Friday, 22 November 2013

AMATEUR RADIO CLUB SARAWAK (ARCS) 2013 AGM


Dear All,
ARCS 2013 AGM will take place as below;
Date : 15th December 2013
Time: 1400hrs-1600hrs
Venue: Malaysia Teachers Institute, Batu Lintang,
Agenda;
1. Welcoming speech (President)
2. Verify Last AGM minute
3.  Secretary Report (2012-2013)
4. Financial Report (2012-2013)
                       5. Elect a new council and to appoint auditors
                       6.  Others matter

Attach with this email was nomination form for office barrier (2014-2016) please send to 9M8MA before 13th December 2013 (pse refer to email that I send)

ALDRIN
(9M8WAT)

Tuesday, 15 October 2013

Amateur Radio Direction Finding (ARDF)

Amateur radio direction finding (ARDF, also known as radio orienteering and radiosport) is an amateur racing sport that combines radio direction finding with the map and compass skills of orienteering. It is a timed race in which individual competitors use a topographic map, a magnetic compass and radio direction finding apparatus to navigate through diverse wooded terrain while searching for radio transmitters. The rules of the sport and international competitions are organized by the International Amateur Radio Union. The sport has been most popular in Eastern EuropeRussia, and China, where it was often used in the physical education programs in schools.
ARDF events use radio frequencies on either the two-meter or eighty-meter amateur radio bands. These two bands were chosen because of their universal availability to amateur radio licensees in all countries. The radio equipment carried by competitors on a course must be capable of receiving the signal being transmitted by the five transmitters and useful for radio direction finding, including a radio receiverattenuator, and directional antenna. Most equipment designs integrate all three components into one handheld device.
File:Ardf 0001.jpg

The sport originated in Northern Europe and Eastern Europe in the late 1950s. Amateur radio was widely promoted in the schools of Northern and Eastern Europe as a modern scientific and technical activity. Most medium to large cities hosted one or more amateur radio clubs at which members could congregate and learn about the technology and operation of radio equipment. One of the activities that schools and radio clubs promoted was radio direction finding, an activity that had important civil defense applications during the Cold War. As few individuals in Europe had personal automobiles at the time, most of this radio direction finding activity took place on foot, in parks, natural areas, or school campuses. The sport of orienteering, popular in its nativeScandinavia, had begun to spread to more and more countries throughout Europe, including the nations of the Eastern Bloc. As orienteering became more popular and orienteering mapsbecame more widely available, it was only natural to combine the two activities and hold radio direction finding events on orienteering maps.
Interest in this kind of on-foot radio direction finding activity using detailed topographic maps for navigation spread throughout Scandinavia, Eastern and Central Europe, the Soviet Union, and thePeople's Republic of China. Formal rules for the sport were first proposed in England andDenmark in the 1950s.[1] The first European Championship in the sport was held in 1961 in StockholmSweden. Four additional international championships were held in Europe in the 1960s, and three more were held in the 1970s. The first World Championship was held in 1980 in Cetniewo, Poland, where competitors from eleven European and Asiancountries participated. World Championships have been generally held in even-numbered years since 1984, although there was no World Championship in 1996, and there was a World Championship in 1997. Asian nations began sending national teams to international events in 1980, and teams from nations in Oceania and North America began competing in the 1990s. Athletes from twenty-six nations attended the 2000 World Championship in Nanjing, China, the first to be held outside of Europe.[dead link][2]
A member of the Republic of Korea national team sprints to the finish line of an eighty meter ARDF course.
As the sport grew in the 1960s and 1970s, each nation devised its own set of rules and regulations. The need for more clearly defined and consistent rules for international competitions led to the formation of an ARDF working group by the International Amateur Radio Union (IARU) in the late 1970s. The first ARDF event to use the new standardized rules was the 1980 World Championship. These rules have been revised and updated over the years, increasing the number of gender and age categories into which competitors are classified, as well as formalizing the start and finish line procedures.[3] While some variations exist, these standardized rules have since been used worldwide for ARDF competitions, and the IARU has become the principal international organization promoting the sport. The IARU divides the world into three regions for administrative purposes. These regions correspond with the three regions used by the International Telecommunications Union for its regulatory purposes, but the IARU has also used these regions for sports administration. The first IARU Region I (Europe, Africa, the Middle East, and ex-USSR) Championship was held in 1993 in Chtelnica, Slovakia,[dead link][2] the first IARU Region III (Asia and Oceania) Championship was held in 1993 in Beijing, China,[dead link][4] and the first IARU Region II (North and South America) Championship was held in 1999 in Portland, Oregon, USA.[3] In addition to participation in international events, most nations with active ARDF organizations hold annual national championships using the IARU rules.
ARDF is a sport that spans much of the globe. In 2012 over 570 athletes from thirty-three countries, representing four continents, entered the 16th World Championships held in Kopaonik, Serbia [5] Organized ARDF competitions can be found in almost every European country and in all the nations of northern and eastern Asia. ARDF activity is also found in ThailandAustraliaNew ZealandCanada, and the United States. Although they represent a broad range of amateur radio interests in their nations today, several member societies of the International Amateur Radio Union were originally formed for the promotion and organization of the sport and continue to use the term radiosport in their society name. These include the Federation of Radiosport of the Republic of Armenia (FRRA),[6] the Belarusian Federation of Radioamateurs and Radiosportsmen (BFRR),[7]the Chinese Radio Sports Association (CRSA),[8] and the Mongolian Radio Sport Federation (MRSF).[9] To promote the sport, the IARU has delegated individuals as ARDF Coordinators for each IARU region to help educate and organize national radio societies and other ARDF groups, especially in nations without prior activity in the sport.

Description of competition and rules

The rules used throughout the world, with minor variations, are maintained by the IARU Region I ARDF Working Group. Although these rules were developed specifically for international competitions, they have become the de facto standard used as the basis for all international competitions worldwide.

An ARDF competition normally takes place in diverse wooded terrain, such as in a public park or natural area but competitions have also been held in suitable suburban areas. Each competitor receives a detailed topographic map of the competition area. The map will indicate the location of the start with a triangle and the location of the finish with two concentric circles. Somewhere within the competition area designated on the map, the meet organizer will have placed five low power radio transmitters. The locations of the transmitters are kept a secret from the competitors and are not marked on the map. Each transmitter emits a signal in Morse code by which it is easily identifiable to the competitors. The transmitters automatically transmit one after another in a repeating cycle. Depending on entry classification, a competitor will attempt to locate as many as three, four, or all five of the transmitters in the woods, and then travel to the finish line in the shortest possible time. Competitors start at staggered intervals, are individually timed, and are expected to perform all radio direction finding and navigation skills on their own. Standings are determined first by the number of transmitters found, then by shortest time on course. Competitors who take longer than the specified time limit to finish may be disqualified.
ARDF events use radio frequencies on either the 2-meter or 80-meter amateur radio bands. These two bands were chosen because of their universal availability to amateur radio licensees in all countries. Each band requires different radio equipment for transmission and reception, and requires the use of different radio direction finding skills. Radio direction finding equipment for eighty meters, an HF band, is relatively easy to design and inexpensive to build. Bearings taken on eighty meters can be very accurate. Competitors on an eighty meter course must use bearings to determine the locations of the transmitters and choose the fastest route through the terrain to visit them. Two meters, a VHF band, requires equipment that is relatively more complicated to design and more expensive to build. Radio signals on two meters are more affected by features of the terrain. Competitors on a two meter course must learn to differentiate between accurate, direct bearings to the source of the radio signal and false bearings resulting from reflections of the signal off hillsides, ravines, buildings, or fences. Large national or international events will have one day of competition using a 2-meter frequency and one day of competition using an 80-meter frequency.[1]
In addition to the rules of the sport, ARDF competitions must also comply with radio regulations. Because the transmitters operate on frequencies assigned to the Amateur Radio Service, a radio amateur with a license that is valid for the country in which the competition is taking place must be present and responsible for their operation. Individual competitors, however, are generally not required to have amateur radio licences, as the use of simple handheld radio receivers does not typically require a license. Regulatory prohibitions on the use of amateur radio frequencies for commercial use generally preclude the awarding of monetary prizes to competitors. Typical awards for ARDF events are medals, trophies, plaques, or certificates.

Friday, 4 October 2013

ARCS upcoming activity

1) Activity : ARCS Eyeball
                   Date: 4th October 2013
                   Time: 2100 hrs
                   Place: Pondok Anis, Kuching

2) Activity:  Swinburne ARDF workshop (fox hunt)
                   Date : 13th October 2013 (Sunday)
                   Time: 0900hrs - 1100hrs
                   Place: Swinburne University
                   Person to contact : 9W8CH






3) Activity : Scout Jamboree On The Air (JOTA)
                   Date : 19th October 2013 (Saturday)
                   Time: 0800hrs - 2359hrs
                   Place: S.K Gawang Empili, Simunjan
                   Person to contact : 9M8WAT





Tuesday, 17 September 2013

ARCS jointly MARTS Emergency Communication ( EmComm ) exercise

Date: 14th September 2013
Venue: Miri and Bekenu District
Time: 0800 hrs-1800hrs

 EmComm exercise being the second one held at Miri after first exercise was at Sematan , Kuching on 2011. For this exercise as many 15 amateur radio stations involved and 5 participants from the public.

The main objective of this exercise was to evaluate for amateur station preparedness if needed, during emergency situation. Also, to enhance knowledge of their equipment how to operate in most simplest operation situation .All the remote stations that were divided into 3 groups only
battery power to operate and same time using NVIS ( Near Vertical Incidence Skywave)
concept antenna.
From what we learnt just using as low 5 watt radio power  that the radio signal coverage able to reach as far to 50km to 100km.Before all groups being deployed to their locations, they were briefed by 9M8DB (Mr, Johnny Tan) as coordinator of this exercise and assisted by 9M2DA
(Mr. Deen). SKMM Miri branch also shared about their role in communication by Mr. Gidah (9W2GM).

After the exercise, all participants did evaluation for what had been done, and  was very encouraging from previous exercise. Being advise to do more frequent such exercises from time to time in order to work and prepare themselves from mental and physically fitness.

9M2IR (MARTS President) also thanked to all who make this exercise a successful and hope will involve more amateur radio stations in future.

After  the exercise

Main station (9M8MBB/9W9KIF)

Briefing by 9M8DB

Rising up HEX beam antenna

Remote 1 Station (9M8WAT/9W8WKF/9W8IQA) at S.K Kuala Sibuti

Remote 2 (9M8MET/9W8CH/9W8VWL) Pekan Bekenu

Remote 2 Station (9M8ADX/9M8MA/9W8PTS) at S.K Beliau Isa




Appreciation from MARTS
Something to discuss on (9M8DB, 9W8CH,9M8WAT)


As for ARCS participated stations,  we hope this exercise had been a fruitful one  and looking to improve further with better skill and radio communication techniques and not forgetting our preparedness for any coming future exercise and real event.

Wednesday, 21 August 2013

16th INTERNATIONAL LIGHTHOUSE & LIGHTSHIP 2013 (9M4LHM)

DATE : 17th August - 18th August 2013
PLACE: Tanjung Lobang Lighthouse, Miri, Sarawak
CALLSIGN : 9M4LHM


The event was jointly organised by Amateur Radio Club Sarawak (ARCS) and Sarawak Marine Department. This is the first time that such an event has been held in Sarawak. Sarawak Marine Department's Director, Tn Haji Zahidin was present and shared with others the importance of lighthouses to the marine navigation.

The main propose of the event was to promote awareness of lighthouses to the public. The Tanjong Lobang Lighthouse was built in the early 1940s prior to the onset of the 2nd World War.

The callsign (9M4LHM) assigned to Tanjong Lobang Lighthouse for this event was applied by MARTS (Malaysia Amateur Radio Transmitter Society) and activated by ARCS.

ARCS would like to give credit to 9W8CH (ARCS President), 9M8DB(station manager), 9W8KIF, 9M8MBB, 9M8MET, 9M8ADX, 9W8SIR ,9W8IQA, 9W8NCT and 9M8WAT (station master) for participating in this event. Also not forgetting Alvin who brought a few Scout members from Bintulu to lend a helping hand in setting up the 9M4LHM amateur radio station and introducing these young scouts to the workings of amateur radio.

Total contact for that weekend was 346 QSOs

QSO by band


10m

15m

20m

40m

9 stn

119 stn

217 stn

1 stn

 1. Worked on 49 different entities
2. Worked on 29 different zone
3. Worked on 29 WAE Europe continent
4. Worked on 50 different DXCC


Station set-up station:

Antennas     1. Hexbeam K4KIO (5Band)
                    2. Yeasu Broadband Dipole
                    3. Ultimax 100 End fed antenna

Trancievers   1. Icom IC756 PROIII
 

                      2. Icom IC738
                      3. Icom  IC 7000
                      4. Yeasu FT897D

Operations were mostly confined to 20m band and 15m band as other bands had poor propagation.

ARCS would like to thank everybody that were involved directly and indirectly and plan to organise the same event next year in Tanjung Dato Lighthouse



Left to right , Alvin, 9M8WAT,9W8IQA,9M8MBB,9M8MET,9W8SIR,9W8CH,9M8ADX,9W8NCT (not around 9M8DB & 9W8KIF)

A short contact in HF with 9M4LHN (Cape Recardo, Port Dickson)

Borneo Post newspaper cutting 21st August 2013

Sarawak Marine Department Director (Tn. Hj. Zahidin)



Principal of Kolej Tunku Tun Datu Hj. Bujang, Tanjung Lobang, Miri (Hajah Hasimah)



9M4LHM main antenna, Hexbeam (5 band) by K4KIO

Some adjustment before event start (Scout from Bintulu, 9M8DB,9W8SIR & 9M8WAT)

Doing radio check by 9M8DB, assist by 9W8KIF & 9W8CH (ARCS President)
 

Tuesday, 11 June 2013

NVIS: Near Vertical Incidence Skywave (Part 2)

What is NVIS?
NVIS, or Near Vertical Incidence Skywave, refers to a radio propagation mode which involves the use of antennas with a very high radiation angle, approaching or reaching 90 degrees (straight up), along with selection of an appropriate frequency below the critical frequency, to establish reliable communications over a radius of 0-200 miles or so, give or take 100 miles. Although not all radio amateurs have heard the term NVIS, many have used that mode when making nearby contacts on 160 meters or 80 meters at night, or 80 meters or 40 meters during the day. They may have thought of these nearby contacts as necessarily involving the use of groundwave propagation, but many such contacts involve no groundwave signal at all, or, if the groundwave signal is involved, it may hinder, instead of help. Deliberate exploitation of NVIS is best achieved using antenna installations which achieve some balance between minimizing groundwave (low takeoff angle) radiation, and maximizing near vertical incidence skywave (very high takeoff angle) radiation.
As hams, we often faithfully follow the advice: get your antenna up as high as you can get it! We do this, and other things (like choosing antennas that have a low angle of radiation) in order to maximize the distance over which we can communicate. An antenna with a particularly high angle of radiation is often somewhat disparagingly referred to as a "cloudwarmer", the implication being that if the signal isn't radiated at a low enough angle, it's being wasted. For NVIS, we ignore all this traditional advice, and select instead techniques which will maximize not our DX, but our ability to reliably communicate with other stations within a radius of 0-300 miles.
 
Not just any old frequency will work for NVIS. Successful NVIS work depends on being able to select, or find (through trial and error), a frequency which will be reflected from the ionosphere even when the angle of radiation is nearly vertical. These frequencies usually are in the range of 2-10 MHz, though sometimes the limit is higher. The trick is to select a frequency which is below the current critical frequency (the highest frequency which the F layer will reflect at a maximum--90 degree--angle of incidence) but not so far below the critical frequency that the D and/or E layers mess things up too much.
 
 
There are two main types of propagation at HF, known as "groundwave" and "skywave". Groundwave propagation occurs when the receiving station is sufficiently close to the transmitting station, and is able to receive the portion of the transmitting station's signal which clings to the ground. The range of groundwave propagation varies with the type of antenna at the transmitting station, the characteristics of the ground between the transmitting station and the receiving station, and other factors. It can be anywhere from a few miles, to a few dozen miles. Distances beyond the range of the groundwave signal are covered by skywaves. Skywaves are the waves which radiate upward at some angle from the antenna, and (we hope) are reflected from the ionosphere, to return to earth further away.
The ionosphere is a high altitude region of the Earth's atmosphere which is composed of gaseous atoms which have broken into ions. The sun is the source of the ionizing energy, so the condition of the ionosphere varies with time of day, season of the year, the 11-year sunspot cycle, and the 27-day rotation of the sun. The layers of the atmosphere that effect radio propagation are the D, E, and F layers. I won't go into much detail in outlining their roles. If you're interested in this topic, entire books have been devoted to it. In a nutshell, it's the F layer which is usually involved in reflecting our signals back to earth, while the D layer absorbs our signals. The E-layer can either help, or hinder.
Long distance propagation of radio waves is usually achieved by their being reflected from the ionosphere, and returning to earth some distance away from their point or origin. (Follow along with the diagram if you wish.) Radio waves which have been radiated at a very low angle of radiation travel a long way before finally making it up to the ionosphere, strike the ionosphere at a very shallow angle (A) and return to earth far away from their point of origin (A'). As the angle of radiation goes up, the radio waves strike the atmosphere at a more moderate angle (B), and return to earth closer to their point of origin (B'). For any given frequency and current state of the ionosphere, there may be some maximum angle of incidence at which the ionosphere will reflect signals back to earth. Signals which strike the ionosphere at a higher angle of incidence than the current maximum will not be reflected at all, but will continue on out into space, instead (C). The area of the earth to which the reflection would have occurred will be in what we call the "skip zone" (unless it's close enough to the signal source to receive the groundwave signal). The skip zone is the region consisting of areas of the earth's surface which are outside the radius the transmitting station's ground-wave will reach, and yet not far enough away to receive reflections of sky-waves.
 
NVIS techniques concentrate on the areas which are often in the skip zone. The idea is to radiate a signal at a frequency which is below the critical frequency, at a nearly vertical angle, and have that signal reflected from the ionosphere at a very high angle of incidence, returning to the earth at a relatively nearby location.  Of course, no antenna radiates all its signal at exactly one angle, so the best we can get is a range of angles, ranging from perfectly vertical, to nearly vertical. The portion of the signal which is radiated at a vertical, or nearly vertical, angle reflects back to earth over some radius, which is determined by the lowest angle at which the antenna radiates much signal. Absorption by the D layer, and other factors, determine some minimum frequency below which the signal will no longer be usable, and usually some distance beyond which signals will no longer be usable.
For areas which are within the groundwave range of the transmitting station, the ground-wave's presence may interfere with the reflecting skywave. It may very well help, too. It all depends on whether the groundwave and the skywave arrive in phase, out of phase, or somewhere in between, and their relative strengths. If the groundwave arrives at about the same strength as the skywave, and the two are out of phase, the signal will disappear. Since the height of the ionosphere varies with time, phase alignment may drift from in phase, to out of phase, resulting in signal fading. For this reason, it's best to minimize groundwave radiation when using NVIS techniques, so that it will be less likely to interfere with the skywave.
Although this discussion has focused mainly on the transmission of signals, there is a corresponding advantage of using NVIS techniques in reception, and a trick or two that are useful mainly for reception. The corresponding advantage is that if your antenna favors high angles for transmission, it will also favor high angles for reception. An antenna optimized for radiating at the high angles used for NVIS will also be optimized for receiving the skywaves which will be arriving at a high angle from the ionosphere. An antenna which does not radiate much groundwave signal will also probably not receive groundwave signals as strongly. When both stations are using antennas which are optimized for NVIS, the mode is favored both in transmission and reception, and those advantages add together, increasing the chances of reliable communication.
There is also an advantage inherent in the use of NVIS style antennas which applies only to receiving. The frequencies which are useful for NVIS (usually 2-10 MHz) are the same frequencies which are most susceptible to atmospheric noise. A major source of atmospheric noise is distant thunderstorms. Nearby thunderstorms are the worst, of course, but the noise from all possible sources adds together. Unless there is a nearby thunderstorm, most noise will be the sum of the noise from distant sources which are all propagated to the receiving antenna. Since an antenna optimized for NVIS is listening mostly to signals propagated from relatively nearby areas, and does not favor the reception of signals, static crashes, and other sources of noise and interference from more distant sources, it will not hear as much noise or interference as an antenna optimized for DX operation. The result is a better signal/noise ratio.
Often, taking measures which optimize a station's NVIS capabilities will drop the noise level substantially. Sometimes, the drop in noise can be maximized at the expense of some signal strength, and result in a communication circuit which has lower signal levels, but even more dramatically lower noise levels, for an even better signal/noise ratio than could be achieved by focusing only on maximizing signal levels.
So, selecting a frequency below the critical frequency, but not too far below it, and selecting an antenna which will radiate skywaves at a high angle, and minimize groundwaves and the reception of noise, are the essential tricks of establishing reliable communication in the 0-200 mile radius which is so often a challenge for HF operation.
What are the advantages and disadvantages of NVIS?
Among the many advantages of NVIS are:
  • NVIS covers the area which is normally in the skip zone, that is, which is normally too far away to receive groundwave signals, but not yet far enough away to receive skywaves reflected from the ionosphere.
  • NVIS requires no infrastructure such as repeaters or satellites. Two stations employing NVIS techniques can establish reliable communications without the support of any third party.
  • Pure NVIS propagation is relatively free from fading.
  • Antennas optimized for NVIS are usually low. Simple dipoles work very well. A good NVIS antenna can be erected easily, in a short amount of time, by a small team (or just one person).
  • Low areas and valleys are no problem for NVIS propagation.
  • The path to and from the ionosphere is short and direct, resulting in lower path losses due to factors such as absorption by the D layer.
  • NVIS techniques can dramatically reduce noise and interference, resulting in an improved signal/noise ratio.
  • With its improved signal/noise ratio and low path loss, NVIS works well with low power.
Disadvantages of NVIS operation include:
  • For best results, both stations should be optimized for NVIS operation. If one station's antenna emphasizes groundwave propagation, while another's emphasizes NVIS propagation, the results may be poor. Some stations do have antennas which are good for NVIS (such as relatively low dipoles) but many do not.
  • NVIS doesn't work on all HF frequencies. Care must be exercised to pick an appropriate frequency, and the frequencies which are best for NVIS are the frequencies where atmospheric noise is a problem, antenna lengths are long, and bandwidths are relatively small for digital transmissions.
  • Due to differences between daytime and nighttime propagation, a minimum of two different frequencies must be used to ensure reliable around-the-clock communications.

What kind of antenna works well for NVIS?
 
Dipole
Once again, the dependable dipole antenna proves itself useful. One of the most effective antennas for NVIS is a dipole positioned from .1 to .25 wavelengths (or lower) above ground. When a dipole is brought very close two ground, some interesting things happen. The most interesting thing, from an NVIS perspective, is that the angle of radiation goes up. In the range of .1 to .25 wavelengths above ground, vertical and nearly vertical radiation reaches a maximum, at the expense of lower angle radiation (which we'd like to minimize, anyway, for NVIS). A dipole can be used at even lower heights, resulting in some loss of vertical gain, but often, a more substantial reduction in noise and interference from distant regions. Heights of 5 to 10 feet above ground are not unusual for NVIS setups, and some people use dipoles as low as two feet high with good results (relatively weak signals, but a very low noise floor).
Another interesting thing that happens with very low dipoles is that their feedpoint impedance goes down. An acceptable SWR with 50 ohm coax is likely. Plan to bring your tuner along just in case, but you may get by just fine without it.
Yet another fortunate thing about low dipoles is that they are easily erected. Finding a tree which will serve as a support is often easy, and it's not hard to get a line in a branch which will suffice. Masts made of PVC tubing are practical at these heights. Very low dipoles can be supported by traffic cones with a notch cut in the top, or a simple tripod made from short sections of PVC pipe or wooden dowels, and bungee cords.
With the exception of the very lowest dipoles, most dipoles will gain an extra 2 db or so of vertical gain if you allow the center to droop a few feet. Allowing the center to droop means that the end supports don't have to be as sturdy, which makes installing a good NVIS dipole that much easier.
 
Inverted Vee
The dipole's close cousin, the inverted vee, is another good NVIS antenna, which can be even simpler to support. An inverted vee will work almost as well as a dipole suspended from a slightly lower height than the apex of the inverted vee, so long as the apex angle is kept gentle--about 120 degrees or greater. An inverted vee is often easier to erect than a dipole, since it requires only one support above ground level, in the center.
Counterpoises
The high angle radiation of a dipole (or inverted vee) can be enhanced by adding a counterpoise wire below it, about 5% longer than the main radiating element, to act as a reflector. The optimum height for such a counterpoise is about .15 wavelengths below the main radiating element, but when the antenna is too low to allow for that, a counterpoise laid on the ground below the antenna is still effective.
A knife switch at the center point of the counterpoise can be used to effectively eliminate the counterpoise from the antenna system. This technique is useful for using a dipole for NVIS and longer distances, too. A counterpoise is installed at ground level, or as high as the switch can easily be reached, and a dipole is mounted .15 wavelengths above the counterpoise. When the switch is closed, the vertical gain will increase, and the noise levels will drop. When the switch is open, lower angle gain will increase, improving the antenna's performance for non-NVIS use.
 
How do I select a frequency for NVIS operation?
The selection of a optimum frequency for NVIS operation depends upon many variables. Among the many variables are time of day, time of year, sunspot activity, type of antenna used, atmospheric noise, and atmospheric absorption. To select a frequency to try, one may use recent experience on the air, trial and error (with some sort of coordination scheme agreed upon in advance), propagation prediction software, near real-time propagation charts (available on the Internet) showing current critical frequency, or even just a good educated guess. Whatever the strategy used for frequency selection, it would probably be best to be prepared with some sort of "Plan B" involving communicating through alternate channels, or following some pre-arranged scheme for trying all available frequency choices in a scheduled pattern of some sort.