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2022 ARRL Field Day – June 25-26

Objective-

To contact as many stations as possible on the 160, 80, 40, 20,15 and 10 Meter HF bands, as well as all bands 50 MHz and above, and to learn to operate in abnormal situations in less than optimal conditions.

Field Day is open to all amateurs in the areas covered by the ARRL/RAC Field Organizations and countries within IARU Region 2. DX stations residing in other regions may be contacted for credit, but are not eligible to submit entries.

Each claimed contact must include contemporaneous direct initiation by the operator on both sides of the contact. Initiation of a contact may be either locally or by remote.

How Many Antennas Do I Need

Recently a student in our Technician License Class realized that it may take quite a few antennas to cover all of the available ham bands. He asked, “So how many antennas do I need?”

Of course, my answer was “you can never have too many antennas.”

This is a very valid question. Radio amateurs have so many bands available to them, it does present a challenge to figure out the antenna situation. Someone recently said to me, “getting the radio is the easy part — figuring out the antennas is the real challenge.” So true.

A new Technician often decides to just focus on VHF/UHF with an emphasis on FM simplex and repeater operation. The focus of this article is broader than that, with the addition of HF operation. Keep in mind that a Technician Class license gives you access to all of the VHF/UHF bands and a relatively small slice of the HF bands (10 meter phone plus 80m, 40m, 15m and 10m CW). The General Class license provides greatly expanded privileges on HF. Imagine that you just bought one of those “do everything rigs” that cover all of the HF bands, 6m, 2m and 70 cm (e.g., Yaesu FT-857, FT-991, Kenwood TS-2000, or Icom IC-7100). That’s a lot of spectrum to cover and no single antenna will do it all efficiently.

DIamond X-50A Dual-Band Antenna (2m+70cm)

DIamond X-50A Dual-Band Antenna (2m+70cm)

A basic antenna setup for such a station is to use a dualband VHF/UHF antenna to cover 2m and 70cm, along with a multi-band HF antenna. This won’t actually result in an antenna system that covers all of the ham bands, but it can be a good start.

The dual-band VHF/UHF antenna could be a Diamond X-50A, a Comet GP-3, or similar antenna. Another popular design is the Arrow Open Stub J-Pole antenna. These antennas are vertically polarized, covering basic 2m and 70 cm simplex and repeater operating. They won’t do a good job with weak-signal SSB or CW operating, where horizontal polarization is preferred. Some folks may argue for just putting up a single-band antenna for 2m only, which is the most popular VHF band.

For operating on the HF bands, you’ll want an efficient antenna that covers multiple bands. You could put up single-band antennas for every band, but that gets complicated and typically results lots of antennas and lots of cable runs back to the ham shack. Focusing on the new ham, it makes sense to go for a multiband antenna and keep the number of individual coaxial cable runs to just a couple.

The first question that pops up is “which bands?” Well, that depends. My biases are towards the higher bands (20m and up) because I like to work other countries around the world during daylight hours. If you are more interested in North American contacts, especially in the evening hours, you might want to cover the 40m and 80m bands. For a new ham, this may be difficult to figure out, until you get some experience and discover your preferred ham bands.

So, a good compromise for the new HF operator is a multiband antenna that allows operations on a couple of higher bands (perhaps 20-meters, 15-meters, and/or 10-meters), and operation on at least one lower band (perhaps 40-meters and/or 80-meters). Some reasonably inexpensive commercial options with such band allowances are readily available as horizontal wire fan dipoles or trap dipoles. Let’s consider these options:

Fan Dipole (also known as a parallel dipole) – This is a half-wave dipole with additional elements added to cover additional bands. While there is some interaction between the different dipole elements, they are normally fed by a common coaxial cable, avoiding the need for multiple cable runs.

Fan dipole diagram

A fan dipole configures multiple dipoles trimmed to different bands using a single feedline. (Not to scale)

Trap Dipole – This antenna uses tuned circuits (“traps”) to enable a single dipole to operate on multiple bands. The dipole length is determined by the lowest frequency band and the traps are used to electrically shorten the dipole for higher bands. Trap antennas can usually be designed to work well with two or three different HF bands, and designs combining fan and trap dipole features can provide more, with some trade-offs in efficiency and performance.

A trap dipole diagram for 10m and 20m ops

A trap antenna has resonant circuits inserted in the radiating element that electrically shorten the antenna for use at higher frequencies. (Not to scale)

End Fed Half Wave (multiband) – This half-wave antenna is similar to a dipole but the coaxial cable is connected to one end of the half wave wire, allowed easier mounting than the typical center-fed dipole. A well designed matching transformer at the end feed point facilitates this antenna configuration. Multiband versions of this antenna exist and are a convenient way to enable several bands at once. The popular Vibroplex Par EndFedZ® product line offers several multiband options.

End Fed half-wave antenna with matching transformer connection.

The Vibroplex EndFedZ EF-Quad antenna operates well on 10m, 15m, 20m, and 40m bands. It is 65 feet long, uses three short stub extensions along the length, and has an end-of-wire feed point transformer with coaxial connector. (Courtesy Vibroplex, Inc.)

Multiband vertical – Quite a few different vertical antenna designs support multiple bands. For example, see the

Cushcraft R9 vertical multiband antenna

Cushcraft R9 Multiband Vertical Antenna (Courtesy Cushcraft, Inc.)

or R9, GAP Challenger DX, Butternut HF9V and the Hustler 4BTV. When considering a vertical antenna, pay attention to whether the design requires ground radials to be installed. Nothing wrong with them, but radials can be critical to achieving efficient antenna performance. If you have restrictive covenants, you might consider a vertical antenna that is also a flag pole (really!). Take a look at ZeroFive Antennas for examples.

Antenna Tuners – When trying to cover lots of bands with just a few antennas, an antenna tuner will be really handy. This may be built into your radio or it may be a separate box inserted into the feedline between the transmitter and antenna.

An antenna tuner does not actually “tune your antenna” but it will tweak up the SWR of the antenna and allow it to be used across a broader range of frequencies. It also will keep your transmitter happily perceiving a nice 50-ohm feedline impedance that circumvents automatic power reductions that come with high SWR from an impedance mismatch.

Other Bands and Modes I’ve focused on the most popular ham bands, but there are many other frequencies to consider. The 6-meter band is a lot of fun and is accessible to Technicians. Most of the time, this band is good for local communication but it often opens up for over-the-horizon skip by sporadic-e propagation, especially during the summer months. Some of the multiband HF antennas mentioned above also cover 6 meters, or you can put up a separate 6m dipole to get started. The more serious 6m operators use a Yagi antenna to produce gain and a big signal. In most station configurations, a separate 6-meter antenna will dictate another dedicated coaxial cable run.

Another fun mode is 2m single sideband (SSB), the workhorse band for weak-signal VHF. You’ll need a horizontally-polarized 2-meter antenna, preferably with some gain. The most common antenna used is a Yagi with many elements, such as the M2 2M9SSB antenna or the portable Arrow models.

So, How Many? – You can make a lot of contacts and construct a superb HF to UHF station with just two quite simple antennas. The VHF/UHF vertical dual-band antenna paired with a multiband horizontal wire dipole is a cost-efficient, easy-to-erect combination providing FM simplex and repeater ops for local communications as well as long-distance HF skip on several bands. It’s a very good way to start.

Putting together an antenna system can seem like an overwhelming task for the beginner, so don’t get too freaked out about it. The main thing is to get something usable up in the air and make some contacts. Over time, you will probably add or change your antennas to get just what you want. That is part of the fun of amateur radio.

Bob K0NR

Ground Wave Propagation

Ground wave propagation is a form of signal propagation where the signal travels over the surface of the ground, and as a result it is used to provide regional coverage on the long and medium wave bands.

Ground wave propagation is particularly important on the LF and MF portion of the radio spectrum. Ground wave radio propagation is used to provide relatively local radio communications coverage, especially by radio broadcast stations that require to cover a particular locality.

Ground wave radio signal propagation is ideal for relatively short distance propagation on these frequencies during the daytime. Sky-wave ionospheric propagation is not possible during the day because of the attenuation of the signals on these frequencies caused by the D region in the ionosphere. In view of this, radio communications stations need to rely on the ground-wave propagation to achieve their coverage.

A ground wave radio signal is made up from a number of constituents. If the antennas are in the line of sight then there will be a direct wave as well as a reflected signal. As the names suggest the direct signal is one that travels directly between the two antenna and is not affected by the locality. There will also be a reflected signal as the transmission will be reflected by a number of objects including the earth’s surface and any hills, or large buildings. That may be present.

In addition to this there is surface wave. This tends to follow the curvature of the Earth and enables coverage to be achieved beyond the horizon. It is the sum of all these components that is known as the ground wave.

Beyond the horizon the direct and reflected waves are blocked by the curvature of the Earth, and the signal is purely made up from the diffracted surface wave. It is for this reason that surface wave is commonly called ground wave propagation.


Surface wave

The radio signal spreads out from the transmitter along the surface of the Earth. Instead of just traveling in a straight line the radio signals tend to follow the curvature of the Earth. This is because currents are induced in the surface of the earth and this action slows down the wave-front in this region, causing the wave-front of the radio communications signal to tilt downwards towards the Earth. With the wave-front tilted in this direction it is able to curve around the Earth and be received well beyond the horizon.

Effect of frequency on ground wave propagation

As the wavefront of the ground wave travels along the Earth’s surface it is attenuated. The degree of attenuation is dependent upon a variety of factors. Frequency of the radio signal is one of the major determining factor as losses rise with increasing frequency. As a result it makes this form of propagation impracticable above the bottom end of the HF portion of the spectrum (3 MHz). Typically a signal at 3.0 MHz will suffer an attenuation that may be in the region of 20 to 60 dB more than one at 0.5 MHz dependent upon a variety of factors in the signal path including the distance. In view of this it can be seen why even high power HF radio broadcast stations may only be audible for a few miles from the transmitting site via the ground wave.

Effect of the ground

The surface wave is also very dependent upon the nature of the ground over which the signal travels. Ground conductivity, terrain roughness and the dielectric constant all affect the signal attenuation. In addition to this the ground penetration varies, becoming greater at lower frequencies, and this means that it is not just the surface conductivity that is of interest. At the higher frequencies this is not of great importance, but at lower frequencies penetration means that ground strata down to 100 metres may have an effect.

Despite all these variables, it is found that terrain with good conductivity gives the best result. Thus soil type and the moisture content are of importance. Salty sea water is the best, and rich agricultural, or marshy land is also good. Dry sandy terrain and city centres are by far the worst. This means sea paths are optimum, although even these are subject to variations due to the roughness of the sea, resulting on path losses being slightly dependent upon the weather! It should also be noted that in view of the fact that signal penetration has an effect, the water table may have an effect dependent upon the frequency in use.

Polarisation & ground wave propagation

The type of antenna and its polarisation has a major effect on ground wave propagation. Vertical polarisation is subject to considerably less attenuation than horizontally polarised signals. In some cases the difference can amount to several tens of decibels. It is for this reason that medium wave broadcast stations use vertical antennas, even if they have to be made physically short by adding inductive loading. Ships making use of the MF marine bands often use inverted L antennas as these are able to radiate a significant proportion of the signal that is vertically polarised.

At distances that are typically towards the edge of the ground wave coverage area, some sky-wave signal may also be present, especially at night when the D layer attenuation is reduced. This may serve to reinforce or cancel the overall signal resulting in figures that will differ from those that may be expected.