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Excess current (but only a little) #qmx

 

Another happy QMX customer, I admit that the built was challenging, but the excellent instructions and various tips from this group made it manageable, with first time switch on. This is a 12v mid band version, where getting the wires into the holes for L401 is very difficult if not impossible in the case of the 2 common wires from the a and b coils. I do think that if the holes were slightly bigger, then the wires could be tinned, easing considerably the uncertainties over wire stripping and proper solder connection of the toroids.
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I do however observe ~100mA current drawn on receive on all bands. ?I have measured this various ways using different meters and via the voltage across a 10 ohm series resistor; so I think that this is accurate. ?The device powers up correctly, I have loaded the firmware, tested the transmitter and as far as I can tell is working properly. ?So, I don't think this is a problem, but 20mA is a significant percentage over the expected value and so I wondered whether there is something wrong, or is it within the observed tolerance seen by others?
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Richard,
What voltage were you powering the QMX with? On my 12 V QMXs, they draw about 90 mA at 12.0 V. However, at 7 V, they draw about 150 mA.?
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73, Dan? NM3A
 

Dear Dan, Thanks for the quick reply.? The measurements are all at 12v.? I realise that it would be higher at lower voltage and did take that into account when using the 10 sense resistor.? I used a linear bench supply and increased the PSU output voltage so that it overcame the 'burden voltage' of the sense resistor leaving 12v at the QMX input.
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If you see 90mA then, while 100mA is higher still, that reassures me a little.
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73 Richard

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