The KiwiSDR 2 online store is open for orders! Please visit kiwisdr.nz
Please visit kiwisdr.com (documentation) and kiwisdr.nz (online store)

G8JNJ

About

Username
G8JNJ
Joined
Visits
3,709
Last Active
Roles
Member
Points
16
  • Use CAT6 shielded communications cable for antenna feedline, rotor control, and LNA power

    Hi Ron,

    The LZ1AQ loop amplifier kit uses CAT6 for power, control and signal.



    CAT 5 & 6 has a characteristic impedance of 100 Ohms per twisted pair. You can build an impedance matching balun or use two pairs connected in parallel and a 1:1 balun. However if you use this method beware, as some CAT cables use different numbers of 'twists per inch' on the different cable pairs in order to reduce cross talk between pairs. This results in some pairs being electrically 'longer' than others., which may cause problems if you connect them in parallel to halve the impedance.

    Regards,

    Martin - G8JNJ
    KA7U
  • Broadcast database application with control of WEB SDR

    Hi John,

    I've now spent a bit more time playing with this application.

    It's not the easiest thing to setup or initially use, but it does have some quite impressive features such as the ability to import various online databases and parse .xlsx files such as the 'Numbers and Oddities' and 'ITU monitoring' databases into a set of local databases that can be searched, sorted and indexed.

    When driving a local radio or the Twente WEB SDR (or others of that type) it's very handy for click tuning, ID'ing or scheduling stations.

    Definitely worth spending a bit of time with to get the hang of it, plus it incorporates some really good ideas and useful features.

    Regards,

    Martin - G8JNJ 




    KA7U
  • Home Brew Broadband Magnetic Loop

    Hi Ron,

    I think the loop is still unbalanced.

    The split is to avoid a continuous 'screen' (Faraday screen to minimise E-Field pickup) around the loop. But if one end of the center conductor is connected to ground you may have a problem.

    Check signal levels with the loop normal and 180 degrees as suggested previously.

    A 1:1 transformer on the loop input may help improve balance. Try six bifilar turns through a BN73-202 core as a starting point. One winding as the (balanced) loop input (primary) the other as the output (secondary) unbalanced connected to the amplifier input, with one end of the winding connected to ground. This will also provide galvanic isolation.

    You can also try a few more turns on the secondary as an experiment as this may improve reception on the LF bands.

    If you made a balanced loop amplifier with a much lower value of input impedance (LZ1AQ or Wellbrook copy) you wouldn't need the loop outer screen to minimise E-Field pickup.

    Regards,

    Martin - G8JNJ
    KA7U
  • Broadcast database application with control of WEB SDR

    Hi John,

    I recently found a broadcast database application that allows control of various receivers (including the Twente WEB SDR).


    Although it's a bit of a pain to setup, it does have some 'interesting' features that may be of interest for KiWi admins and users.

    Regards,

    Martin - G8JNJ
    KA7U
  • Some things I have noticed [problems with a large DX/label database]

    Hi John,

    The change has made a huge difference no sign of any audio 'stuttering' and a very fast and smooth scroll up and down in frequency at all zoom levels.

    Thanks for that :-)

    Regards,

    Martin - G8JNJ
    WA2ZKD