A, B, C's of Dx Fundamentals of the Art of DXing VII

http://www.deltadx.net/ABCDx/Sections/Equipment.htm

A, B, C's of Dx Fundamentals of the Art of DXing VII

W5FKX, Don Boudreau

Station Equipment: Things to Consider

First-things-first!

In this chapter, we'll briefly look into some of the key elements of importance in understanding the equipment that we use for DXing. Whether you're just now planning to begin building your station, or considering some upgrades to an existing station that you have been using, this information should be of interest. In fact, no matter how long you've involved in ham radio, this brief review should be of interest to you.

Before getting into a discussion of things to consider when putting together your first station or upgrading your existing station for DXing, it is important to again emphasize an important point about DXing: if you already have antennas and equipment, then for the beginning DXer, the best station to use is the one that you have at hand! Although upgrading existing equipment is constantly on the minds of all hams, and especially DXers, the importance of equipment "quality" will never surpass the importance of the quality of the operator. This is not just a casual statement - ask any experienced DXer, contester, or Old Timer and they will tell you that operator ability (i.e., P.E.P.S.I.) is orders-of-magnitude more important than the make or model of the transceiver. If you already have a station, then don't hesitate to use whatever you have to develop your DXing experience. In particular:

learn the DX tuning techniques and how to best use your available filters and bandwidth settings;

develop proficiency in split operation;

become familiar with the available DX information sources;

learn about propagation and antennas;

improve your antenna system (truly the most important piece of "equipment");

find a DX mentor, join a DX club, and/or subscribe to one or more of the DX forums ("lists", "reflectors") on the Internet in order to gain additional guidance and information.

The more operating experience that you have, the better you will be to make informed choices of station upgrades that you decide upon.

Station Components

There are three categories of station equipment, discussed below in order of importance: the antenna, the transceiver, and the station accessories.

(1) The Antenna - After experience and operating skill, the antenna is the most important component of a DXer's "equipment". Even the most expensive transceiver will perform only as well as the antenna allows. It is therefore very important to give plenty of thought to your DXing antenna. To put this into perspective, suppose that you had $2,000 to invest in your ham station and did not have to worry about any restrictions on antennas. Given the choice between spending $1,500 on a transceiver and $500 on a multiband vertical antenna, you may want to consider whether a better DXing investment might be to get a small tower and directional antenna ($1,200), and a used, older mid-range transceiver ($800). While this kind of pre-planning consideration is rarely an option for any of us, it does emphasize the importance of your antenna choice. You should certainly try to discuss your antenna plans with local DXers and get as many ideas as possible in order to optimize your antenna. See the chapter on "Antennas" for more on the subject.

(2) The Transceiver - What is the best transceiver for DXing? If you do not yet have a transceiver, it would be difficult to make a poor choice in selecting a unit today, as there are so many good ones at all price levels, both new and used, on the market. The popular manufacturers of transceivers for the last several years have been Alinco, Elecraft, Icom, Kenwood, SGC, TenTec, and Yaesu. All have well-respected product lines with units that are worthy of consideration for a variety of applications. However, depending upon your level of operating experience, it may be hard to decide upon the features that would be advantageous to have in the radio. The purpose here is not to try to select a specific product, but to review the features that are important to good communications, especially for DXing. Having explored these key features, you should then be better-equipped with the information necessary to pursue your own best choice of a "rig".

Let's begin by listing some general features to consider in shopping for a transceiver for use in DXing. While many of these are incorporated in current transceivers, models may differ significantly in their availability as "standard" or "optional" features. Also, should you have an opportunity to purchase an older transceiver, you will certainly want to weigh these factors into the decision of whether to get a newer or an older model radio. A more detailed discussion of some of the technical aspects of these features will then follow below, or in other chapters as indicated. Here's what to look for at first glance:

Dual VFOs - First of all, does it have dual-VFOs in order to be able to operate easily in "split" mode? Many DX stations, especially the rare ones, must operate "split" when pileups become too rowdy, so you MUST have this capability. This means that the transceiver must have an "A/B VFO" button for selecting between the two, and a button that allows you to select "split" mode of operation in which the receiver is locked to one VFO, such as VFO-A, and upon keying the transmitter, the rig automatically relegates the transmitted signal to the second, VFO-B. That way, the two may be set to different frequencies to allow you to receive on one and transmit on the other.

Automatic Antenna tuning unit (ATU) - A very useful (but not necessarily essential) feature is the inclusion of a built-in ATU that will automatically match the 50-ohn impedance of the transmitter output to that of an antenna connected to it. Built in ATUs typically have very limited ranges of operation, so if the intent is to use the transceiver with high-impedance mis-matches (e.g., random or long-wire antennas or single-band antennas on multiple bands) you would be better off with an external wide-range ATU.

Selectable filter bandwidths - with today's crowded bands, it is especially important to have as much selectivity as possible. Selectable filters which offer different tuning bandwidths are a must. While more detail follows below in the Receiver Details section, suffice to say that on firt glance, you should only look at receivers that have selectable filters available, and if optional, how many and at what additional cost?

DSP capability - an increasingly effective means of improving receiver selectivity and sensitivity, it is now being employed more widely in modern receivers and offers great flexibility in filter bandwidth selection.

RTTY Mode - Digital Modes - If you are interested in operating RTTY, then it is advisable that you consider a transceiver that provides FSK output, as this is highly preferable to the alternative of having to use AFSK. For more on this, see the chapter on "Operating Modes".

Memories - selectable memories for storing oft-used frequencies/modes can offer a great advantage when the need arises to quickly switch to another frequency and mode of operation. Standard on all current models, but if not found on an older model, it isn't a show-stopper as long as some of the other more important features are available.

Adjustable power output up to 100 watts - generally a standard feature of most current and older transceivers.

Power supply - with some exceptions, most current models no longer come with internal power sources and must have an external power supply. Unless one is provided for free as a purchase incentive bonus, don't forget to factor this into the cost.

Once you've gotten through the first round of shopping and evaluation of rigs using the above general features, along with your personal preferences about "look and feel", manufacturer, and price, you've probably made your preliminary choices of the top two or three that you favor. It's time now to pay more attention to the details in the technical specifications of the top choices that are provided by the manufacturers and in published reviews.

Reading through an advertising brochure citing the specifications for a modern transceiver can often seem overwhelming. It may be difficult and confusing to try to tease out some of the factors that may be useful in making comparisons among the top choices, especially if there is no standardization of the parameters. For this reason, third-party evaluations are probably the best bet in obtaining as close to objective data as may be available. A "must read" is the thorough and understandable explanation of the procedures and measurements done by ARRL in conducting a product review of a transceiver that appeared in the August, 2004 issue of QST (Tracy, M. KC1SX. "QST Product Reviews - In Depth, In English". pp.32-36, Aug 2004). To get you started, here are a few simplified pointers to consider in evaluating a transceiver.

The Rx (receiver) section: this is the most important part of the transceiver. It is important to have a good combination of sensitivity (ability to hear weak signals) and selectivity (ability to tune out everything but the desired signal). Marketing variations in the way these are presented in the manufacturers' advertising and technical specifications often leads to difficulties in comparing radios, good reason to use third-party evaluations.

Sensitivity is a measure of the ability of the receiver to detect a minimum discernable signal (MDS) and, all else removed, is a balance between the gain of the receiver circuitry vs. the internal noise present in that circuitry. As gain increases, so does the amplification of internal noise, therefore an optimal signal-to-noise ratio (SNR) is what one expects in receiver design, beginning at the minimum detectable ("discernable") signal level. Since the MDS is essentially a measure of the internal noise level, the MDS is also known as the noise floor of the receiver. One wants as low a noise floor as possible, typically referenced to a level of 1 mW and expressed in dBm. Variation among different receivers can be great, ranging between -80 dBm to -140dBm, where the lower (larger negative) values usually indicate the availability of selectable pre-amp. Confusion can arise when, instead of MDS in dBm, sensitivity is expressed in microvolts, as "Sensitivity: 1 microvolt." For those who don't mind a bit of math, one can see that this is equivalent to a MDS of -107dBm:

Selectivity and sensitivity go hand-in-hand. A receiver can be very sensitive to weak signals (very low MDS), but if it has poor selectivity, it may be subject to serious degradation when strong signals or noise are also present. For this reason, many techniques are used to provide a narrow reception passband that will accommodate only the desired signal and exclude all others, including the use of filters. For this reason, receiver selectivity is often quoted in terms of the available filters. There are many filter designs: very early radios only had LC-filter circuits; technological advances led to the development and use of crystal filters and mechanical/ceramic filters; many current receivers now use DSP filter designs (see below). Any filter, independent of type, will provide improved selectivity by narrowing the bandwidth of the passband. Filters are an essential option for a DX receiver, and typical filter bandwidths for DXers are:

CW

500Hz, 250Hz

SSB

2.4KHz, 1.8KHz

Digital modes

Vary by type; should be able to use the available filters in the Rx

Unfortunately, while conceptually simple, receiver selectivity is not an independent variable, but depends upon the interaction of sensitivity and selectivity. As the receiver gain (sensitivity) increases, there is an increased potential for interference from strong signals that are not even in the receiver passband, thereby degrading selectivity. For this reason, determining the quality of a receiver is more difficult than just looking at the MDS and the available filter options. Other parameters are required to be able to understand the actual performance characteristics of a receiver under all operating conditions:

Dynamic ranges are useful parameters that describe the interplay of sensitivity and selectivity. A dynamic range is essentially the difference, expressed in dB, between the weakest signal that can be heard and the strongest signal level at some frequency spacing (20KHz, 10kHz, 5KHz, etc.) outside of the passband that will not adversely affect the reception.

There are several dynamic range measurements used and, while all are useful, they not all equivalent. The two most frequently encountered are the Intermodulation Distortion (IMD) dynamic range and the Blocking dynamic range. The first uses the strong signal level at which intermodulation distortion (IMD) products adversely affect reception, while the second uses the strong signal level at which the desired signal output is reduced due to loss of sensititivity.

Unfortunately, both are often measured at different strong signal spacings (20KHz, 10kHz, 5KHz, etc.) from the center of the receiver passband, and therefore may result in difficult comparability. Nevertheless, one should expect to see dynamic range figures on the order of 80dB - 100dB, where the higher numbers indicate better performance.

Final note: understanding the concept of dynamic range is useful in appreciating why, in the chapter on Tuning, there is a "weak signal reception" tip that suggests reducing the receiver RF gain.

Digital Signal Processing (DSP): As mentioned previously, this is an increasingly popular and useful feature of current receivers. A product of the computer age, DSP is a complex technique and what follows is a highly over-simplified description of the process. A computer-on-a-chip electronically "samples" snippets of the analog signal (either at the IF stage or the AF stage) over the range of the signal and converts each of the snippets (samples) into a number (digit) that represents the amplitude of the sample. A built-in computer program then processes the digitized samples, looking for patterns of amplitude rise and fall (signal), vs. occurrences that seem random (noise), eliminating the latter and passing the patterns through. The result is (hopefully!) a signal that is "cleaned" of noise. This technique can provide some significantly improved signal-to-noise enhancement benefits. While "outboard" Audio DSP filters have been available for some years, and some radios began offering them "built in", the real breakthrough in DSP technology arrived when computer chip processors became fast enough to process the signals at the intermediate frequency (IF) stages, rather than at the final audio stage. In summary, DSP not only offers a new filter design that can allow adjustable bandwidth down to 50 Hz, but it also can provide noise reduction to improve signal intelligibility and is a "must have" when purchasing a new receiver.

Dual receive - Some of the high-end transceivers also have dual-receive capability in which there are not only two VFOs, but also two IF chains that provide the capability of simultaneously receiving on two different frequencies within the same band. Monitoring is done by using a balance control to adjust the mix of audio level of each as they are fed to the speaker. While some find it difficult to learn to use this technique, it can be extremely useful for DXers to monitor split operations, allowing one to listen to the DX operator on one frequency while simultaneously tuning up the band to find the station being worked.

The Tx (transmitter) section - fortunately, this part is simple when compared to the selection of a receiver. The role of the features are easily understood and easy to evaluate. Here are the basics:  

Dual VFOs (A/B) in order to be able to perform split operation, as mentioned in the generally desirable features above.

Availability of all amateur bands is the next criterion of interest. In considering the purchase of older equipment, be aware that some may not provide for operation on the WARC bands (12m,17m, 30m) and even some that are relatively new will not have the 60m band.

CW and SSB operating modes - universally available (see the chapter on Operating Modes).

Most of the newer digital modes (SSTV, PSK31, MFSK, etc) all use SSB, and it can be used as well for the old favorite, RTTY. When using SSB to transmit and receive audio tones (AFSK) for digital modes, the narrow filters that would normally be available with FSK operation are not usually available so, as a rule, RTTY operation is really best when done with FSK. For that reason, the availability of FSK output is a consideration for anyone with an interest in that mode.

Speech compression capability for SSB modes is very useful in tailoring output modulation for optimal performance in pileups. The output power of an SSB signal depends on the level of modulation - speaking louder increases output. Under the extreme operating conditions that usually befall DXers (pileups, weak signals, noise), SSB signal "punch" can be enhanced even more through the use of speech compression. Natural speech has many peaks and valleys, producing high and low amplitude components that result in an output signal power that fluctuates widely, averaging only 25% of the rated transmitter output. By using electronic circuitry to increase the average amplitude of the modulation by clipping peaks and raising valleys, the average transmitted output signal can be increased proportionally.

An internal Antenna Tuning Unit (ATU) - discussed briefly under General Features; if antenna matching problems are an issue, an external wide-range matching unit is a better investment.

Full break-in (QSK) - Many CW operators feel that is essential to breaking DX pileups, so this should be a consideration for CW mode. Most transceivers of the last 10 years offer semi break-in and full break-in.

Finally, transmitter output power is also a consideration. Other than those designed for low-power enthusiasts, most transmitters today provide 100 watts output, with some high-end models having 200w output. With a reasonable antenna (dipole, vertical, long-wire), working 150-200 DXCC entities is definitely an achievable goal with 100w (the author reached 305 confirmed entities before investing in an amplifier). If the need arises for more power, an amplifier can then be driven by the 100w transmitter to provide additional output.

This very brief overview was intended to give you an idea of what to learn about - and look into - when shopping for a new rig. See the QST article cited and the references below for more information. Remember, an important source of data for doing your own "apples-to-apples" comparisons is in the equipment reviews done regularly by the ARRL Laboratory and published in QST. When shopping for older models, do a bit of research to find the old reviews - almost all brands and models have been reviewed and published in QST.

Here are some final points to consider when shopping:

Read about high-scoring DX and contest operators in QST, CQ, DX Magazine, WorldRadio Magazine and other ham publications to see what equipment they currently use. Also, don't be afraid to send them an email asking about their equipment. If considering used equipment, look through publications of 5 -10 years ago to see what these operators were using then.

In fact, subscribe to some of the emailing lists or reflectors on the internet (see below) and post your own queries - you'll be pleasantly surprised at how helpful most hams really are!

Be certain to cost-out all of the necessary optional features, including power supply, filters, tuner, etc.

In shopping for older transceivers, make a list of those that fall into your price range. You may find that the cost-per-feature of the older radios is far less than that of new ones, since upper-end transceivers as old as 10 years can be much better price/performance bargains than new lower-end radios.

Your local library is probably a good source of bound volumes of CQ and QST from yester-year. Take an afternoon to ply the pages of these magazines of 5-10 years ago and look through the ads for a review of the features, or try an Internet search for the models of interest.

(3) Station Accessories:

In addition to the basic station equipment discussed above, a DXer needs a few more items in order to complete the station. A prerequisite for selective tuning is reliable information about the world's DX activities. While much of this is still available in print via DX newsletters and ham magazines (see the chapter on "DX Information Sources"), it is now much more readily accessible via the Internet. Therefore, after acquiring an operational station, the next most important piece of equipment is the Internet-enabled computer and the skill to use it! In addition to Internet information access, the computer also provides an excellent logging platform for maintaining not only the log but also keeping track of achievements towards the various DX award programs (see "Awards" chapter). Also, there are myriad other software applications that are increasingly becoming an essential part of the station: reception and transmission of digital modes, propagation prediction, real-time "spots" of DX stations, and more! In addition to the computer, a few other pieces of accessory equipment are very useful. So, after the transceiver and the antenna essentials are secured, here are a few of the myriad station options to consider:

Computer - a computer capable of currently running available ham-function software has become an important piece of station equipment, and many now even feel that it is an essential accessory. Not only is it useful for running helpful software (some of which is discussed below), but it also now serves as a gateway to the most abundant information resource ever available to mankind - the Internet. The choice of platform and operating system - Windows, Mac, or open source (e.g., Linux) - is wholly a decision to be made by the user. While the Windows-based platforms presently have the most plentiful and diverse selection of readily available software, the Apple Macintosh systems and software are certainly plentiful and enjoy wide user satisfaction. Recently, systems running some version of the Open Source Linux operating system are increasing available, although they are still rare compared to the other two leaders in the personal computer market, and require a greater level of computer expertise. The choice you make will depend upon your level of expertise and familiarity. For beginners, it is best to choose a system that is similar to one used by someone you know who will be able to give you some guidance and assistance as needed.

Internet connection - as with computers, this has become a highly important item in the radio shack. With a connection to the Internet, you have access to a vast wealth of useful information and tools for DXing in particular, and ham radio in general.

Software:

select a good logging program (see references; talk to other DXers) and use it to help maintain good records of your contacts.

DX packet cluster software that allows one to connect to a website or cluster node via telnet. Several software packages are available (see references).

Get a program that provides global daylight vs. dark information in order to keep track of what areas are in daylight, in darkness, or on the grayline (e.g., visit the NIST website or get Geoclock (http://home.att.net/~geoclock/).

Some also like to experiment with propagation prediction, and software can be found on the Internet (below) at modest cost or free.

VHF/UHF transceiver - if you have friends in the area that are interested in DXing, then 2m or 70cm is a good way to alert them to DX that you hear (or vice versa!). If there is a DX club in your community, they may already have an established repeater for fellow DXers to use.

Out-board DSP unit - For many older receivers, an out-board DSP unit can often be of additional help in improving signal-to-noise ratio under certain conditions.

RF Amplifier - There are as many opinions on the subject of the necessity of amplifiers as there are on transceivers. If you don't already have an amp, by the time you're ready to get one you'll have heard all of the arguments more than once, so I will be brief! Many DXers do not have amplifiers and rely solely on the typical 100w output of their "barefoot" transceiver and it is absolutely true that one can work DX with low power. In fact, there are quite a few dedicated QRP DXers who believe that the true challenge is to work DX with 5 watts or less, and many have proven their P.E.P.S.I. by working DXCC and beyond. However, it is also true that as one approaches the 300 mark (having contacted 300 DXCC entities), it becomes increasingly difficult to get those last few as they are generally rare and may have activity only for the brief duration of a DXpedition at 5-10 year intervals. In those instances, competition is fierce! For this reason, one may well want to consider the use of an amplifier at some point. As a long-time (over 50 years) believer in low power, I must confess that after reaching the 305 mark running a barefoot transceiver, I did relent 15 years ago and purchase a 600w amplifier to help work the last few for the DXCC Honor Roll . Today, I have several amplifiers, but use them only as needed and then rarely at more than 800w output. It is strictly a personal preference as to the level of challenge desired, and many argue that there is a much greater level of satisfaction in working a rare one with low power. On the other hand, many retort with the old quip "Life is too short for QRP!". Here are a few considerations:

TVI - An amp will aggravate any existing TVI problems and may very likely initiate new ones, so if this is an issue, beware. You may want to consider a small one (400w - 600w). On the other hand, you can always reduce output power of any amp by reducing the "drive" (power output of the transceiver being amplified), so get a big one and use it only at the power level needed. Also, if you know you're going to generate TVI no matter what, then the larger the output may be your best bet, as it will be more likely that you will work a station in less time than before, thereby causing less of a bother to neighbors (and perhaps that "significant other"!).

AC power - Large amps (and some small ones) generally require a 220VAC service, so be prepared.

Solid state amps - new, solid-state amps are available that are compact, instant-on, and excellent for QSK, but may be intolerant of SWR above 1.5:1.

Ceramic tube amps - metal/ceramic tubes (e.g. 4CX800A/GU74B) offer high efficiency and therefore greater output per unit input, allowing full legal-limit output power with only 50 - 80w of drive from the transceiver. The major drawback of these tubes is that they generally require up to 4-5 minutes of warmup, which can seem like a lifetime when you hear one that you need and the amp is off!

Glass tube amps - the venerable glass vacuum tubes (811A, 572B, 3-500Z) used in the old amps are still used in amps of new design. While requiring more drive per unit output power than the solid-state and ceramic tube types, they do offer instant-on and higher SWR tolerance.

Final Thoughts

Ham radio in general, and DXing in particular, can sometimes seem very complex when your experience with recent developments, equipment, and procedures is not current. Even though I maintained my license and was able to enjoy occasional activity during the 1960s, '70s, and '80s, when I finally was able to return to DXing in the late 1980's, I found that I was practically a neophyte. Indeed, I knew too little to even know how much I didn't know! Things had changed .... big time! For newcomers, or old-timers returning to the game, someone with current operating experience can be of great help in understanding what is going on and what one needs to participate effectively. So, unless you already have an experienced mentor, your best bet is to look around for someone who has been operating for a few years and ask for their help and advice. Join a ham club, or better yet, join a DX club and begin asking questions. Some of the more experienced members would no doubt be happy to have you come over and see their equipment - almost universally, hams like to show off their stations! In fact, you're welcome to visit my station any time that you're in the area. Here is a snapshot of it tucked away in a corner:

When you do visit someone's station for the purpose of evaluting equipment or getting up-to-speed, take a note pad along with some of your questions ready to ask, then make notes as you look around. Don't hesitate to ask if you can try to tune around the band, or even make a contact or two. Do this for more than one rig so that you can get a feel for differences between makes/models. Even if the station that you are visiting seems well out of your cost range, the experience will be useful. Also, remember that excellent buys are often available on the used equipment market, often surpassing the quality of a new low- or mid-range radio. Time spent on evaluating equipment with this type of serious inquiry will be of invaluable help in making a good choice.

Finally, it should not need saying, but I know from experience that it does - once you get your equipment, READ THE MANUALS! It's essential that you try to learn as much as possible about the basic operating functions and capabilities of your equipment. This does not mean that you need be an electronics engineer; but at the very least, you should certainly try to understand how an antenna works and how a receiver works. Spend some time reading the ARRL Handbook and other publications that offer basic tutorial presentations of how things work. The Internet now provides a wealth of resources - check the manufacturer's websites for operational and technical information about their products. Use "key words" to search the Web for useful websites that may offer additional info, explanations, or advice. The more you know, the better choices you will be able to make, and also the better will you be able to use you 

http://www.deltadx.net/ABCDx/Sections/Equipment.htm