New Products: $20 RTL-SDR with 1PPM TCXO, SMA F Connector and R820T2 now available in our store

We have just released a new and improved RTL-SDR unit in our store, which we are currently pricing at $19.95 USD, or $24.95 USD including 2x telescopic antennas. The unit comes with the following improvements:

  • 1 PPM temperature compensated oscillator (TCXO) – Accurate tuning and almost zero temperature drift (2 PPM initial offset, 1 PPM temperature drift)
  • SMA female antenna port – Most dongles use the less common MCX or PAL antenna ports. Ours use SMA which is much more common so more adapters and antennas are available for it. It is also more durable and has lower insertion losses.
  • R820T2 tuner – More sensitive/lower noise floor than the older R820T tuner. 100% compatible with software for the older R820T.
  • Improved component tolerances – Allows the RTL-SDR to work more optimally over all frequencies.
  • Experimental: 4.5V USB powered bias tee – Can be enabled by soldering two pads on the PCB together. This allows the RTL-SDR to power LNA’s (like the LNA4ALL and HABAMP) and active antennas through the coax cable.
  • Experimental: Break out pads for direct sampling – Allows easier soldering to pins 4 & 5 on the RTL2832U for enabling the direct sampling mod.

See our products page to purchase these items!

Shipping Information

For US customers we highly recommend that you buy from our Amazon store as if you spend over $35 you will receive free shipping from a local Amazon warehouse. This usually takes less than 1 week for delivery. Prime subscribers can also get free 2 day shipping if bought on Amazon. If you like you can also use our international cart to buy from our Chinese warehouse with free shipping.

International customers can get free shipping from our warehouse in China. We will always try to use the fastest tracked air mail shipping method available to us, which will be ePacket, EMS air mail or similar if possible. This should get the parcel at your door within 2 weeks, but please note that this time is heavily dependant on the customs and postal agencies within the destination country which we have no control over. Countries such as Italy, Canada, Brazil, Russia and middle eastern countries are known to have extremely slow customs agencies.  If you prefer you can also pay more for express shipping and we will use DHL, UPS, FEDEX or EMS Courier. Just use our cart to select the shipping method you prefer. We also kindly remind customers that with international shipping you are responsible for any customs duties or taxes incurred by the shipment.

Shipping status meanings: ‘In process’ means that your order information has been sent to the warehouse and the parcel is being packed. A tracking number will follow usually by the next business day.

Please note that tracking updates may take a few days to show up.

Warranty Information

We will provide 6 months warranty on manufacturing defects. Please note that if you try the direct sampling or bias tee mods then any warranty will be voided, so please ensure your dongle is working before trying these.

If you suspect a manufacturing fault please email us at [email protected] and include your order number and name. Please include details of the fault and a picture of the fault if it is physical damage. If the unit is faulty we will issue either a refund or send a new unit out depending on your preference.

Specification Discussion

Temperature Compensated Oscillator (TCXO)

The 28.8 MHz oscillator used in most RTL-SDRs is passive and not frequency accurate. This means that when you tune to a known frequency, it will likely be offset by a few kHz. Usually the PPM offset on a normal RTL-SDR is in the range of 30 – 150 PPM. Furthermore, as the dongle warms up, the frequency will drift up to ~20+ PPM until the temperature stabilizes.

The 1 PPM Temperature Compensated Oscillator (TCXO) in our units provides accurate tuning with an initial offset of 2 PPM and a 1 PPM temperature drift over time. This means that a known signal will appear where it should on the frequency spectrum and will not significantly drift in frequency as the dongle warms up. 

SMA F Antenna Port

On standard RTL-SDR’s the antenna port is either a MCX or PAL connector. MCX connectors are relatively uncommon and are susceptible to connector strain when using an adapter. PAL connectors are common with some TV connections, but no decent radio or antenna will use PAL due to its high insertion losses above ~100 MHz.

We’ve made these RTL-SDR dongles with SMA female antenna connectors. SMA is a very common connector in the radio field and provides a sturdy and secure connection. In addition SMA antenna adapters are much easier to find and insertion losses are lower.

We know some people prefer the F-type connector used in the previously sold ThumbNet dongles, but from our previous polling we believe the majority (~80%) of users prefer SMA. We may bring out F-type RTL-SDR’s again in the future if there is demand.

Note: Remember to not get confused between RP-SMA and SMA! RP-SMA or “reverse polarity SMA” is used for WiFi equipment only. In the normal radio world, most devices use standard SMA. RP-SMA is reversed, it has the male pin on the female connector, and the female hole on the male end. To be clear: This device is a radio device so it uses normal SMA connectors.

R820T2 Tuner

As discussed when we brought out our previous generation, the R820T2 tuner has slightly better sensitivity than the R820T and also works better at frequencies around 1.5 GHz. It also works better with the experimental HF drivers.

Improved Component Tolerances

We have these units manufactured with tighter tolerances on all passive components.

Telescopic Antennas

In our $24.95 USD package we provide two telescopic antennas. The smaller one goes from 6 cm to 20 cm, and the larger one goes from 20 cm to 1.5 m. The antenna base is also larger with a 4.5 cm diameter, when compared to the smaller bases shipped with most models. This provides more stable operation when using the larger antenna.

With antennas, usually the larger the antenna is the lower the frequency it can receive. These two antennas allow you to tune to almost the entire range of the RTL-SDR. Of course the antenna should be placed outdoors and up as high as possible to get the best performance. Placing the magnetic mount on a metal surface can also help complete the antenna as a quarter wave ground plane.

When fully collapsed the small antenna works decently at 1090 MHz for ADS-B frequencies.

Experimental 4.5V Bias Tee

A bias tee allows you to power external RF devices such as Low Noise Amplifiers (LNA’s) and active antennas through the coax cable. Since LNA’s should be placed right after the antenna, it can be sometimes hard to get power to them if a bias tee isn’t used.

We have included a simple (experimental) bias tee option in our latest units, inspired by mods made by other experimenters. The bias tee is disconnected by default, but it can be activated by soldering two pads together on the PCB. Connecting the pads connects the antenna output to the USB 5V rail. The resistance in the fuse and inductor can reduce the output voltage to about 4.5V.

Bias Tee Instructions
Bias Tee Instructions

The USB power rail is protected from over current and shorts through a PTC resettable fuse with a hold current of 80 mA and trip current of 200 mA. This means that the fuse will become a short circuit if greater than 200 mA tries to flow through it, which may happen during a short or with faulty equipment. Between 80 mA and 200 mA is an unknown state, where the fuse may or may not trip, depending on the temperature. In practice we’ve tested it with a hold current of 120 mA in a ~16 degree ambient environment (and much hotter inside the dongle casing) and had no issues with premature tripping.

We used a 4.7 uH 250 MHz SRF inductor as the bias tee choke. At the highest frequency tunable by the RTL-SDR (~1700 MHz) this should only give a (simulated) ~1-2 dB loss through the inductor. For better performance at frequencies above 1 GHz you could experiment with a smaller value inductor and possibly with removing the static protection diode, though in our tests we saw very little difference with the diode removed.

We have tested the bias tee with an LNA4ALL and HABAMP both in bias tee mode. Both worked fine running for a number of hours. The HABAMP really improved ADS-B reception a lot and we highly recommend it. We also tested the unit with two LNA’s connected together, both powered by the bias tee and this also worked fine. An LNA like the LNA4ALL draws about 60 mA of current, so running two at once is pushing the hold current of 80mA on the fuse, but we had no trouble with about 120 mA of current, though we need to note that people in hot climates may have different results as the trip current reduces with higher temperatures. We also tested an active GPS antenna (active antennas contain built in LNA’s) which also worked. 

With the bias tee and LNA’s we were able to improve weak signal reception and also receive several signals not usually receivable by the RTL-SDR alone such as L-band satellites like Inmarsat, GPS and Iridium with an appropriate antenna.

Experimental break out pads for direct sampling

The direct sampling mod is a hardware modification that allows you to tune to HF frequencies with an RTL-SDR. The best way to apply this mod is to directly solder your antenna or matching transformer to pins 4 & 5 of the RTL2832U chip. However, these pins are very small and so the mod requires extreme soldering ability.

These units have break out pads for these pins which make soldering to them much easier.

Direct Sampling Instructions
Direct Sampling Instructions

Let us know if you have any questions about these units, or feature requests for future units. We’ve tried to make the most popular changes that don’t increase the cost too much, but we are always open to ideas for future improvements.

52 comments

    • admin

      Is it a V2 dongle as per this post? V2 doesn’t have built in HF direct sampling, so you’ll need an upconverter. If its a V3 enable the Q-branch to get HF mode active.

      The “best settings” are signal dependent, e.g. bandwidth, mode, noise blanker on or off. Do you have any specific settings you want to tune?

  1. M. Hoskins

    Just found out there was a new design, and it’s a big improvement! The break out pads, bias tee, and best of all, a metal case. I’m am quite surprised it’s still the same low price. Thanks! I’m picking one more up as soon as I can.

    • Chris53825

      I’m planning to connect the bias tee for an active GPS antenna. Is it fine to leave the bias tee soldered permanently, even if using other non-active antennas? I’d prefer to leave the bias tee soldered unless it will cause any long term damage or unknown result.

  2. Chris

    Wow, the new aluminum case is SEXY, and it comes STANDARD with all dongles now, and no price increase?!? You guys are incredible! As soon as they are back in stock at Amazon, I’m ordering a bunch of them! THANKS!!!

  3. rfboy

    is the metallic enclosure still in the pipeline ?
    are there any design changes to block the usb noise, like an emi filter ?
    i like a flat metallic case that can act as a heatsink.

  4. Craig

    Long time engineer here. Can you elaborate about any ESD concern on the SMA with the latest shipping dongle vs the blue guys? Assume I have the bias pads open. Lets say that I connect this to a discone with a high, close to infinity, DC impedance center conductor and it starts raining or snowing. What is the DC impedance of the dongle input? I’ve seen precipitation static draw some pretty good sparks first hand.

    Within a day of testing, I am very impressed regarding frequency stability, sensitivity and unfiltered IM performance at $20! Good job.

    Thanks, Craig

    • admin

      Thanks for buying ours! ESD resistance should be the same on both dongles. Both dongles use a BAV99 as ESD protection, but ours have an extra DC blocking cap as per the R820T reference design. This design is also used in other dongles like the smaller white ones, and the Chinese HF RTL-SDR kits you see on eBay.

      Still, you must ground any outdoor antennas properly, the BAV99 can probably only protect against minor to moderate ESD. Plus any outdoor antenna should be grounded to prevent lightning damage etc.

  5. Al-91

    Hi,

    I have got one of your dongles and have been using it with 50 Ohm cable (assuming that all RF equipment uses 50 Ohm, poor assumption i know!)
    I have just realized that I’ve never seen anything saying what the input impedance is and can’t find any details… Could you confirm?

    • admin

      50 Ohm cable is fine. The mismatch loss between 50 and 75 Ohms is very small and completely negligible (~0.2 dB). The input impedance varies over frequency anyway so it’s never going to be exact.

  6. Justin

    Many people seem to want a metal case, but would a conductive paint work? Seems like it would be easier to shield with a some paint instead of a whole new metal case. Unfortunately it’s usually pretty expensive, so I’m not sure if it would make sense.

  7. UserJJ

    I can use these great, one at a time … but if I try to install 2 into the same system, I can never get the second one to work. The first one always shows up as Bulk Interface 0, but the second one shows up as a real long device name. Selecting it (in UniTrunker for example) it will never start. If I remove the first one, then the second one works, but then if I put the first one back in, only one of them works. I noticed in one program that the serial number shows up as 00000001. Is it possible that the serial number is the same for all these devices, so the PC cannot use multiple?

    • Me

      Yes, you are seeing a problem created by the default 00000001 serial number. Each device must have a unique serial number if plugged in with like devices. You want to look (Google, Yahoo, etc) for a program called rtl_eeprom, which allows you to change the serial number of each dongle to what you want it to be.

  8. Luciano ,dr.ing.

    I have just tested this dongle, with sdr sharp.At 30 MHZ test frequency ,the sensivity is very good,from -115 to -130 dBm for AM and CW.The stability and precision at this frequency are amazing, I am impressed.Some quick tests without intruments was done in 145 MHz band NFM, good.
    The plastic case is not so good, it need a metal case .I think that it will be a great idea to sell this dongle directly in a metal case,it worth the money.

  9. azswdxing

    I just bought one of these and I’m very pleased. As in a previous comment, I tested the offset and stability on a NOAA Weather Radio signal, in my case 162.525 MHz. Once warmed up, it needed -2.0ppm in software (gqrx) to correct the dongle (true frequency less than dongle frequency), and it drifted about 0.5ppm during warmup. Of course, there’s no guarantee that NWR is accurate to within 2ppm. I mostly do AM broadcast band and shortwave with an upconverter, and the dongle is working just fine in that configuration.

    Of note, I successfully modified the dongle and one of the well-known “blue” aluminum cases so it fits. Disclaimer: do this at your own risk, I had an extra case lying around and at $20 for the dongle, I was willing to eat the loss if I screwed up. Use fine grit sandpaper to trim the long edges of the PCB and to trim some of the extra PCB near the USB jack. If you trim it enough off the latter to fit the USB slot on the end cap of the case you would run into the solder blobs from the grounding pins of the jack. So, use a small file to put grooves in the case so the extra PCB width fits. You may also need to enlarge the hole a little along the short dimension to get things to line up just right. Using the end cap with the USB slot as a template, drill a 1/4″ hole in the other end for the SMA jack. One may want to fill in the MCX hole with a screw and nut, but it may not make a difference. While you are at it, use the file to remove the paint where the end caps contact the main body of the case, and where the two halves of the main body come together. The USB jack sticks out of the case a couple mm farther than other dongles, so that much more of the jack will be outside the USB port. One mm of that is due to not having a square hole for the lip of the SMA jack to sit so it doesn’t stick out so far.

  10. Chris

    I’m impressed.

    A few months ago, I nearly pulled the trigger on a NooElec TCXO dongle, but the $70 price tag was way too rich for my blood. At that point, may as well consider an AirSpy. A friend recommended this one to me, and 3 days later I had it in my hand thanks to Amazon Prime. Works exactly as described. Initial offset is around -2ppm, settles on -1.35ppm after it gets up to full operating temp. Could not be happier, and I intend on ordering a few more.

    I would also like to see an aluminum enclosure for these dongles. Thanks!

  11. raw aluminium

    yes, a metallic case is a must have! please bring one without painting and anodized colors… for good shielding.

  12. noisemeter

    can you post a picture for the mod ? can the usb noise be reduced with this mod ?

    >So I cut the two traces to the USB socket-pad, one to the bias tee, and one to the regulator, and put two 0603 >400nH inductors to isolate RF on the positive USB supply rail from reaching too much of the circuit board.

  13. Skip Flem

    It’s been ‘mentioned’ that a trimmed board may fit in an aluminum SDR case…
    any thoughts on replacing the FUSE with a poly-type fuse, considering that the
    first ‘shorting of the antenna to ground’ will blow it?

    • admin

      The fuse we used is already a poly type fuse aka PTC or resettable fuse. So if the bias tee is shorted the fuse will reset after the short is removed and the poly fuse is given a few seconds to cool down.

      The PCB is about 2mm longer and wider so it won’t fit into the old alu cases. Trimming might work, but you’ll also need to add a hole for the SMA connector. If we continue to receive good feedback on these units we’ll also try to bring out a matching aluminium case for them later this year or early next year.

    • admin

      They should perform almost identically in terms of RX and frequency drift/offset. The changes are in the connector SMA vs Type F, and the extra addition of the activatable bias tee.

  14. djnixon56

    Initial testing showing low warmup drift:

    startup 162.400.380
    20 min. 162.400.460
    1 hr. 162.400.460

    At 75-85 deg. F room temp with little to no air movement. Retesting after cooldown showed similar results, giving a warmup drift of about 0.5 ppm.

  15. Trevmar

    There has been no attempt to filter the USB power line coming into the dongle. It is multiply bypassed by four capacitors. Any RF currents on this cable will be coupled into the PCB. So I cut the two traces to the USB socket-pad, one to the bias tee, and one to the regulator, and put two 0603 400nH inductors to isolate RF on the positive USB supply rail from reaching too much of the circuit board. I didn’t measure before and after, this mod is a no-brainer (for me). I am very happy with the performance of the dongle, and the long/short whip combo.

  16. John

    One question I have regarding the diamond shape of the dongle will these dongles fit side by side in two vertical usb ports like the prior models?

  17. paul

    This looks like the perfect start for me to get into sdr. Just one question. I’m confused by the sma f connector. The female actually goes “in” the connecting cable and not around seems counter intuitive to me. I want to also buy a sma f to f type coax cable connector so i can experiment with DIY antennas and don’t know the exact term to look up. I’m probably being stupid about this basic stuff but to me it seems like this device has a sma male input based on how generally male and female connections are thought of by me. I apologize for wasting everyone’s time with this basic question. Nice hardware though.

    • admin

      Hi Paul, i’m not sure what you mean when you say the the female goes “in”? On almost all professional radio devices SMA F is used on the device end. Airspy, HackRF and SDRPlay use SMA F as well. Connecting cables need to use SMA M connectors.

      Maybe you’re getting confused between SMA and SMA-RP? SMA-RP is usually used only on WiFi devices and WiFi accessories. In the normal radio world SMA is used. Look up the difference between SMA and SMA-RP. SMA-RP is “reverse polarity”, basically it has a male pin on the female connector – very easy to cause confusion. To be clear this device is a radio device, so we use SMA.

      I believe they originally used the SMA-RP connector on WiFi devices in order to discourage people from attaching more powerful antennas to their routers, since SMA-RP connectors were rare.

    • jlc66

      I understand your point, but although the male has the outer shield connector that goes around the female, it also has a pin in the middle, and the female has a hole that the pin goes into. I think that’s the basis for the gender designations.

      What’s really confusing is that the convention for “reverse-polarity sma” is based on the shield connectors, giving us a “male” with both the wider shield connector that the “female” fits into, and a central hole that a pin on the “female” fits into. But, as the other reply says, reverse-polarity sma is used mostly for WiFi.

  18. soooooil

    Sorry for the stupid question but how do I choose to ship from China? Amazon just tells me that the seller does not ship to my address (I live in Ukraine)

  19. Masoud

    Very interesting improvements with an affordable price.
    In future it would be nice to have an SMA connector for external clock synchronization.

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