Tech Night – Getting Started in EME (Click to View The Presentation)
We recently did a Tech Night Program as part of the Nashua Area Radio Society’s educational program. I wanted to share the presentation and video from this Tech Night so that our readers might learn a little more about how to get started in EME or Moonbounce Communications.
April 2020 Tech Night Video – Getting Started in EME Communications
Now that spring is here, we’ve continued work on our EME station project. The most recent project was to build complete the ground system for our new EME tower. The proper way to ground a tower is shown above. Each leg of the tower is connected to an 8′ ground rod via a heavy-gauge ground cable. The cable is attached to the tower leg using stainless steel clamps meant for this purpose. The three ground rods associated with the tower legs are then bonded together using a heavy copper ground cable ring.
The final step was to connect the bonding run from the tower to the perimeter grounding system around our house. This completed the tower grounding system and enabled us to complete our final permit inspection courtesy of our local building inspector.
Finished Tower Base
With all of this work done and the inspection complete, we added a mulch bed around our new tower to make this area of our lawn easy to maintain.
The next step in our project is to begin building the antennas that will go on our EME tower. You can read more about our EME station project via the links that follow:
Our goal for this phase of our EME Station Project is to get our new tower up, install the Azimuth Rotator and Mast, and run the hardline and coax cables for our antennas from the shack to our new tower. Our EME tower is constructed using Rohn 55G tower sections. It will be 26 ft tall and will have approximately 18″ of our 3″ mast protruding above the tower. The tower is a free-standing/guyed hybrid design with the first section being cemented into the ground.
Matt, KC1XX, and Andrew of XX Towers began by installing a winch and a gin pole on the base section of the tower. They used the Gin Pole to hoist the second tower section into place and secure it. They also attached the top plate to the third tower section in preparation for installing it along with our mast.
Mast and Top Tower Section Going Up
It is always a challenge to install a mast inside a new tower. The mast we are using is a heavy, 22 ft 4130 chrome molly steel mast that weighs over 250 lbs. Getting the mast inside the tower was quite a feat! Matt and Andrew rigged the top tower section and the mast together and pulled both up together on the Gin Pole. Next, one leg of the top tower section was attached and a second pully was used to pull the mast up through the top tower section until it could be placed inside the tower. The last step was to raise the top tower section a second time using the Gin Pole to seat it on top of the rest of the tower. Finally, the mast was lowered inside the tower to the base and the top tower section was bolted on to complete the tower.
Upper Guy Anchor Bracket on Tower
The next step involved attaching the upper guy anchor bracket to the top section of the tower and rigging the guy anchor cables. We decided to use Phillystran Guy Cable to avoid interactions with our antennas.
Guy Anchor Cable
The completed cables are tensioned using turnbuckles. We adjusted the cables to plumb the tower and then safety-wired the turnbuckles so they will not come loose.
Azimuth Rotator in Tower
The next step was to install an M2 Antenna Systems Orion 2800G2 Azimuth Rotator in our tower. The use of the 22 ft mast allowed us to place the rotator about 5 ft above the ground where we can easily service it in the future. The long mast also acts as a torque shock absorber when the rotator starts or stops moving suddenly. With the rotator in place, we attached the mast and clamped it at the rotator and thrust bearing at the top of the tower.
Pushing Coax Cables and Hardline Through the Conduit
We used a cutoff plastic bottle to protect the ends of the coax cables and hardline as we pushed them through approximately 50 ft of buried 4″ conduit. The conduits were constructed to create a gradual turn into and out of the ground and the cables went into the conduit smoothly.
Coax Cables Exiting the Conduit Near Our Shack
With the cables in place, we installed N-female connectors on each end of the 7/8″ hardline. We used rubber reducers to make it easier to deter water from entering the conduits where the cables exit.
We decided to use a pair of LMR-600 coax cables for the receive side of our feedlines. We made these cables from an unterminated length of LMR-600 coax measured to cover the distance from the top of our planned 26 ft EME tower to the ground block at the entry to our shack. The cables are approximately 82 ft long and they must be cut to be equal in length to with 1/16″!
The easiest way to measure the length of an unterminated coax cable is to determine the minimum frequency of resonance of the cable when the opposite end is an open circuit. One can then use the speed of light and the velocity factor of the cable to compute its exact length:
Length = (Speed of Light X Velocity Factor) / (Resonant Freq. X 4)
Doing these measurements with an open circuit at the far end of the cables enables trimming the length of the two cables to be matched in small increments until our two cables are exactly the same length.
Vector Network Analyzer (VNA) Measurement of Open Coax Cable Resonance
We used an Array Solutions VNA 2180 connected to a Windows PC to precisely measure the minimum Resonant Frequency of our LMR-600 coax cables as we trimmed them. Once they were equal in length to within 1/16″, we installed an N-Female connector on the unterminated end and re-verified each cable’s length. A frequency accurate antenna analyzer can also be used to make these measurements.
We will need to repeat these steps of the receiver-end and antenna preamp box jumper cables which will make up the rest of the receive side feedlines for our EME antenna system once these components are installed. We also plan to make a final end-to-end measurement of the receive-side feedline assemblies to fine-tune the phasing of the completed feedline runs.
With this step complete, we are ready to put up our new tower and attach the feedlines.
Here are some links to other articles in our series about our EME Station 2.0 project:
The first part of our EME project is to put up a new tower to support our antennas. Our plans call for a 26′ tower built using three Rohn 55G tower sections. Four feet of the first section of the tower is cemented in a concrete footing to anchor the tower’s base. The tower is also going to be guyed to ensure that it is very stable.
Digging Footings for our New Tower
We are working with Matt Strelow, KC1XX, and Andrew Toth of XX Towers to put up our new tower. Matt brought out his tractor and dug the footings for our tower and for the associated conduits that will carry coax and control cables to our shack. The photo above shows the completed hole and form for the main tower base. Matt is working on the footings for one of the three guy anchors.
First Tower Section and Rebar Cage
Here’s a closer look at the tower base. The footing includes a rebar cage to reinforce the concrete footing. There is also 6″ of crushed stone in the bottom of the hole that the tower legs sit it. It is very important that the bottoms of the tower legs remain open and do not become plugged with cement so that water in the legs can drain. If the legs cannot drain properly, water will accumulate and freeze. This can split open the tower legs and ruin the tower.
Cable Conduits with Drains
We also installed two conduits (a 4″ and a 2″ run of schedule 80 conduits) from the base of our tower to our shack. These conduits will carry coax feed lines and control cables to our new tower. We used a pair of 22° elbows to create a smooth transition to bring the conduits out of the ground. This will ensure that our hardline and other coax cables can be placed in the conduits without creating excessive bends.
Conduits will fill with water even if they are sealed. This happens as a result of the condensation of water in the air. To prevent our conduits from filling with water, we created two drain pits at the bottom of the trench at the two lowest spots in the conduit runs and filled them with stone. We drilled a few holes in the bottom of the conduits above the drain pits to allow the water to drain so our cables will remain dry.
Cadweld’ed Ground Cable Bonded to a Ground Rod
We also created a bonding ground cable run from our new tower to the ground system at our shack entry. The bonding system was created by driving an 8′ ground rod every 10′ in the trench between our new tower and the perimeter ground around our house.
#2 stranded copper ground cable was Cadweld’ed to each ground rod to create a ground path to bond the tower to the perimeter grounding system around our house. Using a Cadweld system is simple and produces strong connections that will not deteriorate.
Here’s a video that shows our a Cadweld is made. We’ll cover completing the ground connections to the tower and the perimeter grounding system in a future article.
Completed Footings – Ready to Pour Cement
Finally, we used some sections of rebar to firmly support the guy anchor rods prior to pouring the cement. If you look closely, you can see a portion of the rebar material in one of the guy anchor footings in the photo above.
The next step in this part of our project was to pour the cement. A large cement mixer brought the proper cement mix to our QTH and Matt used his tractor to transport the cement from the mixer to the forms. We did a bit of finishing work on the cement base for our tower and let the cement dry for a few days.
FInished Tower Base and Cable Conduits
The last step was to remove the forms and backfill the footings. A little work with a cement finishing block was done on the cement base to round off the rough edges left by the forms. The cable conduits emerge from the ground next to the tower base. You can also see one end of the copper bonding cable next to the conduits as well.
Completed Guy Anchor
Here’s one of the completed guy anchor rods after backfilling. We are going to let the cement harden for a couple of weeks and then we’ll complete the construction of our new tower.
Here are some links to other articles in our series about our EME Station 2.0 project:
EME or Earth-Moon-Earth contacts involve bouncing signals off the moon to make contacts. EME provides a means to make DX contacts using the VHF and higher bands. There are also some EME Contests including the ARRL EME Contest that provides opportunities to make EME contacts.
Understanding EME Propagation is a project in of itself. The following is a brief overview of some of the (mostly negative) effects involved.
The path loss for EME contacts varies by Band and is in excess of 250 dB on the 2m band. There are some significant “propagation” effects that further impair our ability to make EME contacts. These include:
Faraday Rotation – an effect which results in the polarity of signals being rotated by differing amounts as they pass through the ionosphere on their way to the moon and back
Libration Fading – fading caused by the adding of the multiple wave-fronts that are reflected by the uneven surface of the moon
Path loss variations as the earth to moon distance varies – the moon’s orbit around the earth is somewhat elliptical in shape resulting in a distance variation of approximately 50,000 km during the moon’s monthly orbital cycle. This equates to about a 2 dB variation in total path loss. An average figure for the path loss for 2m EME might be in the range of 252 dB.
Transit Delays – at the speed of light, it takes between 2.4 and 2.7 seconds for our signals to travel from earth to the moon and back.
Noise – the signals returning from the moon are extremely weak and must compete with natural (and man-made) noise sources. The sun and the noise from other stars in our galaxy are significant factors for EME communications on the 2m band.
Doppler shifts – as the earth rotates, the total length of the path to the moon and back is constantly changing and this results in some frequency shift due to doppler effects. Doppler shift changes fairly slowly compared to the time it takes to complete a 2m EME QSO so it is not a major factor for the 2m band.
Moon’s size vs. Antenna Aperture – the moon is a small target (about 0.5 degrees) compared to the radiation pattern of most 2m antenna systems. This means that most of our transmitted power passes by the moon and continues into space.
Taking the moon’s size, an average orbital distance, and an average Libration Fading level into account, one can expect only about 6.5 % of the power that is directed towards the moon to be reflected back towards earth.
EME “Good Guys”
One might look at the challenges associated with making EME contacts and say “why bother”? EME contacts present one of the most challenging and technical forms of Amateur Radio communications. It is this challenge the fascinates most EME’ers including this one. Fortunately, there are some “good-guy” effects that help to put EME communications within reach of most Amateur Radio stations. These include:
WSJT-X and the JT65 Digital Protocol – In the early days of EME communications, one had to rely on CW mode to make contacts. All of the impairments outlined above made these contacts very challenging and the antennas and power levels required put EME communications out of the reach of most Amateurs. Along came Joe Taylor’s digital JT65 protocol which changed all of this. It is now possible to make 2m EME contacts with a single (albeit large) 2m yagi and 200W or so of input power. As a result of these innovations, many more Amateurs have built EME stations and are active on the 2m (and other) bands. Many DXpeditions are now also including EME communications in their operations.
Ground Gain Effects – a horizontally polarized antenna system will experience approximately 6 dB of additional gain when the antenna(s) are pointed approximately parallel to the ground. Ground gain effects made it possible for us to use our single 2m antenna to make our first 2m EME contacts.
MAP65 Adaptive Polarization – Fading resulting from polarity changes due to Faraday Rotation can cause a received signal to fade to nothing over the period of time needed to complete a 2m EME contact. These polarity “lock-out” effects can make contacts take a significant amount of time to complete. Fortunately, a version of the software which implements the JT65 protocol called MAP65 has been created that will automatically detect and adapt to the actual polarity of signals returning from the moon. More on how this is achieved follows below. MAP65 is most useful for making “random” EME contacts during contests. In these situations, a variety of signals will be present in a given band with different polarities, and the MAP65 software can adapt to each one’s polarity and decode as many simultaneous signals as possible.
Commercially Available Amplifiers for the VHF+ Bands – Modern, solid-state amplifiers have become much for available for the 2m band (and other VHF and higher bands). This has made single-antenna EME on 2m and above much more practical for smaller stations with a single antenna or a small antenna array.
Our 2m EME Goals and Station Design
We began this project by making a list of goals for our 2m EME Station 2.0. Here is that list:
Operation using JT65 and QRA64 digital protocols and possibly CW on the 2m EME band
80th percentile or better station (i.e. we want to be able to work 80% of the JT65 capable 2m EME stations out there)
Operation in EME contests and EME DX’ing; earn a 2m EME DXCC
We have come up with the following station design parameters to meet these goals:
An array of four cross-polarized antennas with an aggregate gain of approximately 23 dBi
The combined gain of the system will be approximately 23 dBi with a 3 dB beamwidth of 12.5°. The XP28 antennas are designed for stacking and have good Gain/Temperature (G/T) characteristics. G/T is a measure of the gain and noise performance of an antenna system. See VE7BQH’s tables for some interesting data on G/T for many commercially available EME and VHF+ antennas.
The antenna system will have separate feeds for the antenna array’s Horizontal (H) and Vertical (V) planes. The Horizontal elements will be oriented parallel to the ground to maximize ground gain when the H plane is used for transmitting (and receive). A pair of 4-port power combiners will be used to combine the H and V polarities of the four antennas into a pair of H and V feedline connections.
M2 Antenna Systems will be supplying a MAP65 Switching and Preamp System that will mount on the tower near the antennas. The MAP65 Housing provides switching and separate receive preamplifiers and feedlines for the H and V polarities of the antennas. Separate H and V receive coax connections bring the Horizontal and Vertical elements of the antennas back to the shack. A third coax connection is provided for Transmit. The transmit feedline can be routed to either the H or the V antenna polarity to help minimize Faraday Rotation related fading at the other end of the contact.
An M2 Antennas S2 Sequencer will provide Tx/Rx sequencing and H/V transmit polarity selection via the MAP65 Switching and Preamp System on the tower. The sequencer is essential to provide safe changeovers between receive and transmit and to protect the preamplifiers and the power amplifier during high power operation.
The signals returning from the moon in an EME system are very, very weak. Because of this, Noise and Dynamic Range performance are critical factors in an EME receive system. In addition, we will need a pair of high-performance, phase-coherent receivers to enable Adaptive Polarization via MAP65.
LinkRF IQ+ Dual Polarity Receive System
We are planning to use a LinkRF IQ+ Dual Channel Receive Converter in our EME system. The Link RF IQ+ features excellent noise and dynamic range performance and its phase-coherent design will support adaptive polarity via MAP65. The IQ+ separately converts both the H and V polarities of the antennas into two separate pairs of I/Q streams.
UADC4 High-Performance 4-Channel A/D Converter
The four channels (two I/Q streams) from the LinkRF IQ+ must be digitized and fed to a Windows PC for decoding. The conventional way to do this is with a 4-channel, 24-bit soundcard. The available computer soundcards add a good bit of noise and therefore limit the overall dynamic range of an EME system. Alex, HB9DRI at LinkRF has come up with the UADC4 – a high-performance 4-channel ADC that is specially designed for software-defined radio. The UADC4 design is based on CERO- IF conversion and is optimized for EME use. The UADC4 should add about 10 – 15 dB of dynamic range improvement over a typical 24-bit PC Soundcard. Alex is currently taking pre-orders for the next run for UADC4 devices. You can contact him at firstname.lastname@example.org for more information.
JT65B Software Block Diagram
Our plans for JT65 software and related components for our EME station are shown above. We are planning on running a combination of Linrad and WSJT software on the same Windows PC to handle JT65B QSOs. There are two configurations that are applicable to our plans:
We are also planning to develop a simple windows application that will read the Moon Tracking data that is generated by WSJT MAP65 and WSJT-X and use it to control the rotator system associated with our EME antennas. More on this to come in a future article.
Well, that about covers it as far as our 2m EME goals and station design go. The plan is to break ground for the new EME tower later this week. We’ll continue to post more articles in this series as our project proceeds.
Here are some links to other articles in our series about our EME Station 2.0 project:
The IC-9700 is a new VHF/UHF radio that is based upon the Software Defined Radio (SDR) platform that Icom uses in the IC-7300 and IC-7610.
It looks like this is going to be an excellent radio for Satellite, EME, and other weak-signal work on the 2 m, 70 cm, and 23 cm bands. The IC-9700 features a pan adapter display which will be very useful for working contacts through linear satellites.
Based upon previous new Transceivers release by Icom, I would guess we are at least 8 months to a year away from the time when this radio will be offered for sale in the USA.
Here’s some video of the forthcoming IC-9700 as well as other gear from Icom. The video also features other new products and updated Firmware capabilities from Icom. Enjoy!
Anita and I were quite active on the bands in 2013. Together we made 20,650+ contacts from a combination of our home and mobile stations and we worked a combined 259 DXCC Entities.
Combined 2013 QSOs By Band
We were active on all of the Amateur Bands available in the USA from 160m through 70cm except for the 60m and 1.25m bands. The picture above shows the distribution of our QSOs across the bands in 2013. Both of us participated in quite a few contests in 2013 and this resulted in the 5 major contest bands dominating our operating activity. I did quite a lot of work on the 160m band this year and I participated in several 160m contests to gain experience and to begin working towards a DXCC on this band. We worked a total of 50 DXCC Entities on 160m in 2013. Our 6m, 2m, and 440 MHz (70cm) contacts were made mostly during VHF/UHF contests that I participated in.
Combined 2013 QSOs By Mode
We like to operate using many different modes. Anita (AB1QB) does quite a bit of RTTY contesting and she accounted for the bulk of the activity in the digital modes from our station in 2013. I made it a point to become active using the CW mode this year and I made 1,550+ contacts using CW in 2013 including participation in several CW contests. Operations in SSB Phone mode dominated our activity this year mostly due to our operations in SSB Phone contests and as one of the New Hampshire Stations in the 2013 Colonies Special Event this year where we made a combined total of 6,200+ contacts.
QSL Cards Ready To Mail
We really enjoy sending and receiving QSL cards. We sent 5,800+ QSL cards this year, averaging approximately 110 cards sent each week. We also QSL’ed via eQSL and Logbook Of The World. I am often asked what percentage of our QSL requests are confirmed. For 2013, we received confirmations for 67% of our direct/bureau cards, 31% of the QSOs uploaded to eQSL, and 37% of the QSOs upload to LoTW. These numbers will undoubtedly rise a time goes by.
Anita has held a DXCC for some time and has been focusing on a number of JARL Awards. She completed her Japan Century Cities Award for confirming contacts with 100 cities in Japan in 2013.
AB1QB Operating In The BARTG RTTY Contest
Contesting was a big part of the operations from our station this year. I was active in several major SSB and CW contests this year and Anita was active in quite a few major RTTY and phone contests as well. We are both licensed for less that 3 years and have been competing in the Rookie or Novice categories in most contests and we have been doing quite well. Anita took 5th place in the world in the 2013 BARTG RTTY Contest and she has placed 1st in our call area in several of the 2013 ARRL Rookie Roundups in both SSB Phone and RTTY.
2013 CQ Worldwide WPX SSB Certificate
I placed 1st in North America/2nd in the World in the 2013 CQ WPX SSB Contest (Rookie High Power) and 1st in North America/2nd in the World in the 2013 CQ WPX CW Contest (Rookie High Power). Contests have provided us a great deal of operating experience and have contributed greatly to our completion of several operating awards.
Mobile Installation In Ford F-150
Station Building was a big part of our Amateur Radio experience again in 2013. We installed a mobile HF setup in our truck and did quite a bit of mobile HF operating. We made 165 contacts from our mobile station in 2013 and worked 41 DXCC entities.
WSJT EME QSO – Waterfall
I also made my first Earth-Moon-Earth Contacts on 2m in 2013. I made 30 contacts on 2m using the moon as a reflector, working a total of 16 DXCC Entities this way.
AB1QB Operating The Flex-3000 Software Defined Radio
We added a Flex-3000 Software Defined Radio (SDR) to our station in 2013 and have been using it to learn about this new technology. The performance and operating capabilities of SDR are making SDR a big part of the future of Amateur Radio in our opinion.
8-Circle Receive Array System Diagram
Antenna projects were also a part of our station building work in 2013. We installed an 8-Circle Receive Array System for 160m – 40m and this new antenna system helped us a great deal with DX’ing and contesting on 160m and 80m. We also began the reinstallation of our BigIR Vertical Antenna but the onset of winter here in New Hampshire caused us to delay the completion of this project until spring. Finally, we made the switch to the excellent DXLab logging and DX’ing software suite. DXLab helped us a great deal with QSL’ing and tracking our progress toward operating awards.
2013 Field Day CW Station Operations
We were part of the 2013 Field Day team at our local radio Club (PART in Westford, MA). We provided and managed the digital station as well as the setup of a portion of the antenna systems for our club’s field day operations.
ARRL At Dayton 2013
Anita and I attended the Dayton Hamvention again in 2013. The Dayton event is always a great opportunity to see the latest in Amateur Radio equipment. We attended the 2013 Contest University which was held as part of the Dayton Event and used the information that we learned there to continue to improve our contesting skills.
Fred Lloyd AA7BQ, Founder Of QRZ.com
The internet was a big part of our Amateur Radio experience again in 2013. We met Fred Lloyd, AA7BQ who visited us to do an article on QRZ.com on our station. We learned a great deal from Fred during the time that we spent with him as part of this project. We published 47 new articles here on our blog in 2013 and have received over 45,000 views from our readers in 152 countries around the world. We really appreciate the interest from the HAM community and we will continue to publish new articles here in 2014.
As you can tell from this article, 2013 has been a very active year for Anita and I. I’ve created the video above to give you some idea of the contacts that we have been fortunate enough to make around the world in 2013. We hope you enjoy it and we want to thank everyone who has taken the time to work us, to end us a QSL card or to read the articles that we have written here.
This past week has been very productive in terms of 2m Earth-Moon-Earth (EME) QSOs. I’ve continued to use the WSJT Software to make Digital EME QSOs on 2m during both the ascending and descending periods of the Moon. To date, I’ve completed 30 QSOs and worked 16 countries on the 2m band using the Moon as a reflector. The countries and stations I’ve worked include:
As you can see from the links to the QRZ pages for some of these stations, many have built fairly sophisticated EME systems.
I2FAK 16×19 EME Array
At this point, I have worked 4 of the 6 continents needed for a Worked All Continents Award via Digital 2m EME. I have set completing and confirming the needed contacts for this award as my next goal. EME contacts are great fun and the EME Ham community has been very helpful to me in getting started.
The first test I did was to bounce some echoes off the moon just as it came up. With the amp on and set for its rated digital mode output of 900 watts on 2m (it will do 1.2 Kw in SSB mode), I heard my signals coming back from the moon for the very first time. The moon was between North America and Europe as it came up and I noticed that several stations from Europe were on 2m EME. After a few CQ calls using JT65B (WSJT mode for 2m EME), S52LM, Milos in Slovenia came back to me and I successfully completed my first EME QSO on 2m! I also worked two other stations on 2m EME from Europe – DK5SO (in Germany) and UT5UAS (in the Ukraine). I suspect some of these folks may have had pretty big EME stations as their signals were very strong. Here’s a snapshot of my first QSO with S52LM:
EME QSO With WSTJ
As you can see from the snapshot, the round trip delay to the moon and back was between 2 and 2.5 seconds. S52LM’s signal was pretty strong at -23 dB or so (he was also using close to 1 Kw on his end). At this level, I could not hear anything audible above the noise in my receiver. The following is what the WSJT waterfall looked like:
WSJT EME QSO – Waterfall
S52LM’s signal is the lines and dots between 0 and 200. These are fairly strong signals by EME standards. The WSJT software’s performance on such weak signals is pretty amazing. (The other lines on the waterfall are very weak “birdies”).
Most of the bigger EME stations use an array of long boom yagi’s so I am pretty lucky to get this done with a single antenna and no elevation rotator. Here’s a picture of a more typical antenna system for EME (this is DK5SO, the station in Germany that I worked):
DK5SO 2m EME Antennas
At this point, I am pretty happy with the performance of our 2m weak signal system.
I heard several stations in Australia a couple of mornings ago before I had my amplifier back. I will try to work them soon. Maybe someday an EME DXCC…. (3 down, 97 to go).