G4DYA

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G4DYA
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  • Flatness of KiwiSDR response < 500 kHz?

    I've done some measurements on the frequency response of the Kiwi below 1 MHz. Using a -53 dBm tone (S9+20) from a calibrated signal generator, I got -53 dB on the S meter down to 50 kHz. It rolled off below that:

    20 kHz: -1 dB

    10 kHz: -3 dB

    5 kHz: -7 dB

    HB9TMCka9q
  • Combining/Diplexing Antennas to Single Kiwi

    I'm using a diplexer to combine a Wellbrook loop with a 27m horizontal terminated folded dipole (TFD). The crossover frequency is about 1.7 MHz. (I found the TFD marginally better on 1.8 MHz.) The TFD has notches for the 4, 6 and 7 MHz broadcast bands. This feeds an Elad ASA16 distribution amplifier which feeds the Kiwis.

    When doing TDoA, I often find that Martin's RX is the only other one in the UK that can hear what I'm hearing. (It's 50/50 which is best.)

    The main factor affecting performance is neighbour QRM which varies enormously.

    http://kiwisdr.lamont.me.uk:8073/

    I attempted to upload a circuit diagram and a photo, but lost my fight with this forum's software and gave up.

    Richard
    Powernumpty
  • Kiwi BBAI software Alpha test instructions [updated 3-Jun-21]

    I'm attempting to provide cooling for a BBAI in a Seeed case. Without the end plates, two 5V 25mm fans side-by-side works well.

    First, I installed the AI but didn't use star washers next to the board - components are too close for comfort. Instead I used two star washers between the standoffs and the case. I didn't use the nylon standoff at all because there's a chip capacitor very close to the hole.

    image

    Next I stuck two fans to the Kiwi board and connected them to the bottom of the 5v barrel jack. I added a bit of draught excluder to the side of one fan.

    image

    Then connected the Kiwi to the AI.

    image

    Then stuck the lid on. Without anything at the end I held it together with Gaffa tape!

    image

    This arrangement keeps the CPU temperature well below 50° C. With the end plates on, it obstructs the airflow quite badly and is noisy. Next step is to try some sort of mesh grille. After that, I might try some sort of conduction cooling with chunky slabs of copper inside and heatsinks outside.

    73,
    Richard G4DYA
    HB9TMCPowernumptyrz3dvp
  • Kiwi BBAI software Alpha test instructions [updated 3-Jun-21]

    The BB version seems to be over-riding the Kiwi's network settings at boot and using DHCP regardless of whether it's configured for DHCP or static. If you're using a non-NATted static IP this can be very confusing.

    To get a static IP, it's necessary to use connmanctl:

    Find a filename in /var/lib/connman/ starting with "ethernet", e.g ethernet_01234567890ab_cable, then as root:

    connmanctl config ethernet_01234567890ab_cable --ipv4 manual ip_address netmask gateway_ip

    Then add the IP addresses for a couple of your ISP's nameservers:

    connmanctl config ethernet_01234567890abcdef_cable --nameservers 8.8.8.8 4.4.4.4
    Powernumpty
  • Kiwi BBAI software Alpha test instructions [updated 3-Jun-21]

    I'm attempting to provide cooling for a BBAI in a Seeed case. Without the end plates, two 5V 25mm fans side-by-side works well.

    First, I installed the AI but didn't use star washers next to the board - components are too close for comfort. Instead I used two star washers between the standoffs and the case. I didn't use the nylon standoff at all because there's a chip capacitor very close to the hole.

    image

    Next I stuck two fans to the Kiwi board and connected them to the bottom of the 5v barrel jack. I added a bit of draught excluder to the side of one fan.

    image

    Then connected the Kiwi to the AI.

    image

    Then stuck the lid on. Without anything at the end I held it together with Gaffa tape!

    image

    This arrangement keeps the CPU temperature well below 50° C. With the end plates on, it obstructs the airflow quite badly and is noisy. Next step is to try some sort of mesh grille. After that, I might try some sort of conduction cooling with chunky slabs of copper inside and heatsinks outside.

    73,
    Richard G4DYA
    HB9TMCPowernumptyrz3dvp
  • Kiwi BBAI software Alpha test instructions [updated 3-Jun-21]

    I'm attempting to provide cooling for a BBAI in a Seeed case. Without the end plates, two 5V 25mm fans side-by-side works well.

    First, I installed the AI but didn't use star washers next to the board - components are too close for comfort. Instead I used two star washers between the standoffs and the case. I didn't use the nylon standoff at all because there's a chip capacitor very close to the hole.

    image

    Next I stuck two fans to the Kiwi board and connected them to the bottom of the 5v barrel jack. I added a bit of draught excluder to the side of one fan.

    image

    Then connected the Kiwi to the AI.

    image

    Then stuck the lid on. Without anything at the end I held it together with Gaffa tape!

    image

    This arrangement keeps the CPU temperature well below 50° C. With the end plates on, it obstructs the airflow quite badly and is noisy. Next step is to try some sort of mesh grille. After that, I might try some sort of conduction cooling with chunky slabs of copper inside and heatsinks outside.

    73,
    Richard G4DYA
    HB9TMCPowernumptyrz3dvp
  • GPS antenna alternatives

    There doesn't seem to be anything wrong with the PCTEL GPS-TMG-40N antenna's current draw. The data sheet says <=40 mA, and I've just measured mine at 23 mA, both well within the Kiwi's 50 mA current limit.
    Powernumpty
  • GPS antenna alternatives

    On second thoughts, I don't think my antenna is going deaf at times. The Kiwi seems to struggle to acquire sats when the server has been running for a few hours. Last night it had 11-12, but by this morning it was down to six. On restarting the server it immediately came back to 11-12. If this is a bug, I suspect it's been there a while.
    Powernumpty
  • GPS antenna alternatives

    This is what my shadow map looks like after 18 hours. As expected, there's not much low-elevation stuff in some directions because of trees. In other directions, where the optical horizon is 20+ km away, satellites are being received at elevations as low as 3°. The 'polar hole' is clearly visible.

    M0TAZ
  • GPS antenna alternatives

    Just to add to this dormant thread, yesterday I installed a PCTEL GPS-TMG-40N antenna with low-loss feeder and it certainly does the trick. I went for the 40 dB version so there's plenty of signal in hand to feed a 4-way passive splitter when I get one. I'm somewhat screened by tall trees in the south-west quadrant, so don't get many low-elevation signals from there.

    The KiwiSDR GPS software only seems to allow a maximum of four Galileo satellites in the 12 channels. Is this intentional? While it all works fine, it would be nice if the limit could be raised - either by allowing more than four Galileo sats, or by allowing more than 12 channels. Also, surely there isn't much point in scanning for QRZZ satellites in Region 1?

    WA2ZKDPowernumpty