Mini whip and Kiwi power issue [power supply issue]

LasiadoraLasiadora
edited November 2019 in Problems Now Fixed
Hi,

Not sure if this is best here, or in antenna advice?!?

I have a mini whip kit aerial attached to my kiwi, (https://www.ebay.co.uk/itm/DIY-KIT-Mini-Whip-Active-Antenna-RTL-SDR/264521132443?hash=item3d96b0299b:g:1jAAAOSwlndZGLex). But I’m experiencing some odd behaviour.

If the mini whip is powered, and I then attach the power to the kiwi, the beagle board will not power up, but the antenna draws 300mw @12v.
If I disconnect the power from the mini whip, the beagle board and kiwi power up and work.
If I connect the power to the mini whip after the beagle board is running, it all works OK, but the antenna draws no power from its power supply.

Does anyone have any idea what is going on here?

Cheers,
David

Comments

  • G8JNJG8JNJ
    Hi David,

    Something strange is going on.

    I would expect the Mini whip to draw perhaps 50 to 120mA of current from a 12v supply, but it's difficult to be sure without seeing a circuit.

    I know it sounds obvious but is the Bias Tee (the power injector board) connected the correct way around to the KiWi so that power is going to the active antenna and not into the KiWi ?

    The next thing to check is the polarity of the power supply feeding the mini-whip. Has it got the positive side of the DC output connected to ground or the AC mains supply ground ? It's normally the negative DC rail that is connected to the outside of the connector and ground but some supplies occasionally have the polarity reversed.

    Does it do the same thing with just the power injector board connected to power supply and KiWi without the mini whip in circuit ?

    Regards,

    Martin - G8JNJ
  • PowernumptyPowernumpty
    I was going to ask the same questions, only other one "is it definitely connected to the HF SMA?"
    Cheers
    Stu
  • LasiadoraLasiadora
    Hi,

    Thanks for your comments. However, it turns out it was the power adapter!

    The Kiwi and the mini whip are both powered by PoE from my network switch, with step-down adaptors (one at 5v for the Kiwi and one at 12v for the mini whip). For some reason the step-down adaptor doesn’t recover properly when power-cycled!

    As a result it was only outputting 5v (hence the strange power use - it was actually 300ma at 5v, so ~125ma at 12v). I still don’t know what was stopping the Kiwi from booting.

    Cheers,
    David
  • G8JNJG8JNJ
    Hi David,

    I'm pleased you managed to sort out your problem.

    However I'm a bit concerned about your general arrangement.

    Mini-Whip antennas, DC switching convertors and PoE have all individually caused problems for KiWI owners due to unwanted noise ingress.

    I think you are very brave to try it and I'm definitely interested to find out what sort of results you obtain when using all three :-)

    Regards,

    Martin - G8JNJ
  • LasiadoraLasiadora
    Hi,

    I’m a radio newbie, so I don’t really know good from bad. I am getting telltale 60khz spurs but at -96dbm at worst, so nothing too bad. I live in a valley in south Wales, but I’m still impressed with what I can receive.

    I’m not, however, a network newbie :-) I’m using a Cisco SG300-52 switch about 12 ft from my Kiwi, but that’s in an earthed rack. As that should output a solid 48v DC on the wire, there shouldn’t be switch mode noise. The step-down devices I’m using (TPLink TL-POE10R) are seemingly noiseless. The room as a whole has a lot of other kit (a *lot* - as well as the switch there in a Cisco 3600 WiFi ap, 12 rtl sdrs, an SDRplay duo, 3 servers, 4 raspberry Pi’s, a 16 channel CCTV system and a big UPS).

    One thing that really stood out was about a month ago I plugged in a cheap wall wart 5v supply in that room and it utterly swamped about a 10MHz chunk of spectrum on the Kiwi despite being 16ft away. That was also replaced for a PoE stepdown and that noise disappeared.

    Cheers,
    David
  • G8JNJG8JNJ
    Hi David,

    OK all good, you are lucky with the Cisco Switch. A lot of the cheaper ones are really problematic.

    Considering the number of devices you are running including the CCTV, your'e doing very well.

    I hope you will be able to put yours publicly on-line, as we could do with another KiWi in Wales for TDoA sessions.

    BTW I used to live in South Wales on the tip of South Glamorgan (yes I know that isn't 'really' Wales) but I used to be up and down the valleys a lot when I maintained TV transmitters and hilltop relays in the area.

    Regards,

    Martin - G8JNJ
  • LasiadoraLasiadora
    Ah, I was brought up in Barry so know the area well. I’m not in “the valleys” just a valley close to Cowbridge.

    I’ll probably put mine online when our broadband gets improved as I have a 2mbps connection at the moment :-(

    Cheers,
    David
  • rz3dvprz3dvp
    edited November 2019
    Hi David,
    One KiwiSDR on 8 channel mode with full busy generated about 1.7 Mbit/s:
    5 minute input rate 1705000 bits/sec, 255 packets/sec
    5 minute output rate 155000 bits/sec, 211 packets/sec

    Regards,
    Yuri
  • G8JNJG8JNJ
    Hi David,

    Ah OK, I lived in Llantwit Major for several years and worked just outside Cowbridge (the big mast).

    My current broadband speed is <10Meg down and <0.9Meg up (which is the critical bit for putting a KiWi on line) and I've been able to run more than one, plus other stuff too, so don't be disheartened.

    Regards,

    Martin - G8JNJ
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