Since I got into rtl-sdr, there really hasn’t ever been enough tuners for me to play around on a given day. Now that I have a substantial tuner collection (three E4000′s, three R820T’s just for experimentation), I always feel the need to explore a bit more.
Traditionally, I’ve always ordered the MMCX (i.e. small, round, golden) connector based dongles, on the belief that such new small connectors are more reliable and better for high frequencies. Interestingly, I’ve had a few break from the angular force exerted by some adapters, or come loose (and repairable with sufficient force).
The other alternative is the IEC PAL or Belling-lee connector (it goes by many names). Basically this is the traditional antenna connector here in Australia – moderately sized, round with a thick pin in the center. I used to dislike it for its oxidation and poor fit (often I would squeeze and make the outside off-circular to ensure it would make good contact), but I decided to give it a go and order some tuners with them.
Full-Size FC0013 Tuner
Already, you might be sighing at my idea of even trying an FC0013 tuner. I actually started my rtl-sdr journey with the FC0012, which was an absolutely awful (in terms of tuning range and sensitivity) tuner, so I should know better right?
Well, I kinda thought that, in such a competitive market where these parts are essentially “interchangeable”, that their performance would get much better. Each component will have its own advantages and disadvantages – I suppose the only paper advantage of the FC0013 is that it can tune down to 22Mhz which is a few Mhz below what the R820T can do.
Here’s the tuner itself – note that it’s very audacious as it advertises SDR on its logo printing. Also interesting is the use of the DVB logo, but the misspelling of broadcasting as iroadcasting, in a possibly deliberate attempt to evade any trademark claims? There’s an array of vents at the top, which are also a way to let the remote’s infrared signal in to the decoder.
On its bottom side, it’s quite confusing. Why is there a microUSB-B sized cut-out in the shell? Was this shell intended for use with something else, say a “smart-TV” dongle that required power? Or maybe they planned a connection for an external IR receiver? Regardless, it makes the product feel a bit poorly made – it’s a hole which sees right into the crystal’s can.
The underside of the dongle itself is vented too. I’m not sure it’s necessary, and might impact on the dongle’s frequency stability. The plastic is molded with the CE mark, although it’s not the “real” CE mark. It’s also molded with the FCC logo, which I find it hard to believe they would go to the effort to actually get it tested. Finally, it has the “no garbage bin disposal” logo, required for EU.
The PCB inside is the “yellow” colour which isn’t visually optimal (I don’t like it as much as green, blue or red, but that’s just a personal preference). The crystal reference is in a can, rather than surface mounted, although mine seemed to have a +7ppm offset, which is quite good. During warm-up, it did “jump” in steps, so maybe the tuner itself has some sort of clock drift correction – I’m not too sure. The IR receiver sits proud of the board significantly. As a difference to most other late-make tuners, this one features an electrolytic capacitor over the power lines, so it might be more stable under demanding situations (say, Raspberry Pi or at the end of very long USB extensions). The dongle has an EEPROM too, but no LED (despite the provision to fit it, along with a resistor).
The FC0013 tuner IC has had all its markings ground away by the factory. I’m not sure why. It looks like it was ground by the texture of the plastic, and the fact they left the Pin 1 indicator in place. The chip itself is correctly identified as an FC0013 by rtl-sdr software.
The RF connector is nicely soldered on the top side.
But it’s not secured at all on the bottom side. My first EzTV 646 (I think it was) was soldered on both sides, giving me more confidence that it won’t be accidentally lifting traces. The underside shows some flux residue from soldering the through-hole components – likely done by hand.
Mid-Size R820T Tuner
I’ll call this one the mid-size R820T tuner since it’s between the mini (which sacrifices a proper USB connector for traces on a PCB leading to contact problems if accidentally knocked) and the full size MMCX ones I’ve been used to using.
It’s actually a pretty good size, but my main gripe with the PAL connector is its tendencies to take up adjacent-port room. Full size sticks are just as guilty for being “extra thick”, although without the casing, they can be persuaded to share adjacent ports. There is no cap for the USB port in this model, and the hole is occupied by the IR receiver, rather than an LED.
The underside follows the same styling, but with the holes actually completely drilled through for venting.
The PCB itself is fairly small, and the chips are clearly identified as the R820T and the RTL2832. THe IR sensor is positioned just so to align with the hole in the casing – but as expected, no electrolytic capacitor in this model. The crystal is also surface mount to save space – and my experience is that they tend to be more stable and accurate! I haven’t yet completely tested the offset yes, but at first trial it seems pretty good (+7ppm or thereabouts). Unusually, this is the first dongle where I haven’t spotted an EEPROM, so it operates off the defaults stored in the RTL2832 chip. As a result, you probably won’t be able to program the serial number string or options using rtl_eeprom. RF connector is attached on the top …
… as well as the bottom! Good work! There’s not much on the underside, but the PCB is marked SBA01 and dated 14th March 2013.
Overall, my experience with the PAL connector based tuners have seen that the connector is big, chunky and durable. Internally they have springy fingers to ensure the outer shell is properly connected, and it’s probably more durable and less easy to disconnect from the tuner. I’m not sure I like the larger size of the connectors, but as usual, the solution is always more adapters!
As for the tuners themselves, the R820T again proves to be “the sensible choice” today. The other FC0013 isn’t really worthy of consideration as it doesn’t seem to have much positive benefits over the R820T – I observed higher noise floors in “overloaded” bands like the FM broadcast bands, and lower sensitivity in VHF and UHF. It’s only just barely capable of ADS-B, with very very weak results (3 packets/second vs 30 packets/second on stock antenna – FC0013 vs R820T). I also observed some “mirror aliases” from strong signals near the edges of the passbands, which seemed worse on the FC0013. The gain range is also limited (and the gains themselves are lower) than the R820T. Another undesirable property is the existence of a wavering “spur” at -38dB at about +/- 1Mhz with some others as well but at weaker levels. The peak and hump in the middle is in common with the E4000, implying this is a DC zero-IF type front-end.
That being said, the choice between the R820T and E4000 is much more difficult to make and will highly depend on your application.