February 2021 Tech Night – Understanding and Using Propagation to Work The World
Anita, AB1QB, recently did a Tech Night Program on Radio Propagation 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 propagation and how to use it to facilitate contacts.
Anita, AB1QB provides a comprehensive overview of HF and VHF/UHF propagation and how to use it to Work the World. Topics include the many online tools to help one determine and measure propagation conditions. VHF+ modes such as Meteor Scatter, Tropo, EME, and Satellite paths are also covered.
We’ve been making good use of our Satellite Ground Station. Our existing 2MCP14 and 436CP30 antennas have enabled us to make over 2,000 satellite contacts; working 49 of the 50 U.S. States, 290+ Grid Squares, and 31 DXCCs. Our station is also an ARISS Ground Station which enables us to help Schools around the world talk to astronauts on the ISS.
The first step in the project was to unpack and carefully inventory all of the parts for each antenna. This included carefully presorting and marking each element as we did during the assembly of our EME antennas.
2MCP22 Completed Antenna
The new antennas are quite large and they took most of the available space in our workshop during assembly. Getting good results from any antenna is all about attention to the details. Small things like turning the boom sections to get a good alignment of the elements, using NOALOX on the boom sections and hardware to prevent corrosion and galling, carefully measuring and centering the elements, etc. are all good things to do.
2MCP22 Feedpoint Assembly including Polarity Switch Upgrade
The feedpoint system on these circular polarized antennas requires careful attention during assembly. It’s important to install drive element blocks, shorting bars, polarity switches, feedpoint splitters, and all phasing lines EXACTLY as shown in the antenna assembly manual. Failure to do these steps will likely results in SWR problems down the road.
436CP42UG Feedpoint Assembly
The images above show the feedpoint assemblies for both of our new antennas.
New Satellite Yagis Ready For Installation
A rough SWR measurement with the antennas on the ground was performed to check for assembly errors. It’s a good idea to use a 12V battery to test the antenna SWR’s in both RHCP and LHCP. These tests checked out fine and we are ready to begin installing the antennas on our Tower.
Old Antenna Takedown and Work Stand
Old Antenna Assembly Takedown Using Boom Lift
The next step in the installation was to take down our existing antennas. We rented a 50 ft Boom Lift for the project. The lift makes the work much easier and safer.
It’s important to fully test a complex antenna system like this on the ground prior to installation on a Tower. We have routinely found and corrected problems this way. This approach also enabled us to properly adjust our cross boom and antenna support trusses and balance the final assembly properly. All of the required adjustments are MUCH easier with the antennas on the ground.
We also run our rotators under computer control for at least one full day before installing the completed assembly on our Tower. We have consistently found and corrected problems with cabling and balance this way.
Antenna Mounting and Trussing
2MCP22 Boom Truss
The new antennas have very long booms (approximately 18 ft) and they have a tendency to sag. Add the ice and snow load that we experience here in New England and you end up with quite a bit of stress on the booms over time. Robert at M2 Antenna Systems came up with a custom truss assembly for our installation to address this problem. It’s important to minimize any metal in a setup like this to avoid distortion of the antenna patterns. The trusses use a solid fiberglass rod and small turnbuckles to support the ends of each antenna boom. There is much more weight on the rear of the booms due to the weight of the attached coax cables and polarity switches. For this reason, we located the truss anchor point for the rear of the boom such that it creates a sharper angle for the truss ropes at that end of the truss. This reduces the compression load on the rear of the boom and enables the truss to better carry the weight at the back of the antenna.
436CP42UG Boom Truss
Installing a truss on the 70cm yagi is much trickier due to the tight pattern of this antenna. We minimized the added metal components by drilling the antenna boom to mount the truss plate directly to the boom via bolts.
We relocated the boom support plates on both antennas as far to the rear of the largest boom sections as possible to improve overall antenna balance. The clamps were also adjusted to change the orientation of the elements from vertical/horizontal to a 45-degree X arrangement. This maximizes the separation between the element tips and other metal components like the cross boom and truss plates.
Tubing Drill Guide
All of this required drilling some new holes in our antenna booms. We used a Tubing Drill Guide and C-clamps to perform the required drilling operations accurately.
Satellite Antenna Boom Assembly
The photo above shows the new antennas mounted on our cross boom. The modifications worked out great resulting in well supported and aligned antennas on the cross boom.
Balancing The Array
Cross Boom Counterweight and Trusses
It’s very important to properly balance any antenna assembly that is used with an elevation rotator. Failure to do this will usually result in the failure of your elevation rotator in a short period of time. We initially had some pretty major balance problems with our new antennas. This is due, in part, to the weight of coax cables that run from the antenna feed points along the L-Brace Assemblies. The added weight of the Polarity Switches near the rear of the booms was also a significant contributor to this problem.
We created a counterweight by replacing one of our cross boom truss tubes with a metal section of pipe about 4 ft long. The pipe acts as a counterweight to the weight of the coaxes, etc.
Wheel Weights Used for Balancing
Next, we added 4 1/2 pounds of weights to the front on the metal pipe. We used several layers of Wheel Weights built up in multiple layers to get the necessary counterweight. A heavy layer of electrical tape and some large cable ties were used to ensure that the weights say in place.
This got us close to a good balance but the boom of the 2MCP22 was still significantly out of balance. Matt at XX-Towers came up with a good solution to this problem. We added a few strips of wheel weights inside the very front of the boom of the 2MCP22 to finally get the antennas balanced. A combination of the adhesive tape on the weights and two small machine screws through the boom ensures that the weights remain in place and do not short the elements to the boom.
A final check and baseline of all of our antennas were made on the ground. Both RCHP and LHCP modes were checked and recorded for future reference.
432CP42UG Installed SWR
We found that some fine-tuning of the locations and routing of the phasing lines on our 436CP42UG improved the SWR curves. This is a common situation and it’s well worth the time to make small adjustments while carefully observing how they impact your SWR readings. The phasing cables are firmly secured to the antenna boom after the fine-tuning is complete.
New Antenna Installation and Integration on Tower
Upgraded Antennas Going On Tower
The next step in our project was to install the updated antenna assembly back on our Tower. We had to push the lower rotator and mast up about 4 ft to accommodate the larger antennas. We removed our 6M7JHVHD Yagi and temporarily fastened it to the side of our tower to make these steps easier. We also took the opportunity to work on our 6M7JHVHD Antenna to adjust the length of the Driven Element for better SWR performance in the FT8 and MSK144 section of the 6m band.
Satellite Tower Infrastructure and Accessories
There is quite a bit of feed line and control cabling involved in a complex antenna system such as ours. The next step in the project was to reconnect all of the cables and coax feedlines.
Control Cable Junction Box at the Base of VHF Tower
We use small junction boxes on our tower and a larger one at our tower base to make it easy to remove and reinstall all of the required control cables. Our approach was to hook up and test the rotators first to ensure that we did not have any new mechanical or balance problems. This step checked out fine. The stiffer chrome molly mast and its added length actually resulted in smoother operation of rotators than we saw during ground testing.
The final step was to work through the other control cables and feed line connections; testing each connection as we went. The Boom Lift makes this work much easier to do.
We took advantage of the availability of the Boom Lift and added some additional enhancements to our VHF Tower. Previously. changing the battery in our Weather Station involved climbing our main tower to 50 ft. We moved the weather station to the 30 ft level on our VHF tower to make this maintenance step easier.
Initial testing of our new antennas is showing some major improvements. The uplink power required to work LEO satellites has been reduced significantly. As an example, I have worked stations using the RS-44 Linear Satellite with just 0.4 watts of uplink power out of our Satellite IC-9700. The signal reports we’ve received have been excellent as well.
More About Our Ground Station
Here are links to some additional posts about our Satellite Ground Stations:
The AO-27 FM satellite is back on the air! AO-27 is an FM V/U Mode satellite that was launched back in 1993. The satellite’s Amateur Radio payload became inoperative about 7 years ago due to an internal communications failure. Thanks to some great work by Micheal, N3UC who was one of AO-27’s original designers, the satellite is back on the air on a limited-time basis (4 minutes, twice per orbit over the mid-latitudes).
I was able to make my first contact through AO-27 this morning. The contact was with AI9IN in Indiana, USA. I’m looking forward to making more contacts using this satellite in the near future. Here are the current frequencies for the uplink and downlink (no PL tone is required):
Uplink – 145.850 MHz FM
Downlink – 436.7975 MHz FM
It’s great to have yet another FM satellite that we can all use. I hope that other satellite operators will give AO-27 a try.
We get quite a few requests from folks to explain how to get started with Amateur Radio Satellites. Requests for information on how to build a computer-controlled ground station for Linear Satellites are also pretty common. I recently got such a request from our CWA class so I decided to put together a session on this topic.
We covered a number of topics and demonstrations during the session including:
How to put together a simple station and work FM EasySats with HTs and a handheld antenna
A recorded demonstration of some contacts using FM EasySats
How-to build a computer-controlled station and work Linear Transponder Satellites
Fixed and Portable Satellite Station Antenna options
A recorded demonstration of some contacts using Linear Satellites
I have joined the ARISS Program as a Mentor to help schools make contacts with astronauts on the International Space Station (ISS). School contacts as part of the ARISS program can take two forms – Direct Contacts and Telebridge Contacts.
ARISS Direct Contacts
Direct contacts involve setting up a space communications ground station at the school making the contact.
ARISS Direct Contact Ground Station Antennas at Council Rock HS
Direct Contacts involve a great deal of preparation and a local Ham Club which has considerable VHF weak-signal experience and equipment to partner with on a school’s contact. There can also be considerable expense involved in assembling the necessary ground station for a Direct Contact. In addition, some locations are much better than others in terms of access to good, high-angle ISS passes and an environment that is relatively free of nearby obstructions like buildings, hills, etc.
Students at Maani Ulujuk High School in Rankin Inlet, Nunavut, Canada
Telebridge contacts involve using an existing ground station in a different location with an audio link to the school making the contact via telephone. This type of contact provides a high-quality experience with an astronaut on the ISS without the need to construct a ground station at the school. It enables the teachers involved in the contact process to focus on the educational aspects of their contact with the ISS.
All of the ARISS Telebridge Ground stations are built and operated to very high standards.
Also, schools in difficult locations or those who don’t have the needed support of a local Ham Radio club with the necessary space ground station equipment can still enjoy making a contact with an astronaut on the ISS. In addition, a Telebridge contact also enables the supporting Amateur Radio Club to focus on providing great Amateur Radio activities and educational support to their partner school.
Adding Telebridge Capability to Our Station
Space Communications Ground Station at AB1OC-AB1QB
We’ve used the station here to make many satellite contacts and to listen to ARISS contacts from the ISS. We’ve also used our station to receive images from the ISS during ISS SSTV events. We’ve decided to add a Phone Patch to our station here to enable it to be used as a testbed for schools preparing for Telebridge contacts.
Adding A Telephone Patch
Phone Patch To Enable Testing and Hosting Telebridge Contacts
A Telephone Patch enables a third party to communicate over an Amateur Radio link using a telephone. A Phone Patch provides a connection between a Transceiver and a telephone line. It also handles creating a proper balance at the 2-wire Hybrid Interface that connects to the telephone line to the radio. A typical Phone Patch device also provides for Transmit and Receive level adjustments.
Setting up the MFJ Phone Patch was pretty straightforward. All that was required to work with our IC-9700 Transceiver was to set the internal jumpers in the MFJ Phone Patch to configure its microphone connection properly. The MFJ Phone Patch came with a cable to connect to the round microphone jack on the IC-9700 Transceiver. A connection between our audio amplifier to bring audio into the Phone Patch was made to complete the installation.
Testing On The Air
The MFJ Phone Patch was adjusted to achieve a good balance on the 2-wire Hybrid Interface to the telephone line and the Transmit and Receive levels were properly adjusted prior to on-the-air use. These procedures are clearly explained in the manual for the MFJ-624E and are easy to complete.
With these steps complete, we set up a telephone call and made several contacts using FM stateless on the air. We received good audio reports and could easily understand the downlink audio using a standard telephone receiver.
Becoming an ARISS Telebridge Ground Station
My initial purpose for adding Telebridge capability to our ground station was to enable it to be used to perform testing of the audio systems in schools that will be hosting Telebridge contacts. I am also going to apply to become one of the ARISS Telebridge Ground Stations in North America. We have an emergency backup power system here and our station’s location in our home makes it a good choice for situations where contacts need to be made at any time of the day or night. More to come on this in the future.
More About Our Ground Station
Here are links to some additional posts about our Satellite Ground Stations:
We’ve recently received our L24TX Transmit Converter from Down East Microwave. The unit is compact, simple, and produces up to 25W output in the satellite section of the 23 cm band (1260 MHz – 1270 MHz, actually 24 cm). The L24TX is a transmit-only device that is intended to enable L-band uplinks for Satellite use. This article is about our most recent project which involved integrating the L24TX into our Flex SDR Satellite System.
24 cm Tx Converter Rear Panel
Connecting the unit is straightforward. The unit requires an IF input, a 10 MHz reference oscillator, DC power, and a transmit keyline. The later two inputs are provided via a 7-pin connector and a DEM supplied cable. We ordered our unit with the following configuration options:
IF 28 Mhz = 1260 MHz output
Max IF Drive Level – +10 dBm
Fan and Case configured for mounting in the shack
Fortunately, our feedlines for the 23/24 cm band are hardline-based and relatively short. The unit is also available in a configuration that would enable it to be remotely mounted in an enclosure on a tower.
24 cm Tx Converter Installation in our Remote Gateway SDR Rack
The unit fits nicely into our Remote Gateway SDR Rack. The L24TX does not include a power output display so we used a 23/24 cm sensor and our WaveNode WN-2 Wattmeter to monitor output power from the unit. The unit does have leads that output a voltage that is proportional to output power. This could be used to build a power output bar display or meter. the front panel indicates display a power-on indication, lock to the 10 MHz clock input, and Tx when the unit is transmitting.
Overall Satellite SDR System Design
Integration into our Satellite SDR System was straightforward. Our system already included splitters for the 10 MHz GPSDO and the 28 MHz Transverter outputs from our Flex 6700 SDR. I had hoped to use one of the leads from the SmartSDR BITS cable we are using to key our 70 cm Transverter but the BITS cable did not have an adequate drive level to key the L24TX.
Remote SDR Gateway Tx Band Settings
Fortunately, the Flex 6700 has configurable TX1-TX3 outputs for keying devices like Transverters. The use of the TX2 output to key the L24TX was easily configured in the SmartSDR’s TX Band Settings.
23 cm Tx Converter Setup in SmartSDR
It is necessary to configure SmartSDR for the L24TX. The required settings are in the XVTR options tab. In addition to configuring the mapping between the Flex 6700’s XVTR IF frequency and the unit’s output Frequency, one needs to set the IF drive levels. We used the default drive level of 6.0 dBm and adjusted the IF Gain Control on the L24TX until the full output of 25W was reached while transmitting a tone. The correct adjustment is apparent when further gain increases do not provide a proportional increase in output power. The proper setting of the RF drive and gain will keep the L24TX’s output in its linear range of operation.
SDR Satellite System Remote Power Control via a RigRunner 4005i
The RigRunner is remotely accessible over the Internet and our network via a password-protected web interface. This enables us to easily power down or power cycle individual components in the Satellite SDR System remotely.
MacDoppler Tracking AO-91
With all of the hardware installation and calibration steps complete, we are turning our attention to the software side of the setup. We will be using MacDoppler for satellite tracking and VFO control of our Satellite SDR System. This creates a need to connect the MacDoppler program which runs on a Mac to SmartSDR and the Flex 6700 which is a Windows-based system. Fortunately, MacDoppler provides a UDP broadcast mode that transmits az/el antenna position information as well as data to control radio VFOs to adjust for Doppler shift.
FlexBridge Software Beta
We are working on a custom windows application called FlexBridge to enable MacDoppler to run our Flex SDR-based Satellite System. FlexBridge runs on a Windows PC. It receives and parses the UDP broadcast messages from MacDoppler and uses the FlexLib API to properly configure and control the Flex SDR’s VFOs.
SmartSDR Operating With AO-92 in L-V Mode
At present, FlexBridge can configure and control SmartSDR (or a Maestro Client) that is operating our SDR Satellite System. The screenshot above shows the MacDoppler, FlexBridge, SmartSDR combination operating with AO-92 in L/V mode. This software is still an in-progress development and we plan to add the ability for FlexBridge to connect to the radio via SmartLink as well as support for the Green Heron RT-21 Az/El Rotator Controller that we are using. We’ll be sharing more about FlexBridge here as the software development progresses.
The next step in our Satellite Station 4.0 Remote Gateway project will be to move our satellite antenna controls and feedlines into the shack and begin testing the complete setup using local control. Once this step is complete, we’ll focus on the final steps to enable remote operation of our satellite station via the Internet.
Here are links to some additional posts about our Satellite Station 4.0 Projects:
We continued to test our Portable Satellite Station 4.0 as part of AMSAT’s 50th Anniversary Celebration WAS Activations. You can read about the activations and our station’s performance via the link above. Overall, we were pleased with how the portable setup performed. The weakest link was the downlink performance of our antenna system. We are working on some ideas to improve this element of our setup – more to come on this project…
It seems that Hams struggle a bit to get their HTs programmed with the right set of repeaters and other memory settings. The Nashua Area Radio Society will be offering a custom HT Programming Clinicat HamXposition @ Boxboro 2019 to help hams get their HT’s programmed…
I’d like to invite our readers who are planning to attend the Northeastern HamXposition 2019 @ Boxboro on September 7th and 8th to bring their HT. We will be providing an HT Programming Clinic at the show and we’d be happy to create a custom program for your HT and location. Our custom programs can also include FM Satellites, Foxes, and more!
Portable Satellite and Grid Square Activation Station
We were up on Mt. Washington here in New Hampshire this past weekend and we decided to use the SOTA activation as a test for our updated Portable Satellite Station 4.0. It turned out that the station was also a great SOTA and Grid Square Activation station for terrestrial contacts.
A Solar-Battery Power system capable of operating the station continuously for a full day
A laptop computer for Satellite Tracking and Doppler correction
Portable Antenna System
Elk Antenna on Tripod
We decided to keep our antenna system simple and quick to deploy. We choose a portable 2m/70cm antenna from Elk and mounted it on a camera tripod. A carpenter’s slope gauge is used as an elevation indicator and our iPhone serves as a compass to point the antenna in the azimuth direction. A weighted bag, Bungie cord, and a tent stake anchor the tripod in the windy conditions on the mountain. A 15 ft length of LMR-240uF coax with N-connectors makes the connection between the antenna and the rest of the station.
Station Transceiver and Supporting Gear
Portable Station Transceiver and Preamps
We decided to mount the station Transceiver and supporting gear on a piece of plywood to make it easy to transport and setup. The components from lower-right moving counter-clockwise include:
The preamps are powered and sequenced by the IC-910H through its coax outputs. The 70cm side of the second diplexer is used as a filter to prevent transmissions on 2m uplinks from de-sensitizing 70cm downlink signals.
Portable Station Electronics
The use of the mounting board for all of the components allows the station to deployed quickly and helps to ensure reliable operation.
We used a MacBook Air Laptop running MacDoppler to control the transceiver’s VFOs (via a USB CI-V cable). MacDoppler also provided azimuth and elevation data used to point the antenna during satellite passes.
Portable Solar-Battery Power System
Powering a 100w radio in a way that allows continuous use for a day can be a challenge. It’s important to do this in a way that does not generate noise so we do not disturb others trying to enjoy the outdoors. We met all of these needs using a combination of solar power and batteries.
Portable Solar Power
The primary source of power comes from a pair of 90w foldable solar panels from PowerFilm. The panels are wired in series and connected to an MPPT Charger which charges a pair of batteries. This approach allows the system to provide usable power when it is cloudy and the voltage output of the solar panels drops.
We use a pair of A123 10 Ah LiPo battery packs to supply high-current capacity when transmitting. The solar-battery combination is capable of maintaining full battery voltage while supporting the continuous operation of our station for a full day.
The MacBook Air Laptop batteries are adequate to operate the station during the available satellite passes. We have a 12V DC to 120 VAC inverter which can power the computer from our solar battery setup if needed.
View from Mt. Washington Summit
Our portable station did very well during its initial test! I had to move the antennas and operate the station by myself on this activation which limited my ability to make a large number of contacts during the limited number of satellite passes that were available. Still, I was able to make 6 solid contacts through AO-91 and AO-85 while on Mt. Washington. I did not have a suitable linear satellite pass to make contacts but I was able to hear the EO-88 beacon with no problems and confirm that the doppler correction system was working well.
The station also put in a great performance visa-vie 2m terrestrial contacts. We made a total of 70 contacts using 2m FM and USB! We received many good signal reports with our longest contacts being some 275 mi from our location. We also worked stations on four other SOTAs this way.
Learnings and Next Steps
Our station exceeded my expectations during our initial test on Mt. Washington – especially in terms of the number of Terrestial Contacts that I was able to make with it. I did notice that the transmit side of the system was quite a bit stronger than the receive side. This is an indication that a better antenna would help.
We changed the antenna polarization to vertical for 2m FM contacts and to horizontal for 2m USB contacts. This helped the receive side performance quite a bit.
I found that a headset was essential for satellite and terrestrial weak-signal operation in USB mode. I was able to use the hand microphone and the radio’s speaker for most of the 2m FM contacts that I made. This gave interested onlookers a chance to experience Amateur Radio.
Satellite operation would have been much easier and more productive with a helper to handle pointing the antenna while we operated. This improvement will need to be coupled with a headset/speaker combination that allows the person that is pointing the antenna to hear the quality of the downlink while moving the antenna and finding the best polarization.
I am looking forward to doing some grid-square activations using our upgraded portable station. It was a pleasant surprise to find as much interest in Terrestial contacts on the 2m band as we did. The Nashua Area Radio Society does several SOTA activations each year and I am looking forward to using that station for these as well.
Here are links to some additional posts about our Satellite Station 4.0 Projects:
We have created a program that we call Ham Bootcamp. Bootcamp to helps recently licensed and upgraded hams to get on the air. We are making this program available to up to 100 HamXpostion attendees on a first-come-first-served basis.
Our Bootcamp program will run from 9 am to noon on Saturday, September 7th in the Federal Room. Bootcamp will feature tracks for both Technician and General class license holders. It is also a great place for folks who are not yet licensed to learn more about Amateur Radio and how to get on the air.
Our Bootcamp program will include:
How to make a contact and join a repeater net
Putting together an HF station
Radio, antenna, and feed line choices
Getting started with FT8 and digital modes
Exchanging QSL cards
Learning Morse code
Tips on upgrading
Introduction to ham radio kit building
Handheld radio programming tutorials
Ham Bootcamp is free. Participants will receive discount certificates for a kit build at the show and for purchase of Ham Radio Gear from Ham Radio Outlet.
I wanted to share our plans for several hands-on activities at HamXposition @ Boxboro in September. We hope that Ham Bootcamp will be of particular interest to folks getting into Amateur Radio. You can learn more about Ham Bootcamp and all of our planned activities via the link above. We hope to see some of our readers at HamXpostion next month!