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Thread: less bulky RTL2832U dongle, that does not block 3 USB ports from the Pi

  1. #21
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    Hi Laslo
    I'm using an RTL dongle same as yours, but I have removed and discarded the plastic cover and swapped out the original antenna connector for a right angle SMA pointing to the end of the board. I have removed the LED and remote control sensor to make more room and lower current consumtion. I then added a transistor preamp in the track to the SMA. The dongle is mounted in a close fitting metal enlosure and is connected to the antenn by about 100mm of thin coax. The antenna is 3x 1/2 wave sections separated by 1/4 wave stubs (1/2 wave total) The stubs are curved so the whole lot slides into plastic tubeing and is mounted over 10 metres on a tower. I use two ten metre boosted USB extensions in series to power and take the data down to the Raspberry Pi indoors. This works very well, but I would recomend using a powered USB hub to protect the Pi. (I haven't done this yet)
    Putting the receiver at the antenna saves the signal losses associated by using lossy coax feeders. I have fitted a couple of long ferrite beads over the 100mm coax at the antenna and some more on the USB cable top end. I am getting very good results (300km) with this and once someone tells me how to make the raspberry Pi keep a static IP address and avoid having to log on, I will start feeding FR24
    I'm using the FR24 easy download and install software but I'm not sure how to modify it.
    Any ideas please.
    Best regards,
    Keith

  2. #22
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    Hi Keith,
    The IP address of the Pi is usually given from the router. Many routers have a function to assign the IP based on the MAC address.
    You may also do it that way: http://www.modmypi.com/blog/tutorial...tic-ip-address but it should not be necessary.
    When you start from NOOBS you have usually autologin from scratch.

    The ferrites should not be very efficient in the GHz area, but it's a good idea to wind 4-5 loops of cable to make a balun.
    Regarding the protection: your Pi is only worth a few bucks. If you have a thunderbold stroke in the vicinity it will probably be fried. With or without a usb hub in the middle.

  3. #23
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    Quote Originally Posted by RIN67630 View Post
    Hi Keith,
    The IP address of the Pi is usually given from the router. Many routers have a function to assign the IP based on the MAC address.
    You may also do it that way: (LInk removed) but it should not be necessary.
    When you start from NOOBS you have usually autologin from scratch.
    The ferrites should not be very efficient in the GHz area, but it's a good idea to wind 4-5 loops of cable to make a balun.
    Regarding the protection: your Pi is only worth a few bucks. If you have a thunderbold stroke in the vicinity it will probably be fried. With or without a usb hub in the middle.
    I needed a static address so I can leave the Pi to start on its own after a power down and to allow me to connect from a PC via Putty. I don't want a monitor or keyboard connected to the Pi when it is fully functional.

    The use of a hub would be to supply current to the Dongle and the the two active 10m USB cables without straining the Pi USB port.
    Thank you for the info regarding the ferrite beads. Next time the antenna is dismantled I'll make up a coax choke, but I am also trying to lower the RF levels from adjacent transmitter antennas a few metres below and on either side of the ADS-b antenna. (50w at 147MHz into 2x 10 element yagis is my main worry).

  4. #24
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    @Keith Browning:
    If you want to access RPi from within your local network, then you dont have any issue. The local IP address for each device is assigned by the router and is static. It is something like 198.168.2.xx, where xx is unique for each device, and is assigned when the device is first connected to the local network, and remains static.

    If you want to access RPi from outside your local network through internet, and want a static address, you have to ask your Internet Service Provider (ISP) to assign you a static address. Alternatively you can setup an alias on sites like noip.com, and install their dynamic update client (DUC) on RPi, which will keep updating current IP address at regular intervals you set (default is 30 minutes).
    Last edited by abcd567; 2016-03-29 at 22:01.

  5. #25
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    Hi Keith,

    The Pi starts always on its own without problem. Mines are all headless.
    I just connected a monitor or keyboard once and immediately installed XRDP.
    Code:
     sudo apt-get install xrdp.
    After that I am controlling them very comfortably and fully graphically from Windows with Remote Desktop.
    I don't even need to know the IP adress since Remote Desktop works well with machine names.
    Just remember to change the Pi Name if you have several machines.

  6. #26
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    Quote Originally Posted by Keith Browning View Post
    ... I am also trying to lower the RF levels from adjacent transmitter antennas a few metres below and on either side of the ADS-b antenna. (50w at 147MHz into 2x 10 element yagis is my main worry).
    If you have a that sender in the vicinity, I really would strongly recommend the 1090 filter. The RTL stick easily saturates since it has absolutely no built-in RF tuning stage.
    If I were you, I would avoid an amplifier stage and put the whole receiver stick in a well grounded metallic can.

    The recent Pi3 has a better USB power management, you should be able to power the stick and the USB boosters without hub.
    Anyhow it is adviseable to power the Pi with 5,3V from a trimmable step-down power adapter.
    If you have close RF sources, less USB stuff in the middle is surely better.

  7. #27
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    Quote Originally Posted by RIN67630 View Post
    If you have a that sender in the vicinity, I really would strongly recommend the 1090 filter. The RTL stick easily saturates since it has absolutely no built-in RF tuning stage.
    If I were you, I would avoid an amplifier stage and put the whole receiver stick in a well grounded metallic can.

    The recent Pi3 has a better USB power management, you should be able to power the stick and the USB boosters without hub.
    Anyhow it is adviseable to power the Pi with 5,3V from a trimmable step-down power adapter.
    If you have close RF sources, less USB stuff in the middle is surely better.
    I would like to fit a passband filter at some point if I continue with with the feeding of FR24. (more expence)
    Yesterday I was trying to figure why FR24 was saying that I was offline most of the day. I checked the RX with SDR# and found while the dongle was working, there were no 1090 signals being received and other usually strong signals were seriously reduced. I realised an earlier full power transmission has taken out the BFP-420 preamp. Tipped the tower and replaced the dongle with a new un amplified sheided type. Is all working again, although FR24 does not seem to be using my data yet. >12 hours online.
    The "failed" dongle was very well shielded. I'm pretty sure that a good 1090 filter will have protected it. Perhaps a series LC circuit tuned to 147MHz from the aerial to the shield may help. I have an earth strap connecing the ground plane to the dongle shield and the tower top. In the mean time I'll stop transmitting throught the VHF antennas close to the dongle.
    In my mind, having the receiver at the antenna instead of using expensive and lossy coax makes it worth while perfecting the long USB approach.

  8. #28
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    Quote Originally Posted by RIN67630 View Post
    Hi Keith,

    The Pi starts always on its own without problem. Mines are all headless.
    I just connected a monitor or keyboard once and immediately installed XRDP.
    Code:
     sudo apt-get install xrdp.
    After that I am controlling them very comfortably and fully graphically from Windows with Remote Desktop.
    I don't even need to know the IP adress since Remote Desktop works well with machine names.
    Just remember to change the Pi Name if you have several machines.
    Thanks for the help. The XRDP software will be loaded as soon as possible.
    I'm very green as far as the Pi goes, I am using a B+ whick I previously thought I had killed it with RF and purchased a new Pi2 B on the mornng of the same day they announced the Pi3 in the afternoon. Later I realised the the older Pi was actually ok. I certainly can't justify buying a 3rd.
    Can I use the pi for other things while it is feeding FR24?
    Can I somehow use the same data on a polar plotter without upsetting the FR24 feed?

  9. #29
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    Dear Keith,
    The collinear might be dangerous, in the worst case you get close to 1/4λ of 147MHz.

    If i were you, i'd prefer the J-pole antenna.
    Here ist the detail view of the balun und the coax connection:
    http://www.cjoint.com/doc/16_03/FCwi...322-090136.jpg
    The dimensions are given here:
    http://www.hamuniverse.com/jpole.html

    Since it has an intrinsic short and a strong resonnance behaviour, you should have a good rejection towards the much longer 147 MHz.
    If you have a piece of coax (from which you know _exactly_ the speed factor) you might place a λ/4 stub before your receiver, that will additionally reject your 147 MHz.
    The best being to buy the flightaware filter, it's not that expensive, but the shipment may take a while.

    By the way: the RF that fried your preamp must not have originated from the antenna. It could also come from the usb shields so be careful and ground very thorougsly everything getting into your reciever's Faraday cage.
    Regards
    Laszlo
    Last edited by RIN67630; 2016-03-31 at 01:17.

  10. #30
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    The B+ is just fine. If you use a good WLAN stick, you will get much more WLAN range that from the Pi3 for which you can't extend the range with an antenna.

    For FR24 the Pi B+ needs between 2 and 4% processing power.
    You many play games with the rest...
    I am running a sound pressure server simultaneously.
    God, it takes me an additional 1% AWAY!
    ;-)
    And the XRDP server takes easily up to 40% while re-drawing your desktop, but returns to 0 when you are not teasing it.
    Its stock web browser is very demanding and IMHO behaves deceivingly slow.

    And of course DUMP1090 delivers all flight data on ports 30002, 30003.
    Which you can use on e.g. a very distant workstation to run fancy stuff like Virtual Radar.

    >I certainly can't justify buying a 3rd.
    How many Pi's do you beleive I own?
    Last edited by RIN67630; 2016-03-31 at 01:10.

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