on my pi(see pics)
              Any ideas what I can place round/over to keep weatherproof without affecting signal? I am close to the ocean and have noticed oxidisation of copper radials and main element. Its waterproof from base of ground plane down coax to dongle but wondering if "greening" of copper radials and main element can cause distortion of signals. I was thinking of chinese takeaway container to keep the weather off the elements. Any ideas appreciated.
              Originally posted by peterhr View Post
              .....or, could use something like clear nail varnish on the elements maybe (somewhat easier than doing construction)
              Originally posted by HermanZA View Post
              ....use a clear lacquor spray (spelling?!) to cover it, usually applying multiple layers. Similar to your DIY aerosol spray paint cans, but just a clear varnish-like spray.....
              The proposal to use clear varnish / lacqer by peterhr & HrmanZA seems good, easy & practical. See post #1483.

              However if you want to use Chinese take away container, you may get some ideas from post #1495, #1497 and #1498
              Also see post #1505 from forum member trigger.

              Just curious:
              (1) What is the maximum Range you get with this antenna?
              (2) The Length & Type of Coaxial Cable from Antenna to Receiver?
              (3) Do you use an in-Line Amplifier?

              I like your nicely built antenna...water protected by rubber gaskets at pipe cap, and heat shrink tube over the coax connectors.

              Last edited by abcd567; 2014-09-14, 22:19.

              Comment


              • Originally posted by Stephen P View Post
                A question? I have home built ground plane antenna about 8m in the air running on my pi(see pics)
                Any ideas what I can place round/over to keep weatherproof without affecting signal? I am close to the ocean and have noticed oxidisation of copper radials and main element. Its waterproof from base of ground plane down coax to dongle but wondering if "greening" of copper radials and main element can cause distortion of signals. I was thinking of chinese takeaway container to keep the weather off the elements. Any ideas appreciated.[ATTACH=CONFIG]4736[/ATTACH][ATTACH=CONFIG]4737[/ATTACH][ATTACH=CONFIG]4738[/ATTACH]
                Although I am in favour of using clear varnish / lacqer coating of antenna as preferred solution, but if you still want to use the "chinese takeaway container", or any other container, then the container should be wide enough to accommodate the ground plane radials. Assuming radials 1/4 wavelength = 69mm, and a 45 degree bend, the radius of ground plane is 0.069 x Cos 45 degrees = 69 x 0.707 = 49mm. The width of a rectangular container or dia of a circular container should be 2 x 49 mm = 98 mm or more.

                A 2 Liter coke bottle is just about this size. However using a bottle requires cutting the bottle into two parts at the point where it starts narrowing, and then after placing antenna inside, rejoining the two parts by a strong adhesive.

                A better option than a bottle is a wide-mouthed Plastic Jar with lid, as it will not require any cutting & joining. Please see the picture below. See post #1444 for full details.

                DSC03294-R_o.jpg
                Last edited by abcd567; 2014-09-16, 15:15.

                Comment


                • Our Experimenter friend from Norway has built AIR INSULATED CoCos using copper tubes, and is now testing/tweaking these.

                  Below is quote from his email:

                  "My test antennas are built from copper alone, so air insulation is exactly what I want.

                  I'm not done testing yet, but one preliminary conclusion I can share with you, is that at these dimensions the elusive "K-factor"[1] or ratio of element diameter to length appears to be very important. My elements need to be a lot shorter than anticipated, but a little more testing and simulation is needed to get an idea of how much of this shortening is needed due to dimensions, and how much is attributable to other factors.

                  I'll also have to run a comparison with an antenna built from normal coax cable: If it is necessary to correct for K-factor in addition to velocity factor, it is no wonder people have seen worse results than they hoped for in their cocos.

                  About my test setup: I'm running two Raspberry PIs with NooElec Mini USB-dongles, with one left unaltered and serving as a reference, and all tweaking being done on the other. I've tested different settings (gain, error correction) in the dump1090 linux software, as well as varying antenna element length, wrapping the antenna in foam, etc. Interestingly, when everything is equal between the two systems, one of them (my reference) consistently decodes about 10% more messages than the other."


                  Brynjars copper.jpg .. Brynjars test setup-2by2.jpg
                  Last edited by abcd567; 2014-09-15, 01:12.

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                  • welcome!

                    If you put your antenna in a plastic container, make sure it has a drain hole. Otherwise water will get via condensation / atmospheric pressure changes, and not be able to get out, and probably go into and ruin your coax cable. PVC pipe is good, inexpensive, and easy to work with. Bare copper should get some insulation, like liquid electrical tape or some UV resistant adhesive or paint.

                    Comment


                    • Stoked for all input. When i first looked at radar setup, spoke to my dad (he turned 80, 3 weeks ago) who has extensive electrical knowledge, regarding best antenna type. We decided "Spidertennas"/groundplane was the way to go for ME. Build wasn't that hard, silver solder and patience is a virtue. I read about waterproofing and found silicones/coatings could affect signal hence straight out copper with seals and heatshrink. Chinese food container was just a sugestion to a means of coverage keeping it simple. Build for me isnt a problem. I have a Clear Polyurethane UV stable waterborn glaze i think would be better than varnish/laquers due to its longevity but based on initial reading of coatings distorting signals i have stayed "clear" (no pun intended) till now.
                      Current best range according to FR24 stats is 192nm with no amp, 6.5 to 7m standard Aussie 75 ohm TV coax(had it in the shed) with $8 chinese dongle running on my pi. In another thread i questioned ADSBscope feed from pi and cant seem to get it to play at present but see pic of same setup below (antenna,cable,dongle) running on pc.
                      Wanted to compare fresh/new antenna vs degradation due to oxidisation of slightly now older antenna and try to find a solution to replicate original range. Any thoughts as always appreciated.
                      Attached Files

                      Comment


                      • Hi Stephen,

                        Awesome coverage you getting there. What Height above Ground is antenna at? AAnd congrats with patience in that soldering job - I attempted it once and burnt my fingers more than once!

                        Not sure if in the other thread you got a resolution to your problem, but in quick what I've done... let my DUMP1090 create a separate stream/port for ADSBScope to connect to, with the following line:
                        cd /home/pi/dump1090
                        /home/pi/dump1090/dump1090 --enable-agc --aggressive --net-http-port 8090 --net --net-sbs-port 30003 --net-ro-port 30002 --net-bo-port 30005 --quiet --lat -27.912 --lon 25.162 >


                        And just tell Scope to connect its RAW-Client to the NET-RO-PORT 30002
                        Last edited by HermanZA; 2014-09-15, 12:30.

                        Comment


                        • Originally posted by Stephen P View Post
                          Stoked for all input. When i first looked at radar setup, spoke to my dad (he turned 80, 3 weeks ago) who has extensive electrical knowledge, regarding best antenna type. We decided "Spidertennas"/groundplane was the way to go for ME. Build wasn't that hard, silver solder and patience is a virtue. I read about waterproofing and found silicones/coatings could affect signal hence straight out copper with seals and heatshrink. Chinese food container was just a sugestion to a means of coverage keeping it simple. Build for me isnt a problem. I have a Clear Polyurethane UV stable waterborn glaze i think would be better than varnish/laquers due to its longevity but based on initial reading of coatings distorting signals i have stayed "clear" (no pun intended) till now.
                          Current best range according to FR24 stats is 192nm with no amp, 6.5 to 7m standard Aussie 75 ohm TV coax(had it in the shed) with $8 chinese dongle running on my pi. In another thread i questioned ADSBscope feed from pi and cant seem to get it to play at present but see pic of same setup below (antenna,cable,dongle) running on pc.
                          Wanted to compare fresh/new antenna vs degradation due to oxidisation of slightly now older antenna and try to find a solution to replicate original range. Any thoughts as always appreciated.

                          [ATTACH=CONFIG]4742[/ATTACH]
                          Thank you Stephen for the detailed information.

                          Why not use a plated copper wire to build a spider antenna?

                          Three of the most common plating materials used with copper conductors are tin, silver and nickel. All three plating types protect copper from green corrosion, and being good conductor of electricity, will not degrade the signal.
                          Last edited by abcd567; 2014-09-15, 14:45.

                          Comment


                          • Silver plated Copper wire, 2mm dia, 50g/1.7m, Price: 4.00 (~€5.04) (Excluding VAT at 20%)

                            http://wires.co.uk/acatalog/cu_sp.html


                            15247895022_a40c997c7d_o.png
                            Last edited by abcd567; 2014-09-16, 15:23.

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                            • I think stainless is the way to go, most commercial discone and spider type antennas use stainless.

                              Take a trip to some local welding shop and ask for few of these filler rods...........
                              most likely they will give them to you...

                              or order a package and build several...

                              filler_rod.JPG

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                              • Gonna build one of these today, I have plenty of RG213.
                                http://f5ann.pagesperso-orange.fr/An..._MHz_FR_EN.jpg

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