Thursday, 1 December 2016

Thumbnet N3 First and Final Impressions

I was really looking forward to the N3, and got the review sample on Monday.
Started with noise profiling, which looked promising:



Proceeded to do noise profile with a switched mode supply, as it was the only one available, but figures and graph looked almost identical.
Did ADS-B testing for 36 hours, N3 had 4 percent more position reports than an rtl-sdr.com v.3.

Emailed Thumbnet for voltage reguriments, got the following answer, quoting:


Recommended power supply 5v regulated +/-10%
Minimum supply 4.5v
Maximum ” 6v (recommended)
Although it will tolerate up to 10v for short periods
(the limit is heat dissipation in the LDOs and the 10v rated
dielectric of the decoupling caps)
Never exceed 10v
NEVER apply a reversed polarity supply.
Damage may result to the N3 or (through overcurrent) the power supply circuits

I did test that and was happy that the N3 took four 1.2 rechargeables, and 4 regular AA batteries. I can only assume, because there was no feedback from the dongle.
Onto noise profile with batteries last night, all is well, then a blackout, laptop and two screens gone. I managed to massage laptop back to life, but as it stands now, one of the USB bus seems completely gone, I'm down to two USB ports, happy that the motherboard seems intact.
I presume the N3 is smoked as well, won't risk anymore by trying with the remaining USB ports.
It is entirely possible that it was my fault, but I checked power leads this morning with a clear, un-panicked head and all was well.
I wished to do further testing, then looked at the N3 this morning with such hatred I'll simply send it back.
I don't know the reason why I had a blackout, why half of my laptop smoked away, an event that has not happened with 20+ other dongles and countless accessories over the last three years. And frankly, I don't care, because the equation is no N3 = no risk.
I wish Thumbnet good luck with the N3.
Update 1: Thumbnet is very supportive with this fault, I am awed by their customer service. I'll add more info as is comes in, right now, I truly don't know what could have caused a blackout.
Update 2: Went through setup with a fine-toothed comb, maybe wires inside power connector caused fault. Thumbnet is the definition of "concerned", on the ball. From what I've seen and think, the N3 will be great when Thumbnet adds self-protection to the N3, like overvoltage, polarity and short-circuit protection. Until then, I won't touch an N3.
The possibility of an RTL-SDR dongle wrecking a computer never came up before:

Damage may result to the N3 or (through overcurrent) the power supply circuit.
rtl-sdr.com v.3 has fuse, and I've never had issues with any other equipment. And I test lots of gear.
I have nothing against Thumbnet or the N3, in fact, I hope they will recall all shipped units and make a new one with proper protection, and at that joyful moment, we will have a great dongle, with "killer N3" strengths - build quality, F connector, great data performance and silky audio. The N3 now is a great dongle with major internal weaknesses.
New one should be a safer one. I'm looking forward to it.
Update 3: Sent N3 to Thumbnet's radio engineer as per manufacturer request. Getting tested.
Update 4: Read rtl-sdr.com's review for recommendations how to avoid such a situation. Thumbnet will add reverse polarity protection to future units.


1 comment:

  1. Will be interested to see what response you get from Thumbnet.

    ReplyDelete