Many hams equate frequencies and bands with colloquial usage. Therefore VHF is 2 meters, specifically 144 to 148 MHz, and HF is 160 through 6 meters, just like on our HF radios.

Oops. VHF refers to Very High Frequency, and is a chunk of radio spectrum from 30 to 300 MHz- all inclusive. That places 6 meters, 2 meters and the 220 MHz band all in VHF. Therefore, 6 meters is NOT an HF band.

OK, then 160 through 10! –Nope-. Technically, the bands within 300 kHz to 3 MHz are Medium Frequency, or MF bands. Since 1.8 to 2 MHz falls squarely within this range, 160 meters is an MF band- NOT HF.

The International Telecommunications Union (ITU) radio bands are designations defined in the ITU Radio Regulations. Article 2, provision No. 2.1, states that “the radio spectrum shall be subdivided into nine frequency bands, which shall be designated by progressive whole numbers in accordance with the following table.”

VLF: Very Low Frequency; 3 to 30 kHz, 10 to 100 km wavelength

LF: Low Frequency; 30 to 300 kHz, 1 to 10 km wavelength

MF: Medium Frequency; 300 to 3000 kHz, 100 to 1000 m wavelength

HF: High Frequency; 3 to 30 MHz, 10 to 100 m wavelength

VHF: Very High Frequency; 30 to 300 MHz, 1 to 10 m wavelength

UHF: Ultra High Frequency; 300 to 3000 MHz, 10 to 100 cm wavelength

SHF: Super High Frequency; 3 to 30 GHz, 1 to 10 cm wavelength

EHF: Extremely High Frequency; 30 to 300 GHz, 1 to 10 mm wavelength

THF: Tremendously High Frequency; 300 to 3000 GHz, 0.1 to 1 mm wavelength

There are the radio bands in a nutshell. So, where does 70cm fit in? UHF, of course! It’s there, along with 33cm, 23cm and 2.4 GHz (12.5cm).

Simple, isn’t it? So, memorize it for a test next Monday.

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Many amateur radio projects use fiberglass tubing and there are some precautions you should take when handling it.

When the tubing arrives – before you open the box – be prepared. There may be fiberglass dust, slivers or particles present when the fiberglass parts were manufactured. Your best bet is to open the box outside, not in your dining room……

The use of typical fiberglass handling safety gear (gloves, dust mask, eye shield, clothing, etc.) when handling and working with fiberglass is highly recommended. Use a disposable damp rag to wipe the parts.

Do NOT use compressed air to clean fiberglass parts. The loose fiberglass particles and dust will fly all over the place.

When working with fiberglass, take precautions, especially when cutting or slitting the tubes. A hand saw or a power saw will make fiberglass dust. Wear protective gear to ensure you do not get any of the particles or dust in your eyes or in your hands. Wear a good dust mask to ensure you do not breathe in any of the particles or dust.

Measures can be taken to reduce exposure after a person has come in contact with fiberglass. Eyes should be flushed with water and any area of exposed skin should be washed with soap and warm water to remove fibers.

Clothing worn while working with fiberglass should be removed and washed separately from other clothing or just disposed. If you do wash the cloths, the washing machine should be rinsed thoroughly after the exposed clothing is done to ensure any loose particles are rinsed away.

Check with your local or state safety and/or environmental agencies for more detailed precautions. The easiest way to find out more information is to Google “Fiberglass Safety”.

 


An antenna analyzer is a useful tool for adjusting commercial as well as homemade antennas.

The primary use of an antenna analyzer is to determine the current resonant frequency of an antenna to allow adjustment to the desired frequency; however antenna analyzers can also be used for other tasks, including:

* SWR, Complex Impedance, Vector Impedance measurement
* Return Loss, Inductive Reactance, Capacitive reactance
* Electrical length of a section of coaxial Cable (Select models)
* Feedline loss of a length of Coaxial cable
* Frequency Counter and signal generation
* Graphing display (Select Models)
* Memory for storing graphs (Select models)
* Multi language display (Select models)
* Frequency range scanning (Select models)

A table of Antenna Analyzers and available features can be found at the following link:

https://static.dxengineering.com/global/images/chartsguides/c/cma- caa500markii_it.pdf

Selection of an appropriate analyzer is primarily based on the range of RF frequencies that you need to measure.
Secondary consideration would be the need for features that are available only on certain analyzers.

In general, HF only analyzers are less expensive than those that also include VHF,UHF
and microwave capabilities. Some analyzers can handle reference impedance SWR measurements
for standard impedances other than 50 ohms, such as 25,
75 and 100 ohms. Depending on the analyzer, the RF connector may be
BNC, PL-259 or N connector; some include N to PL-259 adapters.

Some analyzers have memories and the ability to connect to a USB port on your computer to download memorized measurements for later reference and analysis.
This can be very useful for “what has changed” investigation.


For many decades there was only one choice. Power supplies had heavy iron transformers to convert house current (110/120 volts AC) to the lower voltage required by many solid-state devices. As the demand for more and more current increased so did the weight of the transformer and the complexity of the circuitry making the DC. These are referred to as linear power supplies.

Then a strange thing happened: The heavy transformer went away. Switching power supplies (also called switch-mode power supplies or SMPS) arrived and changed how DC was made. Without the heavy transformer (solid-state devices are used) power supplies could be made smaller and lighter while providing the same output current.

So… which method is best?

The answer to that question depends on your intended application. In applications where size and weight are major considerations the switching supply wins, hands down. Because large iron-core transformers are also expensive, switching supplies can be less expensive than linear supplies. Size weight and cost are three BIG advantages!

In applications requiring a low-noise highly regulated DC output, such as laboratory equipment, sensitive radio receivers, test equipment and bio-medical equipment, linear power supplies still have a slight edge. The requirement for completely noise free output overrides the advantages of the switching power supply in certain circumstances.

Noise?

Switching power supplies use high frequency switching transistors to make the output current. The generation of high-amplitude, high-frequency energy requires that a low-pass filter must block the high frequency noise at the output to avoid electromagnetic interference (EMI) and ripple voltage at the switching frequency and its harmonics. Very complex filtering developments have almost completely eliminated this problem. Very low cost SMPSs may couple electrical switching noise back onto the AC power line, causing interference with Audio/Video equipment and any other electronic equipment connected to the same AC phase. This is still a major problem in poorly designed, cheaply made SMPS units flooding into the US market from overseas.

What’s the bottom line?

Dollar for dollar switching power supplies usually provide more power for less cost. They are also smaller and lighter than standard iron-transformer linear power supplies. In applications where switching noise is not an issue, they are clear winners. Most switching power supplies sold for Amateur Radio use by reputable companies are noise free. Where size, weight and cost are secondary to high-quality low-noise DC output, linear supplies still have an edge.

Understand the requirements for your application and read the specifications for the available power supply types that meet your need. Then make your choice carefully, keeping your application solidly in mind.


 

Choosing the right coax may seem complicated given the wide variety of cable types, their specs and costs. When we talk about coaxial cable loss, keep in mind that it affects transmitted energy as well as received signals. At 38 cents per foot, RG-8X is attractive, especially when putting up a new antenna system.   However, at 150 MHz, 100 feet of RG-8X has 3.8db of loss. So on the 2 meter band with 50 watts transceiver output, you would lose more than half of your transmitted power! Your station’s receive performance would suffer as well.

DX Engineering 400MAX is a better choice for VHF base applications. At 150 MHz, the loss of  100 feet of 400MAX is only 1.8db. RG-8X is fine to use for short coax jumpers and in mobile applications. You have probably noticed that most mobile mounts use either an RG-58 or RG-8X.  That is because at such a short run the loss is negligible. For HF base applications RG-8X is a popular choice with only 0.9 dB of loss at 10 MHz and 1.4db at 30 MHz for every 100 feet. It is certainly acceptable to use higher quality low loss cable on the HF bands. Many amateurs choose DX Engineering 213 or 400MAX because both are suitable for direct bury applications.

Feel free to contact DX Engineering anytime you have questions about the right cable for your application.


Combination SWR Meters (sometimes called SWR Bridges) and RF Power meters (also called watt meters) are useful accessories in the ham shack. They provide information about transmitted and reflected power, and Standing Wave Ratio (SWR). Prices can range from about $80 for utility meters to over $500 for commercial grade meters.

Selection Criteria:

Maximum power you will likely be using: Meter reading accuracy is best when the power reading is over half scale. Some meters are for low power only (20 watts) others high power (2,000 watts) and some meters have switch selectable ranges (20 / 200 / 2,000 watts)

Frequencies you will be measuring: Be sure to select a meter designed for the frequency ranges you will be measuring. Some meters are designed for HF and VHF frequencies, others for VHF and UHF frequencies

Ease of viewing: Meters with larger faces are easier to view. Some meters have lighted meter surface for improved viewing in low light environments (typically requiring a 12V DC power source for the lamp)

Single or Cross-Needle Display: Most users find the cross needle variety more convenient. One needle measures forward power, the other needle measures reverse power, and a graph on the face of the meter beneath the point where the two needles cross reads the SWR.

A single needle meter has a switch to select forward or reverse power display.

Accuracy Requirements: Inexpensive SWR / Watt meters are accurate enough for general amateur use, typically better than +- 10%. Where a greater degree of accuracy is needed, a commercial grade directional wattmeter is needed at a significantly higher cost.


Most amateur radio operators (hams) know they should weatherproof any coaxial cable connections that are outdoors to prevent moisture entering your coax connectors.

However, many hams don’t realize you must also protect lightning protectors if they are mounted where rain, snow or other foul weather may be present.

One of the most popular brands of lightning protectors that have been around for years is PolyPhaser. In their instructions (who reads instructions?), PolyPhaser warns that the lightning protector are NOT weatherproof and need protection. Most other brands are also not weatherproof.

If you don’t weatherproof the lightning protectors, moisture can get inside and ruin the protection and possibly do damage to your transceiver by reflecting too much RF.

Not all products are equal. Some can make disassembly difficult, others can make it easy. At DX Engineering, there are a number of products that can be used to weatherproof your lightning protectors, yet still make them easy to service.

The recommended way to weatherproof a lightning protector, once it is mounted and the coaxial cables are connected, is to completely encase the protector and coax connections with Scotch 33 or Scotch Super 88 tape. Once the tape is in place, use Self-Adhesive moisture sealant pads, tape or Temflex Rubber Tape to again, completely encase the protector and coaxial cable connections. But wait, there’s more – One more layer of the Scotch 33 or Scotch Super 88 and then job is complete.

Someone just asked – ‘Why the first layer of tape?’  Ahhh – that’s what makes getting all that sticky stuff off without having problems with residue left on the lightning protector or coaxial cable connections.

Remember – Three Layers: Tape, Sealing material and then Tape. This winning combination will you keep your station in top operating condition.

Recommended DX Engineering products:

TES-06132      Scotch 33 tape

TES-06143      Scotch 88 tape

TES-06147      Scotch Moisture Sealant Tape

TES-06149      Scotch Moisture Sealant Pads

TES-2155        Scotch Temflex Rubber Splicing Tape

DXE-WK-2    Scotch 33 tape and one 3” x 6” Self Adhesive Weatherproofing material

DXE-WK-3    Scotch Super 88 tape and one 3” x 6” Self Adhesive Weatherproofing material