A, B, C’s of Dx Fundamentals of the Art of DXing IV
W5FKX, Don Boudreau
Tuning the Bands
What is tuning?
One of the things that you’ll hear DXers talking about is “tuning”. This refers to a systematic method of scanning the ham bands and listening for new or interesting DX stations that may be on. Highly refined tuning skills are the hallmark of a good (and successful) DXer, and you will be happy to know that it is a skill that is very easy to learn. Although tuning alone can readily find DX stations, and we will discuss it as an independent method, it is important to emphasize that it is most effective when coupled with the use of two of the other DXing ingredients: information about DX operations and knowledge of signal propagation. We’ll have more about these in other chapters. Also, check the References below for some of the “calendar” websites on which one can find information about upcoming DXpeditions and DX contests.
Today, many neophyte “DXers” (and some not so neo!) believe that tuning is a waste of time because now all one has to do is monitor a DX Cluster for DX station spots, and then pounce on the ones of interest. Before any more about Tuning, let’s take a look at this. In the figure below one can see a screen snapshot of the spots appearing on the DXplorer feature of DXTelNet (by Fab, IK4VYX; see References).
The current worldwide system of reporting spots over local VHF packet nodes as well as via the Internet DX Cluster network, provides a wealth of instantaneous information to the DXer. The DXTelNet software also allows you to connect to any one of the many local packet clusters run by clubs or individual world-wide. In showing what stations are being heard and by whom, one can see how well signals are propagating; also, any breaking news will usually appear in the form of notes in the spots, or as “Announcements”, another feature of the DX Cluster network. As an example, within minutes of its occurrence, worldwide DXers were among the first to know of the earthquake and terrible tsunami in the Indian Ocean on 26-December, 2004. At the time, there was a DXpedition to the Andaman Islands (VU4) in progress, and the VU4 operators began relaying the word of what they were experiencing. DXers hearing this immediately posted the info on the DX Cluster network for worldwide distribution. The figure below displays the results of a search of the DX Summit spots database for 2004 showing how the word first got out on 26-Dec-04.
The use of station spotting among DXers is an old and acceptable practice that preceded the Internet by many years – using telephones and local repeaters, “spots” could be quickly distributed to the local DXers. In fact, “Needs” lists were – and still are – distributed among DXers indicating DX entities being pursued and the members’ interest in being called (at any hour!) if someone should “spot” something on the list. Spotting stations for others is a large part of the fun of ham radio, and especially for DXers. The fun of being the first in your area (and occasionally the world!) to locate and “spot” a DX station on the bands is a thrill, and the availability of local and Internet-based spotting networks are invaluable aides to DXers. The practice of using “Needs” lists and the use of DX Cluster networks is highly recommended for all who are interested in chasing DX and is a very beneficial tool.
However, learning how to actually tune the bands and locate DX stations on your own without dependence upon “spots” is still an extremely important skill that must be developed if one is to become a successful DXer. Here a few reasons for this:
First, Internet access is not always available and that should not mean that you can’t chase DX! For example, my XYL and I periodically spend a weekend at our cabin in the woods of SW Mississippi where there is neither telephone nor Internet service. I always bring my “portable” station along for DXing when I have some time. I have an 80m wire-loop antenna up in the pine trees, fed with twin-lead, and using a small tuner for all-band coverage. Over the 20 years that we’ve been going there, with only occasional DXing (an approximate total of 24hrs per year!), low power, and wire antenna, I have accumulated over 200 entities from that location. During a recent visit, I was up early and tuning on 80m CW when I came across a pileup – that meant there was a DX station somewhere. Carefully tuning down through the pileup, I found the bottom “end” of it, and then came across a station rapidly giving out signal reports: E51PDX. I knew from DX bulletins that he was on North Cook Island and I needed that for a new one on 80m. Hitting the “split” button on the IC-706MkII, I tuned VFO-B up and listened for the next station to work him, then tuned up a tad higher and when the E5 called QRZ? I signed my call twice … he came right back to me and I was in the log! Very satisfying!
A second reason for learning to tune is that if everyone gave up tuning, there would be no more spots for anyone since, in order for spots to appear, someone must be tuning!
The third reason to tune is that, since spots usually lead to a pileup that can be difficult to break, the easiest way to work DX is to find ‘em first before the pileup begins! Suppose you needed T20 (Tuvalu) for DXCC … wouldn’t it be nice to come upon him all alone and calling “CQ”, as you heard in the audio on the Title page? Right!!! … so let’s learn about tuning.
Finally, if all you intend to do is wait for spots to point you to DX, what fun is that? Get in there an TUNE!!
If you’re wondering about “split” operation, it is discussed more in the chapter on “The QSO”.
Where do I tune?
Here is a brief, very general, summary of the propagation characteristics of the HF and 6m bands, with suggestions about those segments in which one would most likely find DX. Some bands have a “DX window” where DX stations of general world-wide interest may call, usually operating “split”, and all others are discouraged from using. Note that the information provided does NOT include the complete band plans or frequency allocations (see References).
160m – Called the “Topband” since it has the longest wavelength and is therefore at the top of the list of our bands, it is essentially a sunset-to-sunrise (night-time) band for DXing because of the high daytime noise and D-layer absorption. However, pre-sunset ionospheric events can sometimes produce interesting propagation opportunities (see RF propagation), so up to an hour or so before sunset may occasionally provide some interesting possibilities. Due to the long (525 ft) wavelength, many feel that antenna size is a prohibitive factor for operating in urban/suburban areas; however, many have managed to overcome the difficulties and work DX (see “Topband? No Way! … but Never say Never” by W5FKX in QST, pp. 52-55, Feb 2007). Plenty of workable DX may be found, especially on CW. It is best during Winter, particularly at the low-phase of the Solar Sunspot Cycle. Vertical radiators are generally best for transmitting, but a separate low-noise receive-only antenna is highly recommended. Optimal windows of opportunity are at local sunset or sunrise, while in the grayline; and during hours of local dark when others are leaving (East of you) or entering (West of you) a grayline. Look for these sunrise/sunset enhancements on the other bands and see the chapter on Propagation for more about this.
1.800 – 1.810 MHz CW, Digital Modes
1.810 – 1.840 MHz CW DX
1.840 – 1.850 MHz SSB DX
80m – Similar to 160m in all respects, except that antenna size is much more manageable and more DX is usually available on all modes, especially CW & SSB. Night-time for DX.
3.500 – 3.520 MHz CW DX
3.580 – 3.600 MHz RTTY
3.700 – 3.800 MHz SSB DX
3.790 – 3.800 MHz SSB DX Window
60m – A relatively new band, it was opened on July 3, 2003 to US hams holding a General, Advanced or Amateur Extra Class license. Maximum Effective Radiated Power (ERP) must not exceed 50 W PEP, and operation is only allowed using USB mode with a maximum audio bandwidth of 2.8 KHz (don’t over-modulate!), and only on 5 designated frequency channels. Although it is not really an ideal DX band, is is certainly possible to find DX there (hams love a challenge!), and channel 5 has become the unofficial “DX calling frequency”:
5330.5 KHz Channel 1
5346.5 KHz Channel 2
5366.5 KHz Channel 3
5371.5 KHz Channel 4
5403.5 KHz Channel 5: DX calling channel
40m – This is the most versatile of all of the bands. Throughout the Solar cycle 40m provides, on average, a longer window than any other band for good DX opportunities, beginning in the late afternoon and continuing through the night and early-morning. Although it may not be quite as “hot” as the higher bands at the peak of the Sunspot cycle, it makes up for this through consistently allowing fair-to-excellent propagation no matter what the Solar activity phase may be.
7.000 – 7.100 MHz CW DX
7.035 – 7.045 MHz RTTY DX
7.080 – 7.090 MHz RTTY
7.050 – 7.100 MHz SSB DX (non-US)
7.150 – 7.225 MHz SSB DX (US)
30m – Propagation on this band is very much like the 40m band, opening in late afternoon, through the night, and into late morning. Only CW and Digital-modes are allowed, and most activity is on CW; but there is increasing activity on RTTY and some PSK31 activity.
10.100 – 10.120 MHz CW DX
10.130 – 10.140 MHz RTTY
20m – The most popular of all of the bands, especially for DXing, 20m has the advantage of being the most consistently productive of the higher-frequency “daytime” bands, with good-to-excellent propagation during the daylight hours. In addition, the 20m wavelength is not so long as to be overly cumbersome when designing multi-element beam antennas. Rotatable beams are common for 20m, so it is not surprising that it is the most popular of the DX bands. Open early AM to late PM.
14.000 – 14.070 MHz CW DX
14.070 – 14.075 MHz PSK31, & other digital
14.080 – 14.100 MHz RTTY
14.100 – 14.150 MHz SSB DX (non-US)
14.150 – 14.275 MHz SSB DX (US + non-US)
14.190 – 14.200 MHz DX window (SSB)
17m – Very similar to 20m, but with the added advantage of smaller antenna size, it has become a very popular band. Mostly daytime.
18.068 – 18.100 MHz CW DX
18.100 – 18.110 MHz PSK31, & other digital
18.100 – 18.110 MHz RTTY
18.110 – 18.168 MHz SSB DX
15m – A great band when open, usually during most of the Solar cycle, but it is generally hit-or-miss during the years of the cycle bottom. Dawn to Evening.
21.000 – 21.070 MHz CW DX
21.070 – 21.080 MHz PSK31, & other digital
21.080 – 21.100 MHz RTTY
21.100 – 21.150 MHz SSB DX (non-US)
21.150 – 21.350 MHz SSB DX (US + non-US)
21.290 – 21.300 MHz DX window (SSB)
12m – Similar to 15m, and even better during Solar peaks, but is usually dead during Solar minimum. Dawn to Evening.
24.890 – 24.910 MHz CW DX
24.920 – 24.925 MHz PSK31, & other digital
24.920 – 24.930 MHz RTTY
24.930 – 24.990 MHz SSB DX (US + non-US)
10m – During the years of the Solar cycle maxima this is the top-performing band, providing a wealth of DX and incredible Dawn to Evening propagation that allows world-wide DX contacts with minimal power and antennas. At Solar minima, it is a dead band.
28.000 – 28.080 MHz CW DX
28.080 – 28.100 MHz RTTY
28.120 – 28.125 MHz PSK31, & other digital
28.300 – 28.550 MHz SSB DX (US + non-US)
28.490 – 28.500 MHz DX window (SSB)
6m – Similar to 10m in many respects, but with less frequent openings. It is called the “Magic Band” because, although it is often devoid of any signals, openings seem to happen unexpectedly (“magically”), giving rise to excellent propagation to distant grid-squares and, on occasion, world-wide communication becomes possible. Six-meter DXers typically leave the radio on to monitor 50.125 with the squelch level set to just suppress the noise – any activity will then be heard if an opening occurs. Due to the short wavelength, multi-element beam antennas may be fabricated, or purchased at modest prices, and roof-top mounting will provide excellent results when the band is open. Generally daytime, with early summer months usually offering the best openings.
50.080 – 50.120 MHz CW DX
50.100 – 50.150 MHz SSB DX
50.100 – 50.125 MHz DX window (CW,SSB)
A final note about the bands: the 30m, 17m, and 12m bands, known as the “WARC bands” because they were allocated in the early 1980s by the ITU as a result of agreements forged during the 1979 Word Administrative Radio Conference (WARC; now called the World Radio Conference – WRC). These bands offer a great refuge for DXers whenever there are non-DX contests that may be causing disruption on the other bands because, as part of the allocation agreements, contests are prohibited in the “WARC” bands.
Here are a few tips on how and when to tune, along with a brief discussion about DX Nets and “List” operations, and some suggestions for tweaking weak signals.
First, there are two categories of tuning: general tuning, in which no particular DX station is in mind; and selective tuning, in which one is in pursuit of a particular station, entity, mode-counter, or band-counter.
– General tuning
Beginning DXers will be looking for any interesting DX station to add to the log, so the best approach is to employ the technique of general tuning, in which all sections of all of the bands are fair game at any available time that one has for ham radio. Learning to use this method is particularly important for beginning DXers in order to develop and hone the listening skills that will be useful in the future when, after working the most readily available DX, the pursuit becomes more selective. Here is a simple, point-by-point description of the general tuning technique:
Begin by switching your receiver to the bottom of the highest frequency HF band and quickly, but deliberately tune from the bottom (CW) to the top (phone) portion of that band, switching among modes of interest (CW, RTTY, PSK, SSB) as appropriate to the segment of the band, looking for any sign of activity. If you find none after a sweep, then go to the next lowest.
The highest frequency band in which you can hear any activity will be the maximum usable frequency (MUF) and will vary with the time-of-day, time-of-year, and the solar activity cycle. Generally, this may be your best bet for interesting DX.
Once the highest frequency band is determined, begin to slowly tune up the band. If you enjoy multi-mode operation, then start with CW, switching to PSK/RTTY, and SSB as you progress through the band segments, listening to – and trying to identify – each station that you hear. The reason for this is not only to find a new DX station to contact, but also to observe the propagation characteristics. If you are chasing Estonia (prefix: ES) for a new one, it would be very encouraging to hear a station in neighboring Latvia (YL) or Lithuania (LY).
Listen for some tell-tale signs of DX: weak signal, signal with polar flutter; accented speech; callsign of interest (or unrecognized), station giving rapid signal reports, station saying “up”, or a pileup.
More about modes of operation in the Equipment chapter; however, here are some key points for tuning:
SSB mode is the most commonly used; a bandwidth filter of 1.8 – 2.4 KHz is a good choice.
CW mode is the second most popular; a bandwidth filter of 450- 600 Hz is recommended; some experienced tuners use 250 Hz BW filters, and very experienced operators use 100 Hz or less.
Although RTTY and PSK are the least used of the available modes as they require additional equipment, connections, and operational skills, they should not be discounted as they provide an excellent gateway to a great deal of DX, usually with less competition than the other modes.
If the noise level seems high, reduce the receiver gain by turning down the RF Gain control and/or inserting some front-end attenuation (see notes below on “weak signal reception”).
After completing your “pass” over the band, you can either begin again or, if you didn’t hear any signals of interest on that band, then drop down to the next lowest available frequency band. Just tune and listen, tune and listen, … successful DXing is a game of P.E.P.S.I..
While you’re tuning, you should also be monitoring the spots on a DX Cluster.
When you find something of interest, begin planning how to make a contact, the techniques for which are discussed in the next chapter on “The QSO”. That’s it! Simple as it sounds, you will find that it does require considerable P.E.P.S.I. to be a good tuner.
– Selective tuning
After you have been at the DXing game for awhile, you will (1) begin to have a better “feel” for where and when to find DX, (2) have a list of “needs” showing the entities that you have not yet worked, and (3) will know of up-coming DX station operations of interest to you. At this point, you may well become more selective in your tuning. While the actual technique is the same as for general tuning, the way it is applied is different. The most frequent use of selective tuning is when information is available about the operating habits of a station of interest. For example, perhaps 5V (Togo) is on your “Needs” list, but despite all of your diligent tuning, you still have not yet heard any stations there yet. The reason may well be that there are no active resident hams. However, you come across a note in one of the DX bulletins about a VE operator who is expected to be active there for two weeks, beginning on 15 March. The blurb also mentions that the operator expects to concentrate on 20 meter CW. Although that is several months away, you immediately make note of it on your handy desk calendar, and continue your general tuning until the day before the operation is to begin. Then, on 14 March, you go into your selective tuning mode:
Determine the local sunrise and sunset times for 5V (see References) and convert that into your local time so that you can definitely plan to be at the radio then. These grayline times are frequently not only the best propagation times, but are also typically the most reasonable times for someone on holiday to operate – before breakfast and before dinner! A convenient source of sunrise/sunset times (and beam headings) by prefix is available as a feature of DXTelNet, the software package mentioned above that allows access to the DX cluster network – a “must” for DXers.
You should also estimate the optimal times and MUF for propagation between your location and 5V by using propagation prediction software (see References; also, see the “Propagation” chapter for more info on propagation and MUF). An added benefit of propagation software is that it will usually indicate the sunrise/sunset times for the entity of interest, along with beam headings for short path and long path if you happen to have a directional antenna. [Note: If the predictions indicate that few or no frequencies will be usable, don’t be deterred, as prediction software are based upon statistical calculations that provide estimates of average propagation for a month at a time. If the predicted conditions are not found on a given day, try again the next – on average, the predictions will hold up! Also, try tuning on all of the bands of interest – the software is only a guide and is far from perfect!
Look through your log for any contacts that you may have made with stations located in entities near 5V in order to estimate the best time to expect good signals. Of course, differing times of year and solar conditions may make such estimates highly variable, but you should make use every bit of information that you can gather.
Do a “Spot Search” for “5V” on the DX cluster that you use (you ARE using it, aren’t you???), or on the DX Summit website. This may turn up some spots of previous activity, giving you some indication of the times of best propagation between 5V and the station(s) posting the spot(s).
Begin tuning at the appointed time (of course it doesn’t hurt to be early!), following the general tuning procedure, but concentrating upon the band of frequencies for the expected activity. If the operation is from a rare location and your station is modest, it is especially important to be early, as very often the first few stations to hear the beginning activity will have the easiest time of working the DX station before the pileup begins!
Depending upon the extent of the information that one collects about a particular DX station activity or the plans for a forth-coming DXpedition, selective tuning can be applied broadly (e.g., over many bands for several modes) or specifically (e.g., a single frequency, mode, and/or time). A notable case of the latter occurred when P5/4L4FN first became active from North Korea, a country in which ham activity had always been banned. After a pair of very limited operations by one of the icons of DXing, Martti Laine, OH2BH, in which a few hundred contacts were made as a demonstration of amateur radio activity, North Korea (P5) was officially added to the DXCC list in early 1995. The DXing community was ecstatic and anticipated an easement of restrictions on ham radio following these sanctioned demonstrations. However, much to our collective disappointment, this did not happen. Since P5 had been officially added to the DXCC list, that meant that anyone who did not work the limited operation (most of the world!) was now one entity short of having “worked ‘em all”. Despite many attempts by other notable DXers through the end of the decade of the 1990’s, no further ham radio activity was allowed. Then, in November of 2000, without prior notice or fanfare, a station began to operate with the callsign P5/4L4FN. Despite the fact that many proclaimed this to be a pirate operation, the experienced DXers knew to WFWL! The operator, Ed, from the Georgian Republic (4L), said that he was with the World Food Program of the UN, and was operating from Pyongyang with a small transceiver and a wire antenna. He indicated that he was not a DXer; however, he soon began to respond more openly to the increasing pileups, trying to accommodate as many of the clamoring DXers as he could. Initially, the only activity was on 28.475 MHz SSB between the hours of 2200 – 0200 UTC. Although the frequency of operation changed to 21.225 MHz after a few months, and he also broadened his time of operation to include 0330 – 0630 UTC and 1100 – 1330 UTC, the tuning for this very rare DX station remained highly selective, generating huge pileups of thousands of stations calling simultaneously.
When the operation was finally approved for DXCC credit in March, 2001, one could almost feel the heat of the joy that emanated from the DXing community! For many of The Deserving, it meant the Top of the Honor Role at last!
– DX Nets
Apart from tuning, there is another way in which some DX stations may be found and contacted, and that is on a HF DX Net operation. A typical HF DX Net meets regularly at a specified time and frequency for the purpose of attracting both local and DX stations to check in, giving each the opportunity to work one another, and it may also provide some useful DX information (see the chapter on DX Info Sources for access to DX net schedules). Note that there are both HF and VHF/UHF DX Nets. The VHF/UHF DX nets are local meetings usually sponsored by DX Clubs to provide a local on-the-air forum for discussion of DXing and for the dissemination of DX news, whereas the HF DX nets have worldwide participation. In this chapter, discussion of nets and lists will refer to HF DXing.
The usual procedure on a HF DX net is for the Net Control Station (NCS) to begin the net with some brief introduction, statement of purpose, and a summary of the net protocol. Regular check-ins are then taken, either by role call or area, and then the NCS calls for any DX stations to check in. If there are no DX stations, the NCS may proceed with some announcements or news, allowing time for stragglers to tune into the net. If there are several DX check-ins, the NCS will then ask whether anyone wants to make a “DX call”, and will stand by to take down any stations, along with the DX station of their choice. In some instances, a relatively rare DX station will check into the net creating a pileup when the NCS asks if anyone would like to make a call. In such cases, the NCS will resort to the List Operation procedure discussed under “pileups” in the chapter on “The Contact”.
It must be mentioned that the use of DX nets to work DX does not meet with universal approval all DXers. Many DXers feel that it is an un-sportsmanlike approach and should not be used. The reasons given are many; here are a few of the criticisms:
it hasn’t anything to do with “real” DXing
it is the lazy person’s way of working DX
it is sometimes (or: “often”, “always”) used to cheat at DXing, i.e.,
NCS repeats the callsigns and reports, so stations that cannot copy can still log contacts
stations call NCS on telephone and get on the list when others cannot
NCS often “plays favorites” in taking lists and/or assisting with contacts
As with any of the myriad human endeavors, some of these criticisms are probably valid in some cases; however, it is highly doubtful that there is a DXer alive today that has not participated in some form of “DX Net” protocol at some time or other in order to work a needed station. Indeed, there have been several occasions in which a relatively rare DX station preferred to operate solely on DX Nets and could only be found there. This is usually due to a combination of factors: an inexperienced operator in a high-demand DX location who may not have a very good command of English, the de facto universal language of ham radio. Being a DX station, especially in a rare location, is not for the timid! It is patently unfair for anyone who has not been “on the other side” of a DX pileup to criticize a novice DX operator for using the assistance of a DX Net. It is also unfair to suggest that all DX Net activities are bogus or otherwise unacceptable. DXing, as a facet of ham radio, is a hobby. As in any hobby, the satisfaction provided is a personal thing that is to be judged by the individual and not the group. Therefore, those who enjoy the DX contacts afforded by DX Nets should be allowed to do so without rude commentary by others.
A final word on DX Nets must include this caveat: the number of DX entities that one can work in this manner is very limited in comparison to the methods of tuning that have been discussed. While you should certainly feel free to learn about and explore the available DX Nets, do not do so at the expense of developing your complete DX skills!
– Weak Signal Reception
Often, the signal of most interest will be weak and “in the noise”. Here are a few tips on weak signal reception for improving the Signal-to-noise ratio:
If using a beam, try different headings, including long-path.
If available, try different antennas for receive – some may be less prone to noise than others.
Try different filter bandwidths; usually narrow is better, but experiment! (SSB: 1.7-2.4KHz; CW: 50-300Hz)
Decrease the receiver RF gain to reduce noise amplification and compensate by turning up the Audio gain (if the noise is low enough, the ear-brain detector system may be able to better perceive the signal):
Reduce the RF gain control setting
Turn off RF preamp
Insert 6-18db of front-end attenuation
Switch the Automatic Gain Control (AGC) to Fast (preferred default for DXing), or turn it off.
If all of this fails to improve the reception of the signal that you know it is a DX station you need, then just wait and keep listening, because conditions very often fluctuate significantly in time, and the signal strength may build up enough for you to hear. Be ready to give a call and make the contact quickly, as improved conditions may last just for a minute or two, or even only a few seconds!
– One more word about Signal Reception
If you operate on CW, you undoubtedly noticed that you can change the tonal pitch of the received signals by using the “Pitch” control on the receiver, or by slightly changing the frequency. In the Equipment chapter, we will discuss Receiver capabilities, such as sensitivity and selectivity, that are important for DXers; but perhaps this is a good point to mention another aspect of signal detection that comes to play when we are tuning. It is that each person’s hearing may be different, although we rarely appreciate this during normal everyday conversation. However, our aural sensitivity and selectivity capabilities are more of an issue when we are tuning for CW signals, and especially when we are searching for weak signal DX! In late 2006, Eric, K3NA, posted an interesting comment on the Topband reflector in regard to adjustment of CW pitch, that led me to draw the receiver analogies below. (See also his subsequent 2-part article, “Can I Hear You Now? Adjusting the Receiver Audio Chain”, in the Nov/Dec 2006 and Jan/Feb 2007 issues of the National Contest Journal – www.ncjweb.com/; also check Eric’s website at www.k3na.org/ for a future posting of the article).
We know that our hearing abilities result from the ear-brain system. Much like the specification of receiver capabilities, we can also categorize the key aspects of our human hearing system. Here are three that DXers may want to consider more closely (Note – the terms in parentheses are those used in audiology):
Tone sensitivity (pitch detection) is the ability to hear a particular tonal frequency. As multiple tonal frequencies mix in the ear and/or tone frequency changes, it takes the ear-brain system some period of time (a few tonal cycles) to process and interpret the change. Difference in this capability may be important in copying CW, where one is trying to process tones that may be fading while being turned on/off fairly rapidly.
Tone selectivity (pitch discrimination) is the ability to discriminate between different tonal frequencies. Generally, we can differentiate between lower frequency tones more easily than between higher frequency tones, and there is usually a range (band) of tonal frequencies over which this discrimination capability is optimal.
Tone blocking (tone masking) is the phenomenon in which loud tones can obstruct the ear-brain ability to detect adjacent higher-frequency tones of lower amplitude. Reported by AT&T scientists in 1924 (“The Auditory Masking of One Pure Tone by Another and its Probable Relation to the Dynamics of the Inner Ear”. Wegel RL, Lane CE. Phys. Rev. (23): 266-285, 1924), they found that “When the masking tone is loud it masks tones of higher frequency better than those of frequency lower than itself.”
From this, we can draw these conclusions: (i) there is a band of tonal frequencies that are optimally perceptible to each of us; (ii) if we select the lowest tonal frequency within this band that we can readily hear (detect), it may be the best for CW tuning, as it will be most readily heard and suffer the least amount of blocking by nearby loud higher-frequency tones.
Usually, most of us will just defer to the manufacturer’s default settings for the pitch of a CW signal when the receiver bandpass is centered on the desired signal, and that tone is generally 900 – 1,000 Hz. However, this may not be the best setting for reception under difficult conditions. How does one determine which tonal frequencies are best? Personal preference and experience usually provides a pretty accurate selection process, but if you want to approach it more analytically, the “Hearing & Speech Lab” at the University of California at Irvine has a really interesting online test at www.ucihs.uci.edu/hesp. Give it a try … it may help you to work that really rare one some day!
Thanks to Eric Scace, K3NA, for his comments and info for this section.
– WHEN should I do General Tuning?
The answer to this question is very simple: aside from all of the issues of propagation and/or prior information, the “best time” to tune is any time that you have a few minutes! Local sunrise and sunset can often provide good propagation conditions, so these should be prime times on your list. For the most likely bands and times, review the band-characteristics summary above, along with the chapter on Propagation, then begin to learn about your local propagation conditions as a function of the phase of the Solar cycle.
As a rule, make it a habit to try to tune for awhile before leaving home in the morning, or during lunch break if you’re lucky enough to be home for lunch, or before and after dinner in the early evening, and finally just before bedtime. Begin on the highest frequency band for which you can hear any signals, working your way down through the lower frequency bands. If you’re still unfamiliar with the characteristics of the various bands, review the chapter on “RF Propagation”, and take a look at the info posted on the DX 101 website below. As noted before, the early morning/evening times within your grayline usually provide opportune propagation conditions, not only by short path, but also frequently by long path. Remember that even 15 minutes of tuning at peak propagation times can often be very productive, once you learn how to do it.
Plan on occasionally tuning during late evening-early morning hours, especially on the 40, 80, & 160m bands. For DXers in North America, late evenings correspond to dawn in the Middle East, Europe, and Africa, while early mornings cover times of sunset in the far-Pacific, Asia, and Australia. Whenever you are tuning, always keep in mind what time of the day it is in the far-reaches of the DX world!
Finally, when you begin to stalk particular DX stations, you will want to use the propagation prediction software described above to provide a guide for tuning times. When tuning for a particular station (or location), determine the times of the local sun-rise/set there, as these can also be prime propagation times from that location. For the path between your location and any specified DXCC entity, this type of software will estimate optimal times and frequencies, depending upon the level of solar activity on the days of interest.