Generic vs Premium dongles


July 6, 2016

Chinese versus branded, cheap versus Nooelec SMArt or rtl-sdr.com blog dongles, call it what you may, $10 dollars gets you a dongle from eBay, or $30 lands an envelope from established suppliers.
Aim is to help beginners to select their first RTL-SDR receiver, because cheaper dongles are not necessarily a good first choice, and to explore what you get with premium dongles for a higher price.

What's an RTL-SDR dongle?



Originally conceived as a TV-tuner, with appropriate free software receives radio signals from 24 MHz, all the way up to 1700 MHz. Plus digital TV (DVB-T) where available, which excludes the USA.
This frequency range covers most of human radio communication, such as commercial FM radio, airplanes, private firms and government workers etc. talking to each other - even images directly from weather satellites, or tracking airplanes can be achieved with suitable antennas and software.

Pro and Contra


For $20 extra, premium dongles are better in every aspect sans price. That money can be spent towards antennas, an upconverter, or food for a month (link).
For a tighter wallet, workarounds are detailed wherever possible.

R820T2 only


Remember the movie Terminator 2?



R820T2 tuner is universally recommended (5-dongle comparison link), so please only R820T2 in the name, older version without T2 after the number is worse performance.
Avoid rip-offs: separate post (link) on bad seller practices.


The unbranded option


For less than $10, sample images from eBay:

There are other alternatives, but the one above is quite common and always available. I bought many generic RTL-SDR dongles with exactly the same details for less than $10, such as the one featured in this post, with free shipping from Hongkong.
If that's not low enough, how does $3.61 incl. shipping sound? (link).


Premium options



Dongles from rtl-sdr.com ($25, link) or the Nooelec SMArt ($28, link). Note: package prices with antennas, rtl-sdr.com blog dongle can be bought for $18 for receiver only.

Both feature R820T2 with TCXO, cooling with metal case, multiple antennas, ease of direct sampling, support and warranty. Plus many unique features, but whether rtl-sdr.com's bias-T and larger telescopic antenna, or the SMArt's long and narrow case and three antennas appeal is up to you, hence not discussed here.
They are alike in many ways, therefore names used interchangeably here, read rtl-sdr.com dongle for Nooelec SMArt and vice versa.
Obviously, they are not the same, but both offer an almost identical feature set and similar packages, so equally competitors to cheap generic dongles.


Shipping



Depends on where you live.
To Ireland and Europe , delivery of a generic dongle from China takes from 10 to 25 calendar days. Shenzen is always faster than Hongkong.
Premium dongles are always here within a week.
USA is probably a different story, as I live in Europe I can't comment.


Support and warranty



Nooelec and rtl-sdr.com are radio-oriented suppliers, so more likely know a solution to a specific problem.
Most eBay sellers offer a 30-day money-back warranty, rtl-sdr.com gives you 6 months, Nooelec gives you 2 years.
I deal with both premium manufacturers for a long time and always received excellent customer service - the same can be said about the majority of Chinese Ebay sellers I ever came across.
Longer warranty with premium gear is an advantage.


Reliability



A large portion of consumer goods are made in China, so the "chinese" adjective in this post refers to the fact that cheap dongles most likely ship from Hong Kong or Shenzen.
Also, all rtl-sdr.com and some Nooelec dongles are made in China. The NESDR SMArt is made in Canada and the USA, this might matter to you.
With that out of the way, I've had three unbranded dongles fail, all after a relatively short period of light use. After the first failure, I bought a Nooelec, looked the same with identical specs on paper as a generic, but despite very heavy abuse, works to this day.
No R820T/T2 - based Nooelec, nor rtl-sdr.com dongles ever had a malfunction.
One rtl-sdr.com dongle is kept in "as-new" factory condition as a comparison baseline, but the other still undergoes rigurous torturing: for example, when bias-T is enabled, it should NOT be connected to a DC short antenna, but if you do, it's protected from overvoltage. Obviously, I had to try it.
Only sign of wear and tear on my workhorse rtl-sdr.com dongle is missing text, which rubbed off, and the slightly flattened metal case, both expected when fondled too much and after repeatedly driving a family car over it to prove metal case toughness.


SMA connectors



It's like a smaller version of common TV cable (USA) or satellite cable (most of the world) connector.
Unbranded dongles use a tiny push-type connector, called MCX. Works, but I have to look real hard where the bloody thing goes every time, plus use adapters or a pigtail with other equipment.

SMA is a widely used radio standard on antennas, upconverters, filters, preamplifiers, and on upgrade path higher class software defined radios like the SDRPlay or HackRF.




TCXO



It's like automatic transmission in a car: makes life easier.
Also known as temperature-controlled oscillator, and advertised such as "0.5 ppm TCXO", means enter a frequency and dongle will tune exactly to that frequency, then stay there no matter what.
Non-TCXO generics need a few minutes to warm up, during that time they "drift" or wander about the tuned frequency. Once at operating temperature, this drift is a fairly constant value, specific with every dongle, and can be compensated in software.
Tune to a known frequency, wait a while, then adjust ppm value until the red line intersects the peak. Value will be the same no matter which front-end software you use: in SDRSharp, Cogwheel - top left on screen, then bottom left in pop-up window. In SDRConsole, directly on the startup screen. In SDRUno, bottom left of pop up window when you do initial setting (step-by-step guide on using SDRUno with RTL-SDR dongles link).
I simply write the ppm value on a generic dongle and wait before using, but having TCXO is soooo much better in daily use.


Manufacturing quality



From above, the $8 chinese dongle looks almost identical to a $23 Nooelec Mini 2+, (that's the predecessor to a Nooelec SMArt, used for demonstration only), telltale signs are TCXO (marked with arrow) and Nooelec sign.

A different story close-up:

No, that's not what I'd call normal.
Other generic dongle:




Both work without any problems so far, but knowing attention to detail behind the cover is not reassuring.


Cooling



All dongles get hot in use, like a smartphone or tablet. This decreases performance, so premium dongles have thermal pads to improve heat transfer to the metal case, which acts as a heatsink.

Similar solution is possible with cheap dongles, lots of thermal pads (link, $3) and separate heatsinks (link, $3) can be bought for the price difference.
You still need a metal case to minimise interference.


Case



A metal case's primary function is to keep unwanted electrical signals out, which decrease performance. Examples are laptop and screen radiation, cheap compact flourescent bulbs, phone chargers and a surprising number of household items running on electricity.
A plastic case lets these nasties, called RF interference, go straight throught.
The shielding benefit of a metal case can be replicated with alu foul: wrap it around the RTL stick, make sure alu foil touches the USB connector metal. Cut vents for hot air exchange, these are a must - performance degradation due to overheating otherwise will counteract the benefit of shielding.
Secondarily, a metal case protects internal electrical circuitry from drops or baggage handlers.
Adding a metal case is possible with generic dongles and will cost $15 (link), but then the price advantage is instantly eroded.
Supplied metal cases surrounding premium dongles will take knocks and bumps easily. Plus, and this is entirely a subjective opinion, rtl-sdr.com's dongle has such a silky, lovely and joyful texture I'm looking forward to handling it every time. Nooelec cases exude a military-grade look and better for heatsinks due to flat exterior surface.


Build a premium dongle



Count together:
Generic R820T2: $8
Metal case: $15 - alufoil and $5 ebay cases are alternatives, former provides no physical protection and latter needs tools and time to fit. Sweet tin cans also work, but so not the same as a screw-together perfectly-fitting factory case.
Heat transfer pads: $3
Heatsinks: $3




Total: $29. Same price as a premium, still no TCXO nor SMA connector nor direct sampling.
It's doable, and a possible alternative if you already have a dongle.


Antennas



Would you buy a car with three wheels?
It's the case with generic dongles, as supplied small antenna is very limited in performance. It can borderline receive broadcast FM radio, very restricted in capabilities for higher frequencies and surprisingly competent for airplane position signals, but at the end of the day, most only use it to test whether the dongle works.
A generic dongle won't bring a smile, you can't give it to a radio layman and expect a happy recipient: the present won't be usable out of the box.
If you want to listen to HF signals (numbers below 30 MHz), a $50 upconverter will be required, but when you buy one, a suitable antenna will be on hand - like the large telescopics supplied with premium dongles.
However, antennas are just pieces of metal, so uncrew the short antenna from the magnetic mount with generic dongles, wrap some wire around the screw, then tape the other end to something, ideally to a window. Length of wire determines what frequencies come in best, but the whole contraption will be fragile, your partner might vocally disapprove, and eventually you'll regret not spending more for convenience and marital happiness.


Receive Performance



R820T2 chips are, in fact, exactly the same from the same manufacturer in generic and premium dongles. But nobody drives just an engine, so you have to look at how parts influence the overall package.
A premium dongle will pull in just a little bit more signal due to efficient cooling, stay on a shortwave frequency for CW decoding due to TCXO, and give you a clearer voice overall due to metal case shielding.
Front-end software matters, and beginners likely start with SDRSharp, which is easy to use and lets you accomplish many wonderful things. Once familiar, try SDRUno (link) - the improvement in signal quality will be larger than the difference between generic and premium dongles.
If you care about performance, buy a premium dongle. The mental reassurance that you got a better receiver is worth the extra alone.


Upgrade path



Pre-amplifiers, gear for shortwave reception, filters for better airplane tracking are available separately for a reasonable price, so you can build a good system step-by-step to suit your preferences.
Want an universal antenna? Buy a discone.
Eager for more local action? Order an LNA4ALL (link).
Fancy signals from the other side of the world? An upconverter is the answer (link).
Fancy really weak signals from the other side of the world? A preamp for HF can be in you mailbox in a week (link).
Want to track airplanes (link), ships (link), weather satellites (link), meteorological balloons (link), or understand hams on shortwave without learning Morse code (link)?
There're free software packages for every scenario, countless websites with spoon-feeding guides.
If money is no object, spend $200 and buy a premium dongle package and an SDRPlay. Antennas will be compatible, and you'll end up with top gear but, frankly, I doubt you're reading this 'cause $200 is pocket change. Even if it is, and you're new to radio, I'd learn to walk first with RTL-SDRs.


But I only got $10



An $8 R820T2 is all you need. My first, and many subsequent dongles were cheap chinese generic dongles. I use them, and love'em, but day-to-day compromises with cheap dongles should be evident by now. These were a necessity a few years ago, but not in 2016 for $20 extra.
If funds are short, a piece of wire wrapped around the golden screw on the antenna base, taped to a window makes lots of signals come in. And it's easy to set up frequency drift. And wrapping in alu foil is makeshift electrical noise shielding. And cooling can be added later. With a little work, you'll have a great radio receiver which didn't break the bank.
Spend $30 for either a Noooelec or rtl-sdr.com premium dongle, get a complete and usable package, screw things together, than the world of radio is yours with less hassle.
Premium branded dongles, either the Nooelec SMArt or the rtl-sdr.com blog dongle offer the best usability and value for money for radio signal reception.

1 comment:

  1. Thanks best advise so far, was looking for a tear down but this will do nesdr smart was the right choice :)

    Here are 2 other good pages to read up on sdr

    http://superkuh.com/rtlsdr.html

    https://www.reddit.com/r/RTLSDR/comments/1uazsw/rtl2832_datasheet_deep_info/cegj1qo/


    Sure you already found these prior to writing this, but for others who have not, have a read up

    ReplyDelete