Dipole and broadband antenna efficiency is a constant debate. Efficiency most commonly is watts in, watts out. It’s well known that to radiate well, horizontal antennas should be at least a quarter-wave above the ground, at minimum, to reduce ground losses. With this in mind a 40 meter monoband dipole antenna needs to be at least 33 feet off the ground; a 20 meter antenna would be at least 16 feet, and so on.
With a multiband broadband antenna, this is not practical. For an efficient 160 through 10 meter broadband operation your antenna would need to be mounted at least 130 feet high. If, on the other hand, the antenna is physically too short (compared to a quarter-wave radiator) you can mount it at 130 feet and the radiated power will be diminished when compared to a longer antenna, even though the broadband VSWR might look fine.
Broadband antennas are a perfect example of “you don’t get something for nothing.” They are convenient to use, but the trade-off is variable levels of “efficiency” at any given frequency. However, when space is limited they are a Ham’s lifesaver!
Now that antenna analyzers are fairly common, you might try this on Field Day: Connect to a resonant 20 meter dipole, then raise and lower the antenna from about 30 feet to ground level. You’ll find it interesting to watch in real-time as the VSWR vs. resonant frequency vs. reactance changes in relation to height. Height above ground does matter!
A word about NVIS: NVIS is Near Vertical Incidence Skywave. That’s a fancy way to say that your signal is going nearly straight up. Horizontal antennas operated below a quarter-wave in height exhibit more NVIS radiation than those placed higher. For a low-mounted 40 meter antenna, that means your signal is going to radiate upward, bounce off the ionosphere nearly above you, and return to Earth a few hundred miles away. No good DX operation there!
So, what’s our bottom line? Higher is better. Higher mounting of all horizontal antennas reduces ground loss, lessens VSWR fluctuation, reduces NVIS radiation and improves efficiency and DX operation.
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Tags: Antenna, Antenna Analyzer, DX Engineering, Tech Tip, Tech Tip Thursday
Below is a guest post written by Hal Turley, W8HC, of the 3Y0Z DXpedition team.
Turley and other members of the Bouvet DXpedition team visited DX Engineering’s headquarters last week to review some of the challenges the remote Bouvet island might present.
One of the many challenges facing the 3YØZ team will be in erecting and securing their antennas within the harsh conditions offered by Bouvet Island.
Current plans call for 10 HF yagi beam antennas, 7 low band verticals and 2 EME antennas, one each for 6m and 2m.
Raising, supporting and guying antennas on a snow packed glacier each present their own set of unique challenges such as, “How do you securely anchor a guy rope in snow pack?” Enter into the equation sustained winds in the 30-40mph category with possible wind gusts of up to 100mph and things can become even more complicated.
Obviously the best case scenario would result in the installation and setup of the antennas only one time — without having to do any maintenance and repair during the operation!
Ask any seasoned DXpeditioner, “What would you rather do, operate a pileup or, go out into the cold, wet, windy weather to fix the 20m beam that has unexpectedly crashed down into the snow?”
The last thing they want to do is antenna and/or mast repair on-the-fly especially when the weather can hand out some pretty nasty conditions in this, the sub-Antarctic region of the south Atlantic.
In an effort to proactively eliminate these visits from “Murphy” before they happen, our team decided to look at the options available for designing, fabricating and installing what might be considered the “best” structural antenna support systems working within the parameters of:
- Transport logistic requirements (truck, cargo vessel and helicopter)
- Ease of assembly
- Ease of installation
- Structural integrity of materials
- Interchangeability of components
- System reliability and security
- Weather and substrate conditions
- The “POM Factor” = Peace of Mind
3YØZ team member Glenn Johnson WØGJ had been tasked with spearheading antenna and mast support procurement for the DXpedition and had developed some ideas for producing a functional system designed specifically for our Bouvet operation.
Glenn readily admits he is not an engineer and so the question was, “Who do we turn to to ensure we have what we need for our antenna support systems within this framework and, in accordance to engineering specs and standards?” After all, we are not talking about rocket science here but rather “DX” and “Engineering!”
So there was really only one place to turn for this solution– the “Big Guns” at DX Engineering, who also happen to be a major sponsor of the 3YØZ DXpedition.
This past Wednesday, January 11th, five members (that’s 25%) of 3YØZ team converged on DX Engineering’s amazing Tallmadge, OH location. DXE Chief Operating Officer Tim Duffy, K3LR, and DXE Projects, Promotions and DXpedition Coordinator Teri Grizer, K8MNJ, rolled out the red carpet for team members Glenn, WØGJ, Ralph, KØIR, Jim, N9TK, Jerry, WB9Z, and Hal, W8HC.
Valerie, NV9L, who will be serving as chief pilot for the DXpedition, was also on hand and did a special on-location broadcast segment that evening providing a first look at the 3ØYZ Bouvet DXpedition for Ham Nation (episode 282). If you haven’t seen it, it’s well worth the watch.
But the primary purpose for the meeting was to have an opportunity to sit down with Tim, K3LR, and members of his outstanding engineering group to discuss the project and arrive at an agreed-upon conceptual model for the 3YØZ antenna support systems.
Glenn had indicated he wanted to utilize the “falling derrick” model and after a couple hours of brainstorming and discussion, it didn’t take long for the visiting members of the 3YØZ team along with Tim, K3LR, and his able DXE engineers Chris Cummings, KD8JKO, Ed Merical and DXE Engineering Manager KC8YSU to arrive at working models for the masts, the falling derrick and the guy anchors for the snow. Prototypes will be available for approval in February and there is a good chance you will be able to see this Bouvet mounting system at the DX Engineering booth in May if you intend to visit the 2017 Dayton Hamvention.
Earlier in the morning at the meeting kickoff, Tim Duffy told the 3YØZ visitors, “DX Engineering wants to be a big part of this incredible DXpedition. We’re all in with you guys.”
By the end of the evening, there was no mistaking that DX Engineering not only supports the 2018 3YØZ Bouvet DXpedition as a “Major Corporate Sponsor,” but they are, in fact, 100% committed to making this DXpedition a success.
Ralph, KØIR, concluded, “We are extremely grateful to Tim and his outstanding team at DX Engineering for this incredible level of support and commitment to the 3YØZ project. We look forward to continuing this partnership with them over the course of the next several months leading up to our trip and successful 2018 DXpedition to Bouvet.”
– Hal Turley W8HC of the 3YØZ Team
See pictures from the 3YØZ DX Engineering visit here:
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Tags: 3Y0Z, Bouvet Island, DXpedition
Do I need an antenna analyzer? If I do, how do I choose which one to get?
This is a question many new (and experienced) amateurs face today. There are many styles and types of antenna analyzers available, and it’s not easy to sort them all out, even for experienced Hams.
Antenna Analyzers have been around in one form or another for a couple of decades, but only recently have essentially “lab grade” hand-held devices become available at reasonable prices.
RigExpert has been producing digital hand-held antenna analyzers for around 10 years beginning with the AA-200 model. The AA-200 introduced a digital display, USB interface, and storage of measurements in on-board memory. Newer RigExpert models offer even more features at a reduced cost. The model number indicates the highest frequency the analyzer is designed for; in the case of the AA-200: 200 MHz.
So, what should you do if you are dabbling with HF and want to build some dipoles, or other simple HF antennas?
Both of these are economical, and offer coverage for HF, and the AA-54 even adds 6 meters!
The AA-54 costs $100 more, is it worth it?
The short answer is: Yes!
The RigExpert AA-54 adds some very useful features and capabilities including the “Multi-SWR” feature, and the ability to store / name 10 different SWR measurements for downloading to your computer.
Rig Expert has several other models ranging up to 1.4 GHz. Some of them use full color displays and more unique features. See them all at DX Engineering’s Rig Expert Antenna Analyzer Page!
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Tags: Antenna Analyzers, Rig Expert, RigExpert, Tech Tip
Much of the newer ham radio receiving gear uses F-Connectors. Most everyone is familiar with this type of connector. You find them on the back of your TV set, your PC’s Router, cable modem, DVD recorder and more.
One thing in common with using the F-Connector in these applications is the frustration of trying to get the connector on tight. The other frustration is trying to get a tightly installed connector loose. This is especially difficult when more than one F-Connectors are near each other, making the a standard wrench or pliers nearly impossible to use.
DRUM ROLL…We have the answer!!
“A picture is worth a thousand words.” So, in this case, here are 5,000 words:
The DX Engineering Connector Tightening Tool makes it easy to install and remove F-connectors in tight and hard-to-reach locations with minimal force.
This handy tool can be purchased by itself (DXE-CIT-1) or you can get it in the complete F-Connector Coax Cable installation kit (DXE-UT-KITF).
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Tags: F-Connector, Tech Tip, Tech Tip Thursday
From Contest University Chairman and DX Engineering Chief Operating Officer Tim Duffy, K3LR:
I am proud to announce that student registration is now open for 2017 Dayton ConTest University (“CTU”) to be held all day on Thursday May 18, 2017 at the Crowne Plaza in Dayton, Ohio.
Check out the NEW CTU Website: https://www.contestuniversity.com/
Eight different countries have hosted CTUs over the eleven years: USA, Australia, Russia, Germany, Italy, England, Brazil and Finland. Over 5,000 students have attended these CTUs with more than 100 CTU Professors sharing their contesting experiences.
2017 will be the eleventh year in a row for CTU Dayton. To give you an idea of the quality of the CTU content and activities, the 2016 CTU topics (last year) are listed on the CTU website.
The 2017 CTU Professor line up will be outstanding and is being finalized. Check the CTU website often for updates on 2017 Professors.
There are scholarships (registration fee) available from CTU through a grant from the Northern California DX Foundation (NCDXF) for those students 25 years old and younger. Please use the ‘Contact Us’ button on the CTU website to get more information. 2017 Student registration information is on the CTU site as well.
Important: as we did last year, if you want to sign up for CTU 2017 Dayton and you have given (or will give one by Dayton 2017) a talk about Amateur Radio to any club, Hamfest or group since May 17, 2016, you qualify for a $10.00 registration fee discount. Please choose the “Registration with Club talk discount” option to get the $10.00 discount. Spreading the word about amateur radio is lots of fun and can save you money at CTU!
Thanks to all the CTU sponsors, including Icom America, DX Engineering, the Northern California DX Foundation, the Radio Club of America and CQ Magazine for making CTU possible. Thanks to K8MNJ and K1SO for all of their help with CTU. Special thanks to Scott, KA9FOX, from QTH.com for hosting and constructing the brand NEW CTU headquarters website.
CU in Dayton at CTU 2017, and Merry Christmas,
Tim, K3LR, Contest University Chairman
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There is a small bit of homework required to establish the turning radius of an antenna. You have to figure out the hypotenuse of a right triangle.
For this exercise we are using the following definitions for the formula:
R = Turning Radius
B = Boom length from center of the mast
L = Longest Element Length from Boom
The diagonal line [R] (hypotenuse) in a right triangle can be figured out using the following information:
Width of the triangle [B] would be the distance from the center of the mast to the end of the antenna boom. Note: some antennas are offset (not balanced 50/50 from the center of the mast), so the boom length on each side of the mast may be different. Choose the longest length.
The Length of the triangle [L] would be 1/2 of the longest element length (usually the rear reflector).
The formula for the hypotenuse is: [R] = Square Root of (B2 + W2)
For the following example:
The longest boom length from the center of the mast of the antenna is [B] = 15 feet.
The longest element length is 24 feet, so use half of that length which makes [L] = 12 feet
The hypotenuse [R] of the right triangle (which is the Turning Radius) would be: 19.209 feet.
(Be safe and round it up to 19.5 feet).
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Tags: Antenna, Tech Tip, Turning Radius
A well-equipped ham shack is chock full of transmitters, receivers, (or at least transceivers), antenna tuners, coaxial switches, radio accessories and all manner of electronic equipment. All of these things have one thing in common: cables.
As you look around your shack, there are cables everywhere. There are antenna cables, power cables, control cables, test cables, cables and cables. Cables everywhere! Just think how much nicer you could make it look if all those cables were neatly bundled!
Ever since Velcro™ was first introduced, hook and loop fasteners have been applied to almost everything…from tennis shoes to biomedical prosthetics, to spacesuits and much more. When it comes to tidying up the ham shack, nothing works better than DX Engineering Hook and Loop Cable Wraps!
DX Engineering offers several products to neaten up your cables. DX Engineering Hook and Loop Cable Wraps are some of the best because they’re reusable. They cling tightly to themselves, allowing you to bundle wires and cables neatly and efficiently. But they also pull apart easily when you need to add cables or re-position cable runs.
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Tags: Cable Wraps, Tech Tip, Tech Tip Thursday