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benson

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benson
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  • GPS antenna trick

    bensonbenson
    If your friend can have access to the roof of the building there might be better options. I had a similar situation in Taipei and managed to install an active antenna on the roof outside the view of the security cameras..hi.

    Got some good results with an active whip design from the 1970's (Burhans) and a similar mini-whip design (PA0RDT) might work equally well. The building lightning protection ground worked o.k. as counterpoise.

    Initially I used 40 m RG-174 coax and changed to LAN cable later which gave improved EMI suppression. For the latter some small baluns with FT-50J toroids were made. The unused cable pairs were used for 2 orthogonal active loops.

    With the torrential monsoon rains in SIN waterproofing is really a necessity. In Taiwan the typhoons are an additional concern and eventually destroyed my high building rooftop installation blowing away most of it while water came running down the LAN cable even though sealed with self vulcanising tape...

    73, Ben

    PS: sri, quite a bit of thread drift from GPS reception
    Powernumpty

  • v1.246: GNSS Kalman filter, LED brightness control

    bensonbenson
    Now that many more Kiwis are updated to V1.246 I do see quite a few more station that can be used for TDoA and some at good locations for multilateration.
    Locally I noticed much improved position accuracies and about 95 pct of time all tracked GPS sattelites shown as "good" for position estimates.

    So I am really impressed by the work and implementation of these extended Kalman filters by Christoph and John. Thank you both.

    73, Ben - SWLOI33
    SWLJO43

  • Noise at roughly 60 KHz intervals

    bensonbenson
    In the addition to all the good points above another thing that might be worth checking is the coax cables going to your receiver. I replaced one low quality cable with poor shield and center conductor connections and noticed almost 15 dB reduction in these 62 KHz EMI signals. Mind you this was a brand new Taiwan made cable, admittedly a low cost version.

    Ben - SWLOI33
    KA7U

  • Receive and Decode DGPS on 306 KHz

    bensonbenson
    Hi John,

    There is a small but functional program called KG-DGPS, showing the actual GPS corrections. A couple of years ago the author "KG" JJ0OBZ made a whole series of mostly freeware and  well designed speciality decoders, but then unfortunately stopped other developments and support due to QRL workload or conflict of interest. Probably one of the Japanese users can find out more about the status of these programs and whether they can be considered abandon-ware or are now permitted to be included in other software. 

    On the other end of the non professional users spectrum there is "Amalgamated DGPS" which can run a large number of parallel decoders covering the complete DGPS LF band and shows a list and map display of received stations and time lines. The cost of the latter is  less than 20 usd.

    Probably many users do have a wish to have certain decoders included in KiwiSDR and perhaps we could have some voting to show which are most requested.

    Which brings me to a more general point about digital mode decoders: one may wonder if it is worth your valuable time and effort to create rather complex demodulators/ decoders for inclusion in KiwiSDR, if affordable third party alternatives are easily available. Such a decision and choice of additional decoders of course remains  with you.



    PS: KG-HFDL is an excellent HFDL (Arinc635) decoder with integrated map mode, hf tuning, database look-up and selcal (Arin714A) decoding and certainly beats PC_HFDL and similar programs. Sometimes I have used it on long flights to monitor surrounding traffic out of VHF or TCAS range.
    KA7U