output voltage from the RF input on KiwiSDR2??
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.
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
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
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.
will the proximity of the GPS antenna to the mag-loop also be causing a potential inductance? that could be it
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).
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.
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.
The IC is a NE592N14, the board seems to be a repackage of this item. https://www.ebay.com/itm/404924557664?