No matter what kind of operating you do, sooner or later you’ll need a “gadget” that isn’t readily available commercially.

Maybe you’ll need a special switch or an interface between connector types or to a radio accessory port. After making one or two of these, you might develop a taste for homebrewing of the electronics variety! Many hams started small and wound up making equipment that rivals professional quality.

One thing you’ll learn quickly, though, is that nice-looking metal enclosures are surprisingly expensive. Even small boxes can cost as much as the electronics inside them.

To keep the cost of building reasonable, I’ve learned to make use of less-expensive materials to make my own, particularly when building something for the first time or just trying out an idea. Low-cost materials encourage prototyping and trying out alternatives—you can then use the money saved on a better enclosure for the final version. Or you might find the inexpensive alternative to be a fine permanent solution.

Here are some tips and tricks that have served me well.

Basic Boxes

One of your most useful discoveries will be that specialty products sold for electronics are often quite a bit more expensive than a very similar product made and sold as consumer and commodity products.

This is true for more than just metal boxes!

If you can use something made and sold by the zillion, you’ll save a lot of money, especially if you are willing to accept a different shape or can modify a commercial product. For example, electric fence insulators and PVC pipe, or conduit fittings, are much cheaper than ceramic insulators!

My favorite source of project enclosures is products made for electrical wiring parts, especially the junction and switch boxes. You can see several examples in the photos below. The boxes are sturdy and cheap, and they are galvanized or plated. They make good shields since they are metal, which is extra important in the ham station where RF is present everywhere.

Most of these boxes have convenient holes for grounding and bonding connections. The boxes are inexpensive so if you make a mistake or decide to change a layout, you can start over very easily and cheaply. Ganged boxes can be joined together to make larger boxes. There are quite a variety of these metallic boxes available online or in the electrical section of your local hardware stores.

Electrical boxes have round “knockouts” for attaching conduit and cable clamps. There are three common sizes specified as “trade sizes” of 1/2, 3/4, and 1 inch. They mount in the body of the box with a small tab. Push on the knockout with a screwdriver to bend the tab, then flex it back and forth to break the knockout free. Threaded conduit clamps mount in the resulting hole. There are a large number of clamps and parts that mount in knockouts for different purposes.

Rubber grommets are available to avoid chafing a cable.

The conduit clamp is threaded and mounts on the box with a large nut similar to a toothed lockwasher. Tighten it by tapping on the nut’s serrations with a screwdriver while holding the clamp with pliers. The clamp is flat-sided to capture electrical cable and is tightened with screws. The clamp will also capture the flat side that is present on most threaded RF connectors. 

Smaller connectors, such as phono or phone plugs, will probably require a drilled hole or you can enlarge a pre-drilled hole. Another option is to use a pair of large flat washers to both fill the hole and hold a threaded connector.

If you are running coax or other shielded cable through the clamp, create a pigtail from the shield braid or wire that is long enough to wrap around one of the clamp screws. This allows you to make a good connection to the metal box.

Another nice thing about electrical boxes is that they are heavier than a similarly-sized aluminum or plastic box. This helps keep them in place when cables are attached or if controls or switches mounted on them are used frequently. Rubber or plastic stick-on feet work as well on steel as on aluminum, but be sure to clean the surface first since there may be some lubricating residue left from the manufacturing process.

Noise Pickup

A caveat about using plastic enclosures—unshielded enclosures for RF projects can allow common-mode noise to get into feed lines. (Noise refers to any unwanted signal picked up on the outside of the shield.) Noise currents flow to the end of shield on the outside and then enter the cable as a differential-mode signal.

If you can’t shield the enclosure, consider feed line chokes from ferrite cores on the cables to block the noise currents.

Surplus and Used Enclosures

An often-overlooked source of project materials is surplus, overstock, or used equipment. Popular online auction websites are a good place to find enclosures and other materials. Local sources include Craigslist and free “buy nothing” sites organized by location. You will also be able to find “service pulls,” which are equipment and devices designated as past their service life. You may have to buy several to get the best price, so share the savings with friends!

Along with hamfests, flea markets, and garage sales often include electronic gear that can be stripped for parts and hardware, with the enclosure left to be reused. Equipment cabinets for outdoor use, like the fiberglass box I bought surplus, are usually weatherproof, too.

Data and cable TV service boxes are widely available as surplus and usually have a basic weather-resistant cable entry. They are mostly plastic and unshielded but make good protective enclosures for cable connections and smaller devices.

The photo below shows such an enclosure used to hold a control circuit for switching a pair of receiving loops. Feed lines come in through the foam inserts at the bottom.

Obsolete instruments and equipment are usually constructed with solid, high-quality cabinets that cost a lot new. Panels and other metal parts can be cleaned in the dishwasher. Disassembling this type of equipment is an education in how electronic devices are assembled and provides a lot of useful hardware.

Taking this stuff apart is a great project for beginning electronics and ham radio hobbyists to build expertise (and a junk box)!

Holes in used enclosures can be filled with metal “hole plugs” that snap in place. Large holes can be covered with a piece of unetched PC board material or scrap sheet metal to maintain shielding. Older outdoor enclosures, particularly fiberglass or plastic, should be painted with automotive primer to protect and seal the surface.

Food and Novelty Containers

A popular activity in the QRP community is to build gadgets in the snap-together tins that hold Altoid mints. After all, they say, if the mints themselves were “curiously strong,” then why not the signal from a transmitter built in the same container?

There are even prototyping kits based on the tins such as this product from QRPme.com.

Don’t expect heavy-duty use from these lightweight, nearly disposable items. They are often painted and need to be scraped or sanded to bare metal around connectors and any overlap joints you expect to act as shielding. There are a variety of sizes from postage stamp-sized to large cookie and chip tins. The metal is quite thin, so drill with caution or use a punch to avoid tearing the metal. People have come up with all kinds of projects for candy tins, such as this Instructables collection.

Not only candy tins are pressed into ham service. Even tuna fish cans get into the act, like the legendary “Tuna-Tin 2” 40 meter transmitter. You can read all about this Doug DeMaw, W1CER, creation from 1976 at DIYRadio. Cans make great sub-enclosures in larger projects, too.

Hobbies and Crafts

Finally, hobby, outdoor, and craft stores sell a wide variety of containers and boxes that can be used for electronics. Metal toolboxes make very nice enclosures for electronics, particularly portable or mobile radios, and can even serve as a ground plane for a mag-mount whip! They are often lockable as a bonus. Larger coolers can carry an entire station, may have wheels, and are almost always water-resistant.

My VHF/UHF emergency communications station in the photo below was built in one such cooler. Watch for seasonal sales at the start of camping, fishing, hunting, and boating seasons.

Although they aren’t often used for projects, tackle boxes, compartmented trays, and storage boxes come in very handy.

These can be used to keep connectors, parts, and hardware organized and ready for action in the field. I save my chewing gum and peanut butter jars to make great hardware kits, even including a crimping tool with the terminals so everything is kept together and sorted.

The Eye of the Beholder

I hope this article gives you the idea that useful materials are all around—not only for enclosures, but for hardware and accessories, too. Using inexpensive materials lowers the “barrier to entry” for building your own gear and will make you a more capable and flexible homebrewer.

Editor’s note: For those less inclined to homebrew enclosures, you’ll find the DX Engineering Utility Enclosure Kit at DXEngineering.com. Check out this article on ways customers have put the DXE-UE-2P Utility Enclosure to work around their stations.

The post Ham Radio Tech: Inexpensive Project Enclosures appeared first on OnAllBands.

Most new hams start with an HT (handie-talkie) radio. They’re very affordable, portable, and will get you on the air quickly. No one has to think about batteries and chargers—they’re almost always included. The only real decision is whether you want to buy a spare battery. 

Going mobile doesn’t take a lot of thought either. You find a place for the radio and remote head, then follow your car manufacturer’s recommendation for power connections. Technically the battery isn’t free, but you already have it.

However, when it comes to field operations like POTA, SOTA, and all the other OTAs, you should consider several factors before investing in a portable battery system. Things like weight, size, durability, and capacity become important considerations.

Understanding LiFePO4 & Other Portable Battery Types

Power for portable operations can come from various sources, like generators, solar, wind, and batteries (the primary choice of portable operators). Lithium-ion (Li-Ion), sealed lead acid (SLA), gel cell, and absorbent glass mat (AGM) are among those available.

However, the most efficient battery choice is a member of the lithium-ion family, LiFePO4 (lithium iron phosphate).

LiFePO4 is superior to other lithium-ion batteries for a couple of reasons. Number one is safety. The LiFePO4 chemistry has better thermal stability than lithium-ion. It will remain cool at room temperature while charging, while Li-Ion heats up faster and may potentially suffer from thermal runaway. LiFePo4 battery systems also contain built-in battery protection modules to address concerns like overvoltage and balancing. You probably remember stories about hoverboards whose lithium-ion battery packs began overheating, which led to sparking, catching fire, or melting.

The voltage supplied by a LiFePO4 is a good match for today’s radios.

Each fully charged cell produces 3.6V. With four cells in series (4S), a typical LiFePO4 battery pack comes in at 14.4V. The nominal voltage is 3.3V per cell, making the working voltage about 13.2V—an excellent choice for a typical 100W transceiver. 

Li-Ion/LiFePO4 batteries maintain a flat voltage curve compared to sealed lead acid or absorbent glass mat batteries, which start dropping voltage right from the beginning. SLA or AGM runtimes will be considerably shorter than a comparable Li-Ion or LiFePO4 battery.

Though people still buy lead-acid batteries because of their low prices, LiFePO4 is a better bargain in the long run. When you consider the lifespan of each type of battery, the LiFePO4 will last more than 12X longer, yet only costs 3-4 times the price. Lithium batteries will also hold a resting charge much longer—LiFePO4 is typically rated at 5% discharge per month.

Each one of these battery types has its pros and cons, and you can find in-depth discussions online about the nuances of each battery chemistry. However, what matters is which best suits your particular application and provides your gear with the appropriate voltage and operating time. If you’re looking for a simple and effective portable battery solution almost custom-designed to power radio gear, invest in a LiFePo4 battery and charger.

Which Battery Works Best for Ham Radio?

Everyone is looking for maximum operation time in the smallest package. SLA, gel cell, and AGM batteries will do the job but have drawbacks for portable operation, especially with weight and available power.

I suggest that those new to these battery packs look for something that is safe, hassle-free, and performs well. The battery management system built into the lithium batteries avoids the “oops” factor—it won’t let you draw more than their rated capacity.

For that reason, the lithium-ion battery—specifically a LiFePO4—is a no-brainer, especially the Bioenno Power line.

For example, Bioenno Power’s BLF-1220A LiFePO4 Battery is ideal for stationary applications requiring a higher capacity and greater power output.

The integrated PCM (Protection Circuit Module) provides complete internal cell balancing and management, protection from overcurrent, undervoltage (over-discharge), overvoltage, and short-circuiting, as well as integrated charging circuitry. As shown above, the BLF-1220A can also be purchased as a combo with a 14.6 VDC charger.

It’s easy to find various lithium-ion batteries online with a casual search. The problem is that you can quickly become overwhelmed by all the choices. I consulted with several hams who have experience with portable operation and got some excellent advice.

• QRP operation (10W or less, CW/SSB): A good starting point is a 6 Ah LiFePO4. It’s relatively small and will keep you going most of the day. If you intend to add digital, consider 10-12Ah instead.

• 100W operation: Sometimes you need an extra boost, especially in crowded bands or with marginal propagation. About a year ago, a friend suggested I purchase a 20 Ah LiFePO4 and use it during the Ohio State Parks on the Air event. It was used for at least five hours on sideband, with power to spare. I prefer a battery capacity that meets my needs so I don’t have to worry about recharging in the field.

When you buy, be sure you have the proper charger for LiFePO4 batteries. Some come in battery/charger combos like the above example. SLA chargers are NOT compatible and may damage a LiFePO4 battery. Whatever you do, don’t compromise on your battery and charging system.

Useful Info

The following will help you get a better understanding of your battery needs and help you narrow the options.

How Much Power Am I Really Using? Weighted Average Calculation

Your radio doesn’t demand a consistent amount of power; rather, it varies according to the transmit time, receive, and transmit modes used. According to the Yaesu FT-891 mobile transceiver manual, the receive takes about 2W while the transmit may take as much as 23W. Sideband will draw less power than a continuous mode like FT-8 or RTTY.

Weighted averages will give you a better picture of power consumption.

Weighted Average Formula:

(x) * (power ₁) + (1-x) (power ₂)

Example

20% of time transmit at 100W

80% of time receive at 2W

0.20*100 + 0.82*2= 21.6 

11 hours of run time on 20 Ah LiFeP04 ([12v x 20 Ah]/21.6)

Don’t forget to account for accessories such as portable tuners.

Live Testing

Inline DC Power Analyzers and wattmeters allow you to measure and monitor the DC power consumption of your portable equipment. These DC power meters read voltage, current, watts, amp/hours, and watt/hours. They’re connected between the power supply and radio to help you monitor power consumption. 

You can also utilize these as part of your portable OTA gear, which gives you real-time information about your battery’s state while operating.

E-Z Match

Bioenno mobile transceiver compatibility guides cover the most popular radios. They are available on the DX Engineering website at the links below.

• Elecraft, Kenwood, Flex Radio
• Yaesu, Icom

In addition, Bioenno provides battery runtime charts for all their models

• Bioenno duty cycle guide 20/80 – normal
• Bioenno duty cycle guide 50/50 – contesting/Field Day

The post Ham Radio Tech: Choosing a Battery System for Portable Operations appeared first on OnAllBands.

This is the second installment of a two-part article about RF when you are operating “in the field,” meaning away from a fixed station.

For example, when you are operating a portable station for Parks On The Air (POTA), that’s considered “in the field” whether you are in an actual field or a parking lot or not even outside. Field Day certainly qualifies in most cases. In both parts of this article, the RF from your transmitted signal is what we’re concerned with.

Mechanical Concerns

We can start with some non-RF considerations that are certainly related to antennas, but not the radiated RF.

Most antennas used in the field are either ground-mounted or lower in height than at a fixed station. This, combined with the likelihood of their being in a public space, presents a variety of hazards to passers-by and other visitors. Your goal is to keep people from walking into, tripping over, touching, or otherwise getting too close to the antennas and feed lines.

The photo below shows a typical portable station with a table, tarp, and temporary antenna about 20 feet away in the background.

You can see the yellow rope placed around the antenna as a warning not to get too close. Plastic fence posts were used to hold the rope. Yellow caution tape is inexpensive and even more visible. Remember that many parks prohibit sticking anything in the ground, even for safety. In such cases, orange traffic cones are a good compromise.

Feed lines and power cords present a tripping hazard to both visitors and operators. If allowed, a stake in the ground next to the cables with a bit of yellow caution tape marks their location and can secure the cables. I always tie or secure the cables to a table leg so that if something does happen, the equipment is not dragged off onto the ground. (Don’t ask me how I learned to do this…)

Finally, don’t install your antenna where it can come in contact with vegetation. The end of an antenna element can present fairly high RF voltages, even at 100 watts output. This is enough to heat up leaves to the point where they will catch fire or at least smolder. Starting a fire is a definite no-no! (Don’t ask me how I learned this, either…)

Choose Your Words Carefully

Before we go any further, I need to remind you that the word “radiation” when referring to our transmitted RF may be accurate, but it is not a word the public or facility staff are comfortable with. I am careful to keep things simple and speak of “radio signals” instead of “field strength” or “radiation.” If someone asks about risks, you could truthfully tell them they might get a slight shock if they touch the antenna while you are transmitting. (If you are using an amplifier, it might be harsher than “slight,” so consider the possibilities.) Then explain that is why you have taken steps to prevent anyone from accidentally coming in contact with the antenna.

This is also a reminder to read or re-read the paragraph on preventing RF burns in the first part of this article, “RF Management—In the Field.”

RF Field Strength

The primary concern of this article is the high RF field strength near an antenna. FCC rules require us to evaluate the RF exposure from our fixed station antennas. Portable stations don’t require the same level of scrutiny, but you can use the same methods to determine whether your portable antennas might present a hazard to you or the public with respect to the Maximum Permissible Exposure (MPE).

Uncontrolled vs. Controlled

The allowed exposure levels are different for two kinds of environments—controlled (or operational) and uncontrolled (or general public). For a fixed station at our home, for example, the antennas are on private property and access to them is limited by property boundaries, fences, etc. This implies that anyone in the vicinity of the antenna either knows it is present or is there with your permission and supervision.

This is a controlled environment, and the MPE levels are higher because it is assumed the person can either take steps to stay away from the antenna or avoid being close to the antenna when the station is transmitting.

Uncontrolled environments are different and assume someone near the antenna is not aware of what it is or that it is present. They may approach the antenna at any time and are not assumed to be under your supervision, nor can they manage their own exposure.

For example, a vehicle-mounted antenna on your car in a parking lot can be approached by anyone in the lot. This is why the MPE levels are lower for uncontrolled environments. It’s safest that you assume these limits apply when considering how to construct and use your station.

High-Q Antennas

Another factor to consider is how your antenna radiates a signal and whether the RF field strength near the antenna will be particularly strong. The antenna’s ratio of stored energy to radiated energy is a measure of the antenna’s Q. Q is also known as quality factor, and for components, measures the ratio of reactance which stores energy to resistance which dissipates energy.

Antennas that store a lot of energy in the near field (within a wavelength or two of the signal frequency) can build up a surprisingly high field strength for any given power. These are known as high-Q antennas.

A high-Q antenna usually has a very low radiation resistance, which represents the antenna’s ability to radiate power into its far field, which is what launches our signals. The low radiation resistance means the antenna has to store a lot of energy for our transmitter output power to be turned into radiated signal (or heating in antenna system losses).

Imagine our antenna as a balloon being inflated by a compressor that delivers a continuous flow of air—this is our transmitter. The antenna’s radiation resistance is represented by a hole in the balloon through which air leaks out to the outside world (i.e., our transmitted signal). The balloon inflates until the amount of air leaking through hole balances the compressor’s output. The smaller the hole (the lower the radiation resistance), the higher the pressure in the balloon must be (the near field strength) for the leaking air to equal the incoming air.

The relationship between stored energy and radiated power and Q is clearly presented in a February 2013 QST article, “Q and the Energy Stored Around Antennas,” by Kai Siwiak, KE4PT. In the article, he describes and illustrates these important relationships and gives examples for real-world antennas.

For example, dipole antennas have a Q ranging from around 7 to 20, while small HF transmitting loops (a.k.a., a “magnetic” loop) can have a Q as high as 1,000. Antennas that are physically small compared to the transmitted signal wavelength generally have low radiation resistances and are high-Q. 

You can tell if you have a high-Q antenna if the SWR bandwidth of the antenna is low compared to a full-size antenna. Along with the small loops, this includes popular antennas like loaded whips that are often mounted near the ground.

Tune the antenna for an SWR of 1:1 at the operating frequency. Then find the two frequencies at which SWR increases to 2.6, F_U and F_L. Divide the square root of F_U x F_L by the SWR bandwidth, F_U – F_L, and that will give you Q.

For example, if SWR equals 2.6 at 14.275 and 14.295 MHz, Q = 714. That’s a high-Q antenna!

Bear in mind that losses in the feed line will make SWR look a little better at the meter than it is at the antenna terminals, so the actual SWR bandwidth is smaller and Q is higher.

How Safe is Safe?

Like most questions about antenna systems, the answer always seems to begin with “It depends…” So do answers about minimum safe distances for transmitting antennas.

The answer depends on operating frequency, antenna Q, and transmitter output power. Since every portable setup is a little (or a lot) different, you can’t be modeling or making complex calculations all the time.

To help amateurs deal with this complexity, the ARRL provides an online RF exposure calculator.

The following is a calculation for a 100-watt, 14 MHz station using unprocessed SSB with a 20% operating duty cycle and a ground-plane antenna with 1 dBi of gain.

Note that it’s safe to get pretty close to the antenna. However, if I turn on speech processing or operate more aggressively, such as during a contest or POTA activation, the minimum distance will increase. Similarly, using a mode like FT8, which has a 50% duty cycle of full power on periods, will increase minimum distances still further.

This short table is an excerpt from Table 5.7 of RF Exposure and You (see this article’s conclusion for how to obtain that book) that provides typical gains for some popular portable antennas. For a vertical dipole or end-fed half-wave antenna, use the half-wavelength dipole gain. For a “hex” beam, use the two-element Yagi gain. Loaded whips are less efficient than a full-size vertical, so that antenna’s safe distances are a conservative estimate for the whip.

Typical Antenna Gains in Free Space (dBi)

• Quarter-wave ground plane – 1.0
• Half-wavelength dipole – 2.15
• 2-element Yagi – 6.0

For the special case of a small HF transmitting loop, the minimum distances are larger, due to the higher stored energy of this very high-Q antenna. Siwiak calculates these minimum safe distances in his May 2017 QST Technical Correspondence item, “RF Exposure Compliance Distances for Transmitting Loops, and Transmitting Loop Current.” 

From that article, for a one-meter-diameter loop with five watts of continuous transmit power on the 40–10 meter bands, the minimum safe distance for the uncontrolled environment is 1.7 meters (5.6 feet). This increases to 2.1 meters (6.9 feet) at 10 watts output power. Table 17 from the FCC OET Bulletin 65B shows the safe uncontrolled distances for 150 watts increasing from 2.8 meters (9.2 feet) on the 40 meter band to 4.2 meters (13.8 feet) on 10 meters. 

Using an amplifier, such as for a special event or contest, with a small loop increases the minimum distances on 40 through 10 meters to 17.4 feet to 42.4 feet, respectively. (A two-meter-diameter loop on 80 meters requires 21.6 feet of separation at full power.) 

See Siwiak’s March 2012 QST Technical Correspondence article, “An Antenna Idea for Antenna-Restricted Communities” for more information.

Please Think About RF Safety

It’s easy to overlook these concerns in the “heat of battle” when you are just trying to get a station put together and on the air. Hopefully, this article will encourage you to consider antenna placement in the field. I see far too many pictures of portable setups where the antenna is a few feet away from a 100-watt transceiver. There are even photos of “mag loops” sitting right on a picnic table next to the operator! Don’t do that.

You can learn a lot more on the ARRL’s RF Exposure website. The excellent text reference RF Exposure and You by the ARRL’s Ed Hare, W1RFI, is downloadable at no cost as a PDF book. It has many helpful tables and examples.

I don’t think RF exposure is something we should be afraid of, but neither should we be careless in how we treat it.

The post Ham Radio Tech: RF Safety—In the Field appeared first on OnAllBands.

Whether you’re a seasoned ham or buying your first antenna, choosing the right one is more about how you operate as an individual and less about the antenna’s capabilities. In previous OnAllBands articles, I’ve explored field antennas and the decision-making process behind choosing the right one. I believe that a practical understanding of your operating style is key to making the best choice.

This article is about vertical antennas—specifically, those designed to be portable and stealthy. These antennas are ideal for field operations like POTA, SOTA, or IOTA, and for those living under HOA restrictions that prohibit permanent antennas.

There are hundreds of vertical antennas on the market, and it’s beyond the scope of this post to cover them all. Instead, I’ll focus on three models I’ve personally used, each representing different concepts and reasons why you might choose one over another.

All of these antennas are multi-band, and while some can be installed permanently with proper sealing, they are primarily designed with portability and ease of setup in mind.

Before diving into the specifics, consider these questions as you search for your next antenna:

1. What modes and power levels do you intend to operate? Ensure your antenna can handle the wattage and duty cycle of your chosen mode (SSB, CW, Digital). For example, an antenna that handles 100 watts SSB may not be suitable for 100 watts FT8.
   
2. What bands do you plan to operate? Confirm that the antenna covers your preferred bands. Portable verticals are effective on 20 meters and above but become less efficient at lower frequencies due to the need for loading coils to electrically lengthen the radiating element. This compromises performance and decreases operating bandwidth. However, I’ve had great success on 80 meters with some portable verticals, though they are less efficient compared to longer wire antennas.
   
3. How far do you plan to hike with this antenna? Check the specifications for weight and element lengths, as these factors will impact your comfort and the feasibility of carrying it in your pack.
   
4. How important is frequency agility? If you primarily operate FT8 and stay on one frequency for extended periods, any antenna will likely suffice. If you frequently move across bands to chase activators or DX, consider an antenna that doesn’t require manual tuning.

***

Three Types of Portable Verticals

Here are three vertical antennas I’ve used in the field, along with their pros and cons:

***

1. Quarter Wave Verticals

One of the simplest vertical antennas is the quarter wave. My first quarter wave antenna was a 5-meter radiator wire (one-quarter the length of 20 meters) with four counterpoise wires on the ground. I attached the radiator to the center of my coax and the counterpoises to the shield. I’ve deployed the radiator vertically in a tree (great for permanent setups) and supported it with a fiberglass telescoping fishing pole (ideal for portable use).

While these antennas are simple to build, I prefer an antenna that works on multiple bands and is easy to deploy and pack. This is why I’m a big fan of the Chelegance MC-750 .

The MC-750 is a portable vertical deployed using either a stainless ground spike or a tripod. The vertical element is a stainless steel whip with silk-screen markings that help you deploy the antenna for resonance on multiple bands.

When I follow the silk-screen markings and all four counterpoise wires (attached to the base), I consistently achieve a near 1:1 SWR. Thus, no ATU is needed. The SWR remains consistent across various topographies.

The MC-750 ships with a coil for 40 meters. Chelegance also offers an optional 80 meter coil as well.

• Pros: Easy deployment, high quality, efficient, multi-band use with no ATU needed, resonates on 20-10 meters and 40/80 meters with coils, comes with a custom padded carrying case. 
• Cons: Not truly a con, but you must adjust the whip length when changing bands if not using an ATU.

***

2. Verticals with Transformers

If you regularly use an antenna tuner in the field, you might prefer a high-quality multi-band vertical antenna equipped with a transformer to reduce potentially high impedances to a level manageable by most tuners. I think of this type of antenna as the vertical equivalent of a random wire antenna. Many of my QRP transceivers have internal ATUs, making this type of antenna very appealing. The one I have the most experience with is the Chameleon CHA MPAS Lite.

Like the MC-750, the MPAS Lite uses a stainless steel whip but includes a transformer at the base, making it easier to match the antenna across multiple bands with virtually any ATU. Additionally, it can operate on lower bands, including 80 meters, without needing a loading coil attached. While not as efficient below 30 meters, it remains highly effective for both POTA and SOTA where you are often the DX.

The MPAS Lite offers excellent frequency agility, which is a major advantage if you frequently hunt or chase other stations in the field. Just change the frequency, activate the ATU, and you’re set.

The MPAS antenna can also be configured as an end-fed random wire using the counterpoise wire. Consult the MPAS Lite manual for multiple configurations.

• Pros: Easy deployment, high quality, multi-band use, frequency agility, only one counterpoise, versatile platform for multiple antenna configurations. 
• Cons: Pricier than the MC-750.

***

3. Loading Coil Verticals

I’ve used several antennas with helically wound coils and a sliding tuning coupler at the base to match the antenna across multiple bands. The coil at the base shortens the antenna electrically, making it portable and low profile—ideal for stealthy use or in neighborhoods with aggressive HOA restrictions.

Among the many coil antennas available, the new REZ Antenna Systems Ranger 80 stands out for its robustness. I was impressed with its ease of setup, high quality, and smooth tuning coupler. The REZ Ranger 80 antenna also handles higher power than other coil systems—100 watts CW/digital and 200 watts SSB.

The Ranger 80 is quick to deploy and incredibly durable. While I’ve never been a big fan of verticals with loading coils and sliding tuning couplers, as they can be finicky to tune, I found the REZ Ranger 80 to be the best of the bunch and more forgiving than others I’ve used.

• Pros: Easy deployment, superb quality, higher power handling capacity, multi-band resonance, no ATU required. 
• Cons: Heavier than other options, tuning coupler needs adjustment for each band change, pricey.

***

Summary

Choosing the right portable vertical antenna is more about matching your equipment to your specific operating style than simply selecting the most capable model. Whether you prioritize ease of deployment, frequency agility, or power handling, the antennas discussed—like the Chelegance MC-750, Chameleon CHA MPAS Lite, and the REZ Ranger 80—offer distinct advantages that cater to different needs.

Before making your decision, consider the nature of your operations. Are you regularly chasing signals across multiple bands, or do you prefer to set up and stay on one frequency? Do you need a lightweight, portable solution for long hikes, or are you more concerned with stealth and ease of use in restricted environments? Your answers will guide you to the right antenna.

Ultimately, the best antenna is the one that enhances your enjoyment of the hobby, allowing you to operate confidently and efficiently in your chosen environment. If possible, try before you buy—borrowing from friends or club members can provide valuable insights that specs alone can’t offer.

The post Ham Radio Tech: Choosing a Portable Vertical Antenna that Matches Your Needs appeared first on OnAllBands.

There is no shortage of thoughts on what’s the ideal rig for making more QSOs when operating away from the home station, especially with the soaring popularity of POTA, SOTA, IOTA, BOTA, and other opportunities to have fun away from the shack.

Truth is, with so many excellent transceiver options, there’s no right answer. And if someone suggests that their answer is definitive, we suggest the following all-encompassing rebuttal courtesy of Jeff “The Dude” Lebowski: “Well, that’s like your opinion, man.”

If you’re new to ham radio or looking to upgrade your portable operating prowess, we’ve put together an informal, completely unscientific breakdown of what transceivers were used during Field Day 2024. The following is based on responses to a question posed on the DX Engineering Facebook page: “What radio did you use during Field Day?”

Like we’ve said many times before on OnAllBands, it never hurts to hear what others have to say about what works best for them. And keep in mind that the chosen radios were deployed to match a range of environments and goals—as well as price ranges.

Bottom line: Not everyone operates on Field Day the same way.

The rigs used on Field Day ranged from out-of-production radios to the latest SDR models from all popular manufacturers.

Editor’s Note: While you won’t find out-of-production transceivers through DX Engineering, items such RT Systems Radio Programming Software and Cable Combos for a wide range of transceivers, interface cables, power cables, tuners, speakers, microphones, transceiver mini-manuals, and other accessories are available for out-of-production transceivers at DXEngineering.com. 

Based on more than 120 responses, the usual transceiver suspects led the pack of the most-used rigs for Field Day 2024: Icom IC-7300 HF Plus 50 MHz Transceiver

Elecraft K3 and KX3 models

Flex 6000 Series Transceivers

Yaesu FT-991A HF/VHF/UHF Multi-Mode Transceiver

FT-891 HF/50MHz All Mode Mobile Transceiver

TS-590SG HF/6 Meter Transceiver

Other Popular Radios for Field Day

The above represents only a small portion of the diverse selection of radios put through their paces during Field Day 2024. Here some of the other Icom transceivers—many of which are no longer produced—that got a workout the weekend of June 22-23:

• IC-705 HF/50/144/430 MHz All Mode Portable Transceiver

Read this OnAllBands article on “Using the Icom IC-705 in the Field.”

• IC-7100 HF/VHF/UHF Base/Mobile Transceiver
• IC-718 HF All Band Transceiver: “A great workhorse,” per one Field Day participant.
• IC-7200 HF/50MHz Transceiver
• IC-7610 HF/50MHz All Mode Transceiver
• IC-905 VHF/UHF/SHF All Mode Base/Portable Transceiver
• IC-9700 VHF/UHF/1.2 GHz Transceiver
• IC-7410 HF/50MHz Transceiver
• IC-746PRO HF/6M/2M All Mode Transceiver
• IC-9100 HF/UHF/VHF Transceiver
• IC-706MKIIG Transceiver
• IC-703 (used for a QRP GOTA station)
• IC-756 All Mode Transceiver

The number of hams who chose Yaesu rigs ran neck and neck with those who opted for Icom. Yaesu transceivers included:

• FTDX10 HF/50 MHz 100W SDR Transceiver
• FTDX-1200 HF/50 MHz Transceiver
• FT-7200 UHF Transceiver
• FT-1000MP
• FT-710 AESS HF/50 MHz Base/Portable Transceiver
• FT-950 HF+6 Transceiver
• FT-847 HF/UHF/VHF Transceiver
• FT-897D HF/UHF/VHF Transceiver
• FT-450 HF/50 MHz Transceiver
• FT-736R VHF/UHF Transceiver

There was also a nice selection of Kenwood rigs on the air for Field Day, including:

• TS-590 HF/50 MHz Transceiver
• TS-2000 HF/UHF/VHF Transceiver
• TS-570D HF+6 Transceiver
• TS-450 HF Transceiver
• TS-850 HF Transceiver
• TS-870 HF Transceiver
• TS-480 HF/50 MHz All Mode Transceiver

The Ten-Tec Century 21 and Xiegu G90 were among other models mentioned.

***

Looking for the latest transceivers to upgrade your station for the next big event? Visit DXEngineering.com.

The post What Transceivers Did You Use During Field Day 2024? appeared first on OnAllBands.

For Guglielmo Marconi, the great challenge was to transmit wireless signals across the Atlantic and to all the ships at sea. He built stations at Poldhu, England; Glace Bay, Nova Scotia; and Cape Cod, United States—all near the ocean.

Was this done with a knowledge of oceanside propagation, or was it because he was in the business of ship-to-shore communication?

Those of us blessed with a waterfront residence on the east or west coast have much stronger communications links across the Atlantic or the Pacific than people living in the middle of the continent. We’ve all heard stories of antenna farms on or near saltwater marshes that get much improved signals. I even heard one about a ham with both feet in the Atlantic operating a low-power backpack radio with a whip and having a QSO with a station in France.

The “saltwater amplifier” is the increased ground conductivity near the sea, leading to more antenna gain. Average soil has a conductivity of 0.005 Siemens per meter, saltwater averages 5.0 Siemens per meter—an improvement by a factor of 1,000.

Do the math and that’s roughly 10 dB of gain. Imagine turning your 10-watt QRP radio into the equivalent of 100 watts.

Medium Wave Beside the Waves

Early on, some AM stations in the metro New York City area learned that oceanside towers can produce big signals. For more than four decades, High Island had been home to two of the biggest New York City AM signals: WFAN (formerly WNBC) on 660 kHz and WCBS on 880 kHz.

CBS’s station was so powerful that it could be heard as far away as Florida and Chicago on good days. Typical coverage included daytime signals up the coast as far as Cape Cod and down to Cape May. Then as now, CBS was one of America’s principal broadcasters, and the company found the saltwater ground system of Long Island Sound ideal for carrying radio waves.

Broadcasters have sometimes found some advantage or necessity to locate transmitter sites on islands. These islands vary from the isolated home of KUHB on St. Paul Island in the Bering Sea to the now defunct WMBL on “Radio Island” near Morehead City, North Carolina. It was the first radio station serving the area and was well known for its clear reception and surprisingly long range.

Gordo’s Ground Shootout

Gordon West, WB6NOA, once did a head-to-head comparison between a traditional copper-foil strip that went nearly all the way around his boat and a seawater ground. The results of his experiment were published in Sail Magazine. Using an Icom marine SSB/ham transceiver and Icom AT-130, he was careful to retune the antenna each time ground systems were switched for an accurate comparison.

While the copper foil capacitive ground did produce a usable signal, the seawater ground improved antenna power output considerably.

In addition, this configuration decreased the noise floor while receiving and increased sky wave signal strength. It also caused a four-foot fluorescent tube to glow brightly with modulation peaks.

He saw the light.

WSPR Test

Greg Lane, N4KGL, did a test comparing two identical verticals, one on the beach near the water and another inland, away from the beach. In addition, a low dipole was added to the mix to see if horizontal polarization made any significant difference. Only simultaneous spots were used for comparison.

Using a pair of identical WSPRlite transmitters on 20 meters, Lane first established a baseline with a WSPRlite attached to each vertical. Both were set up several hundred feet inland at the same distance from the ocean. Evaluating the 55 spots, all were similar in output and operation. Using a low-power wattmeter onsite showed no discernable difference in output.

Two trials were conducted with the saltwater vs. land antenna comparison. The first one had the antenna placed at the shore and the other 700 feet inland. The second trial had them placed 200 feet apart. Results showed the saltwater vertical always beat the inland vertical for any WSPR spot with an average 10.8 dB advantage. As expected, the closer the antenna to the water, the better the gain.

In the low dipole vs. saltwater vertical scenario, the saltwater vertical was better 32 times out of 33 spots, with nearly a 10 dB advantage. The only downside was higher radiation angles.

Overall, his observations appear to support the presence of a significant saltwater gain.

Radial Placement for Maximum Gain

The object of the saltwater effect is to improve the ground system for better efficiency. Rudy Severns, N6LF, reminds us when AC current (RF) flows in a conductor, the current tends to flow only near the surface. The ground current for a saltwater vertical antenna is restricted to a thin layer near the water surface (skin depth). This means radials need to be near the surface to take full advantage of the saltwater effect.  

Running a copper wire with a fishing weight (or several) to the edge of the surf would probably be sufficient for casual use at the beach. A floating radial on an anchored pool noodle would be a good solution in calm inlets and tidal pools.

Tides are a challenge. Local tides can range from a foot to more than 50 feet. That would significantly cover the radials and vertical element, changing the effective length of the antenna system. A workable long-term solution could be a floating dock or a float substantial enough to support the antenna. You don’t need a long radial—attaching a piece of sheet metal or screen several feet long to the bottom or side of the dock can provide a low-resistance ground without a trailing wire.

Several DXpeditions have used pairs of 1/4 wavelength elevated radials connected to vertical antennas directly over flooded reefs. The radials need to be kept well above the water surface, even at high tides, for best results.

Close Also Counts

The objective with a vertical monopole antenna is not just to have any ground connection, but to have a low-loss ground plane under the base of the antenna. Think of the ocean like a huge copper sheet, just not quite as conductive. Being within a few wavelengths of an ocean is the next best thing to having radials near or in the water. Walt, K4OGO, has some videos online that discuss antenna designs and setup for use on the beach.

Going mobile? When you park close to the sea, the radio waves go over the surface, reflect and bounce off into the atmosphere and skip, just like stones or pebbles across a pond.

Reflections on Saltwater Propagation

Seawater is too good of a conductor to pass radio waves—instead, it reflects them like a mirror off of its surface. Saltwater contains Na+ and Cl- ions. Saltwater is electrically conductive because these ions are free to move in solution.

You might argue that 10 dB is only a little more than 1.5 S-units, but it can mean the difference between “can’t hear a thing” and full copy.

This might be a good time to book that beach vacation to fish for some DX!

The post The Saltwater Amplifier Effect (& How it Impacts Your Amateur Radio Station Performance) appeared first on OnAllBands.

Power. It is one of the most important aspects of running an operation. But what if you don’t have access to AC power or a storm knocks out all power in your area?  

What Are Your Backup Power Options?

There are some differences if you are at home or in the field. At home you will want to power more than just a radio and its accessories—things like a refrigerator, air conditioning, and internet service.

What you want is an uninterruptable power supply (UPS). These can be as little or as large as you can afford. Most of us have small units connected to our computers for safe shutdown. There are room size UPS units that back up large data centers, hospitals, and other critical infrastructure.

The big question is how much runtime do you get? This is almost solely dependent on…

…you guessed it. Batteries.

Lead-acid batteries, most often deep-cycle, are a good choice for emergency power. They are rugged and have relatively low energy density. The deep-cycle option also handles a slow discharge well. They can be used with or without a battery box. A battery box can be purchased or homemade. The cost is on the lower side for batteries as well. The main disadvantage is that they can be extremely heavy, which is usually not an issue for home use.

The next option for home use is a generator, like the Generac GP3600 Series Portable Generator shown below. These can provide power for an extended time period and are rugged. However, generators are bulky and not easy to move. You also need to have fuel to power them and keep them running smoothly.

Solar is a good choice for home and portable use. It also has the advantage of being environmentally friendly. A solar cell, or photovoltaic cell (PV), is a device that converts light into electric current using the photovoltaic effect. Multiple solar cells are connected inside modules and modules are wired together to form arrays. The arrays are then tied to an inverter, which produces power at the desired voltage.

A large array for maximum power can become very expensive. Home solar systems often have a way to store excess energy and feed it back into the power grid. Portable solar panels come in many shapes and sizes that you can roll up, fold up, or fold over for easy storage. Straight panels that are more rigid are a good option as well.

You’ll find several solar power options at DXEngineering.com, including Bioenno Power foldable solar panels and solar charge controllers, and the Samlex Solar Portable and Foldable Solar Battery Charging Kit below.

So, what are some good options for people out on a field exercise or during a Parks on the Air activation?

A choice that is growing in popularity is a power station, like the A-iPower 300W Lithium Portable Power Station below. It includes outlets for USB and 12-volt power, with receptacle plugs for easy hookup and power supply. While power stations are relatively lightweight, they may not be the best option for tossing into a backpack from a weight perspective.

Another extremely popular option is the lithium iron phosphate battery. Lithium iron phosphate (LFP) is an inorganic compound with the formula LiFePO4. Some of its advantages include long cycle lifetimes, high power density, wide operating temperature range, and easy transportability due to its light weight. You can find a range of Bioenno Power LiFePO4 12VDC batteries (see the 12 Ah model below) and battery/charger combos at DXEngineering.com.

What is your favorite alternative or backup power? Questions?

Share them in the comments below or email me at KE8FMJ@gmail.com.

The post Backup Power for Home & Field appeared first on OnAllBands.

If you thought Parks on the Air (POTA) was the only portable operation event in town, meet BOTA.

Beaches on the Air promotes ham radio portable operation from beaches. BOTA has awards for activators (those who operate at the beaches) and chasers (those who contact them). Radio amateurs can participate from any beach, country, or region around the world. The program brings together thousands of hams from six continents, and new ones are joining every day.

BOTA now lists more than 30,000 beaches and they’re constantly adding new beaches as they become active. You may activate the same beach as many times as you like, gaining additional points each time. There are no restrictions on how you travel to the activation location or the power source you use for your station. BOTA invites you to submit your beach activation images and videos.

Besides promoting fun amateur radio practices, the program offers other benefits as well. It encourages participants to get out of their shacks, do mild exercise, increase their vitamin D levels, and work on their tans. It’s also relaxing to sit on the beach and sip your favorite beverage. Kick back, chill, and leisurely log those contacts. Don’t forget to tell everyone what a wonderful time you’re having during your QSOs.

Beach Operation

Conditions at the beach are quite different from POTA, IOTA, SOTA, and other ‘OTA activations. Be aware of tide schedules, high winds, and changes in weather. Locate yourself where you won’t have to constantly move away from an incoming high tide.

You’ll likely be inclined to bring more things: beach chairs, umbrellas, coolers, and other items. After all, it’s also a trip to the beach. Be realistic about what you can comfortably carry—sometimes it’s a long walk.

Five-gallon utility buckets are great for carrying coax, antenna parts, tools, and other supplies. After you’ve emptied it, the bucket can be flipped over and used as a stand for the radio. A pack seat will also fit in the bucket and give you a place to sit or set up additional equipment. Tote bags or backpacks will help keep your radios protected.

Securing your antenna properly is important. Most operators prefer a lightweight telescoping pole at the beach, like those from DX Commander or SOTAbeams, to hold a 1/4 wave of wire. These poles have a minimal wind load and those <31 feet will generally not need guys. To make them freestanding, you’ll need a sand spike—a tube for holding fishing rods or beach umbrella holder that screws into the sand. Be sure the bottom of the pole will fit inside before you invest in one.

The beach’s biggest draw for hams is the “saltwater amplifier,” nature’s reflector for your signals. Forget burying a batch of radials in the sand because you only need one. Run it toward the water at the edge of the waves or tie a fishing weight to the end and give it a toss into the waves. Add a quarter-wave wire vertical and you’re good to go. Using the saltwater ocean as counterpoise can give you up to a 10 dB gain. A 10W QRP signal becomes a 100W signal with a very simple antenna system—really awesome!

Getting Started with BOTA

Interested? First, create an account at BeachesontheAir.com. While you’re waiting for your registration to be processed, search for activators listed on the website. Listen to a few QSOs, then call when they’re on the air. The activating station will provide you with a code during the exchange.

After you receive the code over the air from the activator, sign into the BOTA site. Under the user menu, select “Add chaser report redeem code.” Enter the code. If you have just made the QSO, click yes and add the frequency and mode so a spot is placed on the BOTA home page.

You can also keep a log and enter it all later. You have one month to enter the code. If for some reason you have forgotten the code, you can enter the activator’s call sign and then choose the activation site. Activators and chasers are not required to submit logs.

When you’re ready, plan to become an activator. You’ll go to the BOTA website and choose “Announce activation, Generate code.” Search for your beach and complete the information required. Once saved, the Admin will review the beach. If there are no issues, it will be added to the system.

There’s also a Beaches on the Air Facebook group where you can find additional information.

BOTA Operation Procedures

Here’s a basic summary of the definitions, rules, and procedures:

Beach Activation Boundary: Defined as the area between the water and the road that runs parallel to the beach. This usually includes beach car parks and may include grassed areas, paths, etc. Keep in mind the program is “Beaches on the Air,” not “Across the road from a beach on the air.”

• Setup Location: Activators can set up a portable station or activate from a vehicle. Activators should abide by local laws regarding the setup of a portable station and obey any directives given by local authorities regarding station setup. Activators need to be aware of other beach users around them and always make sure that their setup is safe for themselves and others.
• Operating Frequencies and Modes: Any amateur radio frequency can be used and all modes are permitted where the activation code can be clearly transmitted. Repeater contacts don’t count.
• Multi-Person Activations: When two or more stations are activating from the same beach at the same time, all activators need to individually set up their information on the system and use their individual activation code over the air with their chasers. Each activator should take their own photo of the activation site and later upload it. There is no club/team scoring.
• Repeat Activations: It is possible to activate two or more different beaches on the same day using different codes, but you must physically move your entire setup from one activation to the other. There’s a minimum one-hour break between the end of an activation and the start of a different one on a different beach.

The post Getting Started with BOTA, Beaches on the Air appeared first on OnAllBands.

Whether you enjoy portable ops during Field Day, POTA, or SOTA, or just want a space-saving efficient way to get on the 40 to 10 meter bands, the high-inductance Recon 40 HF coil from REZ Antenna Systems is a great addition to your 17-foot HF vertical antenna.

Though the Recon 40 works great with the heavy-duty telescoping whip from REZ Antenna, you can use it with pretty much any 17-foot whip with a 3/8-24 stud mount.

In the video below, DX Engineering technical support specialist Michael Murphy, KI8R, gives you an in-depth look at this versatile HF coil and explains how its fast, easy HF band change capabilities make it a great choice for your amateur radio station.

Check out DXEngineering.com for the full lineup of gear from REZ Antenna Systems, including the Ranger 80 (80-10M) Portable Antenna System featuring HF coil assembly, heavy-duty military whip, radial kit, ground spike or aluminum tripod mount, and MOLLE backpack in your choice of five colors.

The post Video: REZ Antenna’s Recon 40 High Performance HF Antenna Coil—Perfect for 40-10M Portable Ham Operations appeared first on OnAllBands.

Tom K4SWL introduces the new Elecraft KH1 HF QRP portable handheld transceiver during a live POTA activation.