## Signals From Space

Merry Christmas from above! What an interesting present we received. A vision came from on high. Slow Scan TeleVision (SSTV) pictures were sent continually from the International Space Station from December 26 to December 31, 2021 using PD120 format transmitted via 2 meter FM on 145.800 MHz.

The International Space Station (ISS) pictured against Earth’s horizon. [NASA]

If you were in range of their signals it was hard not to receive them! When was the last time you received 2 meter FM from over 250 miles away traveling at
17,000 miles per hour? It was quite an adventure!

Comet dual band vertical at WA2MCR

Several PCARA members downlinked wonderful pictures using the latest MMSSTV software version known as YONIQ. (Free downloads with detailed instructions are available here — Microsoft Windows only). Eagerly awaiting new images from space were Joe WA2MCR, Mike N2EAB, Malcolm NM9J, Rob AC2CT and myself. We learned so much about ISS reception techniques together. The collaboration was brilliant.

Joe was the master of clean images using an Icom IC-7000 with a Comet 2m/70cm antenna raised to roof level. Joe’s results were top notch resolving several near-perfect frames. Joe proved an important lesson: Maximize ISS reception by using an omni-directional antenna free and clear from obstructions, high in the air!

Unless you have a sophisticated tracking system to follow the ISS as it passes, omni-directional antennas will provide the best results. They tend to be more resilient to deep fades and hold the ISS signal for much longer periods of time. My very first ISS attempt was with my 4 element 2m Yagi. The Yagi’s pickup nose was too narrow to hold and sustain receiving the ISS signal. A simple vertical omni antenna is a much better choice.

Mike N2EAB used a homebrew 2m ¼-wave ground plane indoor antenna connected to a Heathkit VF-7401 2m transceiver feeding audio to a HP desktop PC sound card via an audio patch cable. As you’ll see, his ideas really helped our mission.

Malcolm used a Yaesu FT-991A multimode transceiver connected to a Diamond X-200 dual band vertical collinear mounted on his chimney. “The FT-991A has a continuous spectrum display — which allowed me to retune slightly off 145.800 to compensate for ISS Doppler shift.”

Abbree 42.5″ foldable tactical antenna

Rob concocted a novel approach: “I was using a Yaesu FT-3DR (compact digital HT) with an Abbree 42.5-inch antenna, at 5:40 this morning. Indoors by a window with a clear line of sight facing west. I recorded the incoming audio data to a miniSD card, converted the .wav to a .mmv file using Audacity, then used YONIQ to decode. My first SSTV!” It was worth the effort. Rob acquired some beautiful pictures.

My approach echoed my QRP CW reputation. My motto: “Use the very least to get the very most!” My receiver was a beloved Uniden Bearcat BC-350A scanner I bought on sale as a store demo unit for $13 about 25 years ago. I spared no expense for my Earth station’s antenna: A 38 inch tall Larsen mag-mount received as a gift during a visit to the WEPN 1050 transmitter site back when. I placed it out on my porch deck on top of a barbecue grill that became the antenna’s ground plane. I enjoyed consistent predictable reception over and over again all week long. Ubiden BC-350A scanner tuned to 145.800 MHz FM. [N2KZ pics.] ## A Learning Experience We learned many useful and revelatory lessons during the week. One great discovery made all the difference in our results. I had been relying on a NASA site called Spot the Station for alerts telling me when the ISS would be overhead. You can instantly view an up-to-date list of ISS passage times around the world and even sign up for message alerts to be sent to your smartphone. It never failed to inform flawlessly. NASA’s name for the site should have given me a clue regarding Spot the Station’s purpose. The listings and alerts were meant for Space Station fans who want to see the ISS pass over their house. The opportunities multiply wildly when you are trying to receive radio signals from the ISS. We collectively found that you could snag pictures from multiple passes before and after the suggested Spot the Station time. This idea matured into a newfound strategy: The Lazy Man’s Method of receiving ISS SSTV images! We brought this idea to complete fruition. One night, Mike simply left his Earth station equipment on and ready and waited for results. While he was sound asleep, he picked up a formidable frame or two during a pass at 3:15 A.M. We all resolved to adopt his approach immediately. The number of pictures coming in became almost relentless. After up to six viable passes every day you could easily catch a dozen or more frames automatically. Leave your equipment on for the entire duration of the event. You won’t miss a thing! It reminded me of operating an FT-8 station. Sit back, relax and watch the DX find you. ## Many More Tips Why don’t you join us for the next ISS SSTV event (to be announced) coming in 2022? Start with downloading MMSSTV YONIQ software. Audio hook-up is easy. Connect the audio output of any receiver to your computer’s soundcard line-in audio input (look for the jack marked with the microphone icon.) Two-way splitter for 3.5mm mini-jacks can be used on computer’s audio input There is a catch to this. Most computer’s soundcard interfaces do not allow full simultaneous in-out capability. When you plug in the receiver audio into your computer… how do you hear it? I found a clever solution: Use a mini stereo plug two-way adaptor. It now becomes a splitter-combiner. Plug your receiver’s output into one of the adaptor’s female jacks and plug a pair of earpads into the other hole. Then plug the adaptor’s male end into your computer. Now the audio finds its way to your ears and your computer simultaneously. You are all set to monitor your audio! When the ISS is about to pass by you will begin to hear the picture data warble out of the static. Please leave the YONIQ RX mode in Auto mode to receive pictures and also click the Auto history box below the incoming video screen. Now your good pictures will automatically store into the C:\Ham\MMSSTV\History folder on your computer. Up to 32 pictures (default) or 256 (max) will always be waiting for you there. No effort necessary! Make sure ‘Auto history’ (arrowed) is checked and ‘RX Mode’ is set to Auto while on the YONIQ ‘RX’ tab.. [Colors inverted for clarity]. YONIQ software is well-developed and clever. Only the frames with useful content will be stored in History. If you have too much noise and static in your picture the software will disregard it. It doesn’t get more automatic than that! One last tweak: In YONIQ, go to the Option tab, then Setup MMSSTV, then Misc. In the lower right, make sure to press ‘English.’ It will make a lot more sense that way! For more information about everything MMSSTV in a PDF format click here. ## The YONIQ Story YONIQ decoding software is quite a story in itself. The original program is called MMSSTV named after its creator Makoto Mori, JE3HHT from Osaka, Japan. Today’s revised version called YONIQ was developed by Eugenio Fernández EA1IMW and volunteer members of Grupo Radio Galena of Principality of Asturias, a region of northwest Spain. The result is a mature product that is a joy to use. As a free download, it is a blessing and a gift! Yes, they really did think of everything! FT-991A rear panel has a male DB-9 connector (arrow 1) for serial CAT connection as well as a USB Type B connector for both CAT and USB audio. YONIQ was originally composed in Spanish. Detailed instructions will aid you through installation and translate the entire program into English. Scroll down to the bottom of the page to have all your questions answered. You could spend a lot of time experimenting with all its intuitive features! Besides picture handling, there are hooks for logging, automatic SSTV protocol assessment, sophisticated signal displays and CAT (Computer Aided Transceiver) control. You can even record the raw audio data of incoming signals for future processing after initial arrival. Malcolm, NM9J, explained the capabilities of CAT control: “My FT-991A can carry out CAT commands using its DB-9 (serial) connector on the rear panel or using a virtual COM port over the USB cable connection. The FT-991A has a built-in soundcard, so that same USB cable is also carrying digital RX audio from transceiver soundcard to computer for processing, and carrying digital transmit audio to the soundcard built into the transceiver on transmit.” “You can change band, mode and bandwidth from the computer console — and see transceiver parameters such as frequency, LSB, USB etc. displayed on your computer screen. Transmit/receive switching is also available usingCAT computer commands. Some software can complete your computer log entry based on the frequency, start, stop time, call sign of station worked etc. YONIQ/MMSSTV can switch the TX on when a picture is about to be transmitted then switch the transmitter off when the image transmission is completed.” ## Follow the Map Want to know exactly where the International Space Station is right now, where it has been and where it will go in the next pass? Go to the European Space Agency’s indispensable ISS map. Switch to Imperial mode in the bottom right hand corner to convert to measurements you may better understand. European Space Agency map shows current location of the International Space Station, with latitude, longitude, altitude and speed at bottom left. Each ISS orbit takes about 90 minutes. The green circle around the ISS icon on the map shows where the Space Station’s communications coverage area is reaching at any given moment. Very important: Expect the ISS SSTV carrier to go off the air between images! This is normal. Keep listening and don’t give up when you hear the carrier drop. It will be back automatically in just a minute or two with another image. Twelfth picture of series 19 transmitted from the International Space Station in December 2021. Rob, AD2CT’s ARISS SSTV Award Our group quickly understood a grand challenge! This ARISS/TV event transmitted a loop of 12 pictures to be sent in order to Earth by the resident Russian cosmonaut team. Look carefully at the sample picture we received. You might wonder what серия (seriya) means in Russian. It translates to English as “series” — we were receiving frames from the series 19 collection of 12 frames. I suddenly found myself in the same mindset as my childhood pursuit completing sets of baseball cards! I made a list of all the frames I had successfully pulled in. I received some images over and over again. Some images were really elusive! At one point, I put out a public plea: “Hey, guys! I need frames 3, 4, 6 and 11!” I eventually caught them all. Pokémon! Rob, AC2CT, took collecting to the next step. He applied for a commemorative certificate for his accomplishment and was awarded with a custom memento bearing his name and call sign from the Russian cosmonaut team. Well done! The ISS amateur radio antennae seem to be mounted in the rear of the spacecraft. As the ISS icon on the ESA map passes your location, the signal will peak for earthlings down below. The best pictures seem to appear when the ISS icon on the ESA map appears to be just barely leaving your location — and — just north of your location. Is this a hint to where the transmitting antenna is located on the ISS spacecraft? ## Clever Flexible Antennas Shannon Walker KD5DXB uses the Kenwood transceiver with Soichi Noguchi KD5TVP during a recent ARISS amateur radio session with Hisagi Junior High School, Zushi, Japan. [NASA] Malcolm, NM9J, searched the Internet and found remarkable details about the amateur radio transmission equipment onboard the ISS. At the heart of their station are Kenwood VHF/UHF FM Dual Bander Data Communicator TM-D700A/E and TM-D710-GA transceivers perfectly designed for use aboard the ISS. Complete details of these sophisticated units here. Furled antenna for use on ISS is made of flexible metal tape coated in Kapton® polyimide film. [ESA] A highly illustrated tour of the ISS antenna system can be found [here](http://www .marexmg.org/hardware/antennas.html). According to this site: “The orange/black antenna strips are very flexible and will not cut or poke the astronauts’ space suits. The metal portion of the antennas is similar to a metal tape measure and will bend back to its original shape. The metal portion was then covered with a protective plastic material to prevent sharp edges.” You will marvel at this design. It reminds me of the tape measure Yagis that are used during PCARA fox hunts! The ISS Fan Club site provided further detail: “A set of four antenna systems are deployed in the ISS Service Module supporting the current installation of the Kenwood D700 and D710 radios. Each of the four antennas can support amateur radio operations on multiple frequencies and allow for simultaneous automatic and crew-tended operations. Having four antennas also ensures that ham radio operations can continue aboard the station should one or more of the antennas fail. Three of the four antennas are identical and each can support both transmit and receive operations on 2 meter, 70 cm, L band and S band. They also support reception for the station’s Russian Glisser TV system, which is used during spacewalks. The fourth antenna has a 2.5-meter (8 foot) long vertical whip that can be used to support High Frequency (HF) operations, particularly on 10 meters.” “Two antennas are installed in the Columbus module, currently serving the Ericsson radios deployed there. Frequencies available for transmission to and from Columbus are 2 meters, 70 centimeters, L-band and S-band. These antennas will also support the Ham TV DATV transmitter.” Now that we have piqued your interest… watch this simply amazing video . ## Strange DX Skip? Some very brief bursts of specifically PD120 data have been seen when the ISS is far away from our area. On a couple of occasions, I captured PD120 data as the spacecraft was just beginning to fly over Japan. Maybe this is some sort of skip? Was it coincidence? Does the ISS signal bounce off the surface of the Earth and then propagate like a terrestrial VHF signal? Another mystery to be solved. ## Inspirational Antenna Project Turnstile antenna for circular polarization There is so much ISS mind candy to be found on the Internet! The ARRL website offers an easy-to-build crossed antenna array specifically for receiving signals from the ISS. “The turnstile is basically two, two element Yagi antennas that are pointed perpendicular to the ground (pointed up), the two antennas are mounted perpendicular to each other (in a cross configuration) and electrically phased to create a circularly polarized antenna pattern that mitigates signal fading due to polarization shifts that occur as the signals from space traverse through the ionosphere and reflect off of surfaces surrounding the immediate antenna environment.” I know what my next project might be! Detailed plans can be found here. ## A Final Eye-ball QSO The week-long SSTV event transmissions ceased just after noontime on Friday, December 31st. We were sad to see it end. While our memories were still fresh, The International Space Station returned to bid us a fond farewell! Just as dawn was beginning to break in the east on Tuesday, January 4, 2022, the ISS made a perfect pass, high in the sky, from 6:29 to 6:35 A.M. The spacecraft appeared like a bright cylinder to my eyes at 14 degrees above northwest and flew across the sky — reaching as high as 89° above (right overhead) — and then gracefully speeded away leaving at 10° above the southeast into the beauty of the red/orange new dawn. The Space Station caught the morning light, sparkling with glimmer — perfectly centered in the sky and gracefully streaked away until it was out of sight. What a fitting ‘goodbye!’ Dawn breaks as the ISS departs from Karl’s location ## Daily SSTV Transmissions… on 20m HF! Can’t wait for the next ISS SSTV event? You canfind Earthbound amateur radio operators sending SSTV pictures daily (especially during daylight hours) on 20 meter USB. Look for them on 14.230 and 14.233 MHz. Hookup your computer to the audio of your HF receiver, begin YONIQ on your computer and then sit back and wait for results! All sorts of call signs and entertaining graphics will be coming your way! Sample SSTV image as received on 20 meters ## More to Learn and Discover Still to be discovered: I understand positioning data from the ISS is transmitted on 145.825 MHz and this is sometimes used as a live test signal for amateurs to intercept while honing and tweaking their receiving stations. Comprehensive details about various ISS data transmissions can be found here and here. Software specifically written for resolving packet datafrom the ISS can be found here. Get the very latest news regarding future ISS events via the ARISS blog. See the definitive collection of stunning image captures from above and please don’t miss the fascinating ISS Fan Club page. So Major Tom… are you ready to be a Rocket Man? Keep your eyes to the skies! My congratulations to all who participated! What a grand collaborative experience! See you next month! 73 es dit dit de N2KZ “The Old Goat.” #### Coax Cable Tester For a PDF version of this article, please click this link COMPLETED COAX CABLE TESTER This is a simple circuit that can be used to test all those coaxial cables that we have or make. It only uses a few components and will test if the cable is OK, has any shorts between screen and inner and if both screen and inner are continuous. The circuit is shown below along with components required. Note: switch shown in “SHORT TEST” position. Designation Value R1, R2 680R, 0.25W D1, D2 LED, Green D3 LED, Red SW1 DPDT Switch CONN1, CONN2 To suit ### CONSTRUCTION NOTES: 1. Item MUST be built in plastic box. (See NOTE below) 2. Other connectors can be placed in parallel with CONN1 and CONN2 to give more universal DC testing of cables. 3. LEDs can be mounted in holders to ease build. 4. Designed to work from PP3 battery or other 9V source. Resistors R1 and R2 can be re-calculated for other supply voltages. 5. Additional switch can be placed in +9V line to provide an ON/OFF function. NOTE: Box must be of an insulating material otherwise the connector screens are shorted together and braid test will give a false reading. ### METHOD OF OPERATION: 1. Plug cable to be tested between CONN1 and CONN2. 2. With switch in position shown it is in “SHORT TEST”. If there is a short the red LED D3 will be illuminated showing a cable fault. 3. Switch to other position. This is “CONTINUITY TEST”. If centre core is intact then D2 will illuminate green, if screening is intact then D1 will illuminate green at the same time. If only one LED illuminates then there is a cable fault denoted by which LED is not illuminated. INTERNAL CONSTRUCTION OF COAX CABLE TESTER #### Impedance and the j Operator For a PDF version of this article, please click this link ## Introduction You may well have come across impedance expressed in the the terms real and imaginary (or resistance and reactance) when using equipment such an Antenna Analyser or impedance in the form R + jX. This may mean something to some readers whilst it probably means nothing and is somewhat baffling to many others. In this article I am going to try to explain in SIMPLE terms what it is all about. Please do not “get turned off” because it contains some mathematics, it’s all very simple — really! This article is not meant as a mathematical treatise on the subject and covers, for sake of simplicity, only the series circuit. It will, however give your brain, calculator and computer some exercise! ## Basic AC Theory During studies for the old RAE or newer Full Licence the concepts or resistance and reactance have been taught and the following equations will have been given: \text{Inductive reactance:}\quad X_L = 2\pi f L ~\Omega \text{Capacitive reactance:}\quad X_C = \frac{1}{2 \pi f C} ~\Omega (Note: at least X is in Ohms and we have a chance of combining it with resistance R, L and C themselves are not in Ohms). Figure 1: Impedance in a Series Circuit You will also have been taught that inductance and capacitance introduce a phase shift in the circuit between the applied voltage and the current flowing. A circuit has impedance rather than resistance when inductance and capacitance are also involved in a circuit carrying an alternating current. Again, referring to what has been taught, impedance can be represented by a triangle such as shown in Fig. 1 for a series circuit. It is not correct to write that Z = R + X_L or Z = R + X_C as this has not taken into account the phase shift introduced by the reactive element. Rather, you must use the formulae given in Fig 1. It would, however, be very convenient it there was a method whereby R and X could be combined in some form without the use of square roots and trigonometric functions. It would allow a consistent set of units — Ohms — instead of dealing with \text{pF}, \text{μF}, \text{μH}, \text{mH} and so forth and also be convenient if reactances could just be added and subtracted. This would help us in, for example, antenna calculations, where we need to get a series reactance that will make an antenna look purely resistive. The next section explain a method for attaining this with some examples. ## The “j” Operator There is a mathematical tool which uses the j operator (it is often called i in mathematical books but engineers use j). This allows us to write Z=R+jX_L or Z= R-jX_C — note the minus sign for capacitive reactance, it is important. The R and the j terms cannot be further simplified, i.e. if Z = 65 + j40 this is its simplest form. The j term implies a quantity that is at 90\degree (or quadrature) to the resistive term. Two practical examples – see Fig, 2. Using the formulae for reactance given earlier and the frequencies quoted in the examples, then the series circuits can be specified as Z = 220 + j 628.3 and Z=100-j15.9 respectively (note these figures have been rounded off). This gives phase angles of approximately 72\degree (lagging) and 9\degree (leading) respectively. The minus sign indicates the reactance is capacitive and the plus sign denotes inductive. Figure 2: Two Practical Examples If the series circuit as shown in Fig. 3 is used, the combined impedance is given by: Z = R_1 + R_2 + j X_L – j X_C The non j and the$j\$ terms can he collected together which gives:

Z = (R_1 + R_2) + j (X_L – X_C)

Figure 3: Combined Circuits

Thus series resistance can be added together (something that should be known) as also can series reactance — but taking into account the sign. The reactances can only be added together provided that they are quoted at the same frequency. Taking the examples from Fig. 2 and combining them in series gives:

Z = 100 +330 + j(628.3 – 15.9)

Z = 430 + j612.4

This denotes that the combined circuit at 100\text{kHz} has a resistive part of 430\Omega and an inductive reactance of 612.4\Omega (because the j term is positive). This is equivalent to 0.975\text{mH} (or 975\text{μH}). The resulting phase angle of 55\degree is obtained from:

\tan \text{\o} = 612.4/430

A well-known condition is achieved when the resultant j terms equals zero, i.e. when X_L = X_C. From earlier then:

2 \pi fL = 1/(2 \pi fC)

When rearranging this one obtains:

f=\frac{1}{2\pi \sqrt{LC}}

This is the well-known resonant frequency formula.

You are then left with Z = the resistive term only, i.e. a series circuit at resonance is purely resistive — something one learnt for the exams?

Figure 4: Antenna System Impedance

## A Practical Use

You could well ask what is the use of this, is it just a mathematical exercise? No, it is not: a practical use was hinted at earlier. The following example is just one application.

The impedance at an antenna system is measured at 3.7\text{MHz} using an antenna analyser and it is found that the resistive part is 38\Omega and the reactive part is -j100\Omega (ie Z = 38 – j100). To get maximum power into the antenna it is desirable to eliminate the reactive part so that, from terminals AB, the impedance is purely resistive. Assuming the antenna analyser gives an equivalent series circuit, then a reactance must be added in series to cancel the -j100 term. This is obviously +j100 and the value of the inductance can now be calculated as 4.3\text{μH} at 3.7\text{MHz}.

## Conclusion

It is hoped that this short article has provided an insight into the use of the operator j, but the article really only touches the surface regarding the use or this operator.

Sufficient information is given for converting between physical values (ie. farads and henrys and sub-multiples) and equivalent reactances which are expressed in one single unit — the Ohm. The practical examples given will hopefully allow you to use the operator for other applications.

To ease the maths, you can write a simple spreadsheet to do it for you.