output voltage from the RF input on KiwiSDR2??

pantanopantano
in Installation, Antennas and Interference

Hello forum,

I recently purchased this 9V powered magnetic loop kit from ebay. It has a physical power switch that cuts power from the battery.

This is an embed external element. It can be deleted using the delete key or the backspace key. To view the full element, press the preview button below.

AMLA150 Magnetic Loop Antenna Adjustable Gain Low Noise For FM HA SDR Radio | eBay

https://www.ebay.com/itm/154058572374?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=oqzYSWO-T_u&sssrc=4429486&ssuid=rCgiyYxoTfa&var=&widget_ver=artemis&media=MORE
Why AMLA150 antenna is better than MLA30?. MLA30 uses a feeder to power the external antenna, which will further affect the receiving effect and reduce the receiving performance. The solution used by AMLA150 antenna is different from that of MLA30.

When plugged into the rf input of the KiwiSDR2 and the power switch is off on the antenna, the LED next to the SMA output is dim, but on!

I did not find reference that the KIWISDR2 supplies Bias-T power or any setting in the config that states so (so i'm assuming it does not?). Any idea waht may cause this? inductance from the mag loop itself? is this a normal state? pardon my naiveness.

Thank you!

Sam

Comments

  • jksjks

    Make sure you're not really plugged into the GPS port which does have a 3.3V bias tee.

    From a DC point of view the RF input only has a 100k to ground static drain resistor. Schematic: http://kiwisdr.com/docs/KiwiSDR/kiwi-2.schematic.pdf

  • pantanopantano

    it's not. unless the magloop can pickup 6+ satellites and lock on! So, assuming i can connect the devices correctly, would this point to some inductance? the gps antenna wire is running parallel to the RF antenna wire... but geez, my new RF antenna wire is darned well insulated and 3.3 volts of bias on that side shouldn't cause this. and we are talking a 8-10ft run.

  • pantanopantano

    will the proximity of the GPS antenna to the mag-loop also be causing a potential inductance? that could be it

  • jksjks

    There is no way any coupling between the feed lines is causing enough DC to appear to light the LED. What happens if you physically remove the battery? (or power supply connection)

    My guess is that the power switch doesn't really do the full job and there is some DC path through the output. If you traced out the schematic you could probably see this (despite the IC with the labeling removed).

  • pantanopantano

    i'll check with the battery removed this evening.... i'm guessing that you are correct in that the power switch does not fully cut power.

  • HB9TMCHB9TMC

    Another possibility would be that the kiwi's power supply has a Class-Y capacitor that leaks common-mode voltage to the DC side, which is then coupled trough the loop to ground.

    In that case you could measure an AC voltage between the Kiwi GND and PE.

    Nate_R
  • barneyukbarneyuk

    The IC is a NE592N14, the board seems to be a repackage of this item. https://www.ebay.com/itm/404924557664?

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