DX Engineering receives many questions from new (or new to HF) amateurs, and one of the most common is: “What kind of antenna should I use as my first HF antenna?”
Many people recommend a G5RV (which is very popular around the world), a horizontal loop, or some other multi-band “magic” antenna, along with tiny portable antennas to be installed on a photo tripod…the list goes on.
Let’s consider the G5RV for a moment. The G5RV is very well known, many new hams use it, and, sadly, it often ends in frustration because of poor performance, bad SWR, or RF in the shack problems. There are many, many resources on the Internet about the G5RV, so we won’t go into great detail here, but as W0BTU says in this article: “There are some bands where the SWR on the coax is out of sight and the feedline losses are astronomical.” He also has some other well-informed comments that you can read at the link provided.
The RF in the shack problem can be solved, but that costs money. DX Engineering offers products that will help, including an excellent Line Isolator in our Comtek line. Installing one close to the antenna, or two (one at each end of your coaxial feed line) can eliminate that problem for you.
So, what’s better than a G5RV? What’s the best solution?
Quite often, the simplest things are best. In this case, we recommend that you consider a simple, resonant dipole antenna, as shown below.
The best part about the basic dipole is you can get the parts and make your own very easily, and without spending a fortune. While the antenna in the diagram above will function well, it would be much better if you used a 1:1 balun in place of the center insulator, like the COMTEK Jerry Sevick W2FMI Series Current Balun COM-BAL-11150T.
Another option is to get a Bushcomm BA Series Monoband Dipole Antenna BA-40B (shown below). The Bushcomm BA-40B is a 40m dipole kit that has everything you need, including a balun, but without the coaxial feedline.
If you want more information on simple dipoles, the ARRL published a nice article that you can read here. If you have additional questions, call DX Engineering’s tech line at 800-777-0703.
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Tags: Dipole Antenna, G5RV, HF Antenna, Tech Tip, Tech Tip Thursday
There Ain’t No Free Lunch
OK. The English is bad but the title says it all. So many hams are looking for that “all band, does everything” HF antenna.
On VHF and UHF the “tuning” of an antenna is far less critical than on HF. The wavelengths at 144 MHz and above provide a naturally wide bandwidth so that you assemble the antenna and, in most cases, it just works. Nearly all transmitting antennas at VHF and above are resonant types.
There are basically only two classes of HF antennas: Resonant and Non-Resonant. Let’s look at resonant antennas first.
Resonant antennas include (but are not limited to) monoband dipoles, monoband and trapped verticals, mono-band and trapped multiband Yagis, and specialized multiband antennas like fan and parallel dipoles. Resonance may be designed into these antennas by the use of traps, linear loading, stubs, or by the natural resonance of the length of the radiator. With these antennas, resonance occurs only in narrow chunks of spectrum.
Non-resonant antennas include (but are not limited to) long-wires, un-trapped multiband verticals, off-center fed dipoles, and other compromise antennas. These antennas typically require a wide-range antenna tuning unit (ATU).
On HF, the wavelengths are long to very long and resonance becomes more critical. A dipole on 80 meters may have a useful SWR bandwidth of only 60 kHz or so. If you want to work 75 phone with an 80 meter CW antenna, you’ll need an ATU (better referred to as a transmatch) to compensate. All resonant HF antennas – ALL OF THEM – used outside their resonant bandwidth require the use of a tuner. If you are looking for an antenna that will cover 160 through 6 and work efficiently… that hasn’t been invented yet.
Non-resonant antennas may be force-fed using ATUs in conjunction with baluns or feedline current chokes. Baluns and chokes will keep RFI out of your shack and allow the tuner to force-feed the non-resonant antenna so that power is radiated instead of being lost in standing waves or impedance losses. For example, 43 foot verticals are 43 feet long to avoid accidental resonance. In other words, they’re designed to be totally non-resonant. Their balun or unun and associated ATU allow them to work across a very wide spectrum. The lower the frequency, however, the poorer the efficiency of these antennas becomes.
Compromise antennas require compromise solutions and support. There ain’t no free lunch!
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Tags: Non-Resonant Antenna, Resonant Antenna, Tech Tip, Tech Tip Thursday
Parts and tools used:
DXE-6UQ-CTL – Quad Shield 75 ohm Coaxial Cable
CNL-911 – Channellock Cable Cutting Pliers
DXE-CPT-659 – Coax Cable Stripper
DXE-SNS1P6QS-10 – Watertight Snap-N-Seal® Coaxial Connectors (10 per package)
DXE-SNS-CT1 – Compression Tool for Snap-N-Seal® connectors
Xacto style knife
A. Cut the DXE-6UQ-CTL F6 size Quad Shield cable square to the end. Use a CNL-911 cable cutter rather than diagonal cutters, which can compress the coax cable too tight when cutting.
B. Using the CNL-911 Cable Cutter, round the end of the coax cable.
C. Using the DXE-CPT-659 Coax Cable Stripper, prep the quad shield coaxial cable. Following the instructions for the tool, place the quad coax cable into the tool with the end flush to the tab. While holding the coaxial cable, rotate the tool around the coax about 5-10 times. When the cutting is complete, you will feel it move more freely. Remove the tool, pull the two parts off of the ends.
Per the specifications for the Snap-N-Seal connectors, the DXE-CPT-659 Coax Stripper Tool will make two cuts on the quad shield cable. 1/4” of center conductor and 1/4” of the coaxial cable jacket will be removed exposing the braid & foil shield.
Note: Some people like to have a longer center conductor. The DXE-CPT-659 can be modified by removing the small stop tab, which allows you to insert more coaxial cable, which will result in a longer exposed center conductor.
D. Fold back the outer braided shield onto the black outer jacket (a small stiff bristle brush works good for combing the braid back) as shown. Carefully remove the first layer of foil to expose the second braided shield. Once this foil is removed, fold the braided shield onto the outer jacket as shown. You can leave the bottom layer of foil, or remove it to ensure nothing will migrate and short out the connector.
E. Insert the trimmed coaxial cable into the DXE-SNS1P6QS Snap-N-Seal® connector. Pushing in the cable while having the connector braced against a stop helps while you push in the cable. Push until the center insulation is flush to the inside lip looking in the end of the connector.
Note, if you modified the DXE-CPT-659 cutter to allow a longer center conductor being exposed, you will have to ensure that when pushing the cable into the connector, you do not bend the center conductor when you are pushing against a brace. (Just a suggestion: Use a 2” x 4” piece of wood with a small hole drilled that will fit the center conductor and place the connector over that hole while pushing on the cable).
6. Fully seat the coax cable with connector into the DXE-SNS-CT1 – Snap-N-Seal Compression Tool and squeeze the handles completely so the tool completely seats the compression ring end into the connector body.
7. Remove the cable from the compression tool. Done.
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Tags: Quad Shield Cable, SNS Connectors, Tech Tip, Tech Tip Thursday
When assembling any aluminum tubing sections together you should take the following steps:
1. Make sure the edges are smooth and not sharp. Deburring may be necessary, since burrs and shavings can occur on seams as well as edges. All surfaces need to be completely smooth to allow easy assembly of tubing sections. DX Engineering’s aluminum tubing adheres to the stated specs closely so even the theoretical clearance between sections is very small. On the order of 4-thousandths of an inch total clearance (2 thousandths on the radius), it won’t take much dirt to cause a jam when the next size tube is inserted.
The raised particles and shavings that appear when the aluminum tubing is machined are referred to as burrs, and the process by which they are removed is known as deburring.
Deburring is a finishing method used in manufacturing. Our aluminum tubing is machine-cut on both ends. The slit tubing is also machine slit on one end. You should further assure that there are no ragged edges, burrs or protrusions.
DX Engineering recommends the DXE-UT-KIT-DBR Tube Deburring Tools, or the DXE-22600 Deburring Tool with Extending Handle and Extra Blades for this operation.
2. Clean the outside of the aluminum tubing to clear any dirt or foreign material that would cause the clamps to malfunction during assembly.
3. Clean the inside of the aluminum tubing to clear out any dirt or foreign material that would cause the aluminum tubing sections to bind during assembly. Do not use any type of oil or general lubricant between the aluminum tubing sections. Oils or general lubricants can cause poor electrical connections for radio frequencies. The use of JTL-12555 Jet-Lube™ SS-30 is highly recommended. SS-30 is an electrical joint compound which affects a substantial electrical connection between metal parts such as aluminum tubing or other antenna pieces. Using SS-30 assures high conductivity at all voltage levels by displacing moisture and preventing corrosion or oxidation.
4. When assembling the aluminum tubing sections, ensure the area is clear of grass, dirt or other foreign material that could cause problems during assembly of the closely fitted aluminum sections.
Stainless Steel Element Clamps (DXE-ECL Series) are available from DX Engineering. Slide all the DXE-ECL element clamps over each aluminum tubing section as needed before putting the tubing sections together. You can lightly tighten the element clamps just below the slits on each of the aluminum tubing sections to hold them until needed.
Align the element clamp screws on each aluminum tube section to face the same direction. At final assembly, the body of the element clamp should be positioned between the slits in the aluminum tube and approximately 1/8″ from the edge of the aluminum tube, as shown.
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Tags: Aluminum Tubes, Tech Tip, Tech Tip Thursday
Many homeowner associations (HOAs) frown on ham radio antennas. So dedicated hams are forced to get creative, often turning landmarks into operable antennas.
John did just that, and shared his project with us this week.
John lives in The Villages, Florida, where more than 350 other hams reside, and 227 are members of the K4VRC ham radio club. He recently completed a custom-built antenna/flagpole project with the help of DX Engineering, and mailed us the following pictures and descriptions of the project.
John included a note that reads: “Tim, K3LR + Mark, W8BBQ: Thanks for time taken to answer my ‘many one last questions.’ Pictures are worth a thousand words and so is DX Engineering!”
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Tags: Antenna, Flag Pole
It’s Time to Tighten Up!
Every six months I go around to every connector and screw terminal in my station and make sure everything is tight. Many noise problems come from connections or connectors that are not properly seated or tight. It is amazing what I find!
It is a good idea to check your antenna VSWR. If it got better or worse since the last time you checked it, that can be a sign that something has changed and needs to be investigated.
Thanks for reading, and check back each week for new Tech Tips!
– Tim Duffy, K3LR
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Tags: Cable Connectors, coaxial cable, Control Cable, Tech Tip, Tech Tip Thursday