Does Coaxial Cable Choke at Antenna cut RF Noise?

Coaxial cable choke and RF common-mode noise Is it really true that a section of coiled coaxial cable choke at antenna feed-point would effectively cut down the radio RF noise substantially? Will the perceived reduction be enough to make operating especially on the lower frequency HF bands a pleasure? These are some of the questions that come to mind. Well, there are a multitude of opinions with many people suggesting that it is indeed worthwhile. Let us impassionately and realistically examine the effects of such coiled coaxial cable chokes that are often used near the antenna feed-point and figure out with rational scientific logic if they are truly as effective as one might be made to believe… At this point, some readers may feel impatient and say, stop beating about the bush, give us the bottom line… OK, the bottom line is NO! they don’t work well enough to feel jubilant or elated. Especially, on the lower HF bands like the 80m, or 40m. Even on the other higher frequency HF bands, they don’t perform as well as one might... Click Here to Read Full Article […]

Stacked Antenna Arrays

How do Stacked Antenna Arrays work? Stacked Antenna Arrays or Stacked Array is usually referred to as a set of directional antennas like the Yagi, the Cubical Quad, or the Helical antenna being placed in the vicinity of one another while being driven by a common RF transmitter. This scheme would result in additional forward gain beyond what is available from a single constituent antenna. This is the type of Stacked antenna Array that we are going to investigate in this article. Although, antennas like the Yagi, Multi-element cubical Quad, collinear antennas, etc are technically also antenna stacks. Most of these antennas are created by stacking several dipoles or monopole antenna elements. There are essentially two types of antenna stacks based on their radiation pattern directions. Those antennas which radiate in a direction along the stacking plane of the antenna elements are called Endfire antenna arrays, while those which radiate perpendicular (orthogonal) to this plane are called Broadside antenna arrays. Typical examples of the end-fire antenna array are the Yagi, LPDA, Multi-element Quad, etc. Typical Broadside antenna arrays are the... Click Here to Read Full Article […]

Why doesn’t 59 Signal Report on Repeater make sense?

Does 59 Signal Report on a Repeater make any sense? Does a 59 Signal Report exchange during a QSO on a Repeater make sense? Unfortunately, it doesn’t… We so often come across stations who report 59, or 59+20dB, etc to the other station during a QSO that is conducted through a local terrestrial repeater or during a QSO made via FM repeater type LEO amateur satellites. To top it all, I have come across instances where even a net-controller on an FM repeater net doles out this kind of signal reports to other stations and vice-a-versa. None of this makes any sense… Let’s see why? The RST reporting system comprises of three-digit. They are Readability (R), Signal-strength (S), and Tone (T). This is a typical CW signal reporting format most prevalent on HF radio bands. However, for radiotelephony, the third digit (T) is not applicable, and therefore only a two-digit (RS) report without the (T) is given. This is all good when it comes to regular point-to-point Simplex, Half-duplex, or Full-Duplex mode communication. How about repeater-based QSOs? The first digit... Click Here to Read Full Article […]

Radio Rigs

What are Radio Rigs for Amateur Radio? Radio rig is a generic term used by an amateur operator for the radio station equipment. It includes not only the primary transmitter and receiver (or transceiver) but also various other peripherals and station accessories. Although the transceiver performs the core function, several other pieces of hardware work in tandem to make radio communication more efficient. Often an outboard transverter, converter, low noise RF pre-amplifier, linear PA, inline SWR meter, antenna tuning unit (ATU), antenna switcher, iambic keyer, morse key or paddle, panadaptor, scanner, CAT interface unit, antenna rotator control, etc are quite common. These radio rig accessories form a part of station operation. There is however another vital category of equipment that is needed for testing, calibration, and routine station performance evaluation. These include antenna analyzer, oscilloscope, frequency counter, and standard, spectrum analyzer, dummy load, absorption power meter, RF signal generators, two-tone oscillator, etc. Communication ReceiversThe basic architecture of a communication receiver is similar to that of a domestic broadcast receiver. They have RF preamplifier, mixer, oscillator, IF amplifier, demodulator, AGC and... Click Here to Read Full Article […]

The Ubiquitous Dipole Antenna

The Center-fed Half-Wave Resonant Dipole Antenna The Dipole antenna is perhaps structurally the simplest antenna to fabricate and deploy. It requires a minimal set of hardware components and is quite light-weight. All Dipole antennas need not be single-band or resonant antennas, but its most widely used avatar is the monoband half wavelength (1/2 λ) version. Therefore, in this article, we will focus on the Half-Wave Resonant Dipole antenna and leave the discussion on non-resonant Dipoles to another article. A Dipole may present itself to us as the typical stand-alone antenna, or it might also be a part of more complex antennas, very often playing a role as their core sub-component. For instance, an awesome looking multi-element Yagi or even a Cubical Quad antenna are actually formed out of a combination of a set of Dipole elements… Surprised? Nevertheless, it’s true. A dipole is the core building block of most types of antennas that we are usually familiar with. So, when I say that a Dipole antenna is ubiquitous, I really mean it… Despite its simplicity, the Half-wave Dipole is an... Click Here to Read Full Article […]

Multiband End-fed Half-wave EFHW Antenna

Multiband End-Fed Half-Wave EFHW Antenna The End Fed Half Wave antenna or the popularly known EFHW antenna has been around almost ever since the inception of HF radio. Nevertheless, the EFHW antenna had in the past, been rather sparingly used by amateur radio operators due to various reasons. Although it is simple to build and is a multiband antenna, it has several attributes that make its overall performance far less than optimum for any serious HF DX operator’s liking. However, in the present day and age, thanks to many commercially manufactured EFHW antenna available in the market, more and more radio amateurs, especially the newcomers to HF communication are opting for this antenna despite its numerous shortcomings that can only be partially mitigated to acceptable levels by careful adjustments and tweaks that could be done by a knowledgeable and seasoned operator. A rookie operator, on the other hand, might most probably not even be aware of these shortcomings, let alone knowing ways and means of addressing them. Despite this many people take a plunge into amateur HF radio, armed with... Click Here to Read Full Article […]

Will High Gain HF Preamplifier help work Weak Signal DX?

High Gain HF Preamplifier for Weak Signal DX? Is it true that a high gain HF preamplifier will enhance the ability to work weak signal DX stations? Broadly speaking, the answer is NO! it won’t. However, for operation on VHF, UHF, and microwave bands, a good low noise preamplifier surely becomes important under most circumstances, for HF bands it is a different story. Though an experienced HF radio operator knows this too well, there are quite a few people who have a false notion regarding this. On various amateur radio forums, Facebook groups, as well as during personal interactions I have come across people who believe that adding a preamplifier to their HF radio rigs might improve their weak-signal DX prospects. Let us try to examine why such a notion is unsustainable and incorrect. We will also briefly examine why a preamplifier makes sense for VHF/UHF or microwave. What is it that sets HF apart from the higher frequency bands? Recap of Noise levels in Radio Communication Environment The prevalent noise levels in a communication system environment determine the limit... Click Here to Read Full Article […]

Radio Propagation Forecasting

Radio propagation forecasting and assessment With the advancement in technology over the last few decades, we have made giant strides in Radio Propagation Forecasting and Assessment techniques. The highly volatile and variable nature of HF terrestrial radio propagation has always driven us to find more and more accurate means of predicting propagation conditions. Both long term and short term forecasting methods have improved over the years. The VHF and UHF DX communication also faces several challenges of variability, however, the effects are mostly on account of atmospheric phenomena. Prediction of most of these atmospheric variables with reasonable accuracy still remains quite a challenge. When we speak of forecasting and assessment with reference to HF radio, they often mean two different things. Assessing HF radio propagation conditions to plan radio communication has been in vogue for a long time. Various methods have been used by both professionals as well as radio amateurs. One of the cornerstones of long-range HF propagation assessment has been the time-tested method of using radiofrequency beacons. On the other hand, propagation forecasting is more a science-based on... Click Here to Read Full Article […]

Ionospheric Skywave Propagation

Ionospheric Skywave Propagation – A Curtain Raiser The most important propagation mode for HF radio communication is Ionospheric Skywave propagation. Starting at the bottom of the D-layer and all the way till the top of the F2-layer lie a very wide zone where ionization of gasses in the air occurs. Ionization throughout the entire region is contiguous but follows a varying gradient pattern of ion density. The ionospheric layers D, E, F1, and F2 are the distinct areas of high ionization within the broad region where ionized particles exist. These are the positions at which we have significantly more dense ionization compared to the intervening space. Due to high charge concentration, these ionospheric layers interact with the propagating EM wave and produce unique phenomena resulting in the bending of EM radio waves. For the purpose of simplification, we will, for the time being, ignore the presence of lower density ionization in the inter-layer intervening space and presume each ionospheric layer as distinct ionized entities. Each ionosphere layers (D, E, F1, and F2) have a few common behavioral traits which we... Click Here to Read Full Article […]

Space Radio

What is Amateur Satellite Radio? Amateur satellite radio space communication is by-and-large related to conducting two way QSO between stations at distant geographic locations using earth-orbiting satellites which are usually dedicated to amateur radio use. Historically, this started in 1961 with the launch of OSCAR-1 amateur satellite in low earth orbit. Since then there has been an evergrowing interest among the ham community to venture into satellite radio communication. Some of the earlier amateur satellites which became quite popular were OSCAR-6 and OSCAR-7. At present, the amateur satellites consist of those featuring either linear transponders or FM cross-band repeaters. Most of them have a dedicated telemetry channel too. With modern-day micro miniaturization, we also have several smaller satellites called Cubesats and Nanosats. Another interesting facet of amateur space radio communication is to bounce radio signals off the surface of the moon by using it as a passive reflector for communication between stations on earth. This form of communication is known as Earth-Moon-Earth (EME) mode. Although the use of EME amongst radio amateurs is not widespread, it is nevertheless, a very... Click Here to Read Full Article […]