RX-888 sensitivity, comparison to amateur gear?  - Page 1
Forum section: electronics / rf-microwave

author: cdev
author_rank: Super Contributor
timestamp: March 19, 2021, 01:42:25 am
content: How good quality is this receiver?

author: bob91343
author_rank: Super Contributor
timestamp: March 19, 2021, 01:49:47 am
content: https://www.rtl-sdr.com/nils-reviews-the-rx-888-a-sub-200-16-bit-32-mhz-bandwidth-sdr/https://www.hfunderground.com/board/index.php?topic=72973.0

author: cdev
author_rank: Super Contributor
timestamp: March 19, 2021, 04:47:34 pm
content: Does anybody know what device is used at the front end as an LNA, or has anybody done a serious review of the VHF and UHF performance versus the RTL-SDR (whose tuner it shares?) I've found the RTL-SDR is fairly insensitive in UHF above 1400 MHz or so.For example, how is it as an L-band satellite receiver? This is important for me as I'm interested in an all around communications receive capability.

author: cdev
author_rank: Super Contributor
timestamp: March 19, 2021, 05:05:59 pm
content: Quote from: bob91343 on March 19, 2021, 01:49:47 amThere is a bitmore info on the front end setup here, it seems. : Thank you all. It looks pretty interesting.http://www.steila.com/blog/index.php?controller=post&action=view&id_post=32

author: radiolistener
author_rank: Super Contributor
timestamp: March 20, 2021, 01:19:10 am
content: Here is a scheme:https://github.com/ik1xpv/BBRF103/blob/master/HARDWARE/BBRF103_scheme.pdfQuote from: cdev on March 19, 2021, 05:05:59 pmI don't think it's pretty interesting, because it uses R820T on the input, which dynamic range is limited with about 10-12 bit ADC class.Also it looks like it uses TCXO, which has a high phase noise, so you can't get advantage from expensive 16 bit ADC. And even worse, the PCB design of RX888 is intended for SMD TCXO package and is not compatible with DIP package oscillator, so you can't replace it with ultra low noise VCXO.Also it don't have FPGA for DDC processing.

author: cdev
author_rank: Super Contributor
timestamp: March 20, 2021, 01:36:24 am
content: Have you ever played around with one?I am wondering if it plays well with Linux and what receiver programs do people use that I can use, say under wine?Quote from: radiolistener on March 20, 2021, 01:19:10 amWhy does it do that?QuoteIt would be nice if they added external timebase (10 MHz) ability.

author: radiolistener
author_rank: Super Contributor
timestamp: March 20, 2021, 01:45:16 am
content: Quote from: cdev on March 20, 2021, 01:36:24 amNo, I was going to buy, but when I saw the details of the implementation I rejected it. Too many child problems.

author: cdev
author_rank: Super Contributor
timestamp: March 20, 2021, 01:46:17 am
content: It looks like it has that same nasty 144 MHz spuras the rtl-sdr. for the same reason.http://www.steila.com/blog/index.php?controller=blog&action=view&category=software-defined-radioThe newest version is the rx-888-mkiiRX-888 MKII is the new generation of RX888 with the following improvements and enhancements:1. Add a tunable Attention in the HF path, which can tune from 0 to -31.5dB.2. Change the fixed LNA of RX888 to a VGA, which gives the -10dB to +33dB range. VGA applies to both HF and VHF.3. Use the newer generation of tuner chip R828D instead of R820T2.4. Use an enhanced version of 64M LPF to improve image rejection further.5. A jumper can select the internal reference clock or an external 27Mhz reference clock.The primary motivation is giving users smaller granularity control on the RF front-end and a big dynamic range to fit the demands of both strong and weak signals receiving. The tunable range is -41.5dB to +33dB for HFand 0db to 55dB for VHF, which covers most use cases. During the MKII development, we are working very closely with the original author ofBBRF103, IK1XPV, on his new universal driver. The new driver supportsRX888 and RX-888 MKII now. And we expect the power of opensource will significantly improve the software support and the lifetime of RX888.Open-Source Address of Firmware:https://github.com/ik1xpv/ExtIO_sddcSpecifications:1. LTC2208 16bit ADC at 130 MSPS2. Dual RF input, HF frequency range: 1kHz-64Mhz, maximum real-timebandwidth 64M. VHF frequency range: 64M-1700Mhz, maximum real-timebandwidth 10M.3. 0.5ppm VCXO4. ATT adjustment range -32dB to 0dB5. VGA adjustment range -11dB to +34dB6. External 27Mhz reference clock support7. 3.3v software switched Bias-Tee HF/VHF independent control8. ADC PGA Rand Dither software control9. Support mainstream SDR software. For HDSDR SDRConsole SDR# SDR++

author: radiolistener
author_rank: Super Contributor
timestamp: March 20, 2021, 01:55:04 am
content: Quote from: cdev on March 20, 2021, 01:36:24 amR820T is designed for TV receivers. It has 65 dBc image rejection and it's performance is optimized for 8-10 bit ADC.R820T works pretty well, but 16 bit ADC is overprice for that tuner, because it's performance will be limited with R820T

author: cdev
author_rank: Super Contributor
timestamp: March 20, 2021, 08:51:36 pm
content: Seems like the rx-888 mkII has switched to the R 828, the new, current version of the R820. The r820t appears to maybe be EOL?

author: PE1DHI
author_rank: Newbie
timestamp: January 13, 2023, 02:44:17 pm
content: Anyone experience with the RX888 (MK II) ?In my humble opinion it is a 8 bit receiver above 32 MHz, because the signal path has to pass the R820T2. Despite the 16bit LTC2217, the signal is 8 bit processed by the R820T2.Maybe it is a to simple thought and totally wrong?A extensive testing is done by DC4KU:https://dc4ku.darc.de/RX888.pdfThe test is done <30MHz (16bit)

author: Kalvin
author_rank: Super Contributor
timestamp: January 13, 2023, 03:23:56 pm
content: Quote from: PE1DHI on January 13, 2023, 02:44:17 pmR820T2 is just a down-converter, with an analog signal output.https://rtl-sdr.com/wp-content/uploads/2013/04/R820T_datasheet-Non_R-20111130_unlocked.pdfThis down-converted analog signal is then fed into LTC2217, which is sampling and digitizing the signal. This digitized signal is then sent to PC for further processing.Depending on how good or bad the R820T2 actually is, how well the PCB layout is done, and how well the power supply is filtered, the dynamic range (S/N-ratio) of the down-converted analog signal will be less than 16 bits, that is for sure. The actual dynamic range (S/N-ratio) may be anything between 8 to 10 bits.SDRs will typically provide some processing gain which will improve the resulting dynamic range, though.