Several PDF Files Related to RTL-SDR’s and HF/MW Reception

Recently RTL-SDR.com reader Dr. Phil wrote in to let us know about some PDF notes that he has created about the RTL-SDR dongle. There is some good information in his documents and the notes mainly focus on using the RTL-SDR with the direct sampling mod to receive HF.

His other documents also explain concepts such as imaging, interference and gain, how to reduce interference, input impedance of the Q sampling pads, intermediate frequency, and sample rate. In addition he has also uploaded some documents where he has calculated for various AM, FM and SW stations at what frequencies images will show up. His final document also discusses the Mirics SDR chipsets which are used in the SDRPlay.

He writes that any corrections are welcome. Dr. Phil’s main website can be found at http://home.comcast.net/~phils_radio_designs/.

Pocket HF SDR: http://home.comcast.net/%7Ephils_radio_designs/Pocket_SDR.pdf

Pocket HF SDR Cookbook: http://home.comcast.net/%7Ephils_radio_designs/SDR_Cookbook.pdf

RTL2832U: http://home.comcast.net/%7Ephils_radio_designs/RTL2832U.pdf

HF Direct Sampling: http://home.comcast.net/%7Ephils_radio_designs/Direct_Sample.pdf

AM Images: http://home.comcast.net/%7Ephils_radio_designs/AM_Images.pdf

FM Images: http://home.comcast.net/%7Ephils_radio_designs/FM_Images.pdf

SW Images: http://home.comcast.net/%7Ephils_radio_designs/SW_Images.pdf

Generic RTL: http://home.comcast.net/%7Ephils_radio_designs/GenericRTL.pdf

Mirics Chipset: http://home.comcast.net/%7Ephils_radio_designs/Mirics.pdf

A photo of the direct sampling mod with a wire antenna.
A photo of the direct sampling mod with a wire antenna.

 

5 comments

  1. My2Cents

    I own several SDRs, including the R820T, R820T2 as well as the E4000 mentioned in the comparison. For those SDRs I use the HamItUp Converter in a shielded case. The improvement in sensitivity and selectivity the sdrplay offers over those mentioned is obviously noticeable in HF. In addition, the slew of filters included in the sdrplay are amazing sharp. I will say that the configuration for sdrplay can be tricky, but once you understand how it works, the results are impressive. On another note, I am of the opinion that the frequency gap is actually non-existent in the sdrplay if you play with the LO frequency. Mine is certainly capable at those frequencies.

  2. My2Cents

    I own several SDRs, including the R820T, R820T2 as well as the E4000 mentioned in the comparison. For those SDRs, I use the HamItUp Converter in a shielded case. The improvement in sensitivity and selectivity the sdrplay offers over those sdrs is obviously noticeable in HF. I would be embarrassed to even make a comparison and not put sdrplay on top. In addition, the slew of filters included in the sdrplay are amazing sharp. I will say that the configuration for sdrplay can be tricky, but once you understand how it works, the results are impressive. On another note, I am of the opinion that the frequency gap is actually non-existent in sdrplay if you play with the LO frequency. Mine is certainly capable at those frequencies.

  3. Mirics

    Unfortunately, Dr Phil has made a number of significant material errors in his comments on the Mirics chipset. As a consequence of these errors his conclusions are rather flawed.

    To be fair, it is easy to misunderstand the MSi3101 chipset as it operates in a completely different way from the chipsets used in the RTL-SDR platform.

    Firstly, the total gain is not 59 dB as stated by Dr Phil. It is in fact in excess of over 100 dB. 59 dB is actually the IF gain control range. In other words, the IF gain can be turned down by 59 dB from its maximum value, which is in fact 77 dB. Similarly, the LNA gain is not 20 dB. We have no idea where he got this number from. The front end gain depends upon the band that is used, but is typically a maximum of around 28 dB.
    The total amount of gain control available in the chip-set is around 102 dB, so at minimum gain, you can certainly expect the NF to rise somewhat.
    The comments in NF at HF are perhaps a somewhat misleading. The overall NF will be a function of the complete receiver design, but the native NF for the chipset in the range of 100 KHz – 60 MHz is either 8 or 10 dB depending which of the two HF ports are used. What is also misleading is that when comparing the advertised NF of the R820T below 30 MHz, NF becomes less and less important at atmospheric noise becomes more and more prevalent. A receiver with a claimed NF of 3.5 dB will give no better sensitivity than one of 10 or even 12 dB at 1 MHz due to atmospheric noise. The match to the antenna is in fact much more critical and the design of the receiver to ensure isolation of noise from switching power supplies is particularly critical.
    Of course, comparing the NF of the MSi001 and the R820T is meaningless at HF as the R820T only works down to 24 MHz.
    The clock for the MSi2500 not 12 MHz as claimed by Dr Phil. It is 24MHz. The MSi2500 does use a SPI port (data clock, enable), but this is only used for control of the MSi001 (by the MSi2500). all control commands for the MSi2500 come via the USB port.

    We certainly appreciate the efforts made by Dr Phil to understand the Mirics chipset, but we strongly advise people that have questions about the chipset to contact Mirics directly at [email protected]

    Finally, we would politely request that Dr Phil kindly not use the Mirics logo in his documents as this is a breach of our trademark.

    Sincerely

    Mirics

  4. NN4F

    looked at the Mirics doc, not sure whet he compared, but my SDRPlay way outperforms my RTL R820T/T2 and the hamit upconverter …

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