Officially called "Low Noise Amplifier LNA SDR RTL preamplifier HF VHF UHF Receiver" on the manufacturer's eBay page (link), costs $20 + shipping from Hungary (webshop link).
Called Janilab preamp in this review, it's a small electronic circuit which comes between an RTL-SDR dongle and antenna. As the name says, it's supposed to increase received signal strength.
On paper, specs look good:
- 1 MHz to 3 GHz operating range,
- adjustable gain from -20 dB to +19 dB,
- SMA female connectors,
- 5V power with easy Smartphone/Pi/Kindle connector standard,
- 7V to 12V DC power via holes on the board.
Summary: It's a great preamp due to ease of power connection, and because it covers the full tunable range of RTL-SDRs.
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 box and first impressions
Delivery via registered air mail (seller charged exact shipping cost), padded envelope, small green rectangle in antistatic bag.
No instructions, nor any other information available online apart from eBay description.
It's ridiculous: information how to use a product you paid money for should be included in the bag. This customer treatment is not exclusive to Janilab, and I don't fault them as a fringe player, but please: the dog's $4 hair brush comes with an instruction manual. I don't want a paper throwaway, I expect a detailed online how-to guide to ease bewilderment following unwrapping.
Warranty and customer service
14 days warranty. WTF? For 22 bucks, Nooelec gives two years. Anyway, I emailed the maker, and after a quick reply got reassured that every single board is tested before shipping.
Where goes what
PCB board writing is legible and connections should be self-explanatory, just in case:
Top left golden connector: that's an SMA female connector, connect antenna here.
Top right golden connector: that's an SMA female connector, connect receiver here.
Two silver holes: for mounting into an enclosure.
USB connector for power: provides 5V, blue LED comes on (D1 in the image)
Bottom right two holes: DC power, 7-12 V. Worked with 9V battery.
Gain: Screw above USB connector.
From - 20 dB to +19 dB according to product webpage. Turning the small screw clockwise increases gain, you'll need a small screwdriver or a knife tip.
270 degree rotation range translates to really small difference at the top of the scale: eye surgeons will have a distinct advantage dialing in +15 dB gain.
MCX: older Nooelec or generic chinese dongles, use MCX Male to SMA Male pigtails.
SMA: Male to Male pigtails or barrel adaptors, e.g. rtl-sdr.com dongle, Nooelec SMArt, SDRPlay, handheld receivers, Airspy etc.
PAL: Nooelec Nano-P or on really old dongles, use PAL Male - SMA Male pigtail.
Power optionsMicroUSB connector standard means that smartphone/Kindle/PS4/battery bank charger cables work.
7-12 V: two small holes, imbecile-proof markings, 12V means maximum input voltage, worked with 9V battery. GND means negative, if in doubt, check the battery, one terminal is always marked, or red wire or "+" goes to 12V marking, black or "-" goes to GND.
No reverse polarity protection, which is a glowing omission, but when you're using alternative power you probably won't need the following image:
Manufacturer revealed that the board uses a BGA614 IC, stare at datasheet here (link).
Works as advertised, less gain in software will be required.
Shortwave: borderline audible broadcast stations turn into louder and less borderline audible broadcast stations:
On ADS-B, full gain (screw all the way to right) added significantly more position reports, planes and range.
Two Nooelec SMArt receivers, stock cable and half-wave outdoor antennas on a magnetic mount in a first-floor window:
31,872 versus 21,411 total reports. Two stock antennas side-by-side. Enough said.
Versus LNA4ALL or LNA4HF
Not on price: to get the same frequency coverage, you'd need to order both, and it would cost twice as much.
Not on power options: bias-T mod can be ordered for the LNA4ALL, so preamp can be at the antenna, where it should be. However, Janilab's Micro USB cable connection is easier to use if the preamp is at the end of the antenna cable.
Not on performance: even from specs alone, the LNA4ALL has a lower noise figure (1 dB vs 2 dB). By ear, the LNA4ALL sounds cleaner.
What it won't and can't do
"I'm using the short black antenna which came with the dongle, and can't hear anything, maybe I should buy a preamp?"
Reception performance depends on the antenna. It doesn't have to be fancy or expensive, and there are lots of guides how to build antennas, so please realize: a preamp adds extra performance to an existing antenna system, but it's not a magic solution.
Janilab's preamp does the job.
From shortwave to ADS-B, better signal reception for $20+shipping.
Easy power via microUSB cables, adjustable gain, blue LED light when it's happy with power, handy SMA connectors.
I really liked it, and recommend it.