Monday, November 13, 2023
HVDN prime author Steve K2GOG received two of the RTL-SDR V4 during its initial production run.
Here we are about four months later and there have been many other reviews focused on basic differences between the two devices.
There have also been impressively fast integration of the new drivers along with popular software. By mid September, almost everything was solved but I waited a while to do this article now that production has resumed and the V4 is easily found again until the R828T chips run out.
Almost every video or article focuses on the same things like which one works better for HF reception or other pretty basic things. There are some major differences where the V4 really shines and that is what this review is about. Our goal is to NOT focus on the same thing and to not try to force our readers to buy one over the other, unless the below is of interest to you.
Please note, get the right antennae for what you want to do. Using telescoping crap antenna is not going to work well for almost everything we cover below based partially on the spectrum coverage chart below.
Directly from the "RTL-SDR Blog V4 Dongle Initial Release" article, there are some major things to point out.
- 0-30 MHz Spectrum: This has been beaten to death already. The V4 is much better at HF reception compared to the V3, but you still need to have a real antenna. Do not take shortcuts here as a marginal 2-3 foot (1m) telescoping whip is not going to impress you. A major benefit is not having to select Q branch to receive the "short wave" spectrum, so with the right software the overall user experience is still better here. It is worth noting that comparing the V4 to even the inexpensive "knock off" SDRPlay devices for around the same price still offers better HF spectrum coverage along with wider 10 MHz bandwidth compared to the V4's 3.2 MHz bandwidth. Its time to move on. The RTL-SDR is fine for what it is and stop focusing just on this spectrum as a selling point.
- 100-300 MHz Spectrum: There are spots where coverage is slightly better with the V4 compared to the V3. Its not worth getting into much detail here, but the built in triplexer and filtering does a better job limiting out of band broadcast interference from the 88-108 MHz range, especially if you are interested in civilian aviation VHF 118-136 coverage as well as other amateur or utility communications.
- 315 & 433 MHz ISM Spectrum: If you really want to explore what is around you or wish to think you are some sort of "hacker" having better sensitivity and filtering around the 315 MHz range used for tire pressure monitors found on many vehicles in North America and the shared 433 MHz ISM range with many "Internet of Things" devices and amateur radio things is a huge gain here. This was worth the expense for these monitoring target applications.
- 868 & 915 MHz Sub GHz Spectrum: Another area of improvement with the V4 device. Many IoT devices worth sniffing around exist here. While the V4 does seem as if it is not as sensitive compared to the V3, I feel this is not too bad since it forces the user to use more purpose drive antennae to make up for the difference.
- >1000 MHz+ Spectrum: North of 1 GHz, performance is not really that bad with the V4 and with an LNA, better antennae or combination of the two is fine. Over time, the two V4 devices have been tested to have slightly less thermal drift and lower power consumption compared to the V3. In many cases where monitoring L Band spectrum, this becomes important since the RTL-SDR's have been installed in areas not very accessible or have had to contend with heat build up. For applications like HRPT satellites, ADS-B, and so many other things found in the 1000-2000 MHz slice, the V4 has really been great when uses with purpose focused antennae.
We are talking about an under $40 USD device. Stop being cheap. Stop pretending this will be the best radio receiver ever made. Stop using crap antennae and blaming the SDR or the software. Stop thinking the world revolves only around HF spectrum. Buy an RTL-SDR V4 if you are interested in doing many things which will motivate you to explore better antennae and software where you can find really cool things in the airwaves that may just be data signals and not just human voice communications.
I really like the indicator light for when the bias T power is active. The L band patch made by RTL-SDR has an indicator, but its inside the antennae housing so is not viewable. Knowing the small green light on the V4 is on, does help ensure I know the antenna downstream is seeing power has been helpful Many software packages like SDRangel allows control of the bias T power, but a physical indicator is still nice.
Overall design in such a small package is hard to do. We may be at the limits of what else can be done in this formfactor but with thermal management becoming more challenging, its commendable how the power supply has been redesigned. Earlier SDR suffered greatly from power issues, this is not the case with the V4.
If there were two front end major changes, I would love to have a built in dedicated high isolation filter which pretty much knocks out the entire 88-108 MHz range up to 60db since strong signals tend to mix at odd places at times or have a tight filter around 400 MHz for better ISM or radiosonde monitoring between 400-450 MHz. Otherwise I am just picking on things I can solve other ways via outboard filtering or mission specific antennae with usually do a great job at out of band attenuation.
Sunday, November 12, 2023
Long overdue are some filtered playlists for HVDN created videos, such as those focused on SDRangel software.
Part 1 of this series focuses on basic getting started or getting restarted if you tried SDRangel in the past and want to give it another look. The use case also shows how easy it is to use multiple SDR at the same time to monitor spectrum very far apart, such as the 118-136 MHz civilian aviation band plus the 1090 MHz ADS-B used to track aircraft transponders.
Part 2 of this series is focused on how to reserialize your RTL-SDR device since the default is 00000001 and this will need to be changed to allow computers or other devices to recognize them from each other.
Keep an eye on the SDRangel Education playlist as more content gets loaded. Since 2017, HVDN has produced 255 articles to date and 15 have featured this great software plus many others have made a passing mention about F4EXB's labour of love.
SDRangel has evolved so much since the v1.0.1 release back in 2015 and HVDN's official coverage started around version 3.6.5 in 2017. As a follower from the near beginning and an educator across the evolution, if you need to know about SDRangel, please consider us experts.
Also, check out the SIGpi project now which uses SDRangel as one of the core applications. This will become even more important as SIGpi gets ready for a huge update now that Raspberry Pi 5 is here.
Monday, October 2, 2023
If you build it, they will come is how the saying goes, right? When it comes to digital voice modes today in amateur radio, the best way to chart the growth of the most popular modes is by looking at repeater deployments.
No individual, club or group of people will invest the time, money and annoyances to deploy a repeater on common amateur VHF and UHF spectrum unless they know there are people who will use it. And, for people to use a repeater they need the appropriate radio which uses the appropriate mode or modes of communication. This means that people need to coordinate and that is not always easy.
Going into our 13th edition of the global amateur radio repeater round up over the last seven years, no one can argue where the direction of digital voice is headed, but where are the actual users today?
Please review any of the past linked articles for expanded commentary on mode specific drivers such as new radios or features related to different modes because this update will take a different direction.
As we can see in above chart, DMR continues to grow but there are so many splintered networks such as Brandmeister, TGIF and FreeDMR which make it frustratingly interesting for new joiners to figure out how to find people given that each network is separate and each uses its own talk groups/destinations unless they are content with using a hotspot.
A hotspot is under 100% control of the user compared to a repeater, so allowing your hotspot to go to different networks (on DMR) or other modes as well as any of the destinations (talk groups, bridges, reflectors, etc) is possible. Repeaters do not permit that, but that is not the intent anyway.
DMR Networks: Lessons in diplomacy
While Brandmeister is still the most popular, not every DMR repeater will support talk groups the same way which forces some users to use a hotspot. This make programming radios a challenge for some people as well as those that are experienced in keeping radio programming up to date as it relates to repeaters.
For new users who look for local repeaters that have DMR, the same talk group (Example: 31368) will not reach the same people if they are on a different network, unless someone created a bridge but that sort of defeats the purpose for different networks anyway. This frustrates people since DMR is not just DMR, its DMR that is implemented at the network level differently.
This network flexibility has proven to be a benefit and a curse at the same time for DMR, but that is ok because its still the most popular and lowest cost entry to digital voice. DMR has also proven to be the driver behind many innovations on network capability which the others did not focus on.
Any Pi-Star or the WPSD/W0CHP variant running on an inexpensive hotspot is just like having your own repeater though and you can set it up however you wish.
It is estimated by HVDN that there is 70:1 ratio of hotspots sold compared to digital voice repeaters currently online. At any given moment according to Brandmeister, there are well over 15,000 hotspots connected at any time. Currently, there are only a little over 11,000 digital voice repeaters, so that means that its possible there have been over 700,000 hot spots sold.
There are many amateurs, including myself that have had multiple hotspots over the years and those I no longer used, were sold/given to others in the hobby. Its easy to think that many interested in digital voice likely have or have had in excess of three or more hotspots so that 700,000 number is actually pretty modest and is probably too low.
Digital voice repeaters do not all need the internet
DMR also as a reminder does not need the internet and there are repeaters that provide only local coverage and users do not need to be registered via a central user database, even though it helps to have an ID linked to your callsign from https://www.radioid.net/
Yaesu Fusion and Icom's D-Star have a more tightly controlled network to connect repeaters to for those wishing to communicate via the aid of the internet, but also can be configured for local only coverage, but there are likely far less repeaters using these modes which operate that way. Registering on the Icom D-Star network can be annoying and Fusion while easier, still requires registration for internet access.
The commercial modes like P25 and NXDN can be deployed any way the repeater owner wants, but these will never reach the same scale as DMR or dedicated vendor modes because handheld or mobile equipment is not designed with the radio amateur in mind as its main buyer.
Here is the actual data for repeaters globally by mode and surveyed twice a year along with matching compound annual growth for period by period and total growth.