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
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 first transport of the new 3.0 station antenna system turned out to be simple. The booms and counterweights of the new antenna system are easily separated via the removal of a few bolts located at the cross-boom. This allowed the antennas feed-points, rotator loops and polarity switching connections to be removed and transported as complete assemblies. The separation of the longer-boom antennas into two sections also made transporting the antennas easier and made the antenna elements less prone to bending in transport. Setup and cabling of the new 3.0 antenna system as the class site was quick and simple.
The opportunities to make contacts during our Tech Class were limited but the new system performed well with one exception. We saw a higher than expected SWR readings on the 70cm yagi during transmit. We immediately suspected problems with one of the N connectors that were installed during the construction of the new system (component testing during assembly showed the SWR readings on the 70cm side of the system to be in spec.).
Portable Satellite Station 3.0 Antenna System
After the class, we set up the 3.0 system again at our QTH. Transport and re-assembly of the new system are somewhat easier and faster than our 2.0 portable station antenna setup is.
Satellite Antenna System 3.0 Connections
The 3.0 antenna system uses a similar connector bulkhead approach that we used previously. The rotator controls are handled via a single, 8-conductor cable and we have a new connection for the polarity switching controls on the 3.0 system yagis.
Rotator Loop Coax Retention System
We have had some problems with the connections between the preamplifiers mounted at the antennas and the rotator loops which connect the antennas to them. This problem caused several failures in the associated N-connectors on the 2.0 portable antenna system so we fabricated a simple arrangement to prevent the rotation of the antennas from turning the coax inside the N-connectors and causing these failures.
70cm Antenna and Feedline SWR in the Satellite Sub-Band
Some isolation tests were performed on each cabling element of the 70cm side of the 3.0 antenna system and this resulted in the location of an improperly installed N-connector. The faulty connector was easily replaced and this corrected the SWR readings on the 70cm side of the antenna system. The image above shows the SWR readings for the 70cm antenna after the faulty connector was replaced. We checked the SWR performance with the 70cm yagi set for both Left-Hand and Right-Hand Circular Polarization and we saw good results in both configurations.
2m Antenna and Feedline SWR in the Satellite Sub-Band
We also re-checked the SWR performance of the 2m side of the antenna system with the 2m yagi in both polarity settings and it looked good as well.
Portable Satellite Antenna 3.0 Az-El Rotator
The 3.0 antenna system uses an Alfa-Spid rotator. The Alfa-Spid can handle the additional weight of the larger yagis and has a more precise pointing ability (1° accuracy) which is helpful given the tighter patterns of the larger, 3.0 yagis.
70cm Yagi Switchable Polarity Feedpoint
The new yagis in the 3.0 antenna system have feed point arrangements which allow the polarity of the yagis to be switched between Left-Hand Circular Polarity (LHCP) and Right-Hand Circular Polarity (RHCP). These antennas used a relay arrangement at the feed-points that flip the polarity of one plane of the yagis by 180° which in turn changes the polarity of the antennas between LHCP and RHCP.
Portable Satellite Station 3.0 Computer Control via MacDoppler
We are continuing to use the excellent MacDoppler software to control the 3.0 station. MacDoppler provides tracking controls for the antennas and doppler correction for the Icom-9100 transceivers uplink and downlink VFOs.
Satellite 3.0 Station Control Details
The image above shows a closer view of the 3.0 station controls. The box in the middle-left with four LEDs and the knob is used to select one of four polarity configurations for the 2m and 70cm yagis – RHCP/RHCP, LHCP/RHCP, RHCP/LHCP, or LHCP/LHCP. Just to the right in the middle stack is our homebrewed PTT Router which expands and improves the PTT sequencing performance of the station. Our station also uses a WaveNode WN-2 for SWR and power monitoring.
So how does the new 3.0 station perform? The new antennas have a tighter pattern requiring careful pointing calibration of the rotators during setup. This is easy to do with the Alfa-Spid rotator. The new antennas have noticeable more gain as compared to the LEO pack used on the 2.0 station. We are also surprised to see how much difference the polarity switching capability makes in certain situations – sometimes as much as two S units (12 dB) in certain situations. The combination of the new antennas and selection of the best polarity combination allows solid operation on many satellites passes with as little as 2 watts of uplink power. We have made a little over 50 QSOs on the new 3.0 station so far and it works great! For more information on the Portable 3.0 Station as well as the 2.0 and 1.0 stations that we’ve built – see the links below:
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 out 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 with 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 about noon time 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 real 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 on the 12m band that 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) to create such a good opening on 12m. I believe that we may be experiencing Transequatorial Propagation (TEP) which can provide a significant propagation enhancement on paths with 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 just goes to show that it pays to tune the upper HF bands. Especially on days when “they are not open”. Also, 10m also appears to be open to Africa right now – I am hearing a station in Mauritania…
We recently did a Tech Night at our club on Building and Operating a Satellite Ground Station. As part of my portion of our Tech Night presentation, I recorded several LEO satellite contacts and made videos showing the operation of the computer controlling our Satellite Station 2.0 during these contacts. These videos give an idea of what its like to operate through LEO satellites.
Next, we used MacDoppler to generate pass predicts 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 to 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 which 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 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 which 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 null’ing 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 (null’ed 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.
Computers and Digital Signal Processing already play a big role in recent Amateur Radio transceivers. Many HAMs have a good understanding of these features and regularly use them for all manner of filtering, noise reduction and signal processing tasks while on the air. We’ve also seen more and more radios with Spectrum Scopes which make it easier to visualize what is on a given band in real time. Thanks to increasing volumes in color displays, Digital Signal Processor (DSP) applications and low-cost processors, these capabilities are now common – even on entry-level HF transceivers.
Software Defined Radios (SDRs) are the next logical step in this evolution. SDRs are not new, they have been around for some time now. SDR technology has continued to improve as the cost and performance of Analog to Digital Converters, Programmable Logic Devices and other processors that make up the hardware side of SDRs have improved. We are now to the point where it is possible to build an SDR for Amateur Radio applications which can directly sample RF at frequencies as high as 150 MHz.
Direct Sampling SDR receiver designs have some important advantages over more conventional single conversion and super-heterodyne receiver (i.e. multiple conversion) designs. These include:
Higher dynamic range
Low phase noise
Ability to cover multiple bands simultaneously with multiple receivers
Very high-quality spectrum displays
Flexible, high-performance filters
The ability to add new modulation schemes and other features via software updates
The first two items above (dynamic range and phase noise) are particularly important as they result in receiver performance which is significantly better than that which can be achieved with the best direct and superhet designs. Take for example a busy contest environment when a band is very crowded (ex. 40m at night in a worldwide DX phone contest). There are many strong signals crowded closely together on the band. Even the best conventional design receivers will have trouble hearing moderate and weak signals in this environment. The problem is that the strong signals tend to overload the analog circuitry in the conversion stages of conventional radios which produces a great deal of Intermodulation Distortion Design products. Phase noise also compounds this problem.
A direct sampling SDR converts the incoming RF signals with high dynamic range Analog to Digital conversion and then performs all of the filtering and demodulation of the incoming signals in software. This approach limits the potential for Intermodulation Distortion with an end result that all of the signals on the band (including the weaker ones) are much clearer. This approach also allows very high order filtering to be applied in the RF domain which results in greatly improved selectivity and rejection of closely spaced adjacent signals with minimal distortion.
By now some may be think that this all sounds great but I don’t want to have to use my computer to make QSOs. There is good news on this front as well. We are beginning to see the major transceiver manufacturers introduce direct sampling SDR technology in radios with conventional “buttons and knobs” interfaces.
Icom IC-7300 (Pending US Release)
New designs like the Icom IC-7300 can provide a way to gain the performance and feature advantages of an SDR in a radio which has a more conventional interface. The entry of the major manufacturers into the direct sampling space and the resulting competition should help to lower prices for all types of SDRs.
Want to give SDR technology a try without spending a lot of $? There are several very good SDR Dongles available along with SDR software at a minimal cost. Dongles are typically receive-only but some can also transmit as very lower power. The use of this technology in digital TV receivers and set-top boxes has made the cost of SDR Dongles very low and there is some very good SDR software available for free on the web. Dongles are generally broad coverage receivers and they can also be used to listen to signal outside the Amateur Bands.
It is interesting to follow the rapid evolution of SDR technology. We recently integrated a FlexRadio-6700 SDR into our station to enable us to operate remotely via the internet. You can read more about this project on our blog.