Terrestrial VHF Radio Signal Coverage – LOS

Terrestrial VHF Radio Signal Propagation – LOS Though VHF/UHF radio is very popular, why do the terrestrial VHF radio signal coverage losses grow quickly to curtail the useful range to short distances? This is an important question that needs to be addressed, especially, because quite often it leads to a bit of confusion amongst many radio amateurs, who tend to incorrectly believe that VHF-UHF communication range capabilities are inherently limited due to the nature of propagation losses at these frequencies. This is far from the truth. For instance, satellite and deep-space communication over thousands or even millions of kilometers is conducted on the VHF-UHF or microwave bands… Please note that in the course of the narrative, in this article, I would mostly use the phrase “Terrestrial VHF Radio Signal losses” or “VHF Signal Losses” which would usually imply both VHF and UHF even though I may not be explicitly mentioning UHF every time. Amateur radio earth-orbiting satellites of the LEO class are regularly accessed by operators around the world using low-power communication gear that put out a few watts, into... Click Here to Read Full Article […]

VHF Propagation Path Profiler – Web App

Terrestrial VHF Propagation Path Profiler The VHF Propagation Path Profiler presented here is a comprehensive application that allows us to graphically render and mathematically compute various relevant VHF/UHF propagation metrics including VHF propagation path losses, over the realistic terrain profile between any two point-to-point locations on the surface of the earth. The true terrain topological profile including hills, valleys, terrain undulations, etc accounted for. The VHF/UHF signal diffraction over various features of the terrain profile is included in the computation. Moreover, the nature of the TX and RX sites in terms of the built-up area resulting in structural clutter is also taken into account. For graphical signal path rendering and numerical computations over the terrain profile, not only the terrain topology but also the terrain bulge due to the curvature of the earth is factored into the computations. Various input variables like the antenna height over ground, their gain, etc can be set. The frequency band and the TX power levels are also settable. This signal path rendition is not an over-simplified straight line that some people often assume but... Click Here to Read Full Article […]

World Order

World Order – The evolving economic trends The World Order is determined by sets of collectively agreed rules of engagement amongst nations that determine orderly trade transactions, allowing a smooth flow of goods and commodities. However, these rules evolve. Historically, we have witnessed a constant evolution of this world order over centuries. Needless to say, the more powerful nations typically use their clout to influence the rules of world order to their advantage. Very often we consider the military strengths of nations and their geopolitical clout to be the other notable influencers of world order. It may well be so… However, the most important core factor is the economic strength of each nation. Military strength as well as geopolitical influence cannot exist in a vacuum. They can only be built on top of a strong economy. Hence, economic strength is the lynchpin that holds the other dominoes of world order in place. If the economy of a nation strengthens, its military and geopolitical strengths also increase, and vice-versa. Therefore, let us take a journey through the evolution of global economic... Click Here to Read Full Article […]

Ground Wave Propagation

Is it Ground Wave or surface Wave propagation? Both the terms ground wave propagation, as well as surface wave propagation, are relevant. However, we often tend to use them interchangeably and loosely, which is technically incorrect. There is a difference between the two. When most radio amateurs use the term groundwave, it is actually the surface wave that they usually refer to. So, what is the difference between the two terms? Technically, the ground wave is a term used to represent a combination of several subtly different propagation modes. These include the Direct wave mode (LOS mode), surface reflected mode and also the true surface wave. In other words, the Surface wave is only a sub-set of the multi-faceted propagation mode that we collectively call the Ground wave. In this article, we will examine various modes comprising of the Ground wave with special emphasis on the Surface Wave which is quite unique and special with a propagation method that is so different from the others. The properties of the surface waves make them very useful for establishing robust, reliable and... Click Here to Read Full Article […]

Antenna Fundamentals

Introduction to Antenna fundamentals In this section, we will examine some of the fundamentals of radio communication antennas. Acquiring a sound knowledge of antenna fundamentals is very important. In a radio communication environment, for any station to function optimally it is very important to pay great attention to the antenna installation. Although every radio station hardware including the transmitter and the receiver are important but eventually when it comes to overall performance, it is the quality of the antenna that plays the most important role. As the saying goes… “A radio station is as good or as bad as the antenna it has”. Hence we will lay special emphasis to the principles of antenna fundamentals and without going into much mathematics, we will try to keep our discourse as intuitive and simple as possible. most types of antennas that we encounter in the real world are typically some kind of a standing-wave antenna. They are usually dipoles or some derivative or combination of a set of dipoles. One might ask at this stage that what about complex antennas like a... Click Here to Read Full Article […]

Fundamentals of Radio Propagation

An Introductory Primer on Radio Propagation A good understanding of various radio propagation phenomena is vital to leverage propagation conditions to one’s advantage in establishing radio communication. Radio wave propagation is perhaps as important as the clarity on antenna performance and behavior. On our website, we have several in-depth articles that dwell on most of the important propagation phenomena. However, in this introductory article, we will introduce the readers to some of the fundamental building blocks that would be helpful in following the narrative in our other articles related to radio wave propagation. Over here, we will touch upon several concepts related to not only HF radio but also VHF and UHF. In any form of communication scenario over geographic space, the transmission of a signal from one point to another is the fundamental objective. Radio communication systems achieve this objective by exploiting the transmission and propagation behavior of their primary propagation medium which is the free space. The radio waves or the electromagnetic (EM) waves travel through the atmosphere above the earth from one point to another across the... Click Here to Read Full Article […]

100W on a Wire Antenna – How far would it reach?

100W on a Wire Antenna – Is it good enough for DX? 100W on a Wire antenna! … How far could it possibly reach? This is perhaps one of the most hotly debated rookie topics in the world of amateur radio. It has always been like this and it would always be the same. A radio amateur who has been newly initiated into this field takes a while to come to terms with reality. Intuitively, it becomes very difficult for a rookie operator to even imagine that 100W on a Wire might be more than adequate to communicate around the entire world. At times, a station with a plain-Jane dipole antenna and running as low as 5-20W may comfortably work the world. When I say this, I do not mean working via weak-signal digital modes like FT8, FT4, etc. The operating situation cited above refers to radiotelephony SSB QSO. However, for all this to be viable on a reasonably regular basis, there are a few fundamental prerequisites. First of all, the station operator would need to acquire a fair understanding... Click Here to Read Full Article […]

How to get started on ISS Cross band Repeater?

Getting started on ISS Cross band Repeater The new version of the ISS Cross Band Repeater had been activated on 2nd September 2020 at 01:02 UTC. Since it is still in the testing and deployment phase at the time of writing (October 2020) of this article, its service might currently be available on an intermittent basis. Nevertheless, this should be great news for millions of radio amateurs around the world as it is indicative of was is in store for us in the coming days. The ARISS program (Amateur Radio on International Space Station) has been active for many years. Under ARISS, a variety of amateur radio communication activities have been conducted at specified times as per declared schedules. Amateur radio operators around the world have made numerous FM radio voice contacts with astronauts onboard the ISS as well as received SSTV picture transmissions from the ISS. However, the above activities in the past required adherence to ISS activity schedules. Radio amateurs could make radio contacts with the astronauts but only when they were free to operate amateur band radios…... Click Here to Read Full Article […]

VHF/UHF & Free Space propagation

VHF/UHF & Free Space Propagation – A primer Radio wave propagation across the entire spectrum including VHF, UHF, and microwave primarily depends on the principles of Free Space propagation. As the radio waves propagate, they are subsequently acted upon by several other physical phenomena like reflection, refraction, diffraction, absorption, etc to modify their net behavior. It is therefore important to get a fair insight into the basic aspects of Free Space propagation. To brush up the above concepts, please check out our article on Fundamentals of Radio Propagation. In the case of VHF/UHF communication that is nowadays commonly trending amongst radio amateurs, quite often most of these modifier effects rarely come into play. The reason being that over the last 30 years or so, a large section of radio amateurs conduct VHF/UHF communication either on short-distance local point-to-point circuits or use repeaters which are at times trunked using hybrid methods like the internet based Echolink or similar platforms. Moreover, the general trend is to use FM radios. This makes propagation on these bands rather mundane and elementary and one is... Click Here to Read Full Article […]

Space Radio Propagation

An Introduction to Space Radio Propagation The propagation of radio waves for space radio communication primarily takes place by Direct wave (a.k.a. Space wave). The space radio propagation could encompass communication between two or more satellites, communication with a space probe in interplanetary space, earth station communication with a spacecraft, communication between an earth station and an earth-orbiting satellite. The satellite-based communication link may be one-way like in the case of telemetry, or more often it might be a two-way link used either for command, control, or for voice, data, and other modes of information exchange. Normally, there are not many geographic entities or man-made artifacts that come in the way of the propagation path to alter the direct space wave propagation characteristics. However, most earth station based space radio communication scenarios involve using earth-orbiting satellites to form a broader communication infrastructure. In this article, we will primarily focus on two-way communication between an earth station and an orbiting satellite. This type of communication system usually operates in the VHF, UHF, or microwave frequency spectrum. The orbiting satellites may have... Click Here to Read Full Article […]