Thank you to Chris (NNN0BOC) for writing up a glowing review of the RTL-SDR Blog V4. In the review Chris covers the enhancements that the VB4 brings to the HF bands, the driver replacement, and tests it out on various signals such as STANAG S4285, HF FAX, HFDL, GMDSS, MilSpec 141A ALE and various SWL bands. In his tests he uses SDR-Console V3, of which there is now a beta version that has built in support for the RTL-SDR Blog V4 (scroll down the page to find the V3.3 beta download).

Chris makes note that the RTL-SDR Blog V4 does not have the Nyquist aliasing problem that occurs in the RTL-SDR Blog V3 and other RTL-SDRs that enable HF reception through direct sampling. Nyquist aliasing on the RTL-SDR means that signals will be folded around 14.4 MHz. So for example a real signal at 8 MHz would also show up on 14.4 + (14.8 - 8) = 20.8 MHz and vice versa. The lack of Nyquist aliasing makes for a much cleaner spectrum.

Chris summarizes with the following:

I must admit I spent _a lot_ of time just looking at the beauty of HF with the V4, watching all the crazy goings-on, the weird sweepers and random signals popping up and disapearing.

I didn't run into any dynamic range issues or stability issues stemming from the V4, I wondered if I would have to perhaps place the RTL SDR AMBC Filter in line to suppress the many AMBC signals always present, never had a prob. The 120+ foot horizontal loop antenna feeding the V4 only has a 30MHz lowpass filter in line to hinder any rf that impinges upon it.

For such an inexpensive and tiny device, and free-to-use software, the capabilities are really kinda amazing. I now want an RTL SDR embedded into a cheap phone to use as a spectrum display on non-sdr HF receivers!

The V4 seems to atone for some of the sins of the V3, especially on HF with specific regard to Nyquist aliasing, have no fear tuning above 14.4MHz dear friends, this thing won't be making aliases unless you are overloading it.

At this time I can't think of a better value for the money when shopping for an SDR to use with a pc or phone in the sub - $50 price range.

We note that the RTL-SDR Blog V4 dongle only is currently in stock on our store from our international shipping warehouse, and the V4 dongle + antenna set will be in stock in about a weeks time.

Not too long ago we released our first batch of RTL-SDR Blog V4 dongles, and most have been received by customers now. The next batch is coming soon, and we should be able to start sales again within the next 1-2 weeks from this post. It is incorrect rumors that they are totally sold out forever already. There should be sufficient stock for at least a year, so everyone who wants one will can get one.

In his latest YouTube video Manuel Lausmann compares the performance of the RTL-SDR Blog V3 and the RTL-SDR Blog V4. The video is narrated in German, however YouTube's autotranslate + captions feature works well.

In the video he first compares the performance on HF, noting that there are significantly less interference signals in the HF spectrum due to the lack of Nyquist folding around 14.4 MHz, which is a known problem with the direct sampling mode. He later also compares performance in the VHF and UHF bands, notably finding an improvement in the 145 MHz region where the V3 has a pumping noise floor from out of band interference, whereas the V4 does not thanks to it's additional filtering.

Over on his TechMinds YouTube channel Matt has uploaded a new video showing him testing out the new RTL-SDR Blog V4 dongle that we released a couple of weeks ago. In the video Matt explains the differences between the RTL-SDR Blog V3 and V4 dongles, and then goes on to show the Blog V4 dongle in action. He finishes by comparing reception between the V3 and V4, noting the reduced interference on the HF bands due to the lack of Nyquist folding from direct sampling.

We note that the first batch of the RTL-SDR Blog has currently sold out, but a new larger batch will be ready to go on sale around the end of September. So please keep an eye on the blog's main page and store if you are interested in picking one up.