Category Archives: Education and Training

Education and Training information is for folks looking for help to earn or upgrade their license, learn about Amateur Radio, and get help with Ham Radio questions.

Activities, Education and Training, Featured, General, Newsletter, On The Air

Why Would I Want To Be In A Contest?

October 30, 2016 Fred Kemmerer

As I sit here watching the N1FD teamwork the CQ Worldwide DX contest, it got me thinking about what contesting is really about and why we contest.

Let me try to answer the second question first. There are lots of different reasons to operate in contests. Many folks do this to work new countries, states, zones, islands, grids, etc. It seems that you can find a contest that is designed to create opportunities to work just about anything that you can think of on the bands. Others work contests to try to test out their stations and to improve their skills as operators. Of course, many folks compete to win the contest or to place better than they did the last time. Some may even compete to set a record.

Joe KB1RLC in the CQ Worldwide DX Ham Radio Contest — Joe KB1RLC in CQ Worldwide DX at AB1OC

Perhaps the best reason to contest is that it provides one of the best opportunities to be a better operator. You may say, aren’t contesters just QRM on the bands on weekends when we want to use them for other stuff? I can see why some feel this way. I wish that more amateurs who feel this way would take some time to listen more closely to what is going on during the contest.

There is nothing quite like listening to a skilled operator work a pileup from a rare place during a worldwide contest like CQ Worldwide DX. Such an operator will make 100’s of calls in a row. They will accurately get each caller’s information into their logs and the really great ones will also use their skills and energy to ensure that each of their callers gets the contest station’s information correct in their logs as well.

This requires great skill in many areas. First, you need to really learn to listen and to pick out weak and fading callers in the presence of a great deal of QRM. It’s often necessary to piece together a good callsign using several rounds of a QSO. Good contest operators know perhaps 500 or more of the most common calls used in their contest and this information helps them to recognize calls and avoid making errors. The great ones also know how to work with each caller to ensure that they get the correct information to complete the contact and that the other operator does the same.

Jamey, KC1ENX Operating in the CW Worldwide DX SSB Ham Radio Contest — Jamey, KC1ENX Operating in CW Worldwide DX SSB

I like to think of this as getting in the head of the other person during the QSO. Did they get my call right or do I need to slow down and say my call again? Did I hear their callsign and exchange correctly or do I need to give them a chance to ask me to correct something for them? While I am doing all of this, I need to be as fast and efficient as possible. These skills take a great deal of practice to develop. You can get there with less time in the chair during contests if you take some time to listen and pay close attention to the great operators that you will hear during contests. First and foremost, great contesters are great listeners and they can accurately pick out call signs on the first try without making mistakes.

N1MM+ Logger Setup For Our Contest Operation — N1MM+ Logger Setup For CQ WW DX

What, you say that any operator will do great when they are sitting at a big contest station with a lot of power and big antennas? It is true that having a well-built station and good hardware and computers helps make contacts easier. Computers and modern software like N1MM+ also play an important role in making the mechanics of finding and making contacts accurately more efficient. The contest community makes their software available free of charge to everyone. I strongly encourage anyone who contests to set up and learn to use modern contest software. While these tools help, they are just like construction tools in the hands of a carpenter. The master carpenter can create a work of art with a hand saw, a hammer and some basic hand tools while an apprentice can struggle to get good results from the best shop and tools available.

Also, most contests are designed with categories to group contesters with their peers who have setups similar to theirs. Station hardware differences also do not account for the contester who goes to an island in the Caribbean with a 100W radio and a simple antenna and wins an award in a contest.

Julio, HI3A Competing in the WRTC Ham Radio Contest — Julio, HI3A Competing in WRTC

We also saw this clearly during the WRTC competition here in New England a few years ago. We had the best operators in the world competing using the exact same towers and similar antennas that we use for our annual Field Day operation and they made 2,000 or more contacts in a 24 hour period using 100W radios. Many of these operators did this while making almost no mistakes!

So what else makes a great contest operator besides working fast and efficiently to complete and log lots of contacts accurately? For one, these folks know a great deal about propagation and how to take the best advantage of the conditions at hand. They know when it’s time to run on 20m into Europe, when to look for Japan on 15m for those multiples, what time of day and segment in the contest to focus on contacts in the Caribbean and South America, etc. They learn when they need to change bands and when it’s time to work multipliers or tune the band that they are on with their second radio or VFO. They can quickly determine the band and propagation conditions on the contest weekend and adjust their strategy to take the best advantage of the conditions at hand.

A great operator also learns to make the best use of their station and antennas. They understand where their stations work well and they adapt their approach to a contest based upon this. They also spend lots of time looking at and comparing their performance from contest to contest and against other competitors in the same contests to see where they can improve.

So what if you don’t really want to win contests? Why would you bother with this? The most important reason is that contesting will make you a better operator. You’ll learn to hear that really weak DX and get them into your log accurately. When you get on the air, you’ll be an operator that others want to work because they know you will help them complete a contact that they want. You will find and work stations that most others will miss. In short, a bit of dedication to contesting will make you a great operator.

Bands and Modes Worked By N1FD (Noon On Sunday)

As the CQ Worldwide DX Contest weekend draws to a close, I’d also like to add that I am proud of the job that the operators in our club did at our station. Most of them had almost no DX contest experience before this weekend. They worked the contest hard and have made contacts to over 100 counties in about 40 hours of operating. They have all improved their skills greatly and I look forward to working all of them at any time.

73, and see you in the contest!

Fred, AB1OC

Antennas, Education and Training, Featured, General, Homebrewing, Newsletter

Yagi Antenna Construct Part #2: Current, Voltage Profiles, and Dipole Pattern

September 23, 2016 Dave Michaels

In Part 1 of this article series, I presented the “Lego” 2 m 3-element Yagi antenna design that the N1FD ham license teaching team has used over the past year for class demonstrations. The design allows easy assembly of the basic dipole antenna as well as a 3 element Yagi. The configuration of individual elements and spacing between elements can be quickly changed to demonstrate basic physics and behavior of these popular antennas.

The first article described antenna construction details and showed how to demonstrate the criterion for resonance as well as the polarization property of the radio wave. In Part 2 of the series, I will continue a focus on the dipole, specifically the spatial current – voltage profiles on the driven element and the radiation pattern of the antenna. We will use this information in Part 3 of the series next month to demonstrate how a 3-element Yagi works and why it is so popular.

THE CURRENT & VOLTAGE PROFILES ON A HALF WAVELENGTH DIPOLE

Figures 1a and b – Current Profile on a Half Wave Dipole Antenna

Figure 1a reminds us of the basic dipole geometry; and Fig. 1b shows the current and voltage profiles along the driven element. (From http://www.radio-electronics.com/info/antennas/dipole/half-wave-dipole.php)

Note from Fig. 1b that the current profile of a dipole has a maximum current level at the center feedpoint and decreases to zero current at the end of each element arm. Contrasting, the voltage profile has a zero value at the feed point and increases to a maximum level at the ends of the element arms.

Figure 2 – 1/4 Wave Vertical. Note the 7 spaced lamps.

The 1/4 wave vertical antenna seen in Figure 2 can be used to visualize the current profile along the arms of a 1/2 wave dipole. The 1/4 wave antenna is made from a short length of a Christmas tree (incandescent) light string. The string length can be estimated from the standard equation: Length (ft) = 234/Frequency in MHz. Generally, several inches needs to be trimmed off because the lamps add “electrical length”. The shown antenna has the same resonance frequency as the Lego Style dipole we will use later (i.e., 146.550 MHz). The top end of the antenna is marked by the blue tape immediately above the 7^th lamp.

Figure 3 – Transmitting mode. Note pattern of lit and unlit lamps.

The energized antenna with 15 watts RF signal is seen in Figure 3. Compare the pattern of lit and unlit lamps with the current profile sketch shown in Fig. 2b. The three lamps, counting from the picture bottom are brightly lit from an RF current. Lamps 4 and 5 show progressed less light indicating a lower RF current. Lamp number 6 is barely lit and number 7 is dark indicating together very little to no RF current at the element top end. The light pattern is a clear mimic of the diagram in Figure 1b.

Demonstration of the Voltage and RF Radiation Profile on a Half Wave Dipole Antenna

The voltage profile on a center fed 1/2 wavelength dipole is seen in Figure 1b. As mentioned above, the voltage is zero at the dipole center and increases in monotonic fashion to a maximum value at the antenna ends.

Figure 4 – Illustration of Dipole RF Radiation Pattern

The familiar RF radiation pattern of a dipole is shown in Figure 4 (taken from the cited source for Figure 1).

We are all well-schooled on the pattern, so I will just list the three key facts. First, the RF radiation is broadside to the antenna axis. Second, the RF field intensity is equal on the left and right sides of the dipole axis (i.e., there is no discerned “front to back” sidedness. Third, there is (theoretically) no RF radiation off the ends of the dipole wire.

The dipole voltage profile and the RF radiation pattern can be demonstrated using the basic dipole element of our “Lego Style” antenna and two simple tools. The voltage profile, or more correctly, the electric field strength around the dipole is sensed by a small fluorescent light tube. The actual RF radiation from the energized dipole is sensed by the flashlight lamp-bridged receiver antenna introduced last month in Part 1 of this series.

Direct RF Radiation Visual Detection

The video below (double-click in the picture box) demonstrates the use of the lamp-bridged receiver antenna to detect radiated RF power.

The video shows the flashlight bulb bridging the handheld receiver antenna lights up when it detects an RF signal that matches its resonance point at 146.550 MHz The light bulb is dark with no transmitted RF power from the Lego dipole. Keying the radio energizes the Lego dipole and the receiver lights up about equally on the right and left sides of the Lego antenna. This reflects the figure 8 pattern of RF power illustrated in Figure 4.

Voltage Profile witnessed by the Electric Field Strength.

The next video (double-click in the picture box) employs the fluorescent light bulb to map the voltage profile along a dipole arm by sensing its electric field strength. An RF electric field causes a series of chemical reactions within the light bulb that produces a bright fluorescent light.

The light bulb is dark when the Lego dipole is not transmitting an RF signal. Keying the radio generates an RF signal and the associated electric field around the dipole element causes the bulb to light up. Note, the bulb is very bright adjacent with the side end of the dipole arm and extinguishes as it is moved to the dipole centered feedpoint. Also, the light is dimmed at the antenna tip in-line with the dipole axis.

The voltage profile map seen in the fluorescent light bulb video augments the RF signal map seen in the lamp-bridged receiver antenna video. Also, it extends our demonstration to the expected observation that there is (theoretically) no RF radiation off the end tips of dipole elements.

CONCLUSION

In this second installment of our Lego-Style Antenna series, we have shown how this construct together with two simple tools can be used in the classroom to demonstrate basic properties of the ubiquitous dipole antenna; Namely, criterion of resonance, generation of RF radiated waves, the polarization of the RF field (horizontal or vertical) and the general propagation geometry of these waves relative to the antenna orientation.

In Part 3 and last installment of this series we will continue to use the Lego-Style Antenna in its’ Yagi configuration together with the two accessory tools to show how properly designed and placed reflector and director elements on the Yagi antenna can shape and control the dipole rf signal to increase gain via spatial directivity and improve signal selectivity by the “front-to-back” ratio that it creates.

73 & Hope to hear you on the air,

Dave N1RF

Nashua Area Radio Society

Category Archives: Education and Training

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