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.

The perfect tape measure beam for RDF?

 

There are lots of instructions and videos about the 2m tape measure beam available already.  Here are some build ideas based on the different iterations I have built over the years which are originally based on Joe WB2HOL's version before he went SK.

Please visit: http://theleggios.net/wb2hol/projects/rdf/tape_bm.htm 

Mounting the directive and/or reflective elements

Rather than using small hose clamps to secure the elements to the boom, I originally used zip ties. This method worked well, but sometimes warped the elements at an angle.  Using electrical tape works better, is easy to replace, cuts down on weight and improves the radiation pattern of the antenna.

Using electrical tape is inexpensive, secure, neater and
does not influence the antenna pattern like hose clamps do.
(Photo Credit: Steve Bossert K2GOG)

Boom Material 

1/2 inch PVC T and crosses seem the best.  A few antennae I made used 3/4 inch conduit and junctions to improve ruggedness, but 1/2 inch has proven just fine and weighs less.  Only use PVC cement once you are happy with the construction to secure the junctions to the boom pieces.  

Friction fit construction may fail at the worst possible time, so glue your junctions.  The only real major benefit of 3/4 inch construction is that your elements can easily slide into them for storage or transport.  This is still possible with 1/2 inch fittings but is a little too tight and the elements will take up more room during transport.

Here is a 2 element version with the director and driven elements folded up.
(Photo Credit: Steve K2GOG) 

Is a current balun necessary?

After making identical versions of  2 or 3 element antenna with or without the balun, I find the pattern of the antenna is more stable with the balun.   Making sure the balun is close to the feed point is a really good idea.   

I drill two pair of holes a few inches apart to form the balun and the feed point goes into the boom for a clean construction. Drilling the holes as far to the interior of the PVC cross is a good idea in order to leave room for folded element storage.

Where the nut inside the PVC cross is where a crimp ring slides over the screw and is the secured by the nut. Outside the PVC cross is a washer and nut. Outside and on the top of the driven element is a star washer on top of the hairpin match.

Scrap off the tape measure paint on both sides. Use a little De-Oxit to ensure excellent conductivity and to prevent any future rust. The 5 inch hair pin match is made from steel clad copper wire and crimp rings with the insulator removed are used to ensure secure operation. The crimp rings are also soldered to the hair pin match for further reliability.  A flat and star washer keep everything tight together.

How to connect your radio to antenna?

I like making a neat looking antenna and I route the RG-58 through the boom and out the back end.  You can make a long tail with a BNC male on the end to connect to your radio or via an SMA to BNC adapter.  Here is what a 3 element version of the antenna looks like configured that way.

The other option is a little more technically challenging to describe where a female BNC is fitted on to the end of the boom instead.  For the photo below, I also drilled a hole to secure a length of 550 paracord to act as a wrist strap of sorts.  

Using a short jumper cable to connect to the radio is needed, but when traveling, not having a cable dangling is a nice benefit and does not offer that much signal loss or leakage if done nicely.

Make your boom grippy?

Self amalgamating insulation tape works great as a grip and it wont leave a sticky residue behind if you care to remove it later. This same tape is also great for protecting antenna connectors, so pick up a roll or two and I am sure you will find many uses for this stuff. 

Here is a 2 element and 3 element 144 MHz tape measure beam antennae using similar construction practices. Put some electrical tape on the antenna ends to prevent potential cuts or eye pokes.
(Photo Credit: Steve K2GOG)

Measurements 

Many articles like the WB2HOL article cover measurements and you can find what works best for you. The goal of this article was to focus on some construction improvements.

When tuning the antenna it is best to adjust the driven element for lowest SWR at your operating frequency first and then add your reflector or directors after. This should lower the SWR further.

You can squeeze the hair pin match element to get a better match and as long as you are using stiff wire, it will hold its shape. The hardware used in construction of these antenna do not noticeably affect the radiation pattern of the antenna.

If you plan to transmit with these antennae, please ensure you adjust for a good SWR to protect your radio transmit circuitry.

Using these antennae

The original use for this design was for radio direction finding, but both will also do just for for transmitting if you are interested in light weight directional antennae for use with summits on the air (SOTA) or other portable operating scenarios.

Remember, that there is a null in signal off the back of the antenna and to the sides. This will be helpful when finding hidden transmitters.  The null is more pronounced with the 3 element version, but the 2 element design works great for other reasons.

If you are looking for a fun and inexpensive project you can build, please give these a try.

Hudson Valley Digital Network in conjunction with other area amateur radio clubs will continue to hold hidden transmitter hunts, so please check our activity calendar for upcoming events.

Safety first.  Be sure to protect the ends of your antenna elements with
some electrical tape to prevent injury
(Photo Credit: Steve Bossert K2GOG)

Best Video Ever: HV BBQ & RDF (OMARC, HVDN, USMA, QSY)

 

NEW DATE - UPCOMING EVENT ALERT: OMARC RDF BBQ

 RESCHEDULED DUE TO RAIN ON 10/30. NEW DATE IS 11/6

The Hudson Valley will be home again to the premier radio direction finding (RDF) event for our area and this will be taking place on October 30th 2021 November 6th at Ferncliff Forest in Rhinebeck, NY.  GPS address is 68 Mount Rutsen Rd Rhinebeck NY 12572.  

The event will take place from 9:00 AM until about 3:00 PM.  All who are interested are encouraged to pre-register. There is no fee to attend or participate.   Registration survey here.

A combination of area amateur radio clubs will be organizing and participating in this event.

 RESCHEDULED DUE TO RAIN ON 10/30. NEW DATE IS 11/6

Overlook Mountain Amateur Radio Club (OMARC)

With a membership focus on Ulster county and the Northern Dutchess County area, the OMARC club will be providing lunch and hospitality for the event. Lunch will be served from 11:45 AM until 12:15 PM with snacks and drinks available for the duration of the event.

OMARC will also be supplying some of the hidden transmitters for the hunt and the WA2MJM 146.805 MHz repeater will provide educational discussion relating to this event at various times of day and the entire month of October.

United States Military Academy Cadet Radio Club (W2KGY)

Building on the success of past cooperative events, the USMA Cadet Radio Club will be participating in this event to hone practical skills which can be used in real life scenarios which may involve working across civilian and government response teams.

Hudson Valley Digital Network (HVDN)

HVDN will take the lead on education, coordination and technology that will be deployed for the first multi-transmitter direction finding event in our area.  

Additional equipment may be available for those that do not possess some of the tools needed to find the hidden transmitters. Educational session will take place from 9:10 AM until 9:35 AM. Teams of hunters will start off to find the transmitters around 9:45 AM. 

Anyone is welcome to attend and you do not need to be a member of any of these clubs or have an amateur radio license.  Donations are welcome the day of the event.

Radio Direction Finding Basics

We would like to thank Josh KI6NAZ for a pair of excellent videos explaining a little about the basics of radio direction finding and using the antenna we are promoting for the event.

• Tracking a Pirate Radio Station

• How to Make an Incredible DIY Directional Antenna for Almost Nothing

HVDN also has a basic information webpage found at rdf.hvdn.org and here is a past article that may be of interest. 

• November 30th 2020:  RDF in the HV with OMARC and HVDN

Navigation Basics: Using a map and compass

Bob KD2QAK is an experienced search and rescue and medical technician. Bob worked with Steve K2GOG to put together this introductory video.  This will teach some basic skills which will be used during our radio direction finding event on October 30th 2021. 

Using grid squares in a practical environment

If you watched Bob's video, he mentioned the UTM grid system which is often used for search and rescue activities.  Within amateur radio, we use a system called Maidenhead Grid Locator (MLS) and here is a video which Steve K2GOG created.  Grid squares are easy to use to share approximate and fairly specific location with very few characters.  

During our RDF event on October 30th, we will be incorporating MLS into the maps which will be issued to the teams who will be looking for the hidden transmitters along with some other interesting objects in the forest.  

Some of these may include hidden treasure chests, friendly gnomes, persons of interest and a new set of trail markers that Ferncliff Forest has recently installed.  

Please bring your family if this sounds like fun!

October 30th 2021 RDF Missions

Details will be kept a secret, but we will be hiding upwards of 6 different transmitters that will each have different degrees of difficulty to find during this event.   This will help appeal to the widest number of people possible.

All transmitters will be operating on the amateur 2m band (144 to 148 MHz). Some transmitters will even be sending images, so using our SSTV skills in the field will become important and will add a unique perspective to this event.

 Other training exercises to understand how to use a directional antenna and land navigation will be interwoven into this event.

Expect lots of fun and any questions can be asked in the comments below or during any of the many organized discussions taking place on the WA2MJM repeater.

Or, feel free to contact the UNDR Net team who was responsible for putting this great event together 

RSVP IF INTERESTED IN THIS EVENT HERE PLEASE 

CONTACT FOR ANY DETAILS RELATED TO THIS EVENT

Map & Compass Basics with Bob KD2QAK

October 2021 is busy with many educational activities to get everyone ready for our big radio direction finding (RDF) event scheduled for October 30th 2021 at Ferncliff Forest in Rhinebeck, New York.

Here is a great video on some basic skills and understanding for using a map and compass.

Click or or on video below

Ulster & Northern Dutchess Readiness Net

 

I would like to thank everyone who has supported what is now going to be officially called the Ulster & Northern Dutchess Readiness Net moving forward following our October 5th 2021 over the air session.

We still get to keep the UNDR acronym and the reason for changing the word "radio" out for "readiness" helps us provide a more flexible resource and mission. 

As we continue to determine if what we are doing will be a benefit to ARES, RACES or CERT capacities at some point in the future as covered in past articles and live discussion every Tuesday at 8:00 PM local Hudson Valley Time (0000 UTC)

One note sent in a few days after our last UNDR Net is the image that solved a problem for Brad KC2VVJ. Thank you Bob K2LD for sharing your below image via our webform and helping Brad out. Details on the issue can be read here. 

Bob K2LD decoded this image with ROBOT36
using PD50 mode while stopped in his car.
Read more details here 

October: Hudson Valley Fox Hunt Season

Fall is the perfect season for walking around with antennae and radio equipment to find cleverly hidden transmitters, which are some times referred to as "foxes". 

There are many practical applications for radio direction finding and members of the UNDR Net team have put together a curriculum to help teach related skills that are useful to this sort of activity detailed below. From a CERT perspective, understanding land navigation and direction finding are important things to know.

Week 1 Highlights & SSTV Summary

With a total of 12 participants, now spanning across 3 state borders across no fewer than 6 different counties, the UNDR Net continues to show that great content attracts more interest compared to how many standard ARES/RACES net serve those specific purposes.

Continuing on with perfecting SSTVM over FM via the WA2MJM 146.805 MHz wide area repeater, we have increased our ability to decode fantastic images using the PD50 mode.   This slow scan television mode only takes less than one minute to send an image with 320x256 pixel resolution.

Past articles show some practical applications for SSTV to communicate or inform on situational awareness and this week we have a little more free form fun.

Ken KD2TQS started off by sharing a photo of this rather nice butterfly, with photo accreditation going to some Ken is friends with.  

The species of butterfly is battus philenor and is more commonly known as the blue swallowtail.  Sharing an image like this, or a type of snake, could be interesting in a no-cellular network access scenario where sharing a photo of wildlife could be very important.

The next image by Brad KC2VVJ, while it appears a little choppy was part due to interference on the repeater, but the commemorative patch is clearly legible for most of the image which proves resilience in sending an image in less than optimal conditions.

The last official image of the evening sent by Steve K2GOG was used as a quiz to identify someone who might "already be your friend" or perhaps "was your friend" on an early form of social media known as MySpace.  Sharing a photo for perhaps some type of lost persons scenario is important.  

No fewer than six participants decoded the image just fine with perfect clarity and all would have been able to pick this person out in a crowd, had this been a current photo of Tom Andersen. 

Discussion during a directed net goes by quick and the UNDR Net for October 5th concluded at 2122 local time.  An "unofficial" round of images followed which included Tom N2FZC sharing his first sending results using EncoderSSTV and the image quality was reported well across multiple people.

Joining us for the first time from Winchester, CT was Dan KC1RRK who decoded most all the attached images and then shared a simple "QSL" image shown above with no photo in the middle of the text.  Brad KC2VVJ responded back with the below image to acknowledge receipt of Dan's image.

Radio Direction Finding Plans

Here are the plans for the jointly organized RDF day planned for October 30th along with the Overlook Mountain Amateur Radio Club, who will handling hospitality via a nice lunch to thanks its members and for those that are pre-registered for the event.

More details will be shared each week and as part of our curriculum. If you are interested in attending our October event at Ferncliff Forest, please take the below survey.  

PRELIMINARY RDF EVENT SURVEY

Putting the HV on the map with SSTV?

 

For our third SSTV over FM test as part of the Ulster & Northern Dutchess Radio Net on Tuesday September 22nd, we had a lower turnout than past weeks but had the most success in participants decoding images and playing along.

The month of September is National Preparedness Month as sponsored by the Federal Emergency Management Agency (FEMA).  This weeks casual round table theme was "low cost, no cost preparedness".

Natural disasters do not wait for a convenient time. Preparing for them shouldn't wait either. Start today by having a look at various alert tools, gather and safe-guard important documents and take other low cost/no cost actions like ensuring your amateur radio gear is functional, programmed with appropriate frequencies and know how to use it without the aid of a manual or computer programming.  

Doing all of this in advance helps lessen the impact of disasters and emergencies for you and your family.

Local Hudson Valley Weather Status

The WXL37 National Weather Service transmitter which serves the area is currently offline.  It is unknown when this will be again online, so should there be a situation where there is internet or mobile service disruptions, a reliable and timely source of weather information excluding broadcast media is not available for our area. 

Hopefully this is restored soon, especially since any weather alert radio receivers will not function until this is turned back on.

UNDR Net Participants on 9/22/21

Acting as alternate net control this week was Guy KD2TLF and our total participation this week was six and spread across the core of the Hudson Valley.  Special thanks to:

• KD2TQS - Ken - Rhinebeck - Dutchess County
• WA2RKN - Jerry - Hyde Park - Dutchess County
• K9JPT - John - Hopewell Junction - Dutchess County
• KD2VAH - Jim - Poughkeepsie - Dutchess County
• KD2TLF - Guy - Xena - Ulster County  (ANC)
• K2GOG - Steve - Poughkeepsie - Dutchess County (NC)

After a brief discussion about no cost planning, we moved to the SSTV over FM test using the Overlook Mountain Amateur Radio Club's amazing WA2MJM 146.805 MHz repeater located high atop Overlook Mountain. 

As a reminder,  UNDR Net is not currently affiliated with ARES, RACES, CERT or MRC but would love to be if it shows we can add value. 

Finding people without giving away details 

This week we started off making the audience think we were going to play a game of tic-tac-toe by sending images using the very fast PD50 mode compared to last week's PD120 and prior PD90.  

Each mode takes approximately the number of seconds represented in the numbers of the mode, so thusly PD50 is nearly twice as fast compared PD120 with the only sacrifice being resolution and image size.

A picture is worth a thousand words, so a video is worth more than that, right?  

Here is a nice video from John K9JPT showing how he used his smartphone to listen to the SSTV audio signal coming from his radio as sent by Steve K2GOG and is then converted in real time to the image.

For the next image, which Ken KD2TQS sent, included the "O" in grid B2 on the tic-tac-toe board.

Here is where we then changed things up from a simple children's game to something of more importance. This was the third image sent:

Using the details sent in the first two images, it was simple for our end users to then overlay the "X" in A1 and the "O" in C2 to help provide travel directions in the least amount of moves so that a meeting near the barrels located in B3 code happen.

If this were a real life scenario and people on the ground had a printed map with grid lines, it would be easy for a control operator to share locations of key assets with those in the field without giving away detail over the airwaves. 

Instead, ground users would simply marry up the points of interest, obstructions and team members from a simple image and draw them in locally to a map.  This would give HUGE situational awareness while maintaining some level of mission privacy.

Here is the fourth image sent in the evening to give more ideas on that. If the goal of "SB" was to move to the smiley face in the shortest number of grid moves, it would be easy to do so.  Overlaying a grid like this against a real map would be valuable and secure.

What is next for SSTV over FM and UNDR Net?

Bob KD2QAK has been talking about giving a presentation on map reading and orienteering with a compass at an upcoming Overlook Mountain Amateur Radio Club presentation night.  

If this is possible to get scheduled before an upcoming Radio Direction Finding event on October 30th at Ferncliff Forest, its possible we can blend all three topics together to make a really fun event.

If we think back to how Nolan N2WU was able to use APRStt as a way to identify key locations as part of the West Point Triathlon or how Bob Bruninga WB4APR did a case study using grid overlay at a hamfest to help find people, maybe using SSTV is not too crazy after all!! 

Hopefully this is all coming into picture now that amateur radio has some very unique ways to share photos, locations data and valuable information using nothing more than the most inexpensive handheld amateur radio like a Baofeng UV-5R and a smartphone, that may not have internet service but should already have useful applications on it such as ROBOT36, SSTV Encoder and many more which will also be covered in the future on UNDR Net.

Participating in UNDR Net & Activities

If you would like to register to be part of the upcoming RDF & BBQ which the OMARC club is sponsoring on October 30th 2021 at Ferncliff Forest and would like more information about what you may wish to prepare for,  please use the contact form at hvdn.org/undr 

Other Suggested Reading

• Radio Direction Finding Basics

• RDF in the HV with OMARC & HVDN

• What the heck is APRStt?

• SSTV Images from the ISS

• What's in your kit? - SSTV Enabled Missions

• SSTV with the UNDR Net (Sept 2021) 

Winter Field Day 2021: How was it?

January 30th and January 31st of 2021 marked the 4th annual Winter Field Day which the Overlook Mountain Amateur Radio Club participated in. It also marked the first year that Hudson Valley Digital Network (HVDN) was invited to participate in the event and was the first time, due to COVID, that we operated as a group under the pavilion instead of the cabin at Ferncliff Forest in Rhinebeck, NY.

This year rather then setting up antenna in advance on the Friday before Winter Field Day which starts at 2:00 PM Eastern Time on Saturday, we started to setup our scaled back operation at 9:00 AM Saturday morning.

Even with the single digit temperatures for much of the morning, we made short work in getting the fire going and setting up the generator, radios and antenna.

The goal of all this planning was to attempt to make long distance contacts across the US and beyond using amateur radio spectrum under tough conditions while using emergency power, temporary antenna and easy to set up radio stations.

WFD 2021 plan of attack

The plan was to only operate on the 15m, 20m and 40m bands from 2:00 PM until about 5:00 PM Saturday and then resume operations the following morning and until about 2:00 PM when Winter Field Day ended.

This year due to COVID and cold temperatures, it was hard to make as many contacts from Ferncliff Forest compared to years past and our new digital station proved not up to the task when it came to typing with gloves, so the only contacts that K2OMD were on SSB. 

We did however anticipate that the conditions this year would be a challenge and we set up a remote logging server for those to participate in Winter Field Day from home incase they did not wish to join those that were willing to spend a few hours outside with facemasks, gloves and cold feet.

Under tough conditions, as a group we collected 26 contacts thanks to three OMARC members who used the remote logging system and another 30 during our time at Ferncliff Forest.

Not just CQ CQ CQ WFD DE K2OMD 3O ENY

During the warmest part of the day on Saturday, a few brave souls participated in a mini Fox Hunt at around 3:00 PM Saturday.  This proved a good opportunity to further refine group skills in locating a hidden transmitter using a variety of antenna and other radio direction finding equipment. A basic overview of radio direction finding and our nice informational card can be found here that will also be part of future RDF events.

For everyone involved, it seemed that an enjoyable time was had by all who attended.  Courtesy of CJ KD2IIN, there is a nice short video further highlighting the operating conditions during this frigid version of Winter Field Day.

There were way too many people to thank that made this event possible this year, but we are glad that we had such a great team helping to make this a success and lets hope that the 2022 version will be warmer and without a pandemic to deal with.

Quack! Quack! Its time for some RDF fun with LoRa (and HASviolet)

Joe NE2Z,  head of software development for the HASviolet project has been busy working on application specific use cases for our HVDN LoRa project along with the help of Steve K2GOG for user experience function feedback.

Function before feature

Many LoRa projects hit a roadblock after they reach basic objectives such as basic text chat between units where others such as the Disaster Radio go much further.

Since HASviolet has been initially built around a Raspberry Pi Zero instead of the various ESP32 boards, we are able to do a few things differently from a development perspective and most of which will port over to ESP32 based boards in the future. 

RDF:  To find the duck

Use any directional antenna suitable for 900 MHz or make your own by following our instructions for our open source design.

Here are some photos of the user interface that allows easy to navigate function selection without the need for a  SSH connection after initial configuration for things like messages, call sign, SSID and other parameters.

A more advanced version of the basic game involves a laser sensor to detect when someone is near by the Duck and it can either start quacking even more or stop transmitting just to annoy the hunter.

Timing Is Everything: 7 Days With Kerberos SDR

The long awaited Kerberos SDR arrived last month, but I only recently got a chance to really focus my full attention on this unique device this past week. This article covers my first impressions plus setup helpful tips.

What is Kerberos SDR?

A successful Indiegogo campaign which netted 8007% backing sort of is a big deal in my mind and makes for a nice introduction statement.  The Kerberos hardware and software package was under development for some time and required many people to be involved as covered in a past article in the HVDN Notebook focused on tracking radio signals this past November.

Software defined radio has been top of mind in the hobby community for some time, thanks to inexpensive USB TV tuner dongles that have found a dual purpose as wide range radio receivers, such as the RTL-SDR v3 or NooElec and its various offerings for around the same price.

The Kerberos SDR is at its core, four of these inexpensive and capable SDR receivers assembled into one circuit board along with a number of modifications and upgrades to enable some interesting applications.

As the title of the article implies, timing is everything. At the core of the Kerberos is a shared TCXO clock source which ensures all four independent receivers are synchronized with a high degree of stability.

Last month at TCF, Joe N1JTA showed how important a TCXO is to the MMDVM "hot spot" boards that amateur radio operators are using as part of modern digital voice communications.  This same concept applies with the Kerberos, but essentially on steroids.

Having synchronized receivers allows some real fancy computations to be made using newly created open source software that is packaged with the Kerberos SDR.

Computational you say?

There is an already a well written and detailed quick start guide for using a ready made disk image or how to install the packages and related dependencies to get the Kerberos SDR software up and running, so no need to rehash that here.  But, in order to get the most out of this phase coherent software defined radio receiver, here are a few tips.

     Hardware related

• Power source considerations:  Just like with the MMDVM Pi-Star hotspots, DO NOT use some old 500 mAh USB charger from an ancient Palm Pilot!  The Kerberos SDR needs its very own 2 amp or higher current USB power source that will connect into the USB C port. This is to power all 4 receivers and not for data transfer.  A best practice is to use a separate power source for the Kerberos SDR and another for the single board computer running the demo software.

• Connecting things together: The order you connect things together does matter.  Follow these steps to avoid frustration. First, connect your power source to the Kerberos and let it run for a minute or two.  DO NOT yet connect antenna or USB micro cables to the SDR.  If you peak carefully inside the SDR near the USB connectors, you will see white LED and blue LEDs flickering inside to tell you the Kerberos is powered up.  Second, now it is safe to connect a USB micro cable from the SDR to your compute device. If using the recommended RPI 3B or 3B+,  your third step should be to apply power to the RPI after you have inserted the SD card.  Reasons for this order explained later.

• Calibration:  Try not to bug some of the innovators like Corrosive from the popular SignalsEverywhere "vlog" with basic questions so he can find some more new cool stuff to tell us all about even though he may not mind your questions.  Perform the calibration using the built in noise source and 50 ohm terminations your Kerberos came with. DO NOT skip this step.  Not only will you learn more about the software in the process, but you will avoid frustration when testing out direction finding or passive radar functionality.

• Antennae:  You need four identical antennas.  My initial tests were conducted with these small magnetic mount antennas designed for near the 70cm frequency band.  The real key is identical antennae, especially for the signal location application.  The passive radar application would likely benefit from one directional and one non-directional antenna instead, thus two antennas only are needed for that application.   It would also make practical sense to source some type of metal plate if using magnetic mount antennas, so be sure to order an iron pie plate from Amazon too when ordering antennas if you do not already have one handy. Placing magnetic mount antennae on a ground plan makes a huge difference.

• Temperature:  If you have already experimented with single SDR dongles, you know they get a little hot.  The Kerberos SDR will also run warm to the touch and is normal. If using the SDR for an extended period of time, you may want to invest in a small fan to keep it cool. 

• Raspberry Pi:  The image provided on the quick start page is for the RPI 3B or 3B+.  It will not work correctly with an older Raspberry Pi, so save yourself the trouble. The software is also somewhat intensive, so either run the Kerberos on an RPI3 or a real computer. DO NOT try to use an older SBC or anything not supported that is under powered from a CPU perspective. 

• Taking Kerberos SDR apart:  You will be tempted to take Kerberos apart. DO NOT do it unless you have a good reason to do so.  The 40 pin header under the Kerberos is an alternate way to connect a RaspberryPi with an extended header, but is really not needed.  If you did want to do this, you WILL need to open your Kerberos up and remove a 2 pin jumper inside after almost total disassembly.   Also, that tempting regular size USB port is for future use and will not work UNLESS a pair of chip resistors are removed inside the Kerberos SDR.  The bottom line is, just focus on how Kerberos is configured before thinking about hacks and modifications and get the most out of the hardware as it arrived to you first. 

      Software related

• Demo software:  Its not very polished, but gets the job done.  The biggest thing to be aware of is that your Kerberos WILL NOT work if you did not plug in everything correctly first.  If you see no sample rate with numbers being displayed in milliseconds or seconds, you did something wrong or do not have the right power source or good USB cables.  Do not blame the software first, check your hardware. The software is otherwise pretty straight forward.

• Computational stuff:  You may learn quickly that the RPI 3B+ is under powered at times if you are running wider bandwidth than the default setting of 250 kHz. You can trim this down closer to the width of the signal you are interested in.  You can also change the decimation from its default to any higher number for slower sampling speeds. Both changes will give you lower latency overall.   Same goes with shutting off the spectrum display as it does take a number of compute cycles to visualize 4 simultaneous views of the frequency being monitored. 

Additional stuff

There will be future articles about direction of arrival and passive radar related topics here on HVDN Notebook related to the Kerberos SDR as well as experiences running the demo software on a much more capable piece of computing hardware, but for now follow all these tips and best practices.

Feel free to share your experiences on the RTL-SDR forum for Kerberos SDR and enjoy your new toy. 

Basic Overview: Tracking Radio Signals

Finding the source of a radio signal is sort of a fun thing to do for the modern electronics hobbyist.

Confirming the location of a local FM band music broadcaster, amateur radio station or even your cell phone and maybe your car keys is possible with relatively inexpensive equipment since they all transmit RF energy!

With the much anticipated KerberosSDR nearing availability, which will provide unique radio based location capabilities.

Something unrelated recently reminded me to go back to have a look at RTLSDR_Scanner and its latest developments since it offers a lot of great functionality for those interested in radio signal location options available today.

Both solutions use a software defined radio or SDR rather than a traditional radio. This is one reason that makes both of these solutions really exciting!

The conclusion of this article will show you how to generate a map such as the one below that will show signal/power measurements called an "RF Heat Map" using RTLSDR_Scanner.

Kerbo What?

The well funded IndieGoGo campaign of the phase coherent software defined radio that Carl Laufer of the excellent RTL-SDR.com blog, the design team behind the now named Othernet Project and Tamás Pető who is studying electrical engineering at Budapest University.

This trio has created something that will be able to do some amazing things, but let's first take a look at basic radio signal location theory and another modern radio signal location tool.

What is phase coherence?

Let's first look at some basics of radio signal location through some easy to understand math.

If two people (1 &2) knew exactly how far apart they were  (A) and had directional antennas that could help find the maximum signal strength of a transmitter (3), they can use the angles of the signal direction and the known distance between them (A) to guess pretty closely on the approximate direction and distance (B&C) of the signal source (3).

This method of signal location is called triangulation.Radio signals travel at about the speed of light which is about 982 million feet per minute. 

If our two friends standing at location 1 and 2 had identical and synchronized clocks and had radios tuned to the frequency of the transmitter at 3, they could also determine the direction of the signal by moving around a little to see how the signal strength fluctuates, they could also determine the general location of the transmitter with a little more help by use of doppler theory.

Doppler works by sensing how a received signal's frequency (2) fluctuates up or down based on the speed it is traveling and how long it takes to go from source to receiver (1). with multiple antennas (A,B, C, D) .

If multiple receivers/antennas are used at the same time, the difference in time it takes to be received at each can be used to calculate a direction of the signal.

Some form of very fast analog or digital computing and comparison that is part of the receiver is needed since we are talking about nano or millisecond differences.

Phase coherence combines theory behind the speed of which radio signals travel against a known time source along with triangulation in order to find where a signal is coming from.

Police departments have been using a phase coherence system to locate stolen cars for many years called LoJack.  

If you look closely at the roof of the New York State Police cruiser above,  the four antennas on the roof spaced in a square pattern roughly about a foot apart help perform the triangulation and time difference of arrival (TDOA) measurements to quickly locate the stolen vehicle. 

All the police officer generally needs to do is view a display not too different from a no longer in  business company that offered a device called the Ramsey DDF-1 Doppler Direction Finder.

The doppler method of signal location involves the ability to visualize the arrival angle of signals relative to one another of equally spaced antennas through the use of a series of LED lights spaces in a circle pattern.

A special circuit compares the received signal strength at each of four antennas relative time or direction of travel in order to give the direction towards the signal

As the police car travels, the LED lights would blink in the direction where the signal is coming from, if it is in one location. This would tell the officer (or amateur radio operator) which way a signal was coming from and they could try to get close to its location.

Once close enough to a signal, other methods could be used such as a field strength meter to find the smallest of hidden transmitters or chopped out hidden LoJack units. 

HVDN Field Strength Meter Monday is coming back. 

Here is where it started and where it is headed next

Twenty or more years ago, doppler based analog solutions were almost as fancy as one could get in locating transmitters.

In 2018, however, things have come a long way thanks to SDR and even embedded computing devices like the raspberry pi, which can also be used to run RTLSDR_Scanner and the KerberosSDR.

Heat Maps and GPS

The RTLSDR_Scanner application is a little more simple than KerberosSDR. An inexpensive software defined radio (SDR) receiver along with a GPS USB dongle can be purchased together for less than $40 USD.

KerberosSDR, is essentially four SDR's combined into one unit, so should also be able to use the RTLSDR_Scanner software too.

The SDR and GPS along with one antenna, a computer (laptop or Raspberry Pi) and the appropriate software can perform some interesting signal location applications.

GPS provides the function of providing accurate location of the receiver along with a stable time reference.

The locations coordinates, exact time and signal strength of the signal can be combined to provide stunning visualizations of how strong or weak a signal is on mapping programs such as Google Earth

Lets get SDR_Scanner working

In 2016, this program was only operational under a linux computing environment, so was not easy to set up unless you were very involved in computer "stuff".

This program has been available as a much easier to install Microsoft Windows version since last year and is finally what this article is about!

You will need the following hardware and software along with a little patience and clear mind.

Hardware

• SDR dongle (Suggest the RTL-SDR v3, but pretty much any will work)
• USB GPS with NMEA output (Suggest the uBlox7 Gmouse)
• Modern Windows Computer (Meant to run Win7 or later!!)
• Antenna for frequencies of interest (Most SDR come with a basic antenna or add on options)

Software

• RTLSDR_Scanner Software (Versions are clearly explained on Al's website)
• ublox u-center test software (Optional, but nice to have anyway)
• SDR# Receiver Software (Optional, but you should have this already, right?)
• Google Earth (If you want to see the real time location of signals on a map, you need this)

First, lets make sure your SDR receiver is functional.  The best tutorial on this can be found here.  

Step 1:  Get your SDR working:  https://www.rtl-sdr.com/rtl-sdr-quick-start-guide/ 

Try listening to some FM broadcast music between 87-108MHz,  weather broadcasts in the 162.4 to 162.6 MHz range or for local amateur radio or business/first responder activity between 420-500 MHz.

Now, let's get your GPS working

The USB GPS should automatically recognize and install drivers for most people on a Windows 7 or 10 computer.

After installing the ublox center program and just playing around with it to show it can receive location data, make a note of what COM port the GPS has decided it will use. 

Note:  The GPS obtains a virtual serial port over USB. You DO NOT need any outdated USB to 9 Pin serial adapter.

The instructions for getting RTLSDR_Scanner are cracking fantastic, so give them a read here and you should be up and running fairly quickly

Step 2:  RTFM = RTLSDR_Scanner Instruction Manual

Try tuning to local weather or music broadcasts to see what activity looks like in a one megahertz wide segment would look like.

The above image shows from 162 to 163 MHz, with a very powerful signal located at 162.475 MHz (Local weather broadcast) and how the signal fades slightly over just a few seconds from 12:04:19 to 12:15:50 due to driving around at a slightly variable speed.

A pinch of GPS and a cup of Google Earth

Now that you have a feel for how the GPS and SDR with RTLSDR_Scanner function, lets combine the two now by enabling GPS data to get combined with RTLSDR_Scanner output.

Below is what exporting the RF signal data looks like over the same 11 minute period when combined with GPS location data as output against Google Earth map.

Step 3: Use this opportunity to install Google Earth if you do not have it already. 

You will need to enable GPS under the "Edit" menu of RTLSDR_Scanner and ensure you change GPS type to "NMEA (Serial)" and select the COM port your USB GPS has.

When everything is configured correctly, you can use RTLSDR_Scanner to show what GPS satellites are being received and also when you get a location lock, your GPS coordinates and altitude will appear in lower right part of the application.

All that is left now is to go drive (or walk?) around with your laptop and start taking some measurements.

Depending on the refresh rate (dwell setting) and resolution (FFT Size setting), the output image on Google earth may vary.

Helpful Note:  Be sure to set mode to "continuous" and not try to sweep too wide a frequency range. Keep it to the smallest based on the signal you are looking for.  YOu also need to indicate how many sweeps to perform or otherwise, it will just keep overwriting the previous sweep which is not very valuable. The minimal setting is 1 MHz. This will help create the best results viewed on the map. To generate an the images in this article required 115 continuous sweeps.

Major benefits with RTLSDR_Scanner 

Here is a list of possible real life user cases that this application will enable:

• Creating a coverage map for amateur radio repeaters in the 144, 220, 440, 900, 1200 bands

• Determining general radiation patterns of a mobile or home amateur radio antenna installation

• General location awareness of commercial radio or broadcasters

• Interference source location finding

• Figuring out the range of your garage door opener or other pulsed mode transmissions

• Basic passive radar system

Sadly, RTLSDR_Scanner is not really designed as a Wi-Fi mapping tool, but by playing around with the dwell setting and using a device like a LimeSDR Mini, HackRF One or ADALM Pluto which are more expensive could give interesting results.

These other SDR options can go to about 6 GHz and not covered by the inexpensive SDR dongles that usually do not go too far past 1.9 GHz plus monitor wider bandwidth of up to 30 MHz wide at one time compared to the 3 MHz wide capable RTL SDR v3.

So what is special about KerberosSDR?

For the price of under $150 USD, users will be able to use the hardware and software along with four antennas to generate a heat maps just like RTLSDR_Scanner and also show signal direction using phase coherence theory through new software that Tamás Pető is focused on where an early version is demonstrated here:

Hope you found this article about basics of radio signal location interesting and something to keep you occupied while HVDN awaits its pre order of the KerberosSDR which will then be reviewed here later this winter.