A couple of weeks ago, I purchased a highly-modified Vibroplex Standard paddle. Apparently, in making the modification, the previous owner had lost one of the trunnion screws and decorative red dots. As you can see in the photo below, the previous owner found a brass screw to use in place of the missing trunnion screw.
While the paddle worked just fine, I wanted to use the correct parts. Fortunately, these parts are still available from Vibroplex, and I purchased them from Vibroplex. Each part cost $5. I can see charging five bucks for the screw, but I think that $5 for the little piece of plastic is a bit much. Not only was it expensive, it doesn’t even match the dot on the other paddle lever.
At any rate, the parts arrived Friday, and it was relatively simple to install the trunnion screw and get it all adjusted and working properly. I’m still not sure what I’m going to do about the red dot. At the very least, I’m going to complain to Vibroplex about it.
Iambic A vs Iambic B
After getting the paddle back together, I connected it to my WinKeyer and started playing around with it. I was getting some odd behavior, though. It didn’t occur to me at first, but the problem was that the batteries in the keyer were getting weak. Before I figured that out, I’d done a factory reset and tried reprogramming it. Only when all that didn’t work, did it occur to me that the batteries needed replacement.
Even after I’d replaced the batteries, I was getting some odd behavior. When sending CQ or my callsign, I wasn’t getting the final “dah.” After puzzling about this for a while, I figured out that the problem was that I’d programmed the keyer to operate in iambic mode A, and previously I’d been using mode B.
Chuck Olson, WB9KZY, describes the difference between modes A and B in his article, What’s all this iambic keyer mode A and B stuff, anyhow? He says,
The difference between mode A and B lies in what the keyer does when both paddles are released. The mode A keyer completes the element being sent when the paddles are released. The mode B keyer sends an additional element opposite to the one being sent when the paddles are released.
In mode A, to make the K or Q, you actually have to hold the dah lever down until the dah actually starts being sent. Since I’d been operating in mode B, I guess I got a little sloppy about doing so. In mode B, the keyer automatically sends the dah, but in mode A, it doesn’t, and that’s why that last dah would sometimes get dropped whiles sending a K or Q. I now have the keyer programmed to operate in mode B, and everything is working just fine.
A new ham’s first dipole
Yesterday, I spent a couple of hours helping a new ham set up his first dipole. Last weekend, he actually got the dipole up in the air, but when he connected it to the rig, it just wouldn’t load up. After swapping some e-mail about the problem, we decided that it would be best if I came over and had a first-hand look. So, yesterday morning, I threw my box of antenna goodies into my car and headed over there.
Taking my advice, he’d purchased a spool of coax and crimp-on connectors. I didn’t ask him where he’d purchased the crimper, but the first thing I noticed is that his crimps didn’t look right. They were much too tight. He got out his multimeter, and sure enough, the coax was shorted. We cut off one connector and measured again. The coax was still shorted. We cut off the other one and measured both connectors. Both were shorted.
I had brought my crimper and compared mine to his. His crimper had two dies for crimping coax – .213-in. and .255-in. My crimper also has two dies: .213-in. and .235-in. The instructions say to use the .235-in. die for crimping RG-8X connectors. He had used the .213-in. die, which really squeezed the coax. While I can’t actually see the short, my conclusion is that somewhere along the crimp, the shield became shorted to the center conductor, perhaps aided by the heat of soldering the center conductor to the connectors center pin.
Fortunately, he’d bought spare connectors. We put those on, using the .235-in. die on my crimper, buzzed out the cable, and we were in business. We connected the cable to the antenna, connected my antenna analyzer to the other end, and found that the antenna was resonant at 6.9 MHz. After taking about a foot off either end, we pretty much centered the resonant point of the antenna, and as one former president once said, “Mission Accomplished!”
The moral of the story is that you really need to use the right crimper and the right die for crimping coax connectors. My friend certainly had a quality crimper, but didn’t use the right die. He may have been able to use the .255-in die, but I don’t think that would have made a secure enough crimp. .235-in. is just the right size for RG-8X coax.
David De Silva @G7AGI
I’ve just discovered @edinburghmorse. Looking forward to seeing the new web site go live.
Planetary Society @exploreplanets
Amateur radio enthusiasts were able to detect the carrier signal of a decades-old NASA spacecraft: planetary.org/blogs/emily-la…
You don’t have to pay a lot for a Buddipole. By making one yourself, you can not only save money, but learn something in the process.
Jeff Davis @ke9v
Dayton Survival Guide ke9v.net/articles/dayto…
The Dayton Hamvention, still the largest gathering of amateur radio enthusiasts in the world, takes place May 16-18, 2014. While I disagree with Jeff’s statement, “There’s simply no way to facilitate that size of a crowd for three days in an ultra modern facility,” the rest is pretty much spot on.
Smith chart antenna-theory.com/tutorial/smith…
J.Héctor García XE2K @XE2K
After so many Drones in the news, Why not an 160m Vertical wire array supported by Drones ? can be the future?
There were no changes to this section that I could find…Dan
Antenna safety is also of primary concern. There are two aspects of antenna safety—being safe when installing an antenna and safely operating an antenna.
When putting up an antenna tower, an important safety precaution is to look for and stay clear of any overhead electrical wires. (T0B04) When installing an antenna, make sure that it is far enough from power lines, so that if the antenna falls unexpectedly, no part of it can come closer than 10 feet to the power wires. (T0B06) This is the reason you should avoid attaching an antenna to a utility pole. The antenna could contact high-voltage power wires. (T0B09)
You also should position the antenna so that no one can touch it while you are transmitting. If a person accidentally touched your antenna while you were transmitting, they might receive a painful RF burn. (T0C07)
Another safety tip is to use a gin pole designed for use with the tower that you’re installing. The purpose of a gin pole is to lift tower sections or antennas. (T0B05)
At all times when any work is being done on the tower, members of a tower work team should wear a hard hat and safety glasses. (T0B01) Before climbing an antenna tower, it is a good precaution to put on a climbing harness and safety glasses. (T0B02) It is never safe to climb a tower without a helper or observer. (T0B03) When using a crank-up tower, an important safety rule to remember is that this type of tower must never be climbed unless it is in the fully retracted position. (T0B07)
Grounding is very important when installing a tower because the tower is basically a big lightning rod. Local electrical codes establish grounding requirements for an amateur radio tower or antenna. (T0B11)
Separate eight-foot long ground rods for each tower leg, bonded to the tower and each other is considered to be a proper grounding method for a tower. (T0B08) When installing ground wires on a tower for lightning protection, it is good practice to ensure that connections are short and direct. (T0B12) Sharp bends must be avoided when installing grounding conductors used for lightning protection. (T0B10)
Lightning can also be conducted down a feedline and into your shack. To prevent this, several manufacturers make devices designed to shunt this current to ground before it gets into the shack. When installing devices for lightning protection in a coaxial cable feedline, ground all of the protectors to a common plate which is in turn connected to an external ground. (T0A07)
In the 2010 study guide, this section was part of the section on feedlines and connectors. I think it makes more sense to separate it like I have here. There is one added question in this section T7C13 asks what a dummy load consists of…Dan
Standing wave ratio is a term you’ll often hear when talking about antennas and feedlines. In general terms, standing wave ratio (SWR) is a measure of how well a load is matched to a transmission line. (T7C03) In this context, the “load” is the antenna. When we say that an antenna is matched to a transmission line, we mean that the impedance of the transmission line is equal to the impedance of the antenna.
The reason it is important to have a low SWR in an antenna system that uses coaxial cable feedline is to allow the efficient transfer of power and reduce losses. (T9B01) The bigger the mismatch is between the feedline and the load, the higher the SWR will be, and the more power you will lose in the feedline. Power lost in a feedline is converted into heat. (T7C07) Power converted into heat is not radiated by the antenna, meaning your radiated signal will be weaker.
You can measure the SWR of your antenna system with an SWR meter. You usually connect the SWR meter near the output of your transmitter because it is important to have a low SWR at that point. A directional wattmeter is an instrument other than an SWR meter that you could use to determine if a feedline and antenna are properly matched. (T7C08)
1 to 1 is the reading on an SWR meter indicates a perfect impedance match between the antenna and the feedline. (T7C04) 2 to 1 is the approximate SWR value above which the protection circuits in most solid-state transmitters begin to reduce transmitter power. (T7C05) An SWR reading of 4:1 means that there is an impedance mismatch. (T7C06)
One way to ensure that the impedance of the antenna system matches the output impedance of transmitter is to use an antenna tuner. An antenna tuner matches the antenna system impedance to the transceiver’s output impedance. (T9B04)
In addition to the SWR meter and the directional wattmeter, there are a couple of other types of test instruments commonly found in an amateur’s “shack.” One instrument that every shack should have is the dummy load. A dummy load consists of a non-inductive resistor and a heat sink. (T7C13) The primary purpose of a dummy load is to prevent the radiation of signals when making tests. (T7C01)
Another common test instrument is the antenna analyzer. An antenna analyzer is an instrument that can be used to determine if an antenna is resonant at the desired operating frequency. (T7C02) You can also make a number of other measurements that will help you set up an antenna system, such as SWR, capacitance, and inductance.
In the 2010 study guide, I also included questions about SWR and antenna measurements in this section. For 2014, however, I’ve decided to make that a separate section…Dan
Feedlines connect radios to antennas. There are many different types of feedlines, but coaxial cable is used more often than any other feedline for amateur radio antenna systems because it is easy to use and requires few special installation considerations. (T9B03) A common use of coaxial cable is carrying RF signals between a radio and antenna. (T7C12) Note, however, that the loss increases as the frequency of a signal passing through coaxial cable is increased. (T9B05)
When choosing a feedline, it is important to match the impedance of the feedline to the output impedance of the transmitter and the input impedance of the antenna. Impedance is a measure of the opposition to AC current flow in a circuit. (T5C12) Ohms are the units of impedance. (T5C13)
Most amateur radio transmitters are designed to have an output impedance of 50 ohms. Because that is the case, the impedance of the most commonly used coaxial cable in typical amateur radio installations is 50 ohms. (T9B02)
RG-58 and RG-8 are two types of coaxial cable often used in amateur radio stations. Both have an impedance of 50 ohms, but there are important differences between the two. One electrical difference between the smaller RG-58 and larger RG-8 coaxial cables is that RG-8 cable has less loss at a given frequency. (T9B10) The type of coax that has the lowest loss at VHF and UHF is air-insulated hard line. (T9B11)
Moisture contamination is the most common cause for failure of coaxial cables. (T7C09) One way that moisture enters a cable is via cracks in the cable’s outer jacket. The reason that the outer jacket of coaxial cable should be resistant to ultraviolet light is that ultraviolet light can damage the jacket and allow water to enter the cable.(T7C10) A disadvantage of “air core” coaxial cable when compared to foam or solid dielectric types is that it requires special techniques to prevent water absorption. (T7C11)
PL-259 connectors are the most common type of connectors used on coaxial cables in amateur radio stations. One thing that is true of PL-259 type coax connectors is that they are commonly used at HF frequencies. (T9B07)
One problem with PL-259 connectors is that they are not the most suitable connector when operating at higher frequencies. Instead, a Type N connector is most suitable for frequencies above 400 MHz. (T9B06)
No matter what type of connector you use, coax connectors exposed to the weather should be sealed against water intrusion to prevent an increase in feedline loss. (T9B08) Also make sure to tighten connectors well. Also make sure that your antenna connections are tight and the connectors are soldered properly. A loose connection in an antenna or a feedline might cause erratic changes in SWR readings. (T9B09)
Three questions were added to this section, the question on antenna loading and two on mobile antenna installation. I think these are good changes…Dan
The most common, and perhaps the simplest, antenna is the half-wave dipole antenna. As the name suggests, it measures close to one half wavelength from one end of the antenna to the other. A simple dipole mounted so the conductor is parallel to the Earth’s surface is a horizontally polarized antenna. (T9A03) The direction that radiation is strongest from a half-wave dipole antenna in free space is broadside to the antenna. (T9A10)
The length of a dipole antenna is actually about 5% shorter than the value that you would calculate using the formula wavelength in meters equals 300 divided by frequency in megahertz. The reason for this is that the velocity of a radio wave through wire is lower than the velocity of the wave in free space. Consequently, the approximate length of a 6 meter 1/2-wavelength wire dipole antenna is 112 inches. (T9A09) To make a dipole antenna resonant on a higher frequency, you would shorten it. (T9A05)
Perhaps the second-most popular type of amateur radio antenna is the quarter-wave vertical antenna. For vertical antennas, the electric field is perpendicular to the Earth. (T9A02) This makes them vertically-polarized antennas. The approximate length of a quarter-wavelength vertical antenna for 146 MHz is 19 inches. (T9A08)
Because HF antennas can be very long, many amateurs use a technique called “loading” to shorten them. Loading, when referring to an antenna, means inserting an inductor in the radiating portion of the antenna to make it electrically longer. (T9A14)
Another popular type of antenna is the beam antenna. A beam antenna is an antenna that concentrates signals in one direction. (T9A01) The quad, Yagi, and dish antennas are directional antennas. (T9A06) The gain of an antenna is the increase in signal strength in a specified direction when compared to a reference antenna. (T9A11)
Most hand-held VHF and UHF transceivers come with what’s called a “rubber duck” antenna. A disadvantage of the “rubber duck” antenna supplied with most handheld radio transceivers is that it does not transmit or receive as effectively as a full-sized antenna. (T9A04) A good reason not to use a “rubber duck” antenna inside your car is that signals can be significantly weaker than when it is outside of the vehicle. (T9A07)
A better option is to use an externally-mounted antenna. VHF or UHF mobile antennas are often mounted in the center of the vehicle roof because a roof mounted antenna normally provides the most uniform radiation pattern. (T9A13) Many mobile installations use a 5/8-wavelength vertical antenna. One reason to use a properly mounted 5/8 wavelength antenna for VHF or UHF mobile service is that it offers a lower angle of radiation and more gain than a 1/4 wavelength antenna and usually provides improved coverage. (T9A12)
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