Listen In On The Council Rock ARISS Contact on Thursday!

International Space Station (ISS)

International Space Station (ISS)

Students at Council Rock High School South in Southampton, PA will be talking with Astronaut Drew Morgan, KI5AAA aboard the ISS on Thursday. The ISS will be over our area here in the Northeastern Unit States beginning at about 12:55 pm eastern time on Thursday, December 5th. Council Rock’s ARISS Contact is made possible by the ARISS Program

Source: Listen In On The Council Rock ARISS Contact on Thursday!

You should be able to hear Drew on the ISS voice downlink at 145.800 MHz FM. The ISS pass will be a high one over our area. As a result, we should be able to hear the downlink using a good vertical antenna and perhaps even using an HT.

You can join the Council Rock Facebook Group for updates and watch a live stream of the contact on Thursday between 12:30 – 1:30 pm.

I am serving as the ARRIS Mentor for Council Rock H.S. South’s ISS Contact. I am looking forward to the opportunity to be at their school on Thursday to be part of what I am sure will be a very memorable event.

You can learn more about the ARISS Program and how to secure an ISS contact for your school here.

Fred, AB1OC

EME Station 2.0 Part 5 – Control Cables and Rotator Controller

Control Cable Junction Box on EME Tower

Control Cable Junction Box on EME Tower

Snow is coming to New England this weekend so we wanted to get the control cables run to our new EME Tower before the ground is covered with snow. The project involved installing a Utility Enclosure on our tower and running three control cables to our shack for the following devices:

Az-El Rotor and Preamp Switching Control Connections

Az-El Rotator and Preamp Switching Control Connections

We began by install some barrier strips and a copper ground strap in the Utility Enclosure. The copper strap provides a good ground connection to the tower and associated grounding system. The enclosure is clamped to the tower using two stainless steel clamps.

We ran three new control cables through the conduits that we installed between the tower and our shack and terminated them in the utility enclosure. We only needed 6 leads for control of the planned MAP65 Switching and Preamp System which will go on our tower later so we doubled up some of the higher current connections using two wires in the 8-conductor cable.

Green Heron RT-21 Az-El Rotator Controller

Green Heron RT-21 Az-El Rotator Controller

The final step was to hook up our rotator cables to a Green Heron RT-21 Az/El Rotator Controller in our shack.  We do not yet have our elevation rotator so we tested the M2 Orion 2800 Azimuth Rotator that is installed in our tower. The azimuth rotator is configured so that the rotator’s dead spot faces north. This is a good configuration of our planned EME operation.

With all of our control cabling in place, we are ready to begin preparing our Antennas, Elevation Rotator, H-Frame, and MAP65 components to go on our EME Tower. We’re hoping that the weather will cooperate and enable us to get these steps completed during this winter.

Here are some links to other articles in our series about our EME Station 2.0 project:

Fred, AB1OC

Winter Field Day VHF+ Preparations

Jamey AC1DC with Completed WFD VHF+ Mast

Jamey AC1DC with Completed WFD VHF+ Mast

We are continuing to make progress on our preparation for VHF+ Operations at Winter Field Day (WFD) 2020. We had a lot of fun on the VHF+ bands at WFD 2019 and we are planning to add some more bands for our operation this year. We’ve assembled a portable mast system to put us on 3 new bands…

Source: Winter Field Day VHF+ Preparations – Nashua Area Radio Society

We’ve been busy with preparation for Winter Field Day 2020. My part of this project is to increase our participation in operations on the VHF+ bands (6m and above). We are accomplishing this with a 30 ft push-up mast, some new antennas, and using Transverters for the 1.25m and 33cm bands. You can read more about our preparations and the equipment that we will be using on the VHF+ bands via the link above.

Fred, AB1OC

EME Station 2.0 Part 4 – New EME Tower Is Complete

Three Tower Antenna Farm

New EME Tower in Our Antenna Farm

Our goal for this phase of our EME Station Project is to get our new tower up, install the Azimuth Rotator and Mast, and run the hardline and coax cables for our antennas from the shack to our new tower. Our EME tower is constructed using Rohn 55G tower sections. It will be 26 ft tall and will have approximately 18″ of our 3″ mast protruding above the tower. The tower is a free-standing/guyed hybrid design with the first section being cemented into the ground.

EME Tower

FInished Tower Base

The base section and the three guy anchor blocks were completed a little while back. The holes were backfilled and we’ve given the cement a couple of weeks to cure.

First Tower Section Installed Using a Gin Pole

First Tower Section Installed Using a Gin Pole

Matt, KC1XX, and Andrew of XX Towers began by installing a winch and a gin pole on the base section of the tower. They used the Gin Pole to hoist the second tower section into place and secure it. They also attached the top plate to the third tower section in preparation for installing it along with our mast.

Mast and Top Tower Section Going Up

Mast and Top Tower Section Going Up

It is always a challenge to install a mast inside a new tower. The mast we are using is a heavy, 22 ft 4130 chrome molly steel mast that weighs over 250 lbs. Getting the mast inside the tower was quite a feat! Matt and Andrew rigged the top tower section and the mast together and pulled both up together on the Gin Pole. Next, one leg of the top tower section was attached and a second pully was used to pull the mast up through the top tower section until it could be placed inside the tower. The last step was to raise the top tower section a second time using the Gin Pole to seat it on top of the rest of the tower. Finally, the mast was lowered inside the tower to the base and the top tower section was bolted on to complete the tower.

Upper Guy Anchor Bracket on Tower

Upper Guy Anchor Bracket on Tower

The next step involved attaching the upper guy anchor bracket to the top section of the tower and rigging the guy anchor cables. We decided to use Phillystran Guy Cable to avoid interactions with our antennas.

Guy Anchor Cable

Guy Anchor Cable

The completed cables are tensioned using turnbuckles. We adjusted the cables to plumb the tower and then safety-wired the turnbuckles so they will not come loose.

Azimuth Rototor in Tower

Azimuth Rotator in Tower

The next step was to install an M2 Antenna Systems Orion 2800G2 Azimuth Rotator in our tower. The use of the 22 ft mast allowed us to place the rotator about 5 ft above the ground where we can easily service it in the future. The long mast also acts as a torque shock absorber when the rotator starts or stops moving suddenly. With the rotator in place, we attached the mast and clamped it at the rotator and thrust bearing at the top of the tower.

Tower Base, Coax Feedlines, and Guy Anchors

Tower Base, Coax Feedlines, and Guy Anchors

The last step in our project was to install our coax cables and hardlines on the tower and run them through a 4″ underground conduit to our shack. We pre-made the two LMR-600 coax cables for the receive side of our EME Antenna System previously. We cut a section of LDF5-50A 7/8″ Hardline to approximately the same length as the LMR-600 coax cables.

Pushing Coax Cables and Hardline Through the Condui

Pushing Coax Cables and Hardline Through the Conduit

We used a cutoff plastic bottle to protect the ends of the coax cables and hardline as we pushed them through approximately 50 ft of buried 4″ conduit. The conduits were constructed to create a gradual turn into and out of the ground and the cables went into the conduit smoothly.

Coax Cables Exiting the Conduit Near Our Shack

Coax Cables Exiting the Conduit Near Our Shack

With the cables in place, we installed N-female connectors on each end of the 7/8″ hardline. We used rubber reducers to make it easier to deter water from entering the conduits where the cables exit.

Coax Cable Ground Block Connections

Coax Cable Ground Block Connections

We expanded out main shack entry ground block using an 18 position tinned cover ground bar from Storm Copper to make room for additional static arrestors for our EME Antenna System. The LMR-600 receive-side coax cables and the 7/8″ hardline connection for the transmit-side of our EME antennas terminate on N-connector Static Arrestors from Alpha Delta.

Completed EME Tower

Completed EME Tower

Our new EME tower is complete and ready to accept the Elevation Rotator, H-Frame, and Antennas from M2 Antenna Systems when they arrive. We plan to complete the grounding system and get the Azimuth Rotator hooked up and tested with our Green Heron Engineering RT-21 Az/El Rotator Controller in the near future.

Here are some links to other articles in our series about our EME Station 2.0 project:

Fred, AB1OC

EME Station 2.0 Part 3 – Phase Tuned Receive Coax Cables

Measuring Coax Cable Electrical Length Using a VNA

Measuring Coax Cable Electrical Length Using a Vector Network Analyzer (VNA)

Our new 2M EME station will have Adaptive Polarity capability via MAP65. MAP65 requires that received signals from the Horizontal and Vertical planes of our antennas arrive at the receivers in our shack precisely in phase with each other.

We decided to use a pair of LMR-600 coax cables for the receive side of our feedlines. We made these cables from an unterminated length of LMR-600 coax measured to cover the distance from the top of our planned 26 ft EME tower to the ground block at the entry to our shack. The cables are approximately 82 ft long and they must be cut to be equal in length to with 1/16″!

The easiest way to measure the length of an unterminated coax cable is to determine the minimum frequency of resonance of the cable when the opposite end is an open circuit. One can then use the speed of light and the velocity factor of the cable to compute its exact length:

Length = (Speed of Light X Velocity Factor) / (Resonant Freq. X 4)

Doing these measurements with an open circuit at the far end of the cables enables trimming the length of the two cables to be matched in small increments until our two cables are exactly the same length.

VNA Measurement of Open Coax Cable Resonance

Vector Network Analyzer (VNA) Measurement of Open Coax Cable Resonance

We used an Array Solutions VNA 2180 connected to a Windows PC to precisely measure the minimum Resonant Frequency of our LMR-600 coax cables as we trimmed them. Once they were equal in length to within 1/16″, we installed an N-Female connector on the unterminated end and re-verified each cable’s length. A frequency accurate antenna analyzer can also be used to make these measurements.

We will need to repeat these steps of the receiver-end and antenna preamp box jumper cables which will make up the rest of the receive side feedlines for our EME antenna system once these components are installed. We also plan to make a final end-to-end measurement of the receive-side feedline assemblies to fine-tune the phasing of the completed feedline runs.

With this step complete, we are ready to put up our new tower and attach the feedlines.

Here are some links to other articles in our series about our EME Station 2.0 project:

Fred, AB1OC

EME Station 2.0 Part 2 – Excavation, Footings, and Conduits for New Tower

EME Tower

FInished Tower Base and Cable Conduits

The first part of our EME project is to put up a new tower to support our antennas. Our plans call for a 26′ tower built using three Rohn 55G tower sections. Four feet of the first section of the tower is cemented in a concrete footing to anchor the tower’s base. The tower is also going to be guyed to ensure that it is very stable.

EME Tower

Digging Footings for our New Tower

We are working with Matt Strelow, KC1XX and Andrew Toth of XX Towers to put up our new tower. Matt brought out his tractor and dug the footings for our tower and for the associated conduits that will carry coax and control cables to our shack. The photo above shows the completed hole and form for the main tower base. Matt is working on the footings for one of the three guy anchors.

EME Tower

First Tower Section and Rebar Cage

Here’s a closer look at the tower base. The footing includes a rebar cage to reinforce the concrete footing. There is also 6″ of crushed stone in the bottom of the hole that the tower legs sit it. It is very important that the bottoms of the tower legs remain open and do not become plugged with cement so that water in the legs can drain. If the legs cannot drain properly, water will accumulate and freeze. This can split open the tower legs and ruin the tower.

EME Tower

Cable Conduits with Drains

We also installed two conduits (a 4″ and a 2″ run of schedule 80 conduits) from the base of our tower to our shack. These conduits will carry coax feed lines and control cables to our new tower. We used a pair of 22° elbows to create a smooth transition to bring the conduits out of the ground. This will ensure that our hardline and other coax cables can be placed in the conduits without creating excessive bends.

Conduits will fill with water even if they are sealed. This happens as a result of the condensation of water in the air. To prevent our conduits from filling with water, we created two drain pits at the bottom of the trench at the two lowest spots in the conduit runs and filled them with stone. We drilled a few holes in the bottom of the conduits above the drain pits to allow the water to drain so our cables will remain dry.

EME Tower

Cadweld’ed Ground Cable Bonded to a Ground Rod

We also created a bonding ground cable run from our new tower to the ground system at our shack entry. The bonding system was created by driving an 8′ ground rod every 10′ in the trench between our new tower and the perimeter ground around our house.

#2 stranded copper ground cable was Cadweld’ed to each ground rod to create a ground path to bond the tower to the perimeter grounding system around our house. Using a Cadweld system is simple and produces strong connections that will not deteriorate.

Here’s a video that shows our a Cadweld is made. We’ll cover completing the ground connections to the tower and the perimeter grounding system in a future article.

EME Tower

Completed Footings – Ready to Pour Cement

Finally, we used some sections of rebar to firmly support the guy anchor rods prior to pouring the cement. If you look closely, you can see a portion of the rebar material in one of the guy anchor footings in the photo above.

EME Tower

Cement Mixer

The next step in this part of our project was to pour the cement. A large cement mixer brought the proper cement mix to our QTH and Matt used his tractor to transport the cement from the mixer to the forms. We did a bit of finishing work on the cement base for our tower and let the cement dry for a few days.

EME Tower

FInished Tower Base and Cable Conduits

The last step was to remove the forms and backfill the footings. A little work with a cement finishing block was done on the cement base to round off the rough edges left by the forms. The cable conduits emerge from the ground next to the tower base. You can also see one end of the copper bonding cable next to the conduits as well.

EME Tower

Completed Guy Anchor

Here’s one of the completed guy anchor rods after backfilling. We are going to let the cement harden for a couple of weeks and then we’ll complete the construction of our new tower.

Here are some links to other articles in our series about our EME Station 2.0 project:

Fred, AB1OC

EME Station 2.0 Part 1 – Goals and Station Design

The Moon

The Moon

EME or Earth-Moon-Earth contacts involve bouncing signals off the moon to make contacts. EME provides a means to make DX contacts using the VHF and higher bands. There are also some EME Contests including the ARRL EME Contest that provides opportunities to make EME contacts.

We made some 2m EME contacts a while ago using the 2m antenna on our tower at about 112′. This experience created interest on my part in building a more capable EME station at some point in time. Well, the time has finally arrived.

EME Propagation

Understanding EME Propagation is a project in of itself. The following is a brief overview of some of the (mostly negative) effects involved.

The path loss for EME contacts varies by Band and is in excess of 250 dB on the 2m band. There are some significant “propagation” effects that further impair our ability to make EME contacts. These include:

  • Faraday Rotation – an effect which results in the polarity of signals being rotated by differing amounts as they pass through the ionosphere on their way to the moon and back
  • Libration Fading – fading caused by the adding of the multiple wave-fronts that are reflected by the uneven surface of the moon
  • Path loss variations as the earth to moon distance varies – the moon’s orbit around the earth is somewhat elliptical in shape resulting in a distance variation of approximately 50,000 km during the moon’s monthly orbital cycle. This equates to about a 2 dB variation in total path loss. An average figure for the path loss for 2m EME might be in the range of 252 dB.
  • Transit Delays – at the speed of light, it takes between 2.4 and 2.7 seconds for our signals to travel from earth to the moon and back.
  • Noise – the signals returning from the moon are extremely weak and must compete with natural (and man-made) noise sources. The sun and the noise from other stars in our galaxy are significant factors for EME communications on the 2m band.
  • Doppler shifts – as the earth rotates, the total length of the path to the moon and back is constantly changing and this results in some frequency shift due to doppler effects. Doppler shift changes fairly slowly compared to the time it takes to complete a 2m EME QSO so it is not a major factor for the 2m band.
  • Moon’s size vs. Antenna Aperture – the moon is a small target (about 0.5 degrees) compared to the radiation pattern of most 2m antenna systems. This means that most of our transmitted power passes by the moon and continues into space.

Taking the moon’s size, an average orbital distance, and an average Libration Fading level into account, one can expect only about 6.5 % of the power that is directed towards the moon to be reflected back towards earth.

EME “Good Guys”

One might look at the challenges associated with making EME contacts and say “why bother”? EME contacts present one of the most challenging and technical forms of Amateur Radio communications. It is this challenge the fascinates most EME’ers including this one. Fortunately, there are some “good-guy” effects that help to put EME communications within reach of most Amateur Radio stations. These include:

  • WSJT-X and the JT65 Digital Protocol – In the early days of EME communications, one had to rely on CW mode to make contacts. All of the impairments outlined above made these contacts very challenging and the antennas and power levels required put EME communications out of the reach of most Amateurs. Along came Joe Taylor’s digital JT65 protocol which changed all of this. It is now possible to make 2m EME contacts with a single (albeit large) 2m yagi and 200W or so of input power. As a result of these innovations, many more Amateurs have built EME stations and are active on the 2m (and other) bands. Many DXpeditions are now also including EME communications in their operations.
  • Ground Gain Effects – a horizontally polarized antenna system will experience approximately 6 dB of additional gain when the antenna(s) are pointed approximately parallel to the ground. Ground gain effects made it possible for us to use our single 2m antenna to make our first 2m EME contacts.
  • MAP65 Adaptive Polarization – Fading resulting from polarity changes due to Faraday Rotation can cause a received signal to fade to nothing over the period of time needed to complete a 2m EME contact. These polarity “lock-out” effects can make contacts take a significant amount of time to complete. Fortunately, a version of the software which implements the JT65 protocol called MAP65 has been created that will automatically detect and adapt to the actual polarity of signals returning from the moon. More on how this is achieved follows below. MAP65 is most useful for making “random” EME contacts during contests. In these situations, a variety of signals will be present in a given band with different polarities and the MAP65 software can adapt to each one’s polarity and decode as many simultaneous signals as possible.
  • Commercially Available Amplifiers for the VHF+ Bands – Modern, solid-state amplifiers have become much for available for the 2m band (and other VHF and higher bands). This has made single-antenna EME on 2m and above much more practical for smaller stations with a single antenna or a small antenna array.

Our 2m EME Goals and Station Design

We began this project by making a list of goals for our 2m EME Station 2.0. Here is that list:

  • Operation using JT65 and QRA64 digital protocols and possibly CW on the 2m EME band
  • 80th percentile or better station (i.e. we want to be able to work 80% of the JT65 capable 2m EME stations out there)
  • Operation in EME contests and EME DX’ing; earn a 2m EME DXCC

We have come up with the following station design parameters to meet these goals:

  • An array of four cross-polarized antennas with an aggregate gain of approximately 23 dBi
  • A new 26′ Rohn 55G tower to support the antennas
  • A computer-controlled Azimuth/Elevation rotator system to allow us to track the moon
  • Input power in the range of 900W
  • A MAP65 capable SDR-based receive system which can support adaptive polarity
  • Low-noise, high gain preamplifiers located at the antennas
  • A low-loss feedline system for both the transmit and receive sides of the system
  • Use of both the MAP65 and standard versions for WSJT-X for digital operations
  • Use of Linrad as a front-end to the receive side of our system
  • Our existing Icom IC-9100 Transceiver and M2 1K2 2m Power Amplifier for transmitting

Antennas

WA1NZP Antenna System (4 M2 XP32 X-Polarity Antenna Array)

WA1NPZ Antenna System (4 M2 Antennas XP32 X-Polarity Antenna Array)

It takes some fairly large antennas to create an 80th percentile EME station. We are planning a setup similar to Bob, WA1NPZ’s system shown above. We are going to put up a 26′ Rohn 55G tower for our EME antenna system. We will be using four M2 Antenna System XP28 Antennas mounted on an H-frame to create a 15′ x 15′ square array.

The combined gain of the system will be approximately 23 dBi with a 3 dB beamwidth of 12.5°. The XP28 antennas are designed for stacking and have good Gain/Temperature (G/T) characteristics. G/T is a measure of the gain and noise performance of an antenna system. See VE7BQH’s tables for some interesting data on G/T for many commercially available EME and VHF+ antennas.

The antenna system will have separate feeds for the antenna array’s Horizontal (H) and Vertical (V) planes. The Horizontal elements will be oriented parallel to the ground to maximize ground gain when the H plane is used for transmitting (and receive). A pair of 4-port power combiners will be used to combine the H and V polarities of the four antennas into a pair of H and V feedline connections.

Plans call for a combination of the M2 Orion 2800G2 and MT3000A rotators to be used along with a Green Heron RT-21 Az/El Rotator Controller to provide computer-controlled tracking of the moon. A 22′ section of 3″ Chrome Molly mast material will allow the azimuth rotator to be located near the base of the tower where it can be easily serviced.

Tower Mounted Preamps and Polarity Switching

MAP65 Switching and Preamp Housing

MAP65 Switching and Preamp Housing

M2 Antenna Systems will be supplying a MAP65 Switching and Preamp System that will mount on the tower near the antennas. The MAP65 Housing provides switching and separate receive preamplifiers and feedlines for the H and V polarities of the antennas. Separate H and V receive coax connections bring the Horizontal and Vertical elements of the antennas back to the shack. A third coax connection is provided for Transmit. The transmit feedline can be routed to either the H or the V antenna polarity to help minimize Faraday Rotation related fading at the other end of the contact.

S2 Sequencer

S2 Sequencer

An M2 Antennas S2 Sequencer will provide Tx/Rx sequencing and H/V transmit polarity selection via the MAP65 Switching and Preamp System on the tower. The sequencer is essential to provide safe changeovers between receive and transmit and to protect the preamplifiers and the power amplifier during high power operation.

Feedline plans call for a run of 7/8″ Hardline Coax for transmit and a pair of LMR-400uF Coax cables for the H and V receive polarities.

MAP65 Capable Receive Chain

LinRF IQ+ Block Diagram

LinRF IQ+ Block Diagram

The signals returning from the moon in an EME system are very, very weak. Because of this, Noise and Dynamic Range performance are critical factors in an EME receive system. In addition, we will need a pair of high-performance, phase-coherent receivers to enable Adaptive Polarization via MAP65.

LinkRF IQ+ Dual Polarity Receive System

LinkRF IQ+ Dual Polarity Receive System

We are planning to use a LinkRF IQ+ Dual Channel Receive Converter in our EME system. The Link RF IQ+ features excellent noise and dynamic range performance and its phase-coherent design will support adaptive polarity via MAP65. The IQ+ separately converts both the H and V polarities of the antennas into two separate pairs of I/Q streams.

UADC4 High-Performance A/D Converter

UADC4 High-Performance 4-Channel A/D Converter

The four channels (two I/Q streams) from the LinkRF IQ+ must be digitized and fed to a Windows PC for decoding. The conventional way to do this is with a 4-channel, 24-bit soundcard. The available computer soundcards add a good bit of noise and therefore limit the overall dynamic range of an EME system. Alex, HB9DRI at LinkRF has come up with the UADC4 – a high-performance 4-channel ADC that is specially designed for software-defined radio. The UADC4 design is based on CERO- IF conversion and is optimized for EME use. The UADC4 should add about 10 – 15 dB of dynamic range improvement over a typical 24-bit PC Soundcard. Alex is currently taking pre-orders for the next run for UADC4 devices. You can contact him at info@linkrf.ch for more information.

Software

JT65 Software Block Diagram

JT65B Software Block Diagram

Our plans for JT65 software and related components for our EME station are shown above. We are planning on running a combination of Linrad and WSJT software on the same Windows PC to handle JT65B QSOs. There are two configurations that are applicable to our plans:

We are also planning to develop a simple windows application that will read the Moon Tracking data that is generated by WSJT MAP65 and WSJT-X and use it to control the rotator system associated with our EME antennas. More on this to come in a future article.

Transmit System

2m Amplifier And Sequencers

2m Amplifier and Sequencers

A combination of our existing Icom IC-9100 Transceiver and our 2M-1K2 Amplifier will be used for the Transmit side of our system. The 2M-1K2 can generate about 900W when transmitting in JT65B mode.

Well, that about covers it as far as our 2m EME goals and station design go. The plan is to break ground for the new EME tower later this week. We’ll continue to post more articles in this series as our project proceeds.

Here are some links to other articles in our series about our EME Station 2.0 project:

Fred, AB1OC

New 70cm Yagi

M2 Antenna Systems 432-9WLA Specifications

M2 Antenna Systems 432-9WLA Specifications

We decided to replace our current 70cm yagi with a newer, higher performance one from M2 Antenna Systems. We choose the M2 432-9WLA. The new antenna has higher gain and a cleaner pattern than our current 70cm yagi. It also has a longer boom.

New Yagi Ready For Installation

New Yagi Ready For Installation

The first step in the project was to assemble the antenna and check its SWR on the ground. The elements on an antenna like this typically vary by small amounts and are usually not arranged from shortest to longest. It is important to carefully measure each element during installation to confirm that each element is installed at the correct location on the boom.

The folks at M2 Antenna Systems made up a custom boom support truss for us. This is important given the potential for ice and snow accumulation that we face here in New England. We also made up a section of LMR-600uF coax to connect the antenna to the feedline and preamp system on our tower.

Driven Element Details

Driven Element Details

The new antenna uses a Folded Dipole style feed point. This system is essentially a T-matching arrangement where the two sides of the driven element are fed 180 degrees out of phase. It is important to set the locations of the shorting blocks carefully to ensure proper operation of the driven element and a resulting low SWR.

Yagi Going Up The Tower

Yagi Going Up The Tower

Matt, KC1XX, and Andrew from XXTowers handled the installation of the new Yagi on our tower. The installation involved climbing our 100 ft tower and the 25 ft mast at the top to remove the old yagi and install the new one. Note the careful rigging of the new antenna and associated feedline. This allows the new antenna to be pulled up the tower without damaging it.

Climbing a mast is not for the faint at heart! An installation like this one is clearly a job for experienced professionals. Andrew makes this task look easy. Our tower camera captured some video (click on the image above to play) of Andrew’s handy work.

Completed Installation

Completed Installation

The new yagi (top antenna in the picture above) is installed on a 5 ft fiberglass mast extension. The extension is used to ensure that the antenna does not “see” a metal mast which would disrupt the antenna’s pattern. The final installed height of our new yagi is a little over 125 ft. Note Andrew’s good work in attaching the feedline to the mast.

432-9WLA Installed SDR - Shack End

432-9WLA Installed SDR – Shack End

With the new yagi installed and hooked up, we made a final check of the end-to-end SWR from the shack. The antenna’s SWR is very good and the 2:1 SWR bandwidth extends from the bottom of the 70cm band to almost 450 Mhz. The new antenna is optimized for weak signal work up through the ATV sub-band and its SWR is below 1.2:1 in this range.

Fred, AB1OC

Satellite Station 4.0 Part 10 – Adding 23 cm To Our Satellite SDR

Satellite SDR

DEM L24TX Tx Converter

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.

Satellite SDR

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.

Satellite SDR

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 which 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.

Satellite SDR

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.

Satellite SDR

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.

Satellite SDR

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. Proper setting of the RF drive and gain will keep the L24TX’s output in its linear range of operation.

Satellite SDR

Final Power Distribution Design

The L24TX is powered via the power distribution system in our Satellite SDR Rack. Control and current limiting for the 2m LPDA, 70 cm Transverter, and the L24TX are individually controlled via a RigRunner 4005i IP Power Controller.

Satellite SDR

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

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 which transmits az/el antenna position information as well as data to control radio VFOs to adjust for Doppler shift.

Satellite SDR

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.

Satellite SDR

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:

Fred, AB1OC

AMSAT 50th Aniversary Celebration – W3ZM/1 Activations in CT and RI

Source: AMSAT 50th Aniversary Celebration – W3ZM/1 Activations in CT and RI

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…

Fred, AB1OC