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Thread: best antenna

  1. #1051
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    Quote Originally Posted by abcd567 View Post
    Any comments?
    "how to make a coax notch or bandpass filter": http://dl4xav.sysve.de/coax.filter/coax-filter.html
    Not sure what your point is?
    I have made several notch filters this way for hf-vhf.. But cannot see any benefits for this game, measurements would be critical and difficult to achieve without test gear (we would be talking fractions of a millimetre accuracy at 1ghz !

    Sent using Tapatalk from my ZX81

  2. #1052
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    Quote Originally Posted by Rooster View Post
    Not sure what your point is?
    I have made several notch filters this way for hf-vhf.. But cannot see any benefits for this game, measurements would be critical and difficult to achieve without test gear (we would be talking fractions of a millimetre accuracy at 1ghz !

    Sent using Tapatalk from my ZX81
    But the mention further down the page of a grounded bandpass stub to drain static looks potentially useful, you can have DC grounding on both screen and inner without any signal loss, however a well positioned RF choke would probably achieve the same effect without needing such precise measurements.
    The notch filter may be helpful to those close to a strong transmitter, you could make the stubs slightly over length and then using sdr# or similar to see the signal trim them till you get good attenuation of the unwanted signal.
    Ben.
    FR24 F-EGLF1, Blitzortung station 878, OGN Aldersht2, PilotAware PWAldersht, PlanePlotter M7.

  3. #1053
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    I very much doubt static will be an issue.... Plus anything you add to the system causes losses.
    In 30 years of amateur radio, I have never had a radio damaged by static.... I've seen sparks from static, but that was on a large wire antenna, which was disconnected... If left connected to a radio then the front end protection would discharge the voltage before it reached dangerous levels anyway.

    Sent from my ZX81

  4. #1054
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    Quote Originally Posted by Rooster View Post
    Not sure what your point is?
    I have made several notch filters this way for hf-vhf.. But cannot see any benefits for this game, measurements would be critical and difficult to achieve without test gear (we would be talking fractions of a millimetre accuracy at 1ghz !

    Sent using Tapatalk from my ZX81
    Thanks for the info. Actually I have never come across any notch filter before, and wanted to know experienced amateur's opinion about it (I am not a Radio Amature).

    Does not the antenna array of hand-held Alinco looks similar to this notch filter?



    Last edited by abcd567; 2014-05-14 at 14:57.

  5. #1055
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    Quote Originally Posted by Rooster View Post
    I very much doubt static will be an issue.... Plus anything you add to the system causes losses.
    In 30 years of amateur radio, I have never had a radio damaged by static.... I've seen sparks from static, but that was on a large wire antenna, which was disconnected... If left connected to a radio then the front end protection would discharge the voltage before it reached dangerous levels anyway.

    Sent from my ZX81
    You are probably right, however there have been reported problems with some of the sdr dongles that don't have the protection diodes fitted to the input, but tuned stubs are probably overkill for that anyway.
    Still it is always nice to know that such options exist even if you never use them!
    Ben.
    FR24 F-EGLF1, Blitzortung station 878, OGN Aldersht2, PilotAware PWAldersht, PlanePlotter M7.

  6. #1056
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    Quote Originally Posted by abcd567 View Post
    Thanks for the info. Actually I have never come across any notch filter before, and wanted to know experienced amateur's opinion about it (I am not a Radio Amature).

    Does not the antenna array of hand-held Alinco & this notch filter look similar?



    No,
    All I see in the above picture is someone who knows very little about RF using all the BNC couplers he can find to bolt every random object other than the proverbial kitchen sink to his poor hand-held, he probably gets far worse performance than he would by just using the original rubber whip, and is running the risk of breaking the socket if he drops that set-up or knocks it too hard.
    Ben.
    FR24 F-EGLF1, Blitzortung station 878, OGN Aldersht2, PilotAware PWAldersht, PlanePlotter M7.

  7. #1057
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    Quote Originally Posted by Breitling View Post
    I suggest to use rtl1090-beta3, many nice improvements from the version you're using. Download from here

    Set up rtl1090 as shown below (/30003 option, ignore others if they are not of your interest). Then configure a new receiver on VRS, Basestation format on port 30003. It sholud work.

    Attachment 4085
    I did not install RTL1090 beta3. I am still using the same old one, but succeeded in getting VRS work with it.
    The problem was with the Rebroadcast Server I have added to VRS. Both RTL1090 & the VRS Rebroadcast Server were trying to use port 30003, causing the conflict. I simply deleted the Rebroadcast Server, and bingo!!! VRS is working now. See images below:

    Image 1 Rebroadcast Server at port 30003
    VRS server for FR24.png

    Image 2 Rebroadcast Server deleted
    VRS without FR24 server.png

    Image 3 The VRS Map on my browser
    Later Edition: Range Rings in map below are 20 miles apart
    VRS+RTL1090- Map.png
    Last edited by abcd567; 2014-05-14 at 15:38.

  8. #1058
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    Notch filters (well, we are really talking about stub filter) are a beautiful coincidence of physics.... I live in site of a pager mast, which runs many 100s of Watts on several pager channels which is a major interference problem on 2m (145mhz)
    A single stub, approx 10foot of spare coax cable, and the pagers are no longer an issue!
    The stub, cut to resonance on the pagers strongest frequency essentially "short circuits" that one frequency, but leaves all others intact... It really is magic!
    This is a very simplistic explanation... But you get the gist.

    Sent from my ZX81

  9. #1059
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    Quote Originally Posted by abcd567 View Post
    Both RTL1090 & the VRS Rebroadcast Server were trying to use port 30003, causing the conflict. I simply deleted the Rebroadcast Server, and bingo!!! VRS is working now.
    Right, you can't receive and rebroadcoast on the same port. Glad to know it is working now.
    Northwest Spain: F-LECO1, F-LEST1

  10. #1060
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    Quote Originally Posted by Rooster View Post
    Notch filters (well, we are really talking about stub filter) are a beautiful coincidence of physics.... I live in site of a pager mast, which runs many 100s of Watts on several pager channels which is a major interference problem on 2m (145mhz)
    A single stub, approx 10foot of spare coax cable, and the pagers are no longer an issue!
    The stub, cut to resonance on the pagers strongest frequency essentially "short circuits" that one frequency, but leaves all others intact... It really is magic!
    This is a very simplistic explanation... But you get the gist.

    Sent from my ZX81
    Thanks. Now I understand what this "notch" filter is.

    Practically speaking, the filter stub gives same result as a High Q Series LC Circuit, tuned to pager (unwanted) frequency.
    Both short-circuit the unwanted frequency.

    .
    Last edited by abcd567; 2014-05-14 at 16:10.

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