Johnson's Techworld

 Light Dependent Resistors (LDR) or Photoresistors are widely used in automatic street lights and garden lights. Ambient light falling on the device triggers an electronic circuit which switches off the lights. When light falls on the LDR, the resistance falls from a few mega ohms to a few hundred ohms. Lead sulphide and Indium antimonide are two important substances used in the manufacture of LDRs. LDR is a passive device and does not have a PN junction as in active devices like photodiodes and phototransistors. There is a lag between the change in illumination and change in resistance which makes LDR not suitable for fast switching purposes.

 Tropospheric Scatter Propagation is known in short as Troposcatter Propagation. Troposphere is the lowest layer of the atmosphere. Though Troposcatter is typical at microwave or super high frequency or SHF band , it can also occur at VHF and UHF bands. The height of the troposphere is about 20 km near the equator, which comes to about 9 km in polar regions in summer. Height of the troposphere is more in summer than in winter. Troposphere can refract higher end of the radio spectrum. HF is reflected typically by the ionosphere, much above the troposphere. Tropospheric scatter was used mainly by the military prior to the era of satellites. When the transmitting and receiving stations point their antennas to a common scatter volume in the troposphere as shown in the illustration, troposphere refracts the signal towards the receiving station. Troposcatter may work from frequencies as low as 144 MHz to 10 GHz and useful communication can occur from 100 km to 700 km. Typically the transmitt

 Transequatorial VHF propagation was first noted by radio amateurs in August 1947 when Mexican stations could work Argentine stations regularly across the equator in the late afternoon and early evening on 50 MHz. This occurred for few more years during the maximum of Solar Cycle 18. Transequatorial Propagation came down during the period of sunspot minimum and reappeared in 1955 and continued through the maximum years of Solar Cycle 19. We can expect similar conditions as we are heading for the maximum of Solar Cycle 25 in 2025. Two types of transequatorial propagation has been described. One occurring during late afternoon and early evening with maximum distance of about 6000 km in low VHF band of 6 m. Second one was between 7 pm to 11 pm local time with contacts on 2 m and sometimes on 70 cm band. Mechanism by which transequatorial propagation occurs is the presence of equatorial anomaly, which is a high concentration of electrons on either side of the equator in the region of 10 to

 Semiconductor rectifier diodes are PN junctions with P type semiconductor for anode and N type semiconductor for cathode. They are used to convert alternating current to direct current and is widely used in various electronic devices. Simplest form is a half wave rectifier which uses only a single diode and the output has only half of the alternating current as output. It is a pulsating DC at the frequency of the input AC waveform. Full wave rectifier uses a couple of diodes fed out of phase using a centre tapped transformer so that both halves of the AC waveform appears in the output as a pulsating DC with twice the frequency of the supply voltage. Bridge rectifier uses four diodes and a transformer without a central tap. The output waveform is just like that of the full wave rectifier with two diodes. As both these are DC with ripples, smoothening out of the waveform can be done by using a high value capacitor across the output. Further smoothening out can be done using an inductor

 When I started off in amateur radio in 1985, Solar Cycle 21 was nearing its end with sunspot activity going down. Solar Cycle 22 started in September 1986. So I had the opportunity to witness propagation on 40m band going down and that on 80m becoming better. In those days, I had no option for higher bands as my Philips Prestige home radio which I used for RX did not cover them. I was unaware of regional activity on 160m and I do not remember whether my radio had covered that band. I still remember the EC Net also known as East Coast Net on 80m at 10 pm, to which I used to check in, mostly on CW as my homebrew radio, 3 x 807 vacuum tube radio, was not that great on AM for 80m. Now we are in Solar Cycle 25, which started in December 2019 and we are headed for the maximum sunspot activity soon. When we pass that maximum, we will see higher bands going down and lower bands picking up. In the beginning of 2024, my favourite DX band was 10m, due to high sunspot activity. As we go beyond th

 Phased array antennas are those in which the radiation pattern of the antenna can be changed without physically moving the antenna. For the ham radio operator, it would be quite interesting if you can steer the beam without the need for an antenna rotator! The same principle is used in ultrasound imaging to steer the ultrasound beam. If several antenna elements are fed from the same transmitter with a phase shift, the direction of the beam can be changed by changing the phase shift. This is possible when a computer controls the phase shift to each element. It is widely used in the field of radar imaging. In the illustration, computer controlled phase shifter changes the phase of the signal fed to each element. The progressive delay in signals would in effect change the direction of the superimposed signal wavefront to an angle depending on the phase shift given. By altering the phase shift, the angle theta at which the beam is radiated, can be changed without physically rotating the a

  VU2SV Memorial Net on 7090 kHz with VU2NSL and VU3LLL as net controls. Plenty of signals on 40m waterfall display. Excellent band condition here today morning.

 Fractal antenna was initially presented by W1YW at the ARRL convention in October 1994. Fractal antenna uses a self similar design to maximize the effective length of the material used to receive or transmit electromagnetic radiation within a given total surface area or volume. Self similar design can be better understood by having a look at the public domain image from Wikipedia by Nathan Cohen (W1YW) which is shown below: The specialty of design is that fractal antennas are very compact and capable of multiband operations. Hence fractal antennas are useful in cellular telephony and microwave communications. Another advantage is that size is smaller without the use of additional component like a loading coil, which is often used to electrically shorten antennas.  Loading coils though they make antenna size more convenient for mounting, causes loss of RF energy in the resistance of the coils which is not zero! In a way the design can be considered similar to the linear loaded dipole a

Ionosphere is a layer of the atmosphere which gets ionised, mostly during day time, due to the effect of sun rays and it is situated high above the atmosphere, almost the thermosphere. It may extend into the exosphere above and mesosphere below. When radio waves reaching the ionosphere has a critical frequency, above which it will just radiate out into the space. That is why VHF and UHF radiate straight to the space. But HF, below that critical frequency, will be reflected back to the earth, and to the ground, which will skip around the earth, and produce long distance communication. These are the layers of the atmosphere. The lowermost is the troposphere. That is the place where we are all walking about, lowermost layer of the atmosphere. Then comes the stratosphere. Beyond the stratosphere, you have the mesosphere, still beyond is the thermosphere and outermost layer is the exosphere. As you go up from the earth, due to the reduced effect of gravity, the atmosphere becomes thinner. S

 My single band VHF only CP22E antenna has a phasing coil between the upper and lower elements. CP22E is a two-element 5/8λ stacked ground plane antenna with three radials. Upper and lower sections are assembled with the phase coil in between. Coil ensures that the phase of the waveform is same all along the antenna length so that both sections work together. This increases the efficiency of the antenna. Without a phasing coil an antenna with double the length will not work on the design frequency. As a simple example, 20m long center fed dipole antenna meant for 7MHz will not work for 14MHz, being an even harmonic, though it will work for 21MHz being an odd harmonic. In the same way, my CP22E VHF antenna works fairly well on the UHF amateur radio band as it is roughly the third harmonic. Dipole antennas can be made physically shorter than the usual half-wave dipole antenna by adding loading coils. It is useful for single band operation with narrow bandwidth. Of course it is a trade o

 USB printer cable has a type B plug at one end and a type A plug at the other end. Type B plug goes into the type B socket on the printer, while type A plug goes into the type A socket on the computer. Same cable can be used for Computer Aided Transceiver control (CAT control) in amateur radios like FT-710. The type B plug goes into the type B socket on the rear side of FT-710 and the type A plug goes into the computer for connecting it with the radio. This is useful in working digital modes and for automatic logging software in amateur radio.

 Wireless router range extender can be used at home when there is no good connectivity from the home internet wireless router to all the rooms. This router has 2.4 and 5 GHz WiFi channels. There are a couple of antennas, the polarization of which can be changed from vertical to horizontal and anything in between. Signal LED lights up in blue colour when good signal is being received from the router. If not, it becomes red. There is also an RJ 45 LAN port on the lower side of the range extender, which can be used to connect to the internet router through a local area network cable. Then the range extender can be programmed as a WiFi hotspot from which other devices can connect to the internet provided by the internet router. This is useful if you can wire a LAN cable from ground floor where the router is kept and the first floor or higher floors where the range extender is to be used. Mode change can be done using a linked app installed in a mobile phone.

 Light emitting diodes or LEDs produce light when electrons combine with holes in the semiconductor, releasing energy as photon. First ones to be produced were infrared and red LEDs. Other colour and white LEDs were invented later. Initial LEDs were of low power and later high power ones were invented. 7 segment LED displays will be familiar to most of you. Now there are LED TVs and large displays. OLED has an organic compound which produces light and is used in televisions. Three colour LEDs are RGB LEDs which have four leads instead of the two in usual LEDs. The longest of the leads is the common one. In usual LEDs, longer lead is positive. There are also blinking LEDs. Surface mount type of LEDs are used in LED lights which are fast replacing incandescent lights and fluorescent lights. LEDs work on low voltage DC and need a driver unit in LED bulbs, which are usually a small switch mode power supply, which can cause radio frequency interference in amateur radio bands, especially the

 Many of you would have noticed that some of the modern cars have a 'shark fin' antenna, quite different from the whip antenna seen on older cars for radio reception. They are quite sleek and have a better visual appeal than the older whip antennas. Aerodynamic design reduces atmospheric drag and makes it more durable and resistant to weather conditions. Accidental damage as when the car is quickly pulled into an automatic car wash is also unlikely. Beyond the usual function of radio reception, shark fin antennas can have other functions like navigation and tracking using global positioning system (GPS), WiFi data transfer, receiving cell phone and satellite radio signals and even internet signals, depending on the hardware connected to it. Some models have an option to connect an external whip antenna with an SMA connector .

 Capacitors were also called as condensers earlier. Even now, capacitor mics are known as condenser mics! The ones which I am showing are electrolytic capacitors with a polarity. Other varieties likes paper, ceramic and air capacitors have no polarity. Air capacitors are used as tuning capacitors. Tuning capacitors for higher voltage needs more spacing between the metal elements to prevent arcing.

  Happy to work 9W8ZZK from Borneo Island (3964.8 km) on 21.285 MHz SSB. He was coming here quite strong and I wondered why - He is on 50 W only, but with 7 element full size tribander Yagi! So that is the power of the antenna! I was on 100W, but my antenna was just an inverted V dipole for 40m, working on 15m as third harmonic.

  HCF 4017 is a 16-lead dual in-line package monolithic integrated circuit. It is a decadic counter with ten outputs. It can be used in circuits like LED chaser and frequency divider.

 First Contact on the 'Rare Bird' UVSQ-SAT, with VU2TEK! The satellite was at 600 km distance and elevation was 30 degrees, when I heard VU2TEK during the pass starting from 10:17 pm IST (UTC+5.30) on 14 September 2024. I had not luck during the contact on the morning of 14 September 2024, though VU2TEK could hear some station partly. That was a pass with maximum elevation 23 degrees here while the successful pass had 45 degrees maximum elevation. I continued hearing VU2TEK for a few minutes after our contact as well. As the satellite has been activated for 48 hours from 0000z on 14 September 2024, there will be two more passes in this region on 15 September 2024. But they are of lower elevation, 15 degrees and 13 degrees. 

 Today evening by about 5.30 pm local time, I could see several signals on the waterfall on 40m, which was quite unusual. In the morning hours 40m band is busy with several local nets and ragchews. But we have only one net in the evening, the Silicon City Net, that too will be over before 5.30 pm. Hardly one or two signals may be seen on the waterfall by that time on 40m. Today most of the stations on 40m were DX, possibly from Indonesia. There should have been some contest out there. I could hear several YL operators as well.  Checked 20m, which is usually active at that time with several long distance VU stations. It was the same today also, with dense signals on the waterfall on 20m, some even 5,9+20 dB. Moved on to 15m, which also showed a few signals on the waterfall. Seemed like Indonesian stations operating contests. There were YL operators there as well. With all the lower bands wide open, I was hopeful that 10m also will be open and give me a few DX contacts. But contrary to m

 UVSQ-SAT is activated only rarely. That is why I have called it as a 'Rare Bird'! Now it has been activated for 48 hours starting from 0000z on 14 September 2024. AMSAT Live OSCAR Satellite Status Page has shown a few reports of the satellite being heard. The satellite is at a low elevation of 365 km, below the orbit of International Space Station. There are four passes in this region during the 48 hours of activation. Now one in this region seemed to have heard it yet.

 UVSQ-SAT is a CubeSat which was launched on 24th January 2021. Though it was initially mentioned that UVSQ-SAT team will provide an availability of the transponder up to 20% of time for Ham Radio operations, that never happened and activations for Ham Radio were quite rare and unpredictable. Now the UVSQ-SAT team has announced on X that the transponder will be activated for 48 hours from Saturday September 14 (UTC 00h00). Uplink is on 145.905 MHz and Downlink on 437.020 MHz. No tone is needed for access. That is a welcome event when we are facing scarcity of FM satellites after the TEVEL series re-entered the Earth's atmosphere. Let us see if we can have a few contacts through the transponder. There seems to be couple of passes tomorrow and the day after in my region.

 HRC fuses are High Rupturing Capacity fuses. Older types of fuses used a simple wire which would melt and even burn off when a certain level of current is exceeded. That is how we used to have blown fuses in the yester years. The body catridge of HRC fuse is made of heat resistant material like ceramic and there are two metallic end caps which connect to the circuit in the fuse holder. The current carrying element within the fuse is made of silver and the internal space of the fuse body is filled with a powder which prevents overheating and allows the fuse to carry normal rated current. Beyond the rated current, the silver element vaporizes and breaks the circuit. Chemical reaction between silver and the filling powder produces a high-resistance substance which helps to quench the arc in the fuse.   

 This CW paddle was bought from a local ham. It works fine, but I have been a bit lazy to try it out! In this video clip I am demonstrating how to use it for practising Morse Code using the built-in keyer in my FT-710 radio. The same procedure can be used to send CW on air if you enable break-in using the function menu of the radio. While using the keyer for Morse Code practice, break-in should be switched OFF to prevent signals being transmitted.

 Many amateur radio satellite operators are also keen observers of weather satellite data. They regularly post images captured from weather satellite downlinks on various social media. Being in the tropics and going through rainy season currently, I thought of looking at the definitions of some tropical weather events. It may be noted that tropical weather events can occur even beyond the tropics as they spread to higher latitudes before they make landfall. Now what is a landfall? Most of the weather events originate in the sea and the intersection of the centre of a tropical cyclone with a coastline is known as landfall. But the strongest winds may not be exactly at the center. So it is possible get strong winds even before landfall. On the other hand, strongest winds can also be over the water at landfall. Tropical cyclones originate over tropical or subtropical waters with organized deep convection and a closed surface wind circulation about a well-defined center. Once formed, tropi

 Well, I heard of a Quagi Antenna only yesterday, from VU2YE, a veteran LEO satellite operator in this region. He used to do even Moon Bounce with a long Quagi Antenna. Most of you would have heard of Yagi antennas or Yagi-Uda antennas and some of you would have heard of Quad or Cubical Quad antennas. Quagi antenna is one which combines the best aspects of both Quad and Yagi antennas. Typically a Quagi antenna has Quad driven element and reflector and Yagi director elements. Quad driven element is meant to take away the inherent disadvantages of a dipole. Gamma match can become less effective at VHF and UHF frequencies and I have found making and tuning a Gamma match for my VHF and UHF antennas quite cumbersome. Quagi is directly fed with 50 Ohms coaxial cable like RG-8/U as the impedance is around 60 Ohms at resonance. Quad loops can give a little extra gain than dipole driven elements as well. A two element quad may have 1.5 dB extra gain, but this does not increase much as the num

 As soon as radio amateurs establish contact over the radio, they exchange signal reports, typically in the R-S-T format. R-S-T stands for Readability, Strength and Tone, though the last one is meant only for CW signals. The system was developed by Arthur W. Braaten, W2BSR in 1934 and is continuing till date. Readability reports can spread from 1 for an unreadable signal to 5 for a perfectly readable signal. Very often radio amateurs are quite lenient and give readability 5 even if there is great difficulty in copying. Only rarely have I heard people giving a readability report of 4 and hardly do I hear anyone giving reports below that. Coming to signal strength, the range is from 1 for faint barely perceptible signal to 9 for extremely strong signal. Here also, radio amateurs tend to give liberal reports. Special situations are satellite operations and contests. In contests no one gives a report below 9! Similarly, in LEO satellite operations, every one gives a report as 5,9 regardle

 I still have the sweet memories of working a lot DX on CW in late 1980s using my homebrew 3 x 807 radio. That was a great upgrade from my 5W VU2VWN QRP which I homebrewed as soon as I got my amateur radio license in 1985. As the power supply, I was using a 600 V AC transformer made by a local ham and I had homebrewed the solid state bridge rectifier circuit with four diodes and large high voltage capacitors. In those days, I had sourced 807 valves from a local radio shop and if I remember correct, they were made by RCA. 807 is a beam tetrode vacuum tube which used to give me 40 W power each so that my TX was 120W on CW. In those days, 807 vacuum tubes were also being used in audio amplifiers, and that is how I could get them from a local radio shop. Even at that time, vacuum tubes were being phased out as solid state audio amplifiers had become commonplace. For AM, I needed a lot of audio power for modulation and I had homebrewed a solid state audio amplifier for that. But AM was not

 Acrobatics of Working and Recording Space Station Pass!

 Some of my friends have been able to work 10m band over the past few days and I was on the lookout for stations on 10m. I heard a couple of DX stations on 28.475 MHz signing off, but I could not get their callsign. Though I tried calling QRZ, I did not get any reply. Later I heard a very strong station in foreign language on 28.506 MHz working a couple of other stations. After listening for a few minutes, they faded away before I could try a call. Then I came back to 28.475 MHz and gave an automated CQ call. Immediately I got a reply from YC2DOT from a distance of 4343.3 km, at 6.02 pm local time here. We had a quick exchange of reports and he said 73s. As I had not expected a reply as I seldom get replies for CQ calls, I could not record the QSO. After that I tried a few automated CQ calls with recording, but was not lucky to get any more contacts. Anyway I am happy that I could work one DX and hear a few DX on my erstwhile favourite DX band. Some of my DX friends had told me online

 Ever since I came back to HF in January 2024, my friends have been advising me to go for a linear amplifier. In VU land, the General Class licence which I have, has permission for 400 W power, though my radio can only give me 100 W. Almost every other operator who I hear on 40m has a linear amplifier. Then what is it that prevents me from going for a linear RF amplifier to boost my signals? When I came on air with my FT-710 radio with full power of 100 W, there were many on 40m who asked me whether I was using a QRP radio! The reason was simple, I was new to commercial radios and did not know how to adjust the radio. I had kept mic gain low and the processor level also low and I was scared of using the built-in automatic antenna tuner because of the rattling noise it makes! When I increased both mic gain and processor level and started using the auto-tuner, others started hearing me better. Then that was not all. My antennas were highly compromised due to space limitations. I started

 In a response to my post in the HamSCI (Ham Radio Science Citizen Investigation) Google Group, N8SBE mentioned that 700-800 MHz is quite useful for first responders as it penetrates structures well. Within building coverage is of vital importance to firefighters. According to him, building owner is required to place repeaters inside to assist coverage as well. Skimmed through our National Frequency Allocation Plan 2022 and found that 614-890 MHz has been allocated for fixed, mobile and broadcasting services. 806-811 MHz frequency and 851-856 MHz paired frequency has been allocated to Public Protection and Disaster Relief (PPDR). There are also other frequency bands mentioned for PPDR applications. I presume that it will correspond to the first responder use mentioned by N8SBE. In the introduction of NFAP 2022, it has been mentioned that before any part of the spectrum is put to use in India, a licence is required to be obtained from the Wireless Planning and Coordination Wing (WPC Wi

 When I started using computers long back, mouse had only two buttons, a left and a right button. Then came three button mouse with an extra scroll button. I have read that there was also a single button mouse, but I have not seen one. Now here is a six button mouse, that too a wireless mouse with a USB-A Nano Dongle and 2.4 Ghz wireless connection. In the earlier era, mouse had a rolling ball which would gather dirt and sometimes stop functioning well. Now we have optimal mouse which uses a red light source and an optical sensor instead of the rolling ball. The wireless mouse works on a single 1.5 V, AA battery with a projected battery life of one year!

 Yesterday I came across a piece of PVC pipe brought by the plumber who told me that it is ASTM. That prompted a Google search as usual and I could find a bit about ASTM International. ASTM International was formerly known as American Society for Testing and Materials, till they changed their name officially in 2001. That PVC pipe actually showed ASTM D-1785, which is a specification for pressure pipes used in plumbing. Another abbreviation noted on the same piece of pipe was PVC-U which stands for Poly Vinyl Chloride - Un-plasticised.

  The meter in FT-710 radio has several functions. On receive mode it functions as signal strength meter or S meter. On transmit it can have different functions like SWR (Standing Wave Ratio), Power, ALC (Automatic Level Control), VDD (Final amplifier drain voltage), ID (Final amplifier drain current) and COMP (compression level during speech processor operation). These functions can be selected by touching the meter display and choosing the options. Alternatively an external mouse can also be used to make the selections.

 Radio amateurs are very fond of getting signal reports from whichever station they work. When I started off in 1985, I did not have any S meter in the Philips Prestige home radio which I used as a receiver for my ham radio activities along with a homebrew QRP transmitter. I used to give reports 'by the ear' like many other operators in those times. Those with commercial transceivers used to give S meter readings from their radios. Looking back, even that may not have been very accurate as many analog radios did not have a well calibrated S meter. Analogue S meter or signal strength meter was a sensitive microammeter with a full scale deflection of 50-100 microamperes. In 1930s, S9 corresponded to 50 microvolts at the input terminals of the receiver. International Amateur Radio Union (IARU) Region 1 had brought out technical specifications for S meter readings in 1981. According to that, S9 on HF bands corresponded to -73 dBm. That would be 50 microvolts at the receiver's a

Transequatorial Propagation Transequatorial VHF propagation was first noted by radio amateurs in August 1947 when Mexican stations could work Argentine stations regularly across the equator in the late afternoon and early evening on 50 MHz. This occurred for few more years during the maximum of Solar Cycle 18. Transequatorial Propagation came down during the period of sunspot minimum and reappeared in 1955 and continued through the maximum years of Solar Cycle 19. We can expect similar conditions as we are heading for the maximum of Solar Cycle 25 in 2025. Two types of transequatorial propagation has been described. One occurring during late afternoon and early evening with maximum distance of about 6000 km in low VHF band of 6 m. Second one was between 7 pm to 11 pm local time with contacts on 2 m and sometimes on 70 cm band. Mechanism by which transequatorial propagation occurs is the presence of equatorial anomaly, which is a high concentration of electrons on either side of the equ

 Here is a recording of a visible pass of International Space Station in my region at 7.15 pm IST, which was a spectacular sight, in spite of a cloudy sky with city haze. Space Station can be seen as a tiny white dot moving across the sky. Sideways movements are because I tried to adjust the position of the phone to capture a better view. You can make that out form the movement of the faintly seen nearby building outline. Reverse movement occurred again due to readjustment of mobile phone position when the Space Station was going beyond the view of the camera. Visible passes occur either soon after sunset or some time before the sunrise.

  Brief review of some of the common type of radio frequency connectors used in amateur radio, starting from the old BNC connectors to the present day SMA connectors and SO 239/PL 259 combinations. SMA connectors can handle much higher frequencies than the other type of connectors. SO 239 barrel connectors can be used to connect two cables with PL 259 termination.

  Starliner spacecraft  which had autonomously started back from the International Space Station without crew members landed  at White Sands Space Harbor in New Mexico at 12:01 am EDT ( 9:31 pm Saturday 7 September 2024, IST, 4:01 pm UTC ). It had been at the Space Station for three months and is the first American-made orbital crew capsule designed to perform ground landing as a reusable spacecraft. Base heat shield of the spacecraft separated before landing to allow the six airbags to inflate and brace for a ground landing.  Though called as 'airbags' they were actually filled with nitrogen.  Three main parachutes were deployed for slowing down the uncrewed capsule.  During the descent of the Starliner spacecraft, around 30,000 feet after atmospheric re-entry, forward heat shield separated to allow drogue parachutes to inflate and slow down the vehicle. Drogue parachute is also called a drag chute, and is designed for deployment from a rapidly moving object. That will decreas

 Yesterday there was a message on Amsat Bulletin Board mentioning that: 'Astronauts "off-duty" tomorrow ... MIGHT be some FM simplex communications happening!'. So I decided to listen keenly to a pass of Space Station just after 8 pm IST (UTC+5.30), hoping to hear NA1SS. Though I was not lucky enough to hear an astronaut, I was lucky to hear my friend Lucky, VU2LBW loud and clear. Gave a call and I was quite happy to hear his reply, a contact after a long time. VU2LBW is a veteran LEO satellite operator in this region, with an excellent setup for satellite communications and I always hear his signals from horizon to horizon, whenever he is on the satellite pass. Towards the end of the pass I could also hear VU3BGK, but as the satellite was quite far away, I could not reach him. Here is a short recording of the audio from IC 2730 radio during the ARISS pass today evening.

CP22E Antenna is a stacked two element 5/8 λ Vertical Antenna with a phasing coil in between. 5/8 λ Vertical Antenna has a length more than the usual quarter wavelength vertical antenna. It has a similar low angle of radiation useful for local contacts. Hence it is a popular form of mobile antenna which can be mounted on a car. Mounting can be with a magnetic base so that it avoids drilling the car chassis, with obvious advantages when you consider resale of the car. A matching coil is provided at the base of the antenna to give good impedance matching like that of a 3/4 λ Vertical Antenna. Under ideal conditions, 5/8 λ Vertical Antenna has a 4 dB gain over a quarter wave vertical antenna. When it is mounted on the car, the car body acts as the ground plane. 5/8 λ Vertical Antenna mounted on a car is typically used for VHF and UHF amateur radios. It can be used as an HF antenna for a base station as well. In that case, the low angle of radiation will be useful for DX contacts.

Isotropic Antenna is a theoretical antenna which has a perfect spherical radiation pattern, which is never practically achieved in any antenna! Many commercial vertical antennas mention their gain in dBi, in comparison with the theoretical isotropic antenna. They have a 360 degree disk like horizontal radiation pattern towards the horizon all around, unlike the spherical radiation pattern of an isotropic antenna. Dipole has strongest signal radiation perpendicular to the orientation of the radiating element. Radiation from a dipole is weakest from the ends of the radiator. Hence a dipole has a gain of 2.15 dBi compared to the isotropic antenna, in the direction of the main lobe. Gain comparison with a dipole is designated as dBd. Gain expressed in dBd will be 2.15 dB lower than a gain expressed in dBi.

J pole antenna is a vertical omnidirectional antenna popular among Ham Radio operators for 2m and 70 cm operations. As it is an end fed antenna, the feed point of the half wave segment of the antenna will have high impedance which has to be matched to the feedline by a shorted quarter wave parallel transmission line stub. The point of attachment of the feeder coax is determined by sliding the connection back and forth along the stub monitoring for the lowest SWR . J pole antenna has a gain of about 2dB compared to a quarter wave ground plane antenna. The gain is slightly more on the side of the J stub compared to the opposite side. Current and voltage patterns in the J-pole antenna is illustrated in the diagram. Current peaks at lower end of the 3/4λ section while voltage peaks at the upper end. For the quarter wave stub current peak is at the lower end and voltage peak at the upper end. The parallel conductors of the J pole antenna should be kept away from other conducting material b

 I have been hearing about Satellite Roving on Twitter very often and wondered what it was and just thought of finding it out. Satellite Roving is simply operating satellites using portable Amateur Radio equipment from a grid square other than your home location. If you are a little adventurous, you can go to rare and difficult to access grids and other hams will be very happy to work you, if you have informed them well in advance! There is also an AMSAT Rover Award awaiting active Satellite Rovers. Rovers often post their schedule over X or on hams.at so that others can look out for them. There is usually a rush on satellite passes where rovers are active, to get those rare grids. Roving activity is more often on linear satellites and satellites with higher footprints like IO-117 when it was active. Some work the Geostationary Amateur Radio Satellite Qatar Oscar 100 also during roving activities. When no other satellites are available, they also go for regular FM satellites. Recently

 VOACAP or Voice of America Coverage Analysis Program for HF Propagation Prediction is a free software, originally developed for Voice of America by Institute for Telecommunication Sciences, the research and engineering arm of National Telecommunications and Information Administration (NTIA). OH6BG has a web portal which provides predictions for amateur radio HF bands from 3.5 to 28 MHz. That portal has additional options of VOACAP for Marine HF band from 2 to 25 MHz and VOACAP for 11m or the Citizen band which gives from 26 to 28 MHz. There are also VOACAP DX Charts which gives HF propagation predictions for amateur radio DXpeditions, VOACAP Greyline which gives Sun related data for any given location like times for sunrise, sunset, dawn, dusk, solar midnight and Space weather charts and indices. There is a VOACAP for Ham Radio User's Manual in pdf format available for download on the OH6BG website, which runs into 39 pages and is worth going through before using the HF propagat

 As per the current schedule available on NASA website , Starliner spacecraft will autonomously undock from the International Space Station on 6th September 2024 and start its journey back home. It is expected to land at White Sands Space Harbor in New Mexico on 7th September 2024. NASA astronauts Butch Wilmore and Sunita Williams who had gone to the Space Station in the first crewed flight of Starliner on 5th June 2024 and reached there on 6th June 2024, will remain there. Helium leaks and issues with spacecraft reaction control thrusters as the Starliner spacecraft approached the Space Station had caused concern about the safety of the astronauts. That is why NASA decided that Starliner will return to Earth without crew.  Butch Wilmore and Sunita Williams will return to Earth in February 2025 on SpaceX Dragon spacecraft along with two other crew members. Undocking and other details of Starliner's trip back to Earth will be covered by NASA website and YouTube channel . NASA has a

Many of you would have heard the term Cross Yagi in discussions among amateur radio satellite communication enthusiasts. A cross yagi is nothing but two normal Yagi Uda antennas mounted on the same boom, rotated 90 degrees in position. Cross Yagi is used for EME (Earth-Moon-Earth) or Mounbounce in addition to satellite communications. In all these modes, the signal has to cross the ionosphere, which can cause unpredictable polarization rotations. Circular polarization is used to reduce losses in such a scenario, as discussed earlier. Two types of arrangement of Cross Yagi elements on the mast has been described. In X setup, both sets of elements are at 45 degrees to the ground, so that it will look like an X. The other setup is + or cross setup in which the elements are at zero degrees and 90 degrees to the ground, so that it will resemble the plus sign. In the + or cross setup, the mast must be of non-conductive material to prevent strong negative influence on the vertical element

 Yagi-Uda antenna is often called just a Yagi antenna. It was invented in 1926 and consisted of  driven element, a reflector behind the driven element and directors in front of the driven element. In case of Amateur Radio (Ham Radio), the driven element is connected to the transceiver. Yagi antenna was a common sight on rooftops of houses earlier when they were used to receive television stations before cable and satellite TV became popular. Reflector and directors are called parasitic elements. Reflector is usually 5% longer than the driven element while directors are shorter. Yagi antenna has a much higher gain and directivity than a simple dipole antenna. Gain is usually above 10 dB. Gain increases as the number of directors increase, in a decremental fashion. Reflector can give a gain of about 5 dB while directors can add 1 dB and lesser. The interlinking rod is called as boom . Yagi-Uda antenna is very popular in Amateur Radio or Ham Radio. It was also a common sight on houseto

 Raspberry Pi is a series of small single board computers developed by Raspberry Pi Foundation along with Broadcom. Raspberry Pi Foundation is a British charity and company having an aim to promote the study of basic computer science in schools. Broadcom Inc. is an American company. Raspberry Pi is quite popular in hobby electronics and Amateur Radio. Raspberry Pi supports HDMI and USB standards. First model was released in 2012. Raspberry Pi 400 was released in 2020. It has 4GB of RAM and is combined with a keyboard in a single case. It has an upgraded switch mode power supply (SMPS). The processor can be clocked at 1.8 GHz which is 20% faster than the previous version. Raspberry Pi OS is a Unix-like operating system for the Raspberry Pi series. It has been the primary operating system for Raspberry Pi series since 2013. It is free and Open Source, distributed by the Raspberry Pi Foundation. Earlier generations of Raspberry Pi needed external ethernet or WiFi adapters for networkin

 My FT-710 radio has a built-in automatic antenna tuner which can tune up to an SWR of 3:1. It is quite handy as my antennas being homebrewed, do not have exact match from one end of the amateur radio band to the other end. So having a low range built-in antenna tuner makes it comfortable to work the whole extent of the band without any mismatch. But if I want to tune a long wire or to a band for which the antenna is not meant, I need an external antenna tuner with range at least 10:1 of SWR.