Fake RTL2832U? - Page 1
Forum section: electronics / rf-microwave

author: EEVblog
author_rank: Unknown
timestamp: March 09, 2019, 05:54:43 am
content: Some people have told me a bought a "fake" RTL2832U v3 SDR dongle on ebayAnyone know?

author: Treehouseman
author_rank: Unknown
timestamp: March 09, 2019, 06:08:25 am
content: I found this mention of another dongle with a 628 chip in it. The problem is that the R820T2 and the E4000 are both discontinued at this point, they have to use alternatives.https://airspy.groups.io/g/main/topic/rafael_micro_r820t2_now/13916272?p=Created,,,20,2,0,0

author: radiolistener
author_rank: Super Contributor
timestamp: March 09, 2019, 07:29:05 am
content: Quote from: EEVblog on March 09, 2019, 05:54:43 amyeah, it's fake. At a glance it doesn't have direct sampling mod.Also it may use some other tuner chip with different frequency range.As I know 628 tuner chip has a little different frequency coverage.You can buy original RTLSDR v3 from official stores:https://www.rtl-sdr.com/genuine/For example, here is official store on aliexpress:https://www.aliexpress.com/item/RTL-SDR-Blog-RTL-SDR-V3-R820T2-RTL2832U-1PPM-TCXO-SMA-RTLSDR-Software-Defined-Radio-Dongle/32939551915.html

author: 1Ghz
author_rank: Unknown
timestamp: March 09, 2019, 07:33:08 am
content: I just found this yet another dongle with an AT628 chip in it.https://www.linuxtv.org/wiki/index.php/Astrometa_DVB-T2Quote

author: radiolistener
author_rank: Super Contributor
timestamp: March 09, 2019, 07:40:24 am
content: It is hard to obtain original 820T2 chip, so almost all fake uses AT628.This is not replacement for 820T2, it has different frequency coverage.But this AT628 also supported by rtl-sdr drivers. So it will works, but not the same as original 820T2.

author: rtlsdrblog
author_rank: Newbie
timestamp: March 09, 2019, 10:46:47 am
content: Hey Dave, i'm from RTL-SDR Blog, and just want to clarify as I think some people are confused. I don't want people to think we're the inventors of RTL-SDR/RTL2832U, and we are certainly not the original sellers of RTL-SDR dongles. But there are sellers out there falsely advertising things on many eBay & Aliexpress listings.So for background, RTL-SDR came from cheap commodity DVB-T tuner dongles that have RTL2832U chips. It was discovered that the RTL2832U had raw IQ data access, and then an open source org called Osmocom wrote some drivers which enabled RTL2832U dongles to be used as SDRs. So RTL-SDR as a thing was born.I started a hackaday style blog called RTL-SDR.COM a few years ago as a hobby to collect various RTL-SDR related stories and write tutorials, and to my surprise it became very popular. After running the blog for a while I noticed that there were a lot of complaints about the commodity RTL2832U DVB-T dongles having clock drift, no shielding, PLL not locking in the L-band etc, and all dongles back then used an annoying MCX or PAL antenna connector. So I worked with a factory in China (who also made a version of commodity RTL2832U DVB-T dongles) to produce a modded RTL-SDR dongle that solved these issues and added a few extra features, but kept the price as low as possible. I called it the RTL-SDR Blog V3, and soon the V3 became quite popular.Recently there have been sellers on eBay etc who have been selling their own productions of RTL-SDR dongles and calling them RTL-SDR Blog V3 when they're not (my guess is for keyword optimization). Those dongles do of course work as RTL-SDRs just fine. Only problem is when someone sets out to buy a V3 and is expecting those tweaks + extra features, but buys from a false advertiser and gets some other dongle.So the dongle you have isn't 'fake' as there's no such thing as a fake RTL-SDR. It was only well after the Osmocom drivers did people like myself and other companies start getting factories to make custom dongles that were redesigned to be better for SDR users, rather than optimized for TV watchers.But if the store you bought from advertised it as RTL-SDR Blog V3 then they did so falsely. I've been trying to take down some listings that falsely advertise as RTL-SDR Blog V3, but once you take one down, three more pop up... I also see that the enclosure of the blue dongle you have advertises HF+BIAS T features, but from the PCB picture I can see that it's definitely missing those features.Also of interest is that your dongle has an AT628 tuner on it, which is a clone of the R820T2 - the more commonly found tuner chip until recently. I've tested a few AT628 chips, and they actually seem to work similarly to the R820T2, but I haven't tested to see what they're actual max freq range is yet.So in short, if you just need an RTL-SDR and don't care about the tweaks + extras, grab any dongle you can find for the cheapest price. It'll work. If you need/want those extras (as shown in the last image you posted) then the V3 is a good choice in my biased opinion.

author: EEVblog
author_rank: Unknown
timestamp: March 10, 2019, 06:01:15 am
content: Quote from: rtlsdrblog on March 09, 2019, 10:46:47 amAwesome, thanks for joining and explaining.

author: bitseeker
author_rank: Super Contributor
timestamp: March 10, 2019, 06:13:07 am
content: Thanks for the background info, rtlsdrblog. Welcome to the forum!I bought one from your official eBay listing last year as it was my first SDR and I didn't know what I might need. I've only been using it as a radio so far, but its next job will be as a simple verification tool for RF remote controls.

author: pmsr
author_rank: Contributor
timestamp: March 10, 2019, 10:46:58 am
content: Welcome, rtlsdrblog. Still using your rtl-sdr dongle upgraded with the metal case and thermal pad, together with an upgraded antenna kit. Very happy customer here./Pedro

author: radiolistener
author_rank: Super Contributor
timestamp: March 15, 2019, 08:40:40 am
content: Hi rtlsdrblog, nice to see you.Could you please provide schematic of input circuit for RTLSDRv3 stick?It receives shortwave for 0-14 MHz pretty well. But I'm experimenting with VLF and ELF reception and noticed that it doesn't see low frequencies, such as 50 Hz in direct sampling mode.Does it have high pass filter on the input for Q-branch?For example, here is RTLSDRv3:And here is hand made high speed ADC with LPF on the input:As you can see, there is 50 Hz from mains and it's harmonics. Which is missing on RTLSDRv3.What is the low cut-off frequency of the input high pass filter for RTLSDRv3?It will be nice to get schematic of input circuit, so I can model it in software and see it's frequency response and may be to make some mods