The Wonder Whip?
A £10 QRP Portable Multiband Antenna for HF, VHF and UHF
A variation on the “Miracle Whip” and “Wander Wand”.
The Wonder WhipContinue reading
The Wonder Whip?
A £10 QRP Portable Multiband Antenna for HF, VHF and UHF
A variation on the “Miracle Whip” and “Wander Wand”.
The Wonder WhipContinue reading→
on Saturday 25 May 2019 i will take part to the upcoming Florence RadioFest as organizer.
The Florence RadioFest is a local amateur radio HamFest managed by the members of the ARI Section of Florence.
We expect to have over 50 private amateur radio oeprators and more than 10 amateur radio business companies represented.
and how they operate
One of the most useful antennas in the repertoire is the
Marconi or quarter wave grounded vertical antenna. Its invention made
it possible to halve the length of antennas, simplifying communications,
especially at HF and below. This antenna is still used widely today,
especially in marine, land mobile and long distance communications. It
can offer excellent performance when installed well. There are, however,
a number of selection criteria to take into account before you buy…
designing for MF and LF communications
When radio began, it started with low frequency communications, which it was thought was the answer to long distance communications. Since then we have seen the development of sky wave communications on HF frequencies, followed by the proliferation of communications system using the VHF and UHF direct wave and microwave. It may be thought by some that low and medium frequency communications are somewhat outmoded, but in reality they are still very much in evidence today…
Striking a Balance
When you connect centre fed antennas, like dipoles, Vs, triangles, yagis, rhombics, loops and so on, to coaxial cable, unless care is taken, it is not difficult to end up with feeder radiation. Not only can the loss in power be quite significant, but the radiation characteristics of the antenna system will also be seriously compromised.Continue reading→
Invented by Heinrich Hertz in around 1886, the half wave dipole is still one of the most simple and practical of antennas and still very much in use today. It consists of a half wavelength long centre fed conductor. Since these early days, improvements have been made to the initial design by adding a second, and often a third conductor, joined at the two ends to form a loop. This antenna, known as the Folded Dipole, can provide improved performance over the single wire antenna when well designed, constructed and installed…Continue reading→
Solar power or specifically, solar photovoltaic (PV) panels, have become increasingly available as a power source. Solar PV is ideal for powering Amateur radio equipment because PV panels are almost always designed to charge 12 volt battery systems. Coincidently, most Amateur radio equipment is designed to operate from 12 volt power supplies.Continue reading→
Do these things do exactly what they say they do – or are they total hogwash?
Have you seen the ads? This device will match your long wire to your receivers 50 ohm input? Firstly a long wire on HF would be on 28 MHz longer than 120 foot and on the lower bands it just an end fed “EF”
We can also get rid of the “magnetic” and give the balun its true name of voltage balun. My interest in the MLB was started after a friend went out and paid ?30 for one and started to tell me how this little device will produce a 50 ohm match at all frequencies. Any aerial will have differing values of impeadence depending on what band it is used, a 66 foot wire on 80m is about 30 ohms and on 40m the impeadence is about 1000 ohms.
For any sort of balun to be able to match different impeadences to 50 ohms you need to be able to vary one or more of its components. And when you can do this, the balun will match most things to 50 ohms, but you would call this type of balun an ATU. An ATU is a variable balun.
But theory is one thing and practice is another. So mainly for some thing to do I decided to make some MLB’s and see what mystical properties they have. The first balun was made “by the book” using the correct wire SWG and ferrite ring with a type 63 core for 1 to 30 MHz. I used a friend’s MFJ analyser for the tests and a 35 foot wire aerial.
The balun did improve the match to the receiver. Only near the resonant frequency of the aerial was any match close to 50 ohms or a VSWR of 1 to 1, as you would expect. On all other frequencies the match varied from 3 to 1, to 5 to 1 VSWR. Without the balun the match was horrible!
In the real world this means I had some thing like a increase of signal from 1 to 4 “S points” on the receiver from 1 MHz to 30 MHz.
The “VMR version” MLB was made from scrap. 3 core 2 amp lighting flex and an old ferrite rod. The results are just the same as the posh version!
You need about one yard of 3 core, 2 amp flex and a ferrite rod with a length of about 6 inches or longer.
Using 3 core flex it is easy to wire because it is colour coded. Tape one end of the flex to the rod leaving 6 inches for the connections, then wind on as many turns as possible (mine has 10 turns) and again fix the wire with tape etc at the other end. Now you can just twist the wire connections together or better solder them. Connect it up as shown. Blue right hand side to Green left-hand side. Brown right to Blue left. Inner of COAX, to Brown/Blue. Braid to single Green. Aerial to single Brown. Then just bung it into a box.
So is a MLB worth having? They do produce a “better” match to the receiver but you could get an ATU kit for about the same price, which will always produce the right match. If you buy surplus VC’s you can make an ATU for under ?10. Find a couple of broken tranny radios and you can make one for free.
The main advantage of the MLB is you can use COAX to the feed point of the aerial out side and get a reduction in noise pick up from TV’s etc in your home. I would not spend money on one, but a home made MLB in a box is worth having. Because it is a pain to keep peaking the ATU as you tune up the SW bands and anything that helps to give a better match is better than having nothing at all.
Another antenna added from the antenna plan is a 160 meter ¼ wavelength inverted L.
A 130 foot length of 12 gauge PVC covered stranded wire slopes up from the ground system to the 40 foot level of the 45 foot tall fiberglass flagpole (about 60 feet of wire length) and then proceeds about 70 feet toward the far back edge of my property. The 90 foot start-to-finish dimension just fits my city lot. At the end, the antenna wire is terminated at about 15 feet above the level of the back yard. The geometry actually resembles an inverted L that has partially fallen over – in other words, a “lazy L”. This antenna is used on 160 meters only and is coaxial cable fed.
In place of an active tuner, a 10 turn 4 inch diameter tapped coil wound of 0.250 inch diameter copper wire is used to tune the 1.8 to 2.0 MHz band in three segments.
Two vacuum relays are used to select the correct amount of the coil for a particular band segment. No coil turns are added to the top band segment, 7 turns are connected in series for the middle tuning range and the entire coil is used at the bottom end of the band. All of the base load components plus the static discharge arrestor are located in a 7 inch square weatherproof box that is bolted to the ground structure.
The coaxial cable entry point is sealed with silicone sealant to keep the spiders and moisture out. The wire that brings power to the relays is TV rotor cable which is rated to be used outside in the weather.
The transient suppressor and coaxial cable braid bus-work is bonded to the ground system with a heavy braid.
The cross-section of the metal drainage ditch that is used as the ground system for this antenna is shown below.
This metal drainage ditch is about 100 feet long and runs along the top of a five foot high concrete block wall that defines the eastern boundary of my city lot. The drainage ditch measures 12 inches wide and 12 inches deep. All of the 10 foot long metal sections are electrically bonded together along the length. This provides a very good earth ground for this 160 meter 1/4 wave inverted L antenna as well as a reflector / ground reference for the 75/60/40 meter NVIS antenna that is mounted directly above the metal ditch (see the NVIS page for more details about this antenna).
An improvement that I am considering for the ground system is to add a couple of wire radials in addition to the drainage ditch ground system. These radials will be run underground by fishing them through the drainage pipes buried under my driveway and front lawn. I think I’ll connect them with a remotely controlled relay so that I can more easily quantify their usefulness during actual on air contacts.
Another improvement under consideration is to add a number of 10 foot long ground rods along the length of the metal drainage ditch, especially near to the antenna feed point.
Since my back of the envelope calculations indicate that this antenna is only about 35% efficient (at best), these combined improvements could potentially yield as much as another 1 to 2 db of signal strength at the receiving end of my transmitted signal. Very interesting??
The antenna wire coming from the weatherproof box mounted on the metal drainage channel (lower center of the photo) first goes up to the top of the brown painted PVC pole (at the upper right of the photo),
From there it proceeds up to a point about five feet from the top of the 45 foot tall fiberglass flag pole. This places the 160 meter antenna five feet below and at about 30 degrees crosswise to the OCF Windom antenna wire to minimize interaction between the two antennas.
The far end of the antenna is attached to t he fence with a pulley and one gallon paint pail counter weight that takes the sag out of the antenna wire and allows the antenna pole to sway freely with the wind without stretching or breaking the antenna wire.
The maximum SWR at the edges of each of the three segments is less than 2.5:1. At 1.945, the frequency that I use the most, the Rs measures 33 ohms with an Xs of 32 ohms for an SWR of about 1.9:1 according to my MFJ-269 analyzer.
Since the static discharge protection is located at the base of the antenna, the coaxial feed line goes directly to the shack through a 100 foot length of coaxial cable. The antenna loads nicely and shows virtually no change in SWR when operating in either dry conditions or on a rainy day.
The antenna handbooks show that the inverted L has a more or less omni directional pattern that is uniform within about 1.5 db. The signal reports from any direction using this antenna are always as good as or better than the signal reports for other hams using top loaded verticals, full wave loops and dipoles at similar heights. This antenna is not a multi-element full size vertical array using massive towers, but it does work and works quite well. This is the one band where I often run the full power in order to overcome the very noisy band conditions that are typical at the receiving end.
160 meters is also the band where the 38 inch diameter magnetic loop antenna (pictured at the left) really shines. This loop often delivers the best quality receiving signal, especially if there are plasm TVs operating in the vicinity (see the PIXEL loop page for more details about the performance of this loop on the 160 meter band).
Article by W6SDO originally available at http://www.w6sdo.com:80/160M.html
Since I had purchased the Kenwood TS-590 transceiver a few months before I got my license, I needed an antenna (or antennas) right away for listening on the ham bands.
The antenna that I put up first was a vertical dipole for 10, 15, 20 and 40 meters. The reasons for this selection as the first antenna to be installed are that
1. The vertical antenna has many devoted supporters in the ham community who claim to get fantastic results,
2. The vertical dipole has a very small foot print and requires no radials,
3. This vertical is self-supporting and is very easy to install (except for the many tuning adjustments that are needed) and,
4. It is almost invisible from the street view in front of the house.
This last reason was considered important for the first antenna as it would let the neighbors get used to antennas sprouting up on and around the house without being initially overwhelmed by some visually gigantic structure.
Two Hustler Model 6-BTV antennas were adapted to make up a half wave vertical dipole by mounting them butt- to-butt on a twelve-foot long 2 by 12 inch wooden mast attached to the deck railing at the rear of the house.
The center feed point of this combination is only about 22 feet above the ground.
Therefore, I had to eliminate the 75/80 meter sections of the antennas in order to reduce the total length for each side to about 20 feet.
This vertical dipole configuration was chosen because my house and back yard layout (a full coverage concrete patio was already installed) do not lend themselves to the installations of a good ground radial system.
One great feature of the way that this antenna is mounted is that the dipole can be rotated to horizontal and the ends can even be swapped – which makes it very easy to reach any of the tuning traps from ground level or from the deck to which it is mounted! In addition, I have heard some hams say that with an incline angle of 45 degrees the signals come in earlier and leave later as the bands open and close – easy to check out with this setup.
The vertical dipole is fed at the center by a 1:1 balun and is further isolated with a 14 turn coil of RG-8 coaxial cable wrapped around a 7 inch diameter fiberglass form. The coaxial cable is routed at 90 degrees away for the antenna for about 20 feet before it runs across the roof of the house and then finally drops down to a 10 foot long ground stake. Here the coaxial cable passes though an Alpha-Delta 2 KW surge protector with the braid is connected to ground. Next, a 50 foot length of coaxial cable runs up the second floor shack.
This antenna has been found to load great with SWR values of under 2.5:1 over the entire span of the bands that it covers.
A limitation of this antenna was the lack of coverage on the 75/80 and 160 meter bands. This deficiency was quickly and easily remedied by the addition of a Pixel Technologies Magnetic Loop Model PRO-1B all band “listening only” loop antenna.
I have recently made some back of the envelope calculations estimating the performance of this antenna.
The takeoff angle for this antenna should be around 15 degrees for 10 meters and between 25 and 30 degrees at 40 meters. The radiation efficiency should be equal to or slightly better than the typical 1/4 wave vertical antenna with 4 to 8 radials.
Note that due to the 1.25 inch diameter of the aluminum tubing that makes up the elements, the length of each segment of this vertical is about 5% shorter than it would be for a 12 gauge wire antenna. Due to the tuning traps for each of the bands, the physical length of this dipole, compared to a full length dipole, is 99% when it is used at 10 meters, 94% for 15 meters, 83% for 20 meters and 65% for 40 meters.
Taking into account the losses that are associated with the 150 feet of coaxial feed line, the balun that feeds the antenna, the traps and the overall antenna length for each band (listed above), the loss of power for the total antenna system can be estimated. The total power loss is around 1.5 db on 10 meters, 2 db on 15 meters, 2.5 to 3 db on 20 meters and maybe as much as 4 to 5 db on 40 meters when compared to a full length vertical dipole with a short feed line and a core type current balancing choke. If your signal is 10db over S9 at the receiving location, these losses will hardly matter.
Choosing one of the trap free antenna designs that are now available, in place of the Hustler design, could minimize the losses on the 20 and 40 meter bands.
Finally, now that all of the antennas in the plan have been installed the listening results for this antenna can be compared with my other antennas.
So far, some preliminary comparisons have been made on the 17 meter band.
The antennas that I can now select include a hex beam, an inverted V off center feed Windom (a long wire at this frequency) with good omni-directional characteristics due to the inverted V construction), my vertical dipole to which I have added the 17 meter band and a two wavelength horizontal loop antenna. Each has its own advantages and disadvantages and the shoot out between them has been very interesting. The four antennas can be set up to use the four antenna selector switch buttons on the front of the Alpha amplifier which makes A-B-C-D testing very easy and a lot of fun!
The preliminary 17 meter observations are:
1. The hex beam is always the most quiet and has the strongest signal in both transmit and receive mode even though it is only 24 feet above the ground.
2. The loop has an equally quiet noise level but delivers signal strengths that are about 6 db less than the hex beam.
3. The OCF inverted V has a noise level that is 2 to 3 db higher than the hex beam and produces signal levels that are between equal and 4 db lower.
4. The vertical dipole usually has a 3 to 6 db higher noise level, compared to the hex beam, and produces signal levels that are typically 3 to 6 db less than the hex beam. It does much better on transmitting than it does on receiving due to the high noise level when it is used as the receiving antenna.
Article by W6SDO orignally available at http://www.w6sdo.com/VERTICAL.html