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Thursday, June 30, 2011

Updated Malaysia Ham Repeaters Garmin POI

Newly and updated Garmin POI for amateur radio repeaters in Malaysia available for download.
Kindly mail me if there any corrections. Tnx.





Thursday, June 23, 2011

The use of “standby” and “standing by” - 9M2ZC



The two phrases above are probably the most common phrases used in any QSO. One old radio friend of mine asked me whether something could be done to get people to apply it correctly. Well, since I share the same aspirations, to fulfill his wishes here is my piece.

When I say “This is 9M2ZC standing by.....” there are two elements in the statement. One is the person, that is me, and the verb “standing by’ which is the action happening at present and continuously. When there is an “am”, “is”, and “are” in the sentence and followed by “-ing” this constitutes to being a “present progressive tense” or in the old times called the “present continuous” or the “continuous present” tense.

The “am”, “is”, and “are” are the helping verbs and the “standing by” is the main verb. Some examples of present progressive tense are “I am driving right now”, “Muthu is teaching morse code to his students….”, “Hassan and Minah are having lunch …”

So coming back to our issue above, when I say “9M2ZC standby…” not only this is an incomplete statement, it does not fall under the category above although the action is, hence it is grammatically incorrect. On the other hand, it can also be construed as telling oneself (me) to standby!! No one in the right frame of mind should be telling himself what to do in spoken words. One’s own action should be based on voluntary and involuntary reaction.

If I say “9M2ZC standing by….” although the “is” is missing, it can be accepted as a correct sentence because it is taken as a short form of the sentence “This is 9M2ZC standing by…”, and is more appropriate to be used instead of the former. It fits in the category of a present progressive tense quite perfectly.

On a much wider perspective, if used in the context of Bahasa Melayu, eg. “….kembali kepada anda 9W2BBS, disini 9M2ZC standby….”, then it can be accepted as correct, if and only if, the word standby can be adopted as a Malay word. The golden rule is, if a sentence is constructed in Bahasa, then Bahasa must be used throughout, if the sentence is constructed in English, then English must be used throughout, the two languages MUST never be mixed in the same sentence.

I hope I have made myself clear and in summary whichever way the “standby” and “standing by” is used it will not cause your licence to be revoked, hi! Just exercise more caution in your QSO so that we become more ‘professional’ amateurs… and the above represent my personal views, I have no malicious intentions to anybody living or otherwise.

73, All the best, this is 9M2ZC signing off and clear….

from http://uniarm.blogspot.com/2008/07/when-9m2-writes-use-of-standby-and.html

Arduino APRS AVR Using BeRTOS

Arduino APRS [AVR]

Automatic Packet Reporting System (APRS) is an amateur radio-based system for real time tactical digital communications of information of immediate value in the local area.

In its most widely used form, APRS is transported over the AX.25 protocol using 1200 baud Bell 202 audio frequency-shift keying (AFSK) on frequencies located within the amateur 2-meter band.

The messages are usually relayed via radio to internet connected stations that send the data to the APRS-IS network.

The purpose of this project is to implement an APRS tracker using an Arduino 2009.

This device can be used to periodically send a message through a radio AFSK channel and log the received messages to a serial port (UART).
Hardware Requirements


  1. 1 Arduino Duemilanove board
  2. 1 Ham VHF Radio
  3. a few common electronic components

Software Requirements

BeRTOS components used for this project:


  1. Device drivers: UART
  2. AFSK module
  3. AX25 protocol

Implementation

The hardware schematic is reported below:


From the software's point of view, BeRTOS already provides all the required drivers and libraries to decode and encode the AFSK communications as well as loggin messsages to the Arduino UART port.

The application uses a single process to poll for incoming messages on the AFSK channel, decode, and log them to the UART. Finally, it periodically sends out a message via radio back to the AFSK channel.






http://www.bertos.org/

Wednesday, June 22, 2011

9M2PJU Setting Up The Audio With YB0AR's Help



This is my setup on Kenwood TS-570D HF Transceiver with Kenwood MC-80 desktop microphone. mic gain 50%, processor compression level 20, potentiometer at 10 o-clock, transmit EQ high boost. Thanks to my friend, YB0AR from Indonesia for the tips and info and YC6ODD for audio recording.

Tuesday, June 21, 2011

Drag And Drop Microcontroller Programming



Modkit is an in-browser graphical programming environment for microcontrollers. Modkit allows you to program Arduino and Compatible hardware using simple graphical blocks and/or traditional text code. Modkit's graphical blocks are heavily inspired by the Scratch programming environment developed by the Lifelong Kindergarten Group at the MIT Media Lab. Modkit runs in your web browser and requires our Desktop Widget to communicate with your development board. You can use Modkit for free or join our Alpha Club to support Modkit and enjoy additional features before their release to the general public.



New Alpha Club Features!
As an Alpha Club Member, you will get access to the latest features including Code View, Variables and Drag and Drop Hardware. Code View allows you to start with blocks and move on to traditional text code. Variables allow you to add complexity to your programs, storing values for later use. Drag and Drop Hardware allows you to visually configure your hardware components, tying your hardware to the graphical blocks available for programming: A Modkit first. All of these features are planned to be released in our Free Version this summer, but by becoming an Alpha Club Member, you can help support our development and get early access in return. Learn about these and all the other Free and Alpha Club Features now.



Visit http://www.modk.it/ now

Monday, June 20, 2011

Become a Ham Radio Operator


Become a Ham Radio Operator

A Yaesu FT-2000 tranceiver. Photo by Hideki Saito on flickr
A Yaesu FT-2000 tranceiver. Photo by Hideki Saito on flickr
Amateur radio is a popular hobby with over 690,000 participants in the U.S. alone. But you can't just sit down in front of a radio and start transmitting. You must be licensed by the FCC in order to operate a transmitter.



Contents

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Find a Club

The best way to learn about amateur radio is to find a local club. These are hams who get together and do fun exercises like fox hunts (tracing rogue transmitters) and talk shop.
The biggest organization of hams in the US is the American Radio Relay League (ARRL) with around 154,000 members. You can also contact ARRL at 800-32-NEW HAM ) or email newham@arrl.org to learn more. Between reading ARRL's forums and by searching the web, you should be able to find a local club in no time. The ARRL has a searchable Find-A-Club database.

Study

One guide for studying for your Technician Class exam is the ARRL Ham Radio License Manual (ISBN: 0-87259-963-9). Another study that's popular (and free!) is KB6NU's No-Nonsense, Technician Class License Study Guide. You can download this study guide from KB6NU's Ham Radio Blog.
In addition to studying for the test, you can take practice tests online. One example is the QRZ Amateur Radio Practice Test site.

Etiquette

Etiquette is very important in ham radio, and much of the Technician exam involves learning about following correct procedure. The first rule of operation is to not interfere with other peoples' signals. That's not just etiquette, it's the law. If that means moving your contact to another frequency, so be it. Also, remember that the FCC polices the airwaves, which means swearing is a no-no.

Morse Code

As telegraphy becomes less important to commercial radio operators, it is less important for amateur radio operators to learn it, so the FCC reduced their requirements for knowing Morse Code. Over the years the FCC eased the Code requirement for various classes until finally, in 2007, they did away with it altogether. There are still plenty of opportunities to learn and use Code, and there are even certain frequency bands that are Code-only. However, you no longer need to learn Morse Code to pass a license exam.

Get Licensed

There currently are three different classes of licenses available to new amateurs in the US. The entry-level license, called Technician Class, has limited transmitting privileges below 30 megaHertz (MHz), but all privileges above that. Technicians may test for the General Class which grants greater privileges. The highest level of ham is the Amateur Extra which enjoys all the privileges available to an amateur.
The Advanced Class license is an intermediate between General and Extra. The Novice Class was for new amateurs below Technician Class, and restricts their transmitter power. Amateurs who hold current Novice and Advanced Class licenses may renew and modify them indefinitely, but no new Novice or Advanced Class licenses will be issued.
Tests are offered by local radio clubs during their hamfests, and other times. To find an upcoming test near you, check out ARRL's Find-An-Exam page, or contact your local club to see if they'll schedule a test by request. Many of the Volunteer Examiners who offer tests are willing to coordinate a test at a mutually convenient time.

Call Signs

Every licensed ham has a unique call sign. For example, the ARRL president Kay C. Craigie has the callsign N3KN. When you pass your exam you'll be given a callsign by the FCC. However, so-called vanity callsigns can be purchased if you don't like what you got.
The official FCC callsign search page is at: http://wireless2.fcc.gov/UlsApp/UlsSearch/searchLicense.jsp
To know who you're hearing and talking to, the two largest world-wide callsign databases are:

Emergencies

There are several organizations devoted to organizing volunteer radio operators to assist authorities in the event of a disaster. For example, when Hurricane Katrina hit, cell towers and telephone poles were down. Hams mobilized to provide communications. Additional information can be found at the following websites:


Build or Buy Equipment

A swap meet table at Dayton, Ohio's Hamvention, the biggest ham radio convention in the world.Photo by n4zpt on flickr
A swap meet table at Dayton, Ohio'sHamvention, the biggest ham radio convention in the world.
Photo by n4zpt on flickr
Once you're licensed, you still need something to transmit with. That can mean a rather expensive piece of electronics. However, there are alternatives to purchasing new. First, many people who are skilled at electronics simply build their own transmitter. There are DIY kits available. Others shop for used equipment at ham conventions, which usually have a flea market as part of the program.
Several online ham radio communities have used equipment for sale by individuals who upgraded their gear, as well as equipment reviews which cover both current and older gear. Amateur radio technology from years ago still communicates just fine. Many people start with used gear, and some even prefer (and collect) older radios with vacuum tubes and analog dials. 

Transmit

Once your equipment in place, start transmitting! Just make sure you're operating on a frequency you're entitled to, and remember to use your call sign to let everyone know you're out there.

It's a Sport

Radiosport is the word, lots of hams on the air all at the same time. Over 10,000 people participated in the CQ WW (World Wide) contest in 2008. If the ham bands seem under-populated during the weekdays, just wait until a radiosport weekend. More information at Arrl Contest Page

Learn the Lingo

You are officially a New Ham. Try to avoid motorboating (low frequency hum) and busted calls (improperly stated callsigns) while making the trip (transmitting a message successfully). Continue to gather knowledge and experience and you'll be an Elmer (a ham radio mentor of new hams) in no time. Meanwhile, brush up on your jargon. Also, learn the NATO phonetic alphabet for relaying callsigns, spelling, abbreviations and numerals.

Further Reading

  • Ham Universe is a great site with tips for new hams and Elmers alike.

This page was last modified 21:53, 6 January 2011 by vk4yeh. Based on work by wa4jdkb0rwi,mark77dan1101bobbakb6nun8vwhowto_adminrflorencjohndporter and kent. 

from http://howto.wired.com/wiki/Become_a_Ham_Radio_Operator


Antenna Tuner

An antenna tuner, also known as a transmatch, is a device for correcting an impedance mismatch between a transmitter or receiver and an antenna.

The Tuner Fallacy

It is often believed that a tuner actually "tunes" a non-resonant antenna, tricking it into behaving as though it were resonant. This is not the case, as a simple experiment will show.
Suppose that we set up a transceiver system like the one below.


Suppose that the tuner is set to direct or bypass operation, connecting the two SWR meters directly together. If the transmitter is keyed, both SWR meters will indicate the same level of SWR. Assume that the non-resonant antenna has SWR at both meters of 10:1.
Now if the tuner is taken out of bypass mode and its inductors and capacitors adjusted until it produces a perfect match between transceiver and antenna, the SWR meter at left will be indicating 1:1, but the SWR meter at right will still be indicating 10:1. In other words, our "antenna" tuner is actually tuning the transmitter to the antenna, not the antenna to the transmitter. We might better call it a transmitter tuner or transceiver tuner! There will always be feedline losses on the line between the tuner and the antenna. To minimise these keep this connection as short as possible and use the best cable you can afford!

Tuner Models

The most common amateur antenna tuners are the many models made by MFJ. Other manufacturers also produce tuners. The assembly of a tuner is so simple that many hams build their own from scratch using homebrew techniques. Simple schematic:



Duplexer

A duplexer is a device that allows bi-directional (duplex) communication over a single channel.
In radar and radio communications systems, it isolates the receiver from the transmitter while permitting them to share a common antenna. Most radio repeater systems include a duplexer.


  • Note 1: A duplexer must be designed for operation in the frequency band used by the receiver and transmitter, and must be capable of handling the output power of the transmitter.
  • Note 2: A duplexer must provide adequate rejection of transmitter noise occurring at the receive frequency, and must be designed to operate at, or less than, the frequency separation between the transmitter and receiver.
  • Note 3: A duplexer must provide sufficient isolation to prevent receiver desensitization.


WHY ARE DUPLEXERS USED?


Radio receivers can be damaged if high level RF signals, like those directly from a transmitter output, is applied to the receiver antenna.

Additionally, receivers may become ‘desensitized’ (or ‘de-sensed’) and not receive weak signals when high noise levels or another signal near the receive frequency is present at the receivers antenna input.

Obviously, radio receivers and transmitters cannot be directly connected to the same antenna without some device being used to:

  • (1) switch the antenna between the transmitter and receiver so that they are never connected to the same antenna at the same time.
  • (2) When the transmit and receive frequencies are different, filters may he used to reduce the transmit signal levels to an acceptable low level at the receivers antenna input. Naturally, you cannot filter out the transmitter signal when it is the same as the receiver frequency.


Definition of a duplexer:


A device which allows a transmitter operating on one frequency and a receiver operating on a different frequency to share one common antenna with a minimum of interaction and degradation of the different RF signals.

Duplex Operation


Duplexers are often the key component that allows two way radios to operate in a full duplex manner. Full duplex means the transmitter and receiver can operate simultaneously as opposed to the ‘push-to-talk’ manner used in non-duplex (or ‘simplex’) operating modes.

Remember, The radio system must use two frequencies per ‘channel’ to use the kinds of duplexers we are discussing.

Recently, some very specialized digital radio systems that are under development are emulating duplex operation by switching the transmitter and receiver off and on extremely rapidly. This is not real full duplex operation but appears similar to the radio users. This discussion does not address this approach, but instead deals with more common accepted land mobile practices.

Duplexers are the devices that allow a mobile telephone to operate like a wired telephone, with either or both people speaking at any time without using a microphone switch to enable the radio transmitters.



REPEATERS


Most radio systems today use repeaters located on top of buildings, towers or on hill tops. These repeaters use two frequencies in a duplex fashion to extend the range of the radio system and make signals much stronger. In most cases, a duplexer is used as part of the repeater station.
The duplexers at repeaters may serve several objectives:


  1. Reduce the number of antennas required due to cost or space limits.
  2. Reduce the transmission line costs or allow a better and more expensive single cable to be used instead of two.
  3. Reduce the potential of intermodulation generated from the transmitter.
  4. Reduce the nearby broadband noise generated from the transmitter.
  5. Improve the receiver ‘front-end’ rejection of off-frequency interference.



WHY NOT USE TWO ANTENNAS?


Two antennas may be used instead of a duplexer, provided the antennas are placed far enough apart that the transmitter signals do not interfere with the receiver. Two transmission lines will also be required.

The isolation required between the transmitter and receiver is a complex issue and influenced greatly by the specific transmitter and frequencies used, the bandwidth of the channel, the difference in frequencies of the two frequencies to be used and the minimum amount of receiver degradation that is acceptable to the user.

It is not unusual to have a radio system require as much as 80 to 100 dB isolation between the transmitter output and the receiver input.

When two antennas are used, the type of antennas, the physical spacing and the orientation of the antennas to one another are also major concerns.

The antenna to antenna isolation can also be influenced by the presence of other antennas on the same tower as well as other nearby transmitters and mechanical structures. These factors may change over time and be out of the control of the repeater operator.

Antenna separation designs should also consider any additional receiver protection that may be required for other transmitters that may be present on the same tower.

In some extreme cases, duplex filters AND antenna separations may both be required to obtain satisfactory operation. This generally only occurs at lower frequencies with small differences between the transmit and receive frequencies or when closely spaced channels are combined.

Typical Antenna Spacing Isolation Values: (In dB) (Based on vertically polarized half-wave dipoles. Actual experience will vary due to local conditions, antenna variations, etc.)



TYPES OF FILTERS USED IN DUPLEXERS


There are several ways to implement a duplexer, but all rely upon the characteristics of different types of RF filters. Specifically:

- Bandpass filters which allow a specific range of frequencies to pass through them. The filters are designed and tuned to a specific ‘center frequency’ and ‘pass band’ with relatively low losses to desired frequencies and higher losses that increase as the deviation from the center frequency increases.

- Reject or Notch filters which operate opposite of a bandpass filter. These are designed to cause high losses at the center frequency and lesser losses as the frequencies increase from the center frequency.

- Specialized filters such as TX RX Systems “Vari-Notch” (c) filter, which has characteristics of both a bandpass and notch filter in one device.

The filters are usually tubular or square cavity type filters but other types of construction such as combline, ceramic, etc. may also be used in some cases.

Cavity type filters offer the best overall balance of performance, simplicity and costs.

Combline and ceramic filters have some space and size advantages at higher frequencies.

Ceramic filters may have power limitations and higher cost.

Although this discussion centers on the more commonly used cavity type filters, the basic principals will apply to any type of filter used in duplexers.


DUPLEXER AND FILTER TERMINOLOGY

Decibel (dB):
A decibel is a logarithmic scaling value that is used in most RF engineering work because of its universal acceptance and simple manipulation in calculating signal and power levels. A decibel is a relative number, not an absolute value.

For example, a +20 dB difference in a power level is the same as saying the level change is 100 times the starting value. If the change was -20 dB, the change would be 1/100th the original level.

Decibel/one milliwatt (dBm):
This signifies an absolute (real) value, with 0 dBm being one milliwatt of power.

TX RX Systems provides a dB chart in their engineering catalogs.

Selectivity:
Selectivity is a measurement of the ability of the filter to pass or reject specific frequencies relative to the center frequency of the filter. Selectivity is usually stated as the loss through a filter that occurs at some specified difference from the center frequency of the filter.

For example; “- 3 dB bandwidth is +/- 250 KHz.” means the output level of a signal frequency at + or - 250 KHz from the center (tuned) frequency of the filter will be at least 3 dB less than the level of the same signal IF it was at the center frequency.

The greater the selectivity the greater the attenuation of frequencies other than the center frequency.

The greater the selectivity the narrower the lowest loss ‘window” of the filter and the need for good temperature and mechanical tuning stability in the filter design.

The larger the diameter of a cavity filter the greater the selectivity, assuming similar materials and construction of the filters being compared.

Tuning Stability:
Tuning stability is the ability of the filter to remain at tuned at the desired frequency over time and variations in temperature, orientation and vibration. Many aspects of filters are designed to overcome these variables, such as the use of temperature compensating metals, elimination of threaded tuning rods which can store mechanical torque stresses, added cooling, fine tuning adjustments, etc.

Insertion Loss:
Insertion loss is the minimum amount of loss to the signal passing through a filter at a designated frequency. For example, a filter may have 1 dB insertion loss at its center frequency and if two filters are used in series in a duplexer, the duplexers insertion loss would be 2 dB.

Insertion losses occur in both the transmit and receive paths of a duplexer and they may be different amounts.

The greater the insertion loss, the less the output level.

Higher insertion losses generally increase the selectivity of cavity filters. (i.e. A filter bandpass might be +/- 200 KHz at 1.5 dB insertion loss and +/- 100 KHz at 2 dB insertion loss.

The greater the insertion loss, the greater the power dissipation and temperature rise of the filters. High insertion losses may reduce the power capacity of a filter.

Receiver Desensitization:
Receiver desensitization, commonly called ‘receiver desense’, is caused when high RF signal levels enter a receivers antenna input.

When desense occurs, the usual symptom is as though the desired signal was reduced; the signal becomes noisy or even fades out completely.

The frequency of the desensitizing signal can be considerably different than the frequency the receiver is tuned to. The interfering signal can be wideband noise and/or spurious emissions from the associated transmitter or other nearby transmitters.

The susceptibility of a specific receiver to off-frequency signals is dependent upon the receiver design and any external filtering added to the receiver.

Transmitter Noise:
Every transmitter emits signals other than those on the desired frequency. The frequencies and amplitudes of these undesired signals varies greatly and is dependent mainly upon the transmitter design and the modulation used. The amount of transmitter noise can be reduced by external filters and/or physical isolation between the transmitter and any receivers.


TYPES OF DUPLEXERS

There are many ways to combine filters to perform duplexer operations. The more common approaches are:

Bandpass Duplexers:
Bandpass duplexers use several filters to reduce the bandwidths of the transmitter output and the receiver input frequency bands.



Cavities 1, 2 and 3 tuned to pass 458 MHz. 80 dB loss at 453 MHz.
Cavities 4, 5 and 6 tuned to pass 453 MHz. 80 dB loss at 458 MHz.
   Cable lengths between cavity 3 and cavity 6 to "T" are tuned lengths.

The amount of isolation between the transmitter and receiver may be reduced or increased by changing the number of cavities and the size (efficiency) of the cavities. Note that since the transmitter output passes through bandpass filters, therefore transmitter noise and spurious emissions are also attenuated in a bandpass type duplexer, which can help reduce interference to other receivers at the same site.

Bandpass type duplexers are best suited for moderate to wide transmit/receive frequency separations. Close spaced frequencies may require additional notch filters and/or separate antennas.

Notch Type Duplexers:
Notch type duplexers may appear physically similar to bandpass duplexers but their operation and tuning is very different.

There are two types of notch filters that may be used in a notch type duplexer:

  • - The series notch filter, which has two ports (in and out).
  • - The shunt (or common) notch filter which has one port and is linked to the other filter sections by a “T” connector. NOTE: Do not confuse this with the TX RX Systems “T-Pass” filter which is a specialized bandpass filter.


Cavities 1, 2 and 3 are tuned to notch out 453 MHz.
Less than 1 dB loss near and at 458 MHz.

Cavities 4, 5 and 6 are tuned to notch out 458 MHz.
Less than 1 dB loss near and at 453 MHz.

Cable lengths between cavity 3 and cavity 6 to "T" are tuned lengths.

Note that since the transmitter output passes directly to the antenna, therefore transmitter carrier and noise is only attenuated near the 453 notch frequency.

This offers minimal reduction of interference to other receivers at the same site.

Notch type duplexers are cost effective and operate at much closer transmit/ receive frequency separations than bandpass type duplexers.

Shared sites may require additional bandpass filters and/or separate antennas.

Bandpass/Band Reject (BP/BR) type duplexers:
These types of duplexers are combinations of the two preceding duplexer types, having many of the benefits of both and usually at some increase in cost. An bandpass/band reject example; (Actual combinations vary widely)



Cavity 1 and 3 tuned to pass 458 MHz
Cavity 2 tuned to notch (reject) 453 MHz.
Cavity 4 and 6 tuned to pass 453 MHz.
Cavity 5 tuned to notch (reject) 458 MHz.
Cable lengths between cavity 3 and cavity 6 to "T" are tuned lengths.

The TX RX Vari-Notch (c) type Duplexer:
The Vari-Notch type duplexer is a very popular, low cost and small size duplexer that is only available from TX RX Systems. It is very similar to a bandpass/ band reject type duplexer in operation and tuning.

The major difference is the use of TX RX Systems exclusive “Vari-Notch” (c) filter designs which incorporate the equivalents of a broad bandpass filter and a notch filter within the same cavity.

The result is the elimination of separate bandpass sections in most duplexer requirements and an inherent increase in the number of notch filters for a given number of cavities. It is important to remember that there can be interaction between the bandpass and notch frequency tuning of any combination duplexer, especially when the duplex frequencies are close spaced.

Antenna Loading Coil



An antenna loading coil is an inductor placed in series with an antenna element in order to lower the antenna's resonant frequency.
A standard dipole antenna is resonant if constructed with a length of one-half wavelength. A vertical antenna (effectively half a dipole operating against a ground plane) is resonant at one-quarter wavelength. Resonance may also be observed at each of the odd multiples.

For most VHF and UHF antennas, a half or quarter wavelength is reasonable in size and can be readily accommodated in all but the smallest handheld transceiver antenna designs. The same is not true of HF antennas on the radioamateur bands or mobile antennas for 27MHz (11-metre) CB operation. Mobile antennas are inherently limited by the amount of available space, yet reducing an antenna's length increases its resonant frequency.

A loading coil may be used, on its own or in conjunction with a capacity hat, to tune the antenna to resonance at a lower frequency. One coil placed in the centre or at the base of a single-band vertical antenna is sufficient, but a single-band dipole will require two coils - one in each element of the dipole.
For multiband HF antennas, different loading coils (or adjustable coils) are needed for coverage of each band.

An antenna with a loading coil cannot be modelled electrically as an element in which the inductor has been replaced by the corresponding length of straight wire. An inductor will behave differently as current at one end of an inductor creates a magnetic field which immediately induces currents at the opposite end. An inductor also adds electrical resistance to an antenna, incurring a penalty in radiation efficiency compared to a full-size antenna.

An external antenna tuner is often used in conjunction with HF antennas to tune antennas to resonance within a band. In most cases, these are π or T networks in which a variable inductor and capacitors are used to tune for lowest standing-wave ratio as seen by the transmitter.
An antenna tuner must be rated for the full power of the transmitter and both manual and automatically-tuned versions of these units are commercially available. Some late-model transceivers may integrate this functionality, although for best results any tuner or loading coil needs to be at or near the antenna itself.
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