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  • petercr
    replied
    Originally posted by abcd567 View Post
    Hi Peter
    Good that you have decided to make a DIY dc blocker.
    DIY is fun.
    My Dad was an amateur radio enthusiast from the time he got out of the RAF at the end of WWII until he died (about 20yrs ago) and I fondly remember helping build a number of his antennas so this does bring back some memories...

    (and DIY is often cheaper )

    Leave a comment:


  • abcd567
    replied
    Hi Peter
    Good that you have decided to make a DIY dc blocker.
    DIY is fun.

    A 100pF capacitor is ok. The 200pF is not critical, but preferable.

    The impedance added in RF path by 200pF capacitor is 0.73 ohms. As the 100pF has half the capacitance, its impedance is double i.e. 2x0.73 = 1.46 ohms. Both these values are low enough to be acceptable.

    As the prices of 100pF and 200pF are nearly same, I preferred to use 200pF to get slightly lower impedance at no extra cost.

    XC = 1/(2 x pi x f x C) = 1 / (2 x 3.141 x 1090 x 106 x 200 x 10-12)
    = 0.730 ohms

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  • petercr
    replied
    Hi abcd, (having read this far I feel I sort of know you)

    Voltages on both F-connectors are correct (about 17V on the amp side as it's no-load without the amp connected) and 0V on the TV side. I have a spare 2-way splitter that I've gutted and there's a hobbyist electronics store 10mins down the road where I can get 220pf ceramic caps for less than a dollar so I might make a power blocker as well as an extra precaution...

    (or I can put 2x100pf in parallel if 200pf important - caps come in a pack of 2pc so no problem either way)
    Last edited by petercr; 2018-03-19, 04:27.

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  • abcd567
    replied
    @petercr
    1. There are two output ports in power inserter, one for TV, other for Amplifier.
      In the powered-up condition, when measured with a multimeter:
      • The terminal for TV MUST have zero DC voltage to protect TV (or the DVB-T dongle)
      • The terminal for Amplifier MUST have full DC voltage (say 14V DC or similar).
        Zero DC at this terminal means no power supply to amplifier and the Amplifier wont amplify. It will rather attenuate.


      Power Injector - DC Voltages.png

    2. Test continuity of your antenna between core and shield at feed point by a multi tester. If it shows open circuit, then DC Blocker is not necessary. However even with open-circuit antenna, it is safer and desirable to have DC Blocker so as to protect your power insereter and amplifier from damage in case of accidental short circuit.

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  • petercr
    replied
    I did notice that comment while reading through all those pages so I got out my multimeter and measured the DC voltage across the output connection of the power inserter when powered up and it was zero so I know it's safe... (it's also from a well-known Australian antenna manufacturer so I doubt they'd forget about that).

    Edit:
    Same as this except with F-type connectors...
    https://www.kingray.net.au/catalogue...ors/psk06.aspx

    Extra edit: When assembling, I did a continuity check of each segment and all okay. The open end was also encapsulated in non-conductive epoxy to bond it to the end cap on the PVC pipe.
    Last edited by petercr; 2018-03-18, 20:32.

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  • abcd567
    replied
    @petercr:

    The built-in DC blocker of power supply blocks DC only from going to the DVB-T (or Pro Stick). It definitely allows DC to go to the Satellite amplifier, which passes the DC to antenna. If the antenna has a DC short, your DC power supply will fry itself or fry the amplifier.

    The DC blocker MUST be between Satellite Amplifier and antenna. This requires a separate dc blocker.




    https://www.ebay.com/itm/DC-Blocker-...g/132336080669

    DC Blocker F inline.jpg

    https://www.ebay.com/itm/DC-BLOCKER-...-/131036281185
    Last edited by abcd567; 2018-03-18, 14:52.

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  • petercr
    replied
    Here's the antenna with an addition I made this afternoon - the bottom section is a piece of 50mm PVC-U pipe with caps and IP68-rated cable glands that should be totally water-proof. When the satellite amp arrives I intend to fit it in there along with the power supply.
    IMG_20180318_160425_1.jpg

    Leave a comment:


  • petercr
    replied
    De-lurking after reading all 271 pages... Today saw me install an 8-element open top CoCo using RG6 inside a 3m length of 15mm (1/2" for you non-metric types) PVC conduit attached to a j-bracket and with the limited horizon I've got (due to the house and other tall gum trees and palm trees in the area) I've managed to get a max range of just over 130NM after about 12hrs of reporting. Have ordered a Prostick+ and separately from eBay one of those generic 20dB satellite amps (along with a TV amp power supply (with built-in DC blocker) that was lying around) - see which one turns up first... Hopefully I can get my range up even further.

    Leave a comment:


  • lodervsm
    replied
    Thanks for your tips.

    I have reduced my gain in the last couple of days and seems that --gain 42.1 is a good compromise to my system. I also added an extra filter after the antenna. Now my max range has reached 311NM. I noticed that for my position somehow it helps to have a southerly wind for max range.

    Leave a comment:


  • abcd567
    replied
    @lodervsm

    Flightaware antenna is high gain antenna, and with ProStickPlus's built-in amplifier, strong signals from nearby planes may overload the tuner of the dongle, distort signal, and rejected by decoder software. The plane will not show.

    First try to reduce gain in steps. Say max (49.6), 45, 40, 35, 30, 25.

    For each setting observe for some period, say half an hour, to see how is the performance. You may find a setting where you get desired results.

    If above does not solve the problem, then you may need to add a filter. Yes, I know ProStick+ has a built-in filter, but it does not protect the front end amplifier chip, as it is located after the amplifier.

    You may also go through this thread:

    Find Out Existing RF Signals (Cell/Mobile/Pager etc) In Your Area

    Leave a comment:


  • lodervsm
    replied
    I recently switched from a 12 element colinear element antenna (DIY connected to 1m RG-179) to the flightaware antenna fitted to 5m CLF200 coax low loss cable. I noticed a significant increase in range of about 25NM approx. My max range is 240NM now. However I am noticing that I have lost reception of many aircraft below 1,000ft. I live just 2km away from the airport. I have flightaware pro stick plus as receiver connected to pi3. Any ideas what can I do to get the coverage below 1000ft back ?

    Leave a comment:


  • abcd567
    replied
    Originally posted by Rooster View Post
    Shame, as making stuff is really fun !!! Not to mention cheaper AND better than commercial gear... especially antennae !
    Unfortunately most ads-b hobbyists/data feeders are mainly interested in "rank", which is achived by using commercial equipment rather than DIY. They are least interested in fun of doing things themselves. Their focus is only on "how can I increas my rank above other feeders in my area?".

    Leave a comment:


  • abcd567
    replied
    As long as commercial antennas were very costly $100 to $300, most hobbyist were tempted to go for a DIY antenna costing almost free few $ only.

    When Flightaware marketed a 5.5 dBi antenna for $45, lot of hobbyists replaced their cocos and spiders by Flightware antenna.

    Now few think of a DIY antenna. They mostly go for Flightaware 26 inch antenna for $45 and Flightaware Pro Stick (which is a generic DVB-T + integral front-end RF pre-amplifier) for $16.

    Leave a comment:


  • Rooster
    replied
    Shame, as making stuff is really fun !!! Not to mention cheaper AND better than commercial gear... especially antennae !

    Leave a comment:


  • abcd567
    replied
    Originally posted by Rooster View Post
    Quiet in here again :-(
    Yes it is.....
    Frustrating.... This thread used to be so lively

    Leave a comment:

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