Saturday, 15 October 2016

More than half million

Thanks to readers, supporters, and everyone who believed that radio should be for everyone.

Sunday, 25 September 2016

RTL-SDR dongle generations

Sept 25, 2016

This is absolutely my arbitrary classification.

Post heavily features Nooelec and dongles for one simple reason: they support this blog and send me review samples.
Details in Manifesto, links open in new window, tap or click images for full-screen glory.
Subscribe to twitter feed @rtlsdr4everyone to receive updates (blue button on left).


The RTL2832U chipset by Realtek, responsible for converting analog signal received by antenna into a digital form, is the same in every RTL-SDR dongle - hence the "RTL" in the name. All dongles use this chipset, irrespective of cost, size, or accessories.
I distinguish generations primarily by tuner chipset, then secondarily by additional characteristics. Exotics not generally available are not discussed.

Generation One

R820T and E4000 chipsets.

Still with us in various shapes and forms, E4000 no longer available for cheap, R820T is here to stay, because 1) warehouses are probably full of them, and 2) quite a few folks prefer its waterfall cleanliness.
Check the number of spikes in image below:

Countless eBay sellers entice customers with this chipset, often at ridiculous prices (read Avoid Ripoffs Part OneTwoThree).
Nooelec still sells the Mini, my first receiver for $19, and a smaller version called Nano for $19, and the Mini+ Al for $30 is available, looks dear until you realize that the metal case alone costs $12, and dongle comes with TCXO.
R820T is also used by the Soft66RTL3 for $40, features a built-in upconverter and band preselector; read review here before ordering one (summary: don't).
E4000 tuners are a completely different cup of tea, chipset no longer manufactured, better performance on some frequencies and with extended signal reception range. $32 buys you a Nooelec XTR with E4000

Generation Two

R820T2 chipset offers better receive performance across the tunable range - it's the recommended chipset at the moment.
Blue $8 generic chinese dongles, and all current premium dongles feature this chip.
Nooelec sells R820T2 models as well, full-size in the Mini 2 for $19, small size in the Nano2 for $20.
The R820T2 was the last technological milestone, all later developments focus on additional features (some say unnecessary gimmicks) without improving the "brain" of the dongle.
Consequently, a bog-standard R820T2 generic will be very, very close in ultimate receive performance to a premium dongle costing twice as much - those features and warranty cost.

Generation Three

TCXO, Temperature-controlled oscillators make your life easier, entered frequency is spot on, dongles don't change frequency (called drift) with ambient temperature variations.
Do you need TCXO? I was happy without it, as warm-up takes a few minutes, then drift stays the same. For example, SDRPlay doesn't officially come with TCXO for $150. TCXO is good to have, but shouldn't be a deal-breaker.

In Nooelec nomenclature, all "Plus" models come with TCXO, such as the Nano 2+ for $23, Mini 2+ for $21. An E4000 with TCXO is also available, called XTR+ for a whopping $38.
All dongles are TCXO equipped.

Generation Three and a Half

R820T2 and TCXO with LNA on board, should be a separate category, because FlightAware's ProStick is the only one, intended for aircraft data collection on 1090 MHz, but underlying PCB is essentially a Generation Four dongle without metal case and thermal pads.
As explored earlier, despite sold as an ADS-B receiver, it is an excellent RTL-SDR dongle at a fair price of $17.

Generation Four

Parts from TV tuner heritage eliminated by removing LED and IR tuner, passively cooling the dongle with thermal pads and a metal case. offered the first dongle with this architecture, instantly establishing as a dongle manufacturer. Great telescopic antennas supplied for $25 cemented well-deserved reputation.

Generation Five

In 2016 summer Nooelec's SMArt comes on the scene in a ground-breaking USB friendly shape for $28.

Lowered noise, quality accessories, heatsinked plus thermal pad, R820T2 with TCXO, detailed review here.

Generation Six

Further efforts to reduce noise, and adding features. Basics (R820T2 TCXO) remain the same.
Only dongle in this category is the latest v.3 from for $25.

Addition of easy direct sampling to access HF frequencies and improvements to lower noise, plus a few other goodies such as software-selectable bias-T. Review soon.


The easiest way to spot older generation dongles is by antennas offered.
Two common options: small, black fixed-frequency one or silver telescopic.

Always go for the silver telescopic, small black is nearly useless for listening to radio. Works as an ADS-B antenna if cut back a bit and good to check that a dongle works, but pretty much that's it.
Nooelec SMArt and come with their own antennas, read relevant reviews for an overview.


MCX, PAL and SMA are common.

MCX is used on most dongles, small push-in type. PAL is generally found on older Gen 1 or Gen 2 dongles. SMA is the radio industry standard, all premium dongles and SDRs use it. F-type (not shown above) is the TV cable standard in the States and widespread worldwide as satellite TV connector, but not really used on RTL-SDR dongles.
Connector type only affects compatibility with other accessories, pigtails and adapters are widely available for 2-6 dollars for various connector standards.
Some people say that PAL is inferior for GHz frequencies, I've had no problems with it, even for 1090 MHz ADS-B use. It is widespread in Europe as the standard TV coax connector.

Remote controls

If a remote is supplied, the dongle uses TV tuner architecture, and features an onboard IR receiver.
Silver remote in the image is most common, the black one is a curiosity, comes with Nooelec's XTR plus E4000 TCXO dongle.
Remotes actually work for using dongles as TV tuner for DVB-T, which is not available in the USA, but widespread around the world.


Online marketplaces (eBay, Amazon, alibaba, AliExpress, banggood etc) generally offer 14 or 30 day warranty with sub $10 dongles, caveat is buyer pays return shipping, which can be more than the original purchase price.
6 month is standard with dongles.
Nooelec offers two-year warranty with the Plus models.

Manufacturing quality and dependability

No exact figures publicly available at the moment, but I'd wager that 99.9% of RTL-SDR dongles are made in China. This means nothing, as the majority of consumer goods, from $1 toys to smartphones are manufactured there, but quality control varies widely.
Chinese generic dongles used to fail, but recent ones seem to tick along nicely - even when assembly standard in not up to scratch.

I recommend Nooelec and dongles and equipment for one simple reason: they work. Yes, they cost 10-15 dollars extra, and if you're new to the hobby or money matters, $15 seems an unnecessary expense, but additional features and supplied accessories outweigh initial savings.
My experience - which seems to be shared  by quite a few individuals in the RTL-SDR community - is that Nooelec and dongles are also very, very reliable. Even when I rarely read about equipment failure on a forum, next post is usually an update that the relevant manufacturer sent out a brand new one free of charge.

The future?

Efforts to add more customer-enticing features are underway.
Thumbnet recently announced a new receiver based on the RTL-SDR platform; called N3, distinguishing feature is external power for lower noise. Shipping around October, will cost around the $25 mark.
Demand for affordable radio receivers is increasing, but the steady supply of $8-10 generic dongles with R820T2 chipsets make introducing a new dongle with more features, or altering the underlying architecture a risky endeavour. pulled off this feat with the new v.3, but pretty close to the limit of what's possible on a small printed circuit board.
Size is one of the limiting factors choking further development; cramming more components into a device the size of a cigarette lighter (new v.3) or reducing dimensions (Nooelec SMArt and Nano series) is possible, but eventually, dissipating heat becomes problematic - run the new v.3 with bias-T on for a few hours to feel what I mean.

More expensive SDR manufacturers (e.g. SDRPlay above) offer larger device sizes, partially to prevent heat-induced performance degradation with a larger printed circuit board. Reduced sensitivity due to excessive heat does not affect regular listeners or dependability at the moment with RTL-SDR dongles, and purists, or those seeking the last ounces of performance always have cooling options.
I foresee the following features to trickle down or become mainstream within the next two-three years:
- software-selectable LNA: the ProStick, for $17, has a constantly-on LNA at the moment.
- filters: a constant and recurring argument against RTL-SDR dongles is no selectivity. Just like frequency drift, this will be remedied soon. The Soft66RTL3 has filters on board, which work quite well (the rest doesn't).
- software-selectable bias-T: latest v.3 offers this feature.
- upconverter: direct sampling is great, but a proper upconverter is better.
- 12 or 16 bit: higher dynamic range would be nice.
I know it's on your lips, some of the features above are found in the SDRPlay, AirSpy or HackRF. Problem is, all cost in excess of 100 dollars, and each come with unique weaknesses: SDRPlay has no bias-T, AirSpy platform isn't integrated into one box, and the HackRF is more or less on the same performance level as a 10-dollar RTL-SDR dongle (which I won't hold against it, it's not designed or marketed as a radio receiver).
We'll see. Dongle development times are shortening - barely a few months passed between announcing Nooelec's SMArt and's v.3, and there's still potential left in the RTL platform.
What will we get for Christmas?

Monday, 19 September 2016

Direct Sampling vs RTL-SDR with Upconverter vs SDRPlay for HF

Let's hear the difference between a generic chinese RTL-SDR dongle modded in 5 minutes, an RTL-SDR dongle with upconverter, and an SDRPlay on frequencies below 30 MHz with 20 foot of wire.
Background information and testing notes in the Manifesto, underlined text are links, bring you to a new page in a new window. Click / tap images for full-screen glory.

In the video

Direct sampling modded generic chinese RTL-SDR dongle: $8 from eBay, push a wire through a hole (detailed picture guide here link), connected to an outdoor wire.
Premium RTL-SDR with Upconverter: Nooelec SMArt (review link) with Ham-It-Up v 1.3 Upconverter (review link) in a metal case, yours for ~80 dollars from Nooelec (manufacturer link).
SDRPlay: All-in-one DC to daylight software defined radio receiver. $150 or thereabouts (review link, manufacturer link).


The AirSpy platform consists of a receiver and an upconverter. Can't comment on performance as I don't have one. Reviews praise excellent performance (such as this one, link).
Chinese all-in-ones: most of them are rip-offs, direct conversion receivers in nice wrapping (post how to avoid them link). Some of them feature an upconverter for 40-50 dollars, not tested so can't comment - I won't spend 50 dollars on a product with 30 day warranty when I've seen what's inside a chinese dongle (see images here, link).

Software choices and testing methodology

SDRUno for SDRPlay, SDRSharp for RTL-SDR with upconverter and direct sampling, because:
1) beginner RTL-SDR users will likely start with SDRSharp, so a familiar software environment can be presented,
2) two separate programs let me to use SDRPlay's dedicated software on one screen, and SDRSharp for RTL-SDR based dongles on other screen,
3) SDRUno requires a restart when removing a dongle, and I'm not immortal.
Hunting for signals: Find a station with SDRPlay, adjust gain and LNA for best audible audio, record, find same with RTL-SDR based setup, adjust settings for best audible audio, record, find same with a direct converter, record. Or the other way round. Switching between receivers took less than a minute.
I'll be the first to admit that I'm nowhere near proficient with either SDRSharp or SDRUno; nobody is, save the guys who's written the software. I simply adjusted available settings to enjoy a particular broadcasting station, then recorded results.
Broadcasting stations only due to availability, plus moral issues with ham SSB or CW conversations.
Personal moaning: how much I hate SDRSharp, especially after this: constantly crashes. Wanted to record more, but given up after two days and the umpteenth computer restart. SDRUno was stable as a rock.

Testing setup

Two 20 foot / 6.5m multi-stranded 1mm diameter copper wires strung from a first-floor window.
SDRPlay and RTL-SDR with upconverter sharing the same antenna with the SMArt's supplied antenna cable and mount, antenna wire wrapped around base screw.
Wire for direct conversion dongle wrapped around RG6 coax center conductor on one end, other end of center conductor goes directly into direct sampling RTL-SDR dongle.
Above antenna configuration takes less time to sip a cup of tea: throw wire out from a window, wrap antenna wire around center conductor, connect other end to receiver. Done.
Yes, grounding, capacitors, antenna isolation, better antenna to receiver connection, metal shielding, devoting time to software intricacies, a dedicated antenna tuner, an LNA4HF, bandpass filters, soldering, living in the Australian Outback, a T2FD, inviting NASA radio engineers over to dinner and listening to suggestions, a better sunspot cycle, plus countless other variables will undoubtedly increase receive performance.

The video

First: Direct sampling modded generic chinese dongle (frequency in SDR#), then
Second: Nooelec SMArt with Ham-It-Up v1.3 versus (125+frequency in SDR#), then
Third: SDRPlay (frequency in SDRuno).
Same stations, displayed frequencies are off due to drift and no TCXO in generic dongle and SDRPlay.

If doesn't play here, copy-paste the following YouTube link:


Direct sampling works to an extent, such as a <insert crappy automobile name here> is better than walking. Inserting a wire into an RTL-SDR dongle can be done in a few minutes, and provide an opportunity to listen to stations below 30 MHz.
Using an upconverter, such as the Ham-It-Up v1.3 here, is better in most cases, but an upconverter costs around $50.
The SDRPlay is a great receiver, however, it costs $150 - you get what you pay for.

RTL-SDR Travel Kit with Pi 3

I'm just back from holidays, and as usual, been carrying a lot of equipment.
Here's what worked:

Latest v.3 dongle

The workhorse during the trip, not only due to testing, but because it receives everything out of the box, without an upconverter. I'm writing a detailed post at the moment, as a teaser, let me state here and now: look no further, order one.

Cable length is my only grief, not an issue as I carried a SMArt mount as well.

Nooelec SMArt

USB friendly shape and longer supplied cable made life and setup so much easier; a go-to solution when I didn't want HF or felt the need to enjoy local commercial FM.

Raspberry Pi 3 with powerbank

Used for ADS-B signals by creating a local WiFi hotspot with Nooelec's 5dBi antenna, sharing information to my tablet or smartphone. Completely portable with 20,000 mAh battery bank, see a plane on the beach and have detailed information with a few taps.

Nerdism galore: you'll survive without knowing which streak in the sky does what, but every moment is transformed into a planespotting event with a mobile ADS-B station.


1. Huge telescopic: came with v.3 from, extremely versatile.
2. Nooelec 5dBi ADS-B antenna: works extremely well as a general receiving antenna for local action, screws right onto either premium dongles. Secret favourite, looks like a WiFi antenna, can be used anywhere.
3. Medium telescopic: comes with Nooelec dongles. Used this for years, good if you don't chase faraway signals. Adjustable length is good for airband and to feel smart doing 75 divided by frequency for quarter-wave calculations.
4. Nagoya knock-off from eBay: extendable telescopic, works great, saves time rummaging around in bag for magnetic mounts for RTL-SDR dongle antennas.


Nooelec One Nine takes a few seconds to screw on, insert wire / antenna connector into terminal, done.

Space-saving, light and efficient kit

Two receivers and two magnetic mounts provide backup, antennas above cover all frequencies except weak signals on HF and the Gigahertz range.
For HF: recent v.3 in direct sampling mode, larger extendable telescopic with SMArt's magnetic mount and cable, balun One Nine via barrel adaptor.
Grab n' go: SMArt with smaller telescopic on magnetic mount, or with 5dBi. I used the 5dBi plus SMArt combo extensively, because finding a magnetic mount is just one more item on the to-do list, right after locating the aloe vera gel and putting out swimming gear to dry, whereas plugging in said combo takes 3 seconds. And looks cool.

ADS-B: Either receiver with Nooelec 5dBi antenna with RasPi 3 and power bank.

Pointless to carry

For me, or when size or weight is at a premium.
Upconverter: Heavy and cumbersome to assemble, especially when v.3 in direct sampling mode does the job on strong stations, and weak signal's incessant noise wasn't on the wish list for evening listening.
Dedicated T2FD shortwave antenna: used for testing weak signal reception, finding a syphatetic tree and erecting antenna in the dark is not an experience I'll likely repeat. Large v.3's extendable antenna on magnetic mount snaps onto balcony steel railing - done.
Additonal dongles: Had a Nano 2 Plus, Mini 2 Plus, and two generic chinese dongles along to test v.3 against competition. All performed well, and I love the Nano 2 Plus for its small size, but finding MCX to SMA pigtails or adapters was annoying after a while.
Homemade 9:1 Unun: Nooelec's One Nine is smaller, easier to connect, and nearly same performance.
Long Wire: takes up little space, but hanging it from the balcony was an extra worry. Huge telescopic on SMArt mount with v.3 in direct sampling mode was great; SDRPlay with UnUn and long wire was better, but too much hassle.


Two receivers: one v.3 dongle and one SMArt package provides the best two receivers out there, two magnetic mounts and five antennas. Both receivers have their unique strengths and weaknesses, so I carry both. $55 seems a lot, until you're faced with the evening meal tab in a tourist restaurant.
Raspberry Pi 3: backup to main laptop, and affordable enough at $60 with accessories to leave in the car without second thoughts. ModMyPi's kit contents really work in the real world, travel adapter and 6.5 ft / 2m microUSB cable was handy.
Battery bank: $20 from eBay, soaks up sunlight to power Pi 3 above if left in back window of rental car. Rarely needed evening recharge.
Balun One Nine and connectors: maybe $15 together, makes a small difference for HF reception. Probably unwarranted, but small enough not to think whether it will fit in the bag.
Total: $150, give or take depending on where you live and supplier, which is not too bad for a computer with WiFi, two software defined radio receivers and five antennas covering DC to daylight and most man-made communication forms.

Review: Nooelec 5dBi High Gain ADS-B Antenna

Review: Nooelec 5dBi High Gain ADS-B Antenna

These are the big brothers of the previously reviewed 3dBi antenna bundle; only larger with more gain, cost 2-3 dollars more on the manufacturer webpage. Antennas in the pack are also available separately for around 6 dollars.
5dBi gain means that claimed figures are in the territory of FlightAware's $45 large antenna. Separate post here comparing four antennas, results versus FlightAware antenna:

22 percent less position reports from an antenna costing nine times less and measuring four times less.
They are larger than 3dBi brothers, with corresponding performance improvement:

As a general receiving antenna

Works extremely well for daily use; large enough to receive local and medium-strength signals, small enough to be unobtrusive.
Worked flawlessly on handheld general communications receiver due to shared SMA connector standard, and on handheld transceiver. Furthermore, both look identical to larger WiFi antennas, so no questions from onlookers.


Quickly became one of my favourite antenna for daily use due to versatility, small size and decent performance. Fits into an airport screening plastic bag or into your pocket, and the whole kit costs around $16 for two antennas and two adapters for generic dongles with older MCX connectors.
Highly recommended.

Sunday, 18 September 2016 v.2 dongle versus bus

Torture testing goes this far,'s metal case survives.

A bus. 30,000 pounds, 15 metric tons, or thereabouts, but works.

New v.3 has the same case. No, I won't try this again, 'cause my heart was crying.

Saturday, 17 September 2016

Comparison: Four ADS-B Antennas

Comparison: Four ADS-B Antennas

Should you fork out $45 for a FlightAware antenna?
Quarter wave (2.7 inches / 6.88 cm) or Half-Wave (5.41 inches / 13.76 cm)?
How does Nooelec's 5dBi antenna perform?
To find out, I used four Raspberries with PiAware and four SMARTs (review link, manufacturer link).

Antennas tested

1. Nooelec 5dBi ADS-B antenna, $6,
2. Large FlightAware antenna, $45,
3. Telescopic supplied with SMAart, extended to half-wave on metal plane cost: $0,
4. Telescopic supplied with dongle, extended to quarter-wave on metal plane, cost: $0.


Outdoors on a first-floor windowsill, top of antennas at the same level, height above ground 4 meters, overlooking local international airport and Europe - USA flight corridor.
Same vertical plane, but not in the same horizontal location; polar plots might reflect slight positioning differences, but for all intents and purposes except serious hair-splitting, differences are negligible.


Maximum range at 250 degree indicated on plots from Planefinder, all data from FlightAware.

Large FlightAware antenna was best performer, unsurprising considering its humongous size and $45 price tag. To get the most position reports, it is the antenna to buy.
Half-wave came in second, 22 percent difference in total reports received versus FlightAware antenna.
Nooelec's 5dBi high gain antenna is a solid performer for $6, 44 percent less position reports than FlightAware's significantly larger antenna.
4. Quarter wave antenna had worse performance than any other competitor. Cutting black solid antenna supplied with Chinese dongles back to an interim solution, but it's a solution nonetheless.

Draw your own conclusions, data is above.