EME II Tech Night – Station Construction and Operation
We recently did a second Tech Night Program on EME as part of the Nashua Area Radio Society’s Tech Night 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 build and operate an EME station for the 2m band.
January 2021 Tech Night – EME II: Station Construction and Operation
A key part of optimizing our EME Station was to reduce RFI from the network in our home. You can read about the installation of Fiber Optic Networking to reduce RFI and improve our EME station’s performance here.
Fred’s New Hampshire First Place Finish in the ARRL June VHF Contest
I haven’t had the chance to work the ARRL June VHF Contest from our home station for several years. A combination of Nashua Area Radio Society activities and preparations for ARRL Field Day has taken a higher priority. ARRL June VHF is a great contest and I was looking forward to working it this year. A few days before the contest Anita and I were talking about the contest and she suggested that I do a 6m Digital Entry. E-skip has been pretty good on 6m this year and we wanted to sort out how we’d do digital and 6m for our upcoming 2020 Field Day Operation from our home so I decided to take Anita’s advice and focus on 6m Digital for June VHF. I entered the contest in the Low-Power Category.
June VHF Operating Setup
AB1OC Operating in 2020 June VHF
We built a Remote Operating Gateway that allows our station to be operated both over the Internet and from any room in our home via our Home Network. I decided to set up a 6m Digital Station upstairs in our dining room so I could be with Anita more during the contest. The setup consisted of a laptop PC with an outboard monitor and a Flex Maestro as the client for the Flex 6700 SDR in our shack.
The three antennas can be pointed in different directions and selected instantly via the computer. This provided to be an advantage during the contest. I kept one on Europe, one point due West, and the third pointed at the Tip of Florida and the Caribean during the contest.
Operating Setup – N1MM+ and WSJT-X
Having two monitors (the Laptop and an outboard one) allow me to arrange all of the N1MM+ Logger and WSJT-X windows for efficient operating. The image above shows a snapshot of the screen layout during the contest. N1MM+ has some nice features that integrated with WSJT-X to make it easy to spot new grids (Multipliers) and stations that have not yet been worked. The windows on the very right side allowed me to control antenna switching and monitor power and SWR while operating. I use the PSTRotator application (lower-left center to turn my antennas.
Band conditions on 6m were amazing from here in New England almost the entire contest period! The band was open right at the start of the contest on Saturday and remained open to 11 pm local time on Saturday evening. I was up early on Sunday and was working folks in the Northeastern Region right from the start. After being open all day on Sunday, the band shut down around 5 pm local time and I was afraid that the fun on 6m might be over. I ate some dinner and took a 45-minute nap and got back to my station at around 6:30 pm. About 15 minutes after I resumed, 6m opened again to most of the United States and I was able to work DM and DN grid squares in the Western States! The band stayed open right until the end of the contest at 11 pm local time.
What About the VUCC…
100 Grids Worked on 6m
Conditions on 6m were so good on Saturday that I almost worked a 6m VUCC by 11 pm on Saturday evening when the band closed. I had 93 grids worked on 6m in just 8 hours! The band opened again early on Sunday morning and I worked my 100th grid square before 10 am – working a 6m VUCC in less than 18 hours!
Final 6m Grids Worked
By the end of the contest, I had worked a total of 162 Grids! They ranged from the West Coast of the US to Western Europe and from Southern Canada to Northern South America.
6m Grids Worked During 2020 June VHF
The image above shows most of the 6m grids that I worked plotted on a world map (the EU grids are not shown).
Final Claimed Score
I was able to make a total of 402 unique contacts on 6m by the end of the contest with a final Claimed Score that was a bit over 65K. All of my 6m contacts during the contest were made using a combination of FT8 and FT4 modes on 6m.
New Ones on 6m for AB1OC
AB1OC Worldwide 6m Grid Map
I was hoping to work some all-time new Grids and June VHF did not disappoint. I worked a total of 11 new Grids and one new DXCC (Dominica) on 6m during the contest. The image above shows my worldwide grid coverage including the new ones worked during June VHF (my grids in Argentina and Uruguay are not shown above). I now have worked 432 grids on 6m and have confirmed 408 of them with 63 DXCC’s worked and 62 confirmed on the Magic Band.
Summing It All Up…
I must say that I had as much fun working 6m during June VHF this year as I have ever had in any contest! The band openings on 6m were really good and I was busy making new contacts for the entire time that I operated. The combination of the 6m Band and the contest certainly made some Magic for me!
We’ve been pretty active in Operating Award programs since we built our station a few years back. Operating Awards provide incentives to get on the air and chase all kinds of contacts and they also help us to understand our station’s and our personal operating strengths and weakness. They also provide motivation to improve the latter.
Yesterday was a banner day for me in terms of completing Operating Award goals. I was able to make the needed contacts to complete two that I’ve been working on for quite some time:
Worked All Japan – Requires working and confirming all 47 Prefectures (similar to US states) in Japan
Top Band DXCC – Working and confirming 100 DXCC Entities (basically countries) on 160m
Both of these goals were completed using the FT8 digital mode for the remaining handful of contacts. I wanted to take a little time and share some of the techniques that have worked for me in hopes that they might help our readers have more fun and meet their operating goals on the air.
DX’ing Basics and Tips
Here are some general techniques and tips for working DX (in no particular order):
Use spotting clusters such as DX Summit to find the DX
Subscribe to DX Notifications such as DailyDX to learn about planned operations in rare places
Make time to operate in and BEFORE major DX contests
Vary the times of day, days of the week, and bands on which you operate
Vary the times of the year when you operate
Learn about propagation and how to take advantage of short enhancement effects such as grey line enhancements
Learn how to identify days when the bands are particularly good (and bad) for working DX. Good conditions include very low noise levels, undisturbed ionosphere conditions, and favorable sunspot conditions.
Learn how to use Reverse Beacon Network Tools such as PSKreporter to assess propagation conditions and the real-time performance of your station. Pay attention to how these measurements change relative to the days, times, and band that you operate on and related conditions such as solar weather, grey line location, etc.
Equip your station for CW, Digital (FT8 and RTTY), and SSB phone modes and develop your operating skills using all three of these modes.
Learn to use the filtering and other capabilities of your radio and your digital mode software to hear and work very weak signals
Successful DX’ing requires BIC (Butt In Chair); sometimes at challenging hours during the day and at night
You can learn more about items 1 – 3 via the links above and by spending some time on the associated websites.
Item 4 is a big one when you are starting out. There are more “big” DX stations on during major DX contests such as CQ WW DX, CQ WPX, etc. than at any other time. We routinely work a DXCC here in less than 24 hours during these contests. An additional tip here is to set plenty of operating time aside the week BEFORE the contest begins. Many folks travel to interesting DX locations to operate in contests and spend lots of time on the air before the contest checking their stations and assessing propagation from their location. These are excellent times to work the DX as they are not as busy and can often take more time to help you make a contact.
Items 5 – 6 are often overlooked by operators who are just beginning to focus on DX. Many of us have busy daily schedules and we sometimes tend to set somewhat regular times aside to operate our stations. Propagation to different parts of the world varies wildly depending upon the time of day and frequency bands available to the operator. Switching both up will usually add significant numbers of new DX contacts to your log.
In my view, items 7 – 9 are key skills that begin to distinguish the serious DX’er from the pack. A good working knowledge of propagation effects, band openings, and how to measure conditions in real-time are essential skills and are not difficult to learn. I’ll reference a very good book in a bit that has some great basic information on propagation and how it relates to effective DX’ing. I’d also encourage you to set up your station for FT8/WSJT-X and learn to use PSKreporter to measure propagation and your station’s performance as well. If you pay attention to how the band conditions that are shown by PSKreporter change during different times/days and solar conditions, you can learn a great deal about how propagation actually affects your ability to make DX contacts and when the interesting (and sometimes brief) band openings occur to distant parts of the world. You can learn more about how to set up and use WSJT-X, FT8, and PSKreporter here.
Items 10 and 11 relate to both your basic operating skills and your station. Many DX’ers will focus on SSB Phone when they first start out. This is a great way to gain operating experience and have fun on-the-air. I strongly encourage the addition of the FT8 Digital Mode (and RTTY) to one’s station early on for two reasons:
You will likely find a great deal more DX that is workable with a modest station using the FT8 mode that can be had with either SSB Phone or CW
You will also want to add basic CW skills to your toolkit as soon as you can as there will be some important rare and semi-rare DX that you can only work using DX. Developing your CW skills to the level required to work a DX contact is pretty easy and is a good stepping stone to developing contesting and conversational DX’ing skills. Learning to use the features of your radio and your digital SW is a topic unto itself. The book which follows has some great information on using your rig and other capabilities of your station to work DX. FT8 software tools such as JTDX and JTAlert also bring some important capabilities that the DX’er can take advantage of (read more via the preceding links).
Item 12 probably does not require any explanation…
One DX’ing Book To Read…
AC6V’s DX101x HF + Six Meters DXing Reference Guide
Before I share my recent experiences and how the items above fit in, I’d like to share one more resource. While there is no substitute for getting on the air and operating, I would recommend AC6V’s DX101x Book as a comprehensive beginner’s guide to DX’ing. I read this book cover to cover several times when I was starting out and found it to contain a wealth of great information on all of the above topics and more.
Back To Yesterday’s DX…
Now I’ll share how I used these ideas yesterday to complete WAJA and Top Band DXCC. I began the day with a focus on completing my Worked All Japan (WAJA) award. Prior to this time, I had completed over 800 contacts with stations in Japan, working and confirming over 250 cities there. I had also managed to work and confirm 46 of the 47 prefectures in Japan. These left needing just 1 contact with someone in the Miyazaki Prefecture for my WAJA. This prefecture seems to be a beautiful place with 12% of its land being designated as Natural Parks. Hams in Miyazaki have area 6 callsigns.
The Search for Noda San, JA6FUV
My initial approach to securing my contact with someone in Miyazaki was to work as many JA6’s as I could find on 40m, 30m, and 20m (the most open bands from New Hampshire to Japan over the last year). After months of trying without success, I decided that I needed a better approach.
40m FT8 Opening to Japan
I decided to use PSKreporter to see if I could identify a station in Miyazaki that I could contact. The data in PSKreporter is time sensitive so it’s important to do this analysis at the times of day that you expect band openings to your target location (in my case Japan early in the day). For my conditions here in New Hampshire, the best time to work Japan is in the morning between about 9:30z and 11:15z. My analysis of the PSKreporter data identified one, and only one station, JA6FUV owned by Katsuyuki Noda. I next contacted Noda San to learn about his station and see if he might help me with a contact. He was happy to try but cautioned me that he had a 100W rig and a dipole antenna for 40m and warned that making a contact with the USA would be difficult. He also indicated that he was on most days at around 11:00z (7 am local time at my location).
The next several days were marked by poor solar weather and associated band conditions. The K was 3-4 and the A rose to 20. Noda San heard me only one time during this period and I did not hear him at all. As of early this past week, we had both given up. Here’s where the BIC aspect and propagation assessment skills came in. I was up every day at 9:00z (5 am local time) and on the 40m band trying to work Japan. Some days I made only a few contacts, others were a little better but no sign of JA6FUV. What I learned from this was the very best time for propagation was to Japan on 40m is a 30 minute period from 11:30z – 12:00z and I shared this information with Noda San.
Two days ago, I found the K to be 0 and the A to be 3 with the resulting band conditions to Japan on 40m as quiet as I had seen them in a while. I alerted Noda San and the following morning I found the band wide open to Japan at 9:30z. I worked maybe 15 JA’s before JA6FUV appeared on PSKreporter. JA6FUV is the station at the very bottom center of the PSKreporter image above. I began a series of directed FT8 calls to JA6FUV. After a few minutes, Noda San answered and my Miyazaki Prefecture contact was finally completed! The signal report on my end was only -19 which is right on the edge of what I can hear. Noda San reported my signal as -15 which was solid but not particularly strong. All of this shows how the various tools and tips can come into play to make an important but difficult DX contact happen.
The Path To Top Band DXCC
My other goal for this past winter season was to complete my Top Band DXCC (100 countries on 160m). We have an Inverted-L transmit antenna and some good low-band receive equipment here at our station so I felt that this was a reasonable goal. Given we are at the bottom of the solar cycle, it’s also a good time to work DX on 160m and 80m. Things got busy and I did not get the time to operate that I would have wanted nearly the end of winter. Still, I got my first 90 and then 95 confirmed DXCCs on 160m.
Upon seeing the expected solar conditions and the very quiet band conditions while working JA6FUV, I decided to take another run at DXCC 160m. While operating sporadically on 160m since the beginning of the year, I learned that there are two primary DX openings each day on 160m from here in New Hampshire. The first occurs early in the morning at about 9:00z (5 am local time) and lasts until just before the grey line turns to daylight. This is a good time to work Australia, New Zealand, and the Pacific on 160m. Contacts during this time helped to get me to 95 on Top Band.
The most productive opening occurs just as it begins to get dark here (grey line enhancement again) at about 22:00z and lasts through the night until the grey line passes over Europe at about 06:30z (2:30 am local time). There are many more DXCCs that I can work in Europe so I decided to try this second opening last evening to complete my Top Band DXCC.
160m FT8 Opening to Europe
Again, the combination of propagation, band opening, and solar weather experience paid off. As you can see from the PSKreporter view above, I caught a very good opening into Europe and South America on 160m last night. I was able to work over 70 stations on Top Band – including CN2FA (Morocco), LX1JX (Luxembourg), IS0CDS (Sardinia), HR5/F2JD (Honduras), and ES4IN (Estonia) – the last 5 DXCC’s needed for 100 on 160m.
BTW, I have had a great experience with confirmations on Top band and have managed to confirm all 95 DXCC’s that I had worked prior to last evening. Hopefully, these last 5 will all confirm as well.
A Final Through – It Really Takes BIC…
Again, there is no substitute for BIC when trying to meet DX’ing goals. It took me exactly 850 contacts to work the required 47 prefectures for my WAJA. It took 1,252 contacts on Top Band to work (and hopefully confirm) the required 100 DXCC’s there. Both awards involved many contacts using SSB, CW, and Digital modes to get there. I certainly had a lot of fun meeting these two goals and I learned a great deal about the associated bands and propagation in the process.
AB1OC Operating Awards In Our Shack
I hope that this will help our readers to have fun DX’ing and to become accomplished DX’ers. What this is really all about is building your operating skills, experience, and station. The paper awards are like earning an educational diploma – the award is a reminder of the path you’ve walked and the knowledge that you’ve gained along the way.
The new antennas will require some modifications to our portable antenna system arrangement. They will need to be mounted on a cross-boom near their centers. As a result, a non-conductive fiberglass cross boom will be required to avoid problems with pattern distortion.
FGCB60 Non-Conductive Cross Boom
We will be using an M2 Antenna Systems FGCB60 Cross Boom which has removable, non-conductive end sections made from fiberglass material. The removable ends will make it easier to transport the antenna system. We will also need to make a new mast which is 24″ longer than our current one in the 2.0 Station to create the needed ground clearance for the longer antennas.
Alfa Spid Az-El Rotator
We are also planning to use a larger Alfa Spid Az-El Rotator. This unit will handle the extra weight of the longer yagi antennas and cross boom assembly and is more precise than the Yaesu unit used on the 2.0 station.
We have a DXEngineering EC-4 Control Box from a previous project and we can use it to control the relays in the Polarity Switches which will be part of the 3.0 Station antennas. The box will allow us to select any combination of left and right-hand circular polarization on the 3.0 Station uplink and downlink antennas.
We should have all of the parts here for the 3.0 upgrade by the end of the year. We’ll post more as the project proceeds. Other articles in the Portable Satellite Station series include:
Today proved some simple, tried, and true advice for me – it pays to take some time and tune through the bands. I just got a Maestro Remote Control Device for our FlexRadio SDR, and I took a break around lunchtime to tune through the higher HF bands to see what I could hear. We use a Flex SDR as a Remote Operating Gateway into our station, and the Maestro allows me to run our station over our home network without going down to the shack.
I am not sure why but I decided to give the 12m Band a look today. When I did, I was stunned! It is noon, and the 12m Band is wide open between Africa and the US!
I worked two DX stations on 12m SSB. The first was XT2AW, Harald, in Burkina Faso. Harald was working split and was not really loud, but I had no trouble completing the contact with him. Excited, I tuned across 12m some more and found an old friend – Theo, ZS6TVB, in South Africa. I had a very nice QSO with him. We both marveled over the propagation of the 12m Band we were experiencing. He was 57-58 here in New Hampshire!
12m DX – ZS6TVB South Africa
The sunspot conditions are pretty weak (SFI 85, SN 26), so such a good opening on 12m was unexpected. I believe that we may be experiencing Transequatorial Propagation (TEP), which can provide a significant propagation enhancement on paths that traverse the equator. Anita and I experienced similar TEP propagation on 10m when we were on Bora Bora Island early in 2012 with similar solar conditions.
It shows that it pays to tune the upper HF bands. Especially on days when “they are not open.” Also, 10m appears to be open to Africa right now – I hear a station in Mauritania…
We recently did a Tech Night at our club on Building and Operating an LEO Satellite Ground Station. As part of my portion of our Tech Night presentation, I recorded several LEO satellite contacts. I made videos showing the operation of the computer controlling our Satellite Station 2.0 during these contacts. These videos give an idea of what it’s like to operate through LEO satellites.
Next, we used MacDoppler to generate pass predictions for the weekend of our Technical Class. We assembled this data for all of the potential satellites and color-coded the available passes to identify those which had the best chance of producing contacts.
With this done, we loaded our portable tower, antennas, and all of the rest of the gear into our pickup truck and transported it to the class site.
Here’s a closer look at the LMR-400 UF coax cables which connect the antennas to the rest of the system. The loops just behind the antennas are necessary to keep the coax from affecting the pattern of the antennas. The coax cables shown were made long enough to allow the antennas to be rotated through their full travel in the azimuth and elevation directions without binding.
Satellite Station Portable – Radio and Supporting Equipment
The final step in the portable setup was to put the IC-9100 Transceiver and Supporting Equipment together in the building and check everything out. As soon as we got everything hooked up and working, we heard an ON4 station through FO-29 which was near the end of a low-angle pass. A very good sign!
We took some time to fine-tune the calibration of our rotators and to check the operation of the computer controls – everything checked out fine. The video above shows MacDoppler controlling the Azimuth/Elevation rotator and the IC-9100 Transceiver during the testing.
First Contact using New 2.0 Station (via AO-85)
With all the setup done, it was time to try to make our first contact. Fortunately, we did not have long to wait. We caught a medium-angle pass of AO-85, a U/V Mode FM Easy Sat. With MacDoppler setup and tacking, we immediately heard contacts being made through AO-85. I gave a whistle and adjusted my uplink VFO until I heard my signal coming back through AO-85. I gave a quick CQ call and immediately got a response from Jonathan, NS4L in Virginia, USA! It took on a few seconds to exchange call signs and grid squares and our first contract with our new station was in the log.
We learned several things during our first use of the new station. First, while the 35 ft. maximum separation allowed between the antenna system and the rest of the station is adequate in many applications, the antenna system’s close proximity to the building we were in blocked passes to the west of us with this separation. We have subsequently made up an additional set of feed lines using a pair of 100 ft. long 7/8″ hardline coax cables to allow for a greater separation in portable deployments such as this one.
We were glad that we had the Heil Pro 7 Headset with us and we used it for most of our contacts. The separate speaker allowed our students to hear the contacts well and the boom microphone on the Pro 7 Headset eliminated feedback due to our own voice coming back through the satellites. We improvised a mono-to-stereo converter cable to connect the Heil Pro 7 Headset to one of the two speaker outputs on the IC-9100 Transceiver. This allowed the radio to drive the separate speaker and the headphones at the same time.
We were glad to have the low-noise preamps available. These were especially useful during low-angle satellite passes and the sequencing setup that we built worked well.
All in all, the first test of our new 2.0 Portable Satellite station was a success. Our license classes students enjoyed learning about Amateur Satellites and had fun along with us making contacts through a few of them. Our next goal will be to get packet modes and APRS working with our setup. We plan to do another article in this series when this part of our project is completed. Other articles in this series include:
We are planning to add larger antennas and switchable polarity to our portable satellite station in the near future. This will enable us to make contacts with Satellites and the ISS in more difficult conditions.
NCC-1 Receive Antenna System Control Unit and Filters
Anita and I like to take advantage of the mild fall weather to do antenna projects at our QTH. We have completed two such projects this fall – the installation of a Two-Element Phased Receive System and a rebuild of the control cable interconnect system at the base of our tower.
The NCC-1 System can be used to peak or null a specific incoming signal. It can also be applied to a noise source to null it out. The direction that it peaks or nulls in is determined by changing the phase relationship between the two Active Antenna Elements via the NCC-1 Controller.
NCC-1 Filter Installation
The first step in the project was to open the NCC-1 Control Unit to install a set of 80m and 160m bandpass filter boards. These filters prevent strong out-of-band signals (such as local AM radio stations) from overloading the NCC-1. The internal switches were also set to configure the NCC-1 to provide power from an external source to the receive antenna elements through the connecting coax cables.
Installed Active Receive Antenna Element
The next step in the project was to select a suitable location for installing the Receive Antenna Elements. We choose a spot on a ridge that allowed the two Antenna Elements to be separated by 135 ft (for operation on 160m/80m) and which provided a favorable orientation toward both Europe and Japan. The antenna elements use active circuitry to provide uniform phase performance between each element’s 8 1/2-foot whip antenna and the rest of the system. The antenna elements should be separated by a 1/2 wavelength or more on the lowest band of operation from any towers or transmit antennas to enable the best possible noise rejection performance.
Received Antenna Element Closeup
The two Antenna Elements were assembled and installed on 5 ft rods which were driven into the ground. To ensure a good ground for the elements and to improve their sensitivity, we opted to install 4 radials on each antenna (the black wires coming from the bottom of the unit in the picture above). The Antenna Elements are powered through 75-ohm flooded coax cables which connect them to the NCC-1 Control Unit in our shack. The coax cable connections in our setup are quite long – the longer coax of the pair being approximately 500 ft. The use of flooded coax cable allows the cables to be run underground or buried. Should the outer jacket become nicked, the flooding glue inside the cable will seal the damage and keep water out of the cable.
Receive RF Choke
It is also important to isolate the connecting coax cables from picking up strong signals from nearby AM Radio stations, etc. To help with this, we installed Receive RF Chokes in each of the two coax cables which connect the Antenna Elements to the NCC-1. These chokes need to be installed on ground rods near the Antenna Elements for the best performance.
Underground Cable Conduit In Our Yard
We ran the coax cables underground inside cable conduits for a good portion of the run between the antenna elements and our shack. The conduits were installed in our yard when we built our tower a few years back so getting the coax cables to our shack was relatively easy.
Receive Antenna Coax Ground System
The last step in the outdoor part of this project was to install a pair of 75-ohm coax surge protectors near the entry to our shack. An additional ground rod was driven for this purpose and was bonded to the rest of our station’s ground system. We routed both of the 75-ohm coax cables from the two Antenna Elements through surge protectors and into our shack. Alpha-Delta makes the copper ground rod bracket shown in the picture for mounting the surge protectors on the ground rod.
Antenna Equipment Shelf In Our Shack (The NCC-1 Control Unit Is At The Bottom)
The installation work in our shack began with the construction of a larger shelf to hold all of our antenna control equipment and to make space for the NCC-1. The two incoming coax cables from the Antenna Elements were connected to the NCC-1.
microHAM Station Master Deluxe Antenna Controller
Antenna switching and control in our station is handled by a microHAM System. Each radio has a dedicated microHAM Station Master Deluxe Antenna Controller which can be used to select separate transmit and receive antenna for the associated radio. The microHAM system allows our new Receive Antenna System to be shared between the 5 radios in our station.
The Antenna Elements must be protected from overload and damage from strong nearly RF fields from our transmit antennas. In a single radio station, this can be handled via a simple sequencer unit associated with one’s radio. In a multi-op station such as ours, it is possible for a different radio than the one which is using the Receive Antenna System to be transmitting on a band that would damage the Receive Antenna System. To solve this problem, we built a multi-radio sequencer using one of the microHAM control boxes in our station. The 062 Relay Unit shown above has one relay associated with each of the five radios in our station. The power to the Receive Antenna System is routed through all 5 of these relays. When any radio transmits on a band that could damage the Antenna Elements, the associated relay is automatically opened 25 mS before the radio is allowed to key up which ensures that the system’s Antenna Elements are safely powered down and grounded.
Updated microHam Antenna System Diagram
With all of the coax and control connections complete, I was able to update the microHam system design information for our station and add the new receive antenna system to our setup. You can find more about the programming of our microHam system here.
So how well does the system work? To test it, we adjusted the NCC-1 to peak and then null a weak CW signal on 80m. This is done by first adjusting the Balance and Attenuator controls on the NCC-1 so that the incoming signal is heard at the same level by both Antenna Elements. Next, the B Phase switch is set to Rev to cause the system to operate in a signal-nulling configuration, and the Phase control is adjusted to maximize the nulling effect on the target signal. One can go back and forth a few times between the Balance and Phase controls to get the best possible null. Finally, the incoming signal is peaked by setting the B Phase switch to Norm.
Peaked And Null’ed CW Signal
The picture above shows the display of the target CW signal on the radio using the NCC-1 Antenna System. If you look closely at the lower display in the figure (nulled signal) you can still see the faint CW trace on the pan adapter. The difference between the peak and the null is about 3 S-units or 18 dB.
NCC-1 Used For Noise Cancellation
The NCC-1 can also be used to reduce (null out) background noise. The picture above shows the result of doing this for an incoming SSB signal on 75m. The system display at the top shows an S5 SSB signal in the presence of S4 – S5 noise (the lower display in the picture). Note how clean the noise floor for the received SSB signal becomes when the unit is set to null the noise source which comes from a different direction than the received SSB signal.
We are very pleased with the performance of our new Receive Antenna System. It should make a great tool for DX’ing on the low bands. It is a good complement to our 8-circle steerable receive system which we use for contesting on 160m and 80m.
Tower Control Cable Interconnects (Bottom Two Gray Boxes)
Our other antenna project was a maintenance one. We have quite a number of control leads going to our tower. When we built our station, we placed surge protectors at the base of our tower and routed all of our control leads through exposed connections on these units. Over time, we found that surge protection was not necessary and we also became concerned about the effects that sunlight and weather were having on the exposed connections. To clean all of this up, we installed two DXEngineering Interconnect Enclosures on our tower and moved all the control cable connections inside them.
Inside View Of Interconnect Enclosures
We began with a pair of enclosures from DXEngineering and we mounted screw terminal barrier strips on the aluminum mounting plates in each enclosure. The aluminum plates are grounded via copper strap material to our tower.
Closer Look At One Of The Interconnect Enclosures
The picture above shows one of the interconnection boxes. This one is used to connect our two SteppIR DB36 Yagi Antennas and some of the supporting equipment. The barrier strips form a convenient set of test points for troubleshooting any problems with our equipment on the tower. There are almost 100 control leads passing through the two enclosures and this arrangement keeps everything organized and protected from the weather.
With all of our antenna projects complete, we are looking forward to a fun winter of contesting and low-band DX’ing.
Skip, K1NKR a local friend and VHF/UHF expert and I began talking about the idea of building a Fast Scan Amateur Television (ATV) System some time ago. Our early research and the antenna equipment which we had in place at our stations led us to plan our ATV project around the 70 cm band. The 70 cm band plan in the United States has allocations for Fast Scan ATV transmissions with a bandwidth of up to 6 MHz. Our research led us to Jim Andrews, KH6HTV’s excellent website where we discovered that it was possible to build a Digital ATV station using reasonably priced commercially available DVB-T format Modulators and Demodulators. Jim’s site has a wealth of great Applications Notes on Digital ATV and it’s a great place to start learning about this technology. A combination of a DVB-T Modulator and Demodulator from Hi-Des was chosen as the heart of our Digital ATV System. We also worked with Jim to secure the needed Wideband Linear Power Amplifiers for the 70 cm band. We began receiving the equipment to build our Digital ATV Stations late last year. We’ve done quite a bit of testing on the air and some custom development work which has resulted in a pair of excellent-performing Digital ATV stations. The picture above shows a Digital ATV “CQ” that I sent to initiate one of our early QSOs.
Digital ATV Transceiver
Here’s a picture of Skip receiving my “CQ” at his end. The picture quality produced by the equipment that we’re using and the DVB-T format is phenomenal. The Hi-Des Modulator which we are using has a large number of parameters that can be set to determine the format and bandwidth of the signals we generate. After some experimentation, we have settled on using QPSK modulation and a 6 MHz signal bandwidth. This combination delivers excellent picture quality with more than adequate motion performance. We see very few if any picture artifacts using our current format. We’ve also done some experimentation with QPSK and a 4 MHz signal bandwidth. I plan to share more on signal formats in a future article on our blog.
Digital ATV System User Interface
We are both using HD Digital Camcorders as our primary video signal sources and 1080p monitors to display our received signals. I opted to include an HDMI Video Switch from Gefen in my setup which also allows me to send video and graphics from a variety of different sources including my PC over the air. The monitor in the picture above on the right is a touchscreen display that I use to control my ATV Transceiver system.
AB1OC Digital ATV Transceiver
Early on, I decided to build a Transceiver-like setup. I wanted to create a unit that was simple to use just like the HF Transceivers that are available today. Some of the key capabilities that I wanted to create include:
Real-time selection and switching between multiple HD video sources
Transmission of PC sourced Video and Graphics over the air
Preview and cueing of the next video transmission while receiving
Simultaneous display of both receive and pending transmit video
Built-in Transmit/Receive (T/R) switching with termination and protection of the Tx power stage
Power and SWR monitoring with an automatic trip on high SWR
An internal low-noise RF preamplifier to provide additional receive signal gain if needed
Touchscreen graphical interface for configuration and operating the station
Recording of both sides of on-air video QSOs to an attached PC
To achieve these goals, I decided to build a Raspberry Pi 2-based Linux controller for my ATV Transceiver and to package all of the ATV components and video switching/conversion gear needed in a small rack mount enclosure. Many of the components in the system communicate with each other over an Ethernet LAN and the transceiver is networked to computers and other devices via an external Ethernet connection. More on the details of the Transceiver design to come in a future article.
Skip and I recently produced a short video to demonstrate how Fast Scan Digital ATV works and to show the quality that these systems are capable of producing. Our project is still a work in progress and I expect that we will continue to learn as we perform more tests and continue the development of our systems. I plan to post additional articles here to share the details of our designs and learnings from our on-air testing as we proceed.