BA5SBA Direct Sampling Kit English Build Instructions

The BA5SBA direct sampling kit is a kitset PCB that combines with a standard (included) RTL-SDR dongle in order to enable the direct sampling mod. The direct sampling mod is a hardware modification that can be applied to any RTL-SDR dongle in order to enable HF reception capabilities. The BA5SBA kit improves upon some of the problems with the direct sampling mod by adding additional features such as a low pass filter to block broadcast FM interference, a matching transformer to better match the RTL2832U’s input impedance, extra power supply filtering, SMA connectors for HF and VHF/UHF (UV), an aluminium case and a bias tee.

The BA5SBA direct sampling RTL-SDR can be bought as a kit that requires hand assembly for about $30 USD or as a fully assembled product for about $50 USD. It is usually listed on Amazon and eBay as a “100KHz-1.7GHz full band UV HF RTL-SDR USB Tuner Receiver/ R820T+8232 Ham Radio”

Recently, reader Simon (MW0SGD) bought one of these kits and discovered that the English instructions were very rare and hard to come by. We’ve decided to post these English instructions here for any future buyers who may search for them as this post should show up on Google. Simon also notes that “most of the instructions on the internet wind the inductors on a 5mm former. This says to use a 3mm one, which I did and it works ok.”

The English pdf instructions can be downloaded here.

The BA5SBA Direct Sampling RTL-SDR Kit
The BA5SBA Direct Sampling RTL-SDR Kit
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Is there any existing TCXO mod available for this kit, as I think the supplied dongle doesn’t have any.
Soldering was pretty straight forward – except for the wire that goes to the RTL pin, which was rather pure luck:-)
Workes great now though!


Hi Guys,

Don’t loose your valuable time with this bullshit Chineese SDR. I did the same mistake and finally I bought an SDR module from nooelec and they sell the best quality and best price SDR modules.



Should the center pin of the transformer be connected to the ground?
I checked and is not connected to anything.


what does c23 connect too


There is something wrong with the coil inductance! We see 300 nH written on the PCB but it seems this information is not correct. If we turn .42mm copper wire 11 times on 5 mm diameter, it makes 0.97 nH inductance.
Please use this calculator:
( Relative Permeability of the air is 1 )

Jason Stanley

damed if I didnt do something wrong or got a bad board. i didnt test the dongle before i started the mod like a dummy. KC3INH


qUESTION. can this be used with Apple ipad and lightning cable??


how do you solder those tiny wires to the chip from the torroid transformer? I’ve got all the rest done and don’t see a good way to do that. HELP! please.


I bought one of these in kit. For the price is better than a typical dongle, with a shielding case etc. I could do everything in a breeze except soldering pins 4 and 5. Being a RF engineer and having good quality working microscope, etc… this probed beyond (my) human capability, and is pretty humiliating.
Don’t buy the kit version unless you are prepared to pain.
Any soldering tips welcomed.


TS 100 soldering iron ~ 50 $
TS-I 0.2 mm tip ~ 10 $
A digital microscope ~ 50 $


Here is another English description about how to assemble such a kit:


Isn’t better to buy a 8$ dongle and a 40$ upconverter spending about the same price (assembled) ?


How come nobody ever tells people that a RF amplifier and a preselector is need for the HF part of the device ??????????????????????? Now I have seen the schematic of this device all it has in front of the matching transformer is a frequency cutoff filter that cutoff frequency’s higher than 30 MHZ . That means with the tuner being by pasted by the matching transformer the 8232 A to D chip is seeing 0HZ to 30MHZ all at once . Now comes the problem of how do you know what you are listening to is at the frequency the software is indicating . The 8232 A to D chip is not a turner so it has no selectivity it just locks on to the strongest signal and decodes it .


Your understanding is incorrect. The filter is used to avoid overload of A to D by out of band signals. As long as it is not overloaded, the software acts as the final filter and decoder, not the chip.


Well your not right in what your saying . I know as a fact that frequency’s are read wrong by the chip or the software well something is messing up .I can tune to 10 meters than hit the bypass switch my preselector and pickup the AM broadcast station and be reading some 10 meter frequency .


Sounds more like you are getting an image/aliasing of a strong/close broadcaster at a multiple in the 10m band rather than anything else. Turn your LNA setting down and or uncheck both AGC settings to make that image go away. In plain terms the rtlsdr does not have enough bandwidth to cover the entire 30MHz of HF all at once. The hardware won’t support it. Otherwise we’d all be using it that way.


To start with I would like to thank KD0CQ and Mike for expressing thoughts . I just have a dongle that I set up as direct sampling so if and in all probability what KD0CQ has described is happening , it could happen with the BA5SBA . I would think a good reason to use a preselector , it filters all that out .


Purchased one.
Question : how about ESD protection ? Is there a diode at the antenna input?