My subscription to Life expired, but I still have a subscription to Mad.

Saturday, September 23, 2017

Noise Gone At Last

As I wrote here in June 2016, I am very happy with my ELAD FDM-S2/SW2 SDR receiver, but there was a problem: interference from the MacBook Pro battery charger/power supply. The interference was so strong that only the strongest AM stations are above the noise.

I eliminated some of the noise when I reconnected an antenna switch to ground (after it had become mysteriously disconnected), but that did not eliminate the noise completely.

I installed ferrite cable clips on the charger's cable, but that made no difference. I wrapped the cable 20 times around a toroid ferrite core, but that made no difference.

The only solution that worked was to use the ELAD-MacBook Pro combo without the battery charger. This gives me a few hours operating without the interference, but sooner or later, the battery would need to be recharged.

A few days ago, I was using my MacBook and the battery was getting low. I was too lazy to go upstairs to fetch my charger, when I noticed my daughter's MacBook Air battery charger/power supply on the kitchen table unused. So I decided to try it even though it is a different model than the one bundled with my MacBook Pro (45W vs. 85W). Despite the difference, it charged my MacBook Pro without working up a sweat.

I wondered how my daughter's 45-watt charger would perform with the ELAD receiver, so I took it to the radio shack, made all the connections and voila! the 45-watt charger was clean. No noise at all!

I did a little Googling to see if there were any gotchas about using the wrong charger with my MacBook Pro and found this, which claimed that the charger, "will not charge the machine at all while in use, and will only trickle-charge the machine while asleep."

That was just the opposite of my experience, but to make sure I was correct, I used the 45-watt charger while running the ELAD FDM-SW2 software and it took my MacBook Pro's battery from 75% to 99% in about an hour.

That was good enough for me. I Googled the 45-watt charger, found it for sale here for $55 and ordered it as fast as PayPal could handle it.

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