ThumbNet N3 Unboxing and Nongles.com: SDR Lego

A few days ago we received a production sample of the new ThumbNet N3 receiver. Our sample came with the works, which includes the green aluminum enclosure and shielding can soldered on over the PCB. This full set costs $33.50 USD + $4.50 USD international shipping, but there are cheaper options if you do not want the aluminum case or the RFI shield.

We’ve only had a brief time to play around with it so far, but it’s performance seems very similar to the prototype unit that they sent us earlier. We intend to give the N3 a longer review next week but our first impressions are favorable. In this post we’ll simply unbox the unit, show some photos and give it a quick turn on test.

The N3 comes in a protective cardboard box with the N3 and Thumbnet/Nongles logo on it. Inside sits the ThumbNet N3 unit itself, and there is a power plug terminal block adapter located on the bottom of the box. Excluding the F-type connector, the ThumbNet unit has dimensions of 6.2 cm x 4 cm x 2.1 cm, and weighs 58g. The green enclosure is strong and rugged.

Unlike the prototype they sent, this unit can run direct from USB power alone. We saw that it draws about 400 mA of power, and we had no trouble running it from our 1A capable USB ports. Of course one of the main advantages to the N3 is the ability to power it with a low noise external power supply, and we will be testing that in the next review.

TN_box
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TN_unboxed
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Nongles SDR Lego

ThumbNet have also announced their new sister site, Nongles.com. On this site they intend to soon begin selling something called “Nongles” which is a mashup of “NOt a dONGLE”. Nongles are an idea that can be best described as a type of “SDR Lego”, and we think will be very interesting to people interested in experimenting with different SDR set ups and for use in education. Nongles will be based on the RTL-SDR design, but they are going to be split the RTL-SDR up into several discrete PCB modules/blocks such as:

  • R820T2 Module
  • RTL2832U Module
  • Experimenter Module
  • External Clock Module
  • LNA
  • Bias Tee
  • Signal Amplifier
  • 50 – 75 Ohm Transformer
  • Filter blocks such as SAW/FM Bandstop/High Pass/Low Pass and other DIY kits

Obviously you’ll at least need the R820T2 and RTL2832U blocks to have a working system. Then the other blocks can then be added in as needed. The Nongles are not ready for sale yet so keep an eye on their website for news of their release.

8 comments

  1. AD5NL

    Over on Akos’s review of the prototype there was a discussion about how to power the unit.

    What was left out of those comments was any sense of the tolerance for V_in. How close to 5 volts is needed? Would 4.8 V from four rechargeable batteries work? What about 3 or 4 alkalines (4.5 or 6 volt approximate)? Or a 6 volt gel cel?

    It seems most switching power supplies nominally range from 4.5 to 5.5 volts. And most uab power packs are going to vary as well depending upon charge level (even the voltage regulator cant totally compensate for these swings).

    As part of your review can you please discuss which of these inexpensive options are valid? Even though Nongles has a low cost linear supply, it really shouldnt be necessary if the tolerances are reasonable.

    • Akos Czermann

      I’writing the N3 review and N3 manufacturer replied to a similar question:

      From Thumbnet:

      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

      During testing, worked with 4 rechargeables, 4 1.5V batteries, and 6V battery. Also with 4.75V and 5V mobkle chargers.
      Full review soon.

      • AD5NL

        Thank you Akos! After posting my comment I saw that you had put +4.5/+5.5 V as the range, but good to know that 6v is an acceptable solution (and that the absolute worst case value is much higher, about 10V).

        To be on the “safe” side I built myself a simple linear power supply using an LM7805, two electrolytic capacitors (100 uF each) and a 12V gel cell battery. I got a fairly consistent output around 4.9 V but also it generates a lot of heat. An altoid tin (with some washers and some aluminum foil HVAC tape to interface the regulator to the tin) was barely acceptable as a heatsink.

        BTW I also noted that it’s important to add a ferrite bead to the V+/GND lines (I used 16 gauge speaker wire as the power cables in/out of my power supply).

        I would *much* prefer to use a 6V gel cel or lantern battery, or 4 alkaline batteries. No regulator losses and wasted heat!

      • AD5NL

        Also, I didn’t notice a significant change in noise level when I had my battery plugged in, and not. Is that to be expected? Is there anything that must be done to disable USB power, or is the noise difference just not that significant?

        At the very least external power is a great solution to prevent overheating a single-board computer (Raspberry Pi), but the main reason I bought the N3 was its low-noise design.

        • Akos

          Hi,

          Posted my first and final impressions on the blog, half of my laptop smoked away during testing yesterday. Could be my fault, but I ain’t gonna go near an N3 ever again.
          The low-noise design meant 4% more ADS-B reports over 36 hours in my location.

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