My Kraken Installation... Let's Go!

When I took delivery of my Land Rover Discovery mid COVID era,  I thought I looked at every "radio hobbyist" related important thing to help in antenna, power cable and radio placement. One thing I overlooked was that this vehicle had an aluminum roof.

If I ever wanted to use magnet mount antenna this would not be good. I was also not planning to drill holes in the roof like in my last vehicle. After experimenting with hood and lip NMO mounts for VHF/UHF communications it was clear that performance from all locations was not as good as I had wanted, so I needed to try something different on this vehicle since I like omni directional patterns as much as possible.

After changing out the OEM roof rails for aftermarket ones plus getting some higher cross pieces with T slot centers,  this opened up more antenna options after a tip from a local ham about using carriage bolts instead of over price T-slot posts to help mount things. Thanks Jim! 

Now. before I get to the Kraken,  just to explain the vehicle roof further in the photo above, the rear most cross bar antenna mount I fabricated from  1 1/2 steel stock drilled out to accept 2 NMO mounts plus one 3/8 24 thread mount for different antenna needs.  This mount was then elevated using 1/2 inch spacers to give clearance for the underside of the mount and the coaxial cables.  This should be visible towards the rear of the Kraken array. 

The antenna shown is a 17 inch dual band NMO whip that is the perfect height for garage parking.  The high radiation take off angle works well in the Hudson Valley known for its geographic features which make for challenging communications at times.  

When I go on longer trips I add on a much taller tri band 144/220/440 whip and then run the 17 inch whip for an auxiliary radio.  My mount rail has proven to give me much flexibility while at the same time being low profile to the general public.

As example, I can screw on a ham stick for HF operation or use a 70 inch whip with a tie down while mobile for HF via an antenna tuner and balun. This antenna mount bar was a quick project and has proven to work well.

Currently my daily driver radio is the Yaesu FTM-300 for VHF/UHF plus Civ/Mil air band monitoring while in motion.  For HF, I sometimes use the Icom IC-705 or Xeigu G90. Perhaps a Yaesu FT-891 may find a home in the car eventually, we shall see.

Now to the Kraken!

You came here based on the photo right?  When it came time to figure out how to use the Kraken in this vehicle on a "when needed basis" , I used the same type of steel stock from my antenna mount for the five Kraken antenna arms and I came up with the perfect removable mount for it in the process.

Parts Required

One 3/4 inch flange mount has a pair of 1/4 inch spacers which some carriage bolts pass through along with two washers.  One wing nut on each bolts allows me to tighten the mount to the roof quickly and easy via the T-slot. It is easy to unlock my cross bar, loosen the wing nuts and slide the mount in or out.

The spacers were needed so I could pass the five coaxial cables through a 3/4 inch diameter coupling which connect the two flange mounts together.  This allows the coax to pass through the bottom and up to the top to each antenna arm easily.

The actual "list" of materials for those that like it that way is as follows:

• 2 - 3/4 Inch Flange Mount Pipe Fittings
• 1 -  3/4 Inch threaded black steel MPT Nipple - 1 Inch length
• 3 - 1 1/2 Inch wide plain steel. Each is 48 inch and cut down as needed
• 10 - Matching #10-32 3/4 Inch screws and matching steel nylon lock nuts
• 1 - 1/4 Inch 3/4 Inch carriage bolt and matching lock washer and nut
• 2 - 1/2 Inch Carriage bolts, washers and wing nuts.
• 1 - Package of 50 reusable velcro ties. (HD Item # 90924HD/202261940)

Assembly should be easy to visualize. I did not make plans for legality reasons as I can not control how well people can build things strapped to a roof and potentially driving at highway speeds. All hardware can be found at most any decent or general hardware retailer.

Testing in phases

Driving around with just this center mount with no antenna arms for about a week whistled a little while in motion so a velcro wrap is put around the two spacers to deflect the wind. This cleaned up the whistle between the roof rail and the antenna hub mount and its near silent. The coax fed through the NPT nipple is not affected with the velcro 

Each of the antenna arms made from 40 inches each of 1 1/2 steel was needed to space the antennae out in a pentagram for frequencies as low as 120 MHz.   Some velcro wire ties are used to keep the cables from flopping around in the wind.   

Each antenna is magnetic and easily stays attached on the arms at highway speeds. No whistling is heard so the aerodynamics must be pretty good.  Each end of the antenna arms were rounded off and both edges sanded down prior to painting in flat black paint to create better aesthetics. 

Antenna arm zero faces directly ahead with element one being to its approximate 2 O'clock position and the opposite side at about 10 O'clock is element four.   These three elements are each held in place with a pair of machine bolts secured with nylon insert lock nuts.  This makes for quick disassembly or maintenance as needed.

The rear two most elements roughly at the 4 O'clock and 7 O'clock positions are  cold welded together along with a short cross piece of steal stock that has a single carriage bolt and nut to hold it down with some precision against the other antenna arms.   Removing this single bolt allows for smaller storage space when the system is not on place and the front three elements stay in place.

Each of the coax lines have thoughtful cable markers on them to make it easy to known which coax goes to which receiver port on the Kraken.

I added some marker points on each antenna arm at key frequency ranges to aid in changing use cases such as for 2m Fox Hunts and other RDF related interests across the VHF and UHF spectrum.

A few more velcro ties secure the five cable bundle to the cross rail and then are all carefully pulled flat against each other before closing the car door so as to not pinch the thin coax.

With each of the five coax connected to the right ports, the only other connections to the Kraken are minimal.  If you wish to learn more about the Kraken SDR,  please use Google. This is just about my implementation and not a review.

The "Non-Antenna" Stuff. 

A nice orange hard case from you know where was pressed into use to keep the Kraken safe but I am still deciding how to make it a permanent home inside.

The red colored 1 foot length USB-C cable is used for data transfer and is connected between the Raspberry Pi 4B and the Kraken.   Both the Kraken and RPI4 have grey USB-C USB cables for power only and plug in to a USB power hub which offers the 2.5A amps needed per device.  

The power hub also has the ability to be powered from a range of 8-20 Volts which is nice to provide the 5V and 2.5A needed to each of the devices. Two ports on the USB power hub are not used.   This is the power hub used if you are interested on Amazon. https://www.amazon.com/dp/B08MCZNYZN 

Finally, the USB power hub which originally came with alligator clips were removed and replaced with power pole connectors as shown.  An easy and useful upgrade for USB power!!

Shown in the photo is a Westinghouse power station which supplies 12V power to the USB hub but is easily changed to other power sources such as vehicle power or some other battery if desired. I like using the power station since it can monitor current draw and wattage.

During use, the Kraken plus Raspberry Pi seem to draw an average of about 10W which is not too bad.  With intermittent use for a whole day plus forgetting to turn it off overnight, the power station still was at 40% capacity.

The photo of the Raspberry Pi,  Kraken and USB power hub and its minimal cables should be easy to understand.  The row of blue lights on the Kraken show each receiver is in use and the five coaxial cables lead out the window topside.

So how does the Kraken work?

A few comments to share is that the Kraken is sensitive. Do not transmit near to it. For a recent Fox Hunt where we used 146.565 MHz as the target frequency, I used the Yaesu FTM-300 on low power only on a local UHF repeater.  I did not see to have any issues but was still careful to not overload the Kraken while doing RDF.

The antenna elements were all extended for about five hours and driving for about two of those.  Everything held up just fine.

I paired the Kraken/RPI4 to my mobile phone using the Android App, but also monitored the spectrum and DOA via the web server on an iPad Mini. This worked out well but even though the Raspberry Pi 4B is overclocked, I really need to upgrade to a Raspberry Pi 5 when it is reasonable.

Some experimentation with the ability to track more than one signal on the same frequency was interesting. I tried it with two after making the adjustment in settings.  Technically up to six signals can be tracked but I was not able to try that.

After a few earlier uses of the Kraken on my past vehicle, everything worked well at the 20.7db gain setting for VHF.   Using this new mount, I found overload easily and backed the gain down to below 10db.  

During our fox hunt, we had three search areas each 3 by 4 miles. I started out as a hider in the lower quad listed in FN31bp.  Driving up to where the "Charlie" fox was in FN31bs, the turn by turn directions after getting a fix roughly a mile away was fun.  However, this fox was hidden in a cemetery and I had to use normal eyeball navigation to reach my destination. Pretty much everyone was impressed with this setup and how fast I got to the fox. 

Also worth mentioning that the 17 inch VHF/UHF NMO whip did not seem to affect the Kraken array pattern which was a major added bonus!

During the hunt, I was also tracking the western fox via a different bearing the whole time which was cool to see on the map as I drove north.

I can not say enough great things about the Kraken. It is expensive, but it paid for itself well before this fox hunt via other missions where I needed to find transmission sources. My favorite test location was a local aviation VOR since it was ground level.   During that test I even used a separate SDR running with SDRangel to track its bearing, but that is best left for a different article.

Hope you enjoyed this overview and no, I do not plan to share my dimensions used in my build since you can use the calculator and details found in Kraken Forum where I drew inspiration from.  All I can say that the materials for my mount ended up costing around $100 in total and that does not include brainstorming and fabrication time.

If I had to build this again, I would make a few changes but nothing major as this has proven to be really nice so far for me.

RTL-SDR V4 compared to RTL-SDR V3

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.

Lazy Summary

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.

Other Things

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.

How To: SDRangel Education Series (Focus on Release 7)

 

Long overdue are some filtered playlists for HVDN created videos, such as those focused on SDRangel software.

With SDRangel Version 7 Series, many changes have confused people on how to get started, so our part 3 series should be a good education source when using RTL-SDR V3 or V4 devices.

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.