Fishing In the Woods: Looking for Radio Signals

This was the first Winter Field Day that justified a reason to purchase an ice fishing tent.

The tent manufacturer claims you can set this up in under a few minutes and pack it up even quicker.  Lets see what the breakdown looks like.

 

Inside the Tent:  Gear needed

We all like lists right?  Here is what was in use in the photo below.

• Icom IC-705

• Emtech ZM-2 Manual QRP Tuner

• Heil HTHD-Y headset

• Lenovo T495 laptop

• 12aH DIY LiPoFe4 battery pack

• Polaroid Brand Travel Tripod

(Photo Courtesy:  Ken Campbell AD2T)

Excluding the table, chair and propane heater, this was a minimal operation which proved pretty comfortable even in the low temperatures during Winter Field Day.

The goal was to operate 10m or 15m  PSK31, JS8CALL or SSTV but most of the time it seemed that FT8 was more popular, so that would not count for Winter Field Day. Too bad!!   The 15m band was wide open which was really nice.  A few contacts were made on 40m SSB, hence the need for the headset.

Antenna Questions

A 40m Off Center Fed home made dipole was used with good success.  This design allows for 40m, 15m and 10m operation without really needing the tuner..  One leg of the dipole is 44 feet and the other is 22ft.  At the center point is a 4:1 DIY balun.  The antenna center was mounting with velcro ties on the 20ft orange Jackite fiberglass mast.   

The mast was secured to the ground with a ground stake and length of PVC pipe which the mast simply slides over.  The longer end of the dipole was attached to a nearby tree with a length of paracord.  The shorter end was attached to an artificial tree known as a tripod.

Even with heavy winds, the antenna system as expected maintained upright for the 24 hour event in the frigid cold!

This antenna system works great and easily stows in a bag designed for audio equipment.  Many other accessories for additional HF and VHF antenna also fit in this bag along with a few 25 and 50 foot RG-8X feedlines. 

I would estimate that my entire antenna kit which includes the storage bag, surplus tripod (RIP KE2EJ), feedlines, support stake, full wave 2m loop, Arrow II antenna, 40m OCF, 10m-17m-20m-30m linked dipole,  End Fed 40m/80 and a few other odds and ends cost less than $200.  This is a lot of antenna gear for different applications mostly meant for POTA operations and not SOTA activity which is much smaller scale.

(Photo Courtesy:  Ken Campbell AD2T)

An article like this can get really long if I wanted to detail how to set up Wi-Fi on the Icom IC-705 to talk to the laptop with virtual com ports and audio cables, but there are great tutorials on YouTube which cover that already.  

The only issue I really ran into which continues to be a level of annoyance is that the "705" has such a broad front end that semi decent antennae can easily overload things, so backing the RF gain down is a good idea.  

Nearby strong out of band signals also are problematic and an external band pass filter will be needed for the 705 to perform better during group special events like Hudson River Radio Relay coming up in June..

Last year during that event, the 705 on the 6m band was useless when nearby 20m or 40m CW and SSB activity was taking place.

Not really sure if this article answered any questions for anyone, but it was fun setting this up for Winter Field Day and spending some time playing radio plus teaching others about how to set up a minimal self contained field station.

RDF in the HV with OMARC and HVDN

As the article title suggests, the recent radio direction finding (RDF) event in the Hudson Valley (HV) thanks to both the Overlook Mountain Amateur Radio Club (OMARC) and Hudson Valley Digital Network (HVDN) was a fun time to be socially distanced and educational simultaneously.

Here is a summary of the first "Fox Hunt" to take place in northern Dutchess County since COVID-19 disrupted normalcy while using directional antennae to find a hidden transmitter.

Did we find Alf at Ferncliff Forrest?

Funny things happen when amateur radio operators invade local nature preserves when waving around strange looking antenna contraptions.

The goal of this joint radio direction finding event between two great organizations and its membership was to hide a remotely controlled transmitter box known as a "Fox" and participants were going to try to find it/catch it somewhere in the well maintained Ferncliff Forest Game Preserve located in Rhinebeck, NY. 

Ahead of the hunt which took place on November 21st, many hunters constructed a directional antenna known as a Yagi which was optimized for finding the location of transmitters thanks to Joe WB2HOL, formerly of the Hudson Valley and charter member of the Putnam Emergency & Amateur Radio League (PEARL) club before relocating to warmer weather in North Carolina.  

Made from inexpensive materials such as PVC pipe and discarded tape measures, each hunter was able to find the peak and null of the hidden transmitter to help find which direction to travel and be the first to find the transmitter hidden which was inside a common case found at Harbor Freight Tools. 

While conducting some pre-event education in the parking lot and during the hunt, a number of families who were out enjoying the day commented about our antennae and some children thought we were looking for aliens when they heard the signal coming from each hunters radio. 

1st Hunt Near Success Story

Steve K2GOG was the organizer of the event and was tasked with hiding the fox after a basic  demonstration of antenna and radio direction finding theory for those who would go and try and find the transmitter.

Beyond the easy to build Yagi antenna designed for the amateur radio 2m wavelength band at a frequency of 146.565 MHz, Steve showed off other options he has used such as a handheld TDOA from Rainbow Kits (Time Delay of Arrival) and UHF half Egg Beater, of Steve K2GOG own design and inspiration for the HVDN HASviolet antenna V1 on 900 MHz.

Lloyd K2JVX brought his Arrow DF loop antenna which amazed other attendees at how small it was. Rob W2RWS was eager to try his Arrow II antenna and its 70cm capability for tuning to the harmonic of the transmitter found on 439.965 MHz. All these mentioned types of antennae are easy to build or purchase and each offers unique benefits and challenges when used for RDF.

The hidden transmitter was based around the combination of a Byonics Piccon V2 and a Lanch HG-UV98 radio. This arrangement provided the primary ability to remotely control the transmitter by sending a DTMF tone to sequence the transmitter which sent out a combined set of random tones followed by a cryptic Morse code message on 146.565 MHz that the hunters used to find the fox. 

The secondary ability was to also transmit an APRS beacon on 446.500 MHz which allowed GPS, temperature and voltage to be sent back to Steve K2GOG should the fox become abducted by someone or malfunction in some way.

Lloyd K2JVX was the first to find the transmitter hidden towards the rear of the pond.  Rob W2RWS was close behind and both hunters almost found the fox before it stopped responding to command codes, which meant a rescue operation was needed.

Bob KD2QAK used a different method to find the fox by taking signal readings at known locations and plotted the direction of the signal on a map. He drew lines to see where they intersected and clearly defined the general area where he thought the signal was coming from.

This first hunt was very successful as it taught everyone that multiple techniques and equipment could be used to find the general location of a fox, but the strong 1 watt signal actually made it hard to find the fox as each hunter got pretty close to it, even within the last 15 feet. Other equipment designed for closer detection was needed.

Attention about attenuation

While a 1 watt signal radiated from a simple Radioshack telescoping antenna sounds like it would be easy to find, its strength made it hard for all hunters, so a demonstration using a dummy load as the antenna was done to show how to better tune to the null of the fox or how to attenuate the received signal through the use of methods like the "body fade" method using a standard rubber duck or better design or selection of antenna or receivers.

Certain radios like the Kenwood TH-D74 and Icom IC-R20 seemed to work the best due to advanced attenuation and  RF gain features. Much more inexpensive radios like the Yaesu FT-70DR, Yaesu FT-4XR did not due as well since the receivers in them were easily overloaded by strong local signals. 

Guy KD2TLF found success by tuning away 10 or more kHz away from the actual signal to attenuate the signal in his Yaesu FT-4XR while both Bob and Zina focused on using the harmonic and null to get closer to the fox with the FT-70DR. 

We also learned as a group that the dummy load Steve used radiated its signal horizontally compared to the RadioShack antenna which was vertically polarized. This knowledge may come in handy for the future to confuse future hunters.

Walk in the woods: 2nd hunt results

As Lloyd found the first fox, he was elected to hide the transmitter for the next round. After an unexpected malfunction with an external blinking safety light on the fox, the hunt was declared open season and the hunters took off to see where Lloyd hid the fox.

Steve K2GOG decided it may be an unfair advantage to use some of his more advanced tools like the TDOA array or even his specialty field strength meter, so he started the hunt using nothing more than the standard rubber duck with his Kenwood TH-D74 and relied upon the body fade method of signal detection.  

He got his bearing by holding the radio close to his front and rotated around until the signal decreased towards his rear.  Walking another 15-20 away, he took another bearing and did this every so often to see if he was headed in the right direction.

Not too much later, he came across Ken KD2TQS (Official event photographer) who had followed Lloyd into the woods to hide the fox.  Steve knew he was getting close and pressed onward.  

Soon after Steve got to a location that the transmitter must be close to, he found Lloyd sitting on a nearby log having a snack.   Just after a few minutes later while trying to get closer to the fox, Rob W2RWS and Guy KD2TLF showed up from a different direction trying hard to find the fox.

Because Lloyd was tricky in where he hid the fox next to a thick tree that was tilting over at about a 30 degree angle and some rocks that are known to contain iron ore, it took the 3 hunters more than 20 minutes to find the fox which was covered with leaves and its antenna just barely poking out.

Steve followed by Rob and Guy finally found the fox and we decided to call it a day after roughly 3 hours and 10,000 steps in Ferncliff Forest. 

Final words

After the group met back up with Bill KD2UEN and Zina KD2UEO back at the parking lot, some prizes were awarded to commemorate the event.  An offset attenuator kit courtesy of KC9ON was awarded to Rob, a dual band rubber duck was given to Lloyd and a set of orange and black zipties were given to all other participants.

Much was learned during this on foot fox hunt and the day was enjoyed by all who came out to brave the nice weather and clean air away from home.

We are going to be planning future events like this and weather permitting, the next fox hunt will likely take place during the Winter Field Day event that OMARC has done the past few years.

Please visit the 146.805 MHz repeater broadcasting from high atop Overlook Mountain in Hurley NY to talk to those mentioned in this article and to learn about Winter Field Day 2021 or other OMARC activities. 

OMARC/HVDN Fox Hunters pictured right to left are Guy KD2TLF, Zina KD2UEO, Bill KD2UEN, Rob W2RWS, Lloyd K2JVX and Steve K2GOG

AO-92 & 3 steps for communication success

In January of 2018, the AO-92 satellite was put in orbit and was soon operational for amateur radio operators looking to communicate with other like minded enthusiasts.

A recent contact made between Steve K2GOG in FN30 and Alan VY2XU in FN86 using AO-92 satellite on April 26th morning to show a typical satellite communication footprint.

The AO-92 satellite, also known as Fox 1D was launched from the Satish Dhawan Space Centre in Sriharikota, India.  This small "cubesat" allows users on Earth to transmit on 435.350 MHz and then get real time repeated back out from the satellite over 145.880 MHz for others to hear.

The orbit height is about 250-320 miles above Earth at any time, so any station within a radius covered below the satellite is possible for just a few minutes until the next time the satellite passes over again. The potential range of communications is almost 800 miles!

30 other "cubesats" were deployed at the same time from the PSLV-C40 rocket

It is very easy to hear the AO-92 using a basic directional or whip type of antenna and appropriate radio. The receive or "down-link" frequency of 145.880 MHz is not as affected by the speed at which the satellite is traveling which is about 5 mile per second.

However, the transmit or "up-link" frequency is and the user needs to slightly adjust above or below 435.350 MHz depending if the satellite is headed towards or away the user location. This is known as "Doppler Shift".

The AO-92 satellite will appear to be on frequency when it is as close to the user as possible, but as it moves further away it will seem up to 15 kHz different which makes communicating through a satellite like this a little challenging at time.

The higher up in frequency has a greater affect when it comes to the Doppler affect which is why the satellite uses a lower 145.880 MHz in order to make it easier hear and encourage people to listen for it.

Beyond knowing the correct transmit and receive frequencies, the user also needs to transmit a sub audible tone of 67 Hz.  This is needed to prevent interference from getting into the satellite.  This tone is almost like a secret password needed to use the satellite. Without it, you can hear the satellite fine, just not be able transmit and be repeated back to Earth.

Helpful tips for using the AO-92 satellite

• Listen a few times to get familiar what satellite users talk about before transmitting
• Program your radio in advance of the satellite pass
• Be courteous to other users and keep communications short

Using less than 2 watts of transmit power is all that was needed to contact Alan 600 miles away thanks to the AO-92 satellite.   To generate a helpful grid overlay to easily identify where other stations are located using as few as 4 characters, here is a nice file provided by Ari  OH2ECG to be used with Google Earth.