Download Files
These are 200 Morse Code QSO`s which might typically be heard on the HF bands. They were designed to give people who are learning Morse Code some practice with real life Morse contacts, rather than using text passages from books, or random letters generated my computer.
It is intended that the QSO`s are “played” by a morse code computer program such as “Supermorse” . This is an ideal way for a student to learn on their own.
There are quite a few ways to make full-sized dipoles that can be rotated.
How you attack this mostly depends upon what band is to be covered (basically how big) and whether the wire is to be horizontal or is permitted to slope downward from a central post.
In the horizontal case, the wire is threaded through the spreaders and may extend out the ends. The ¼” tubes have an adequate ID that #16 wire is easily passed through the tube, so extenders can be added to the usual fiberglass ½” tubes that fit the hub.
In doing this, you should be aware that the velocity factor will be less than unity, so the physical size of the dipole will be slightly smaller than that of free space. In order to make connections to the feed line at the hub, two ¼” diameter holes have to be drilled at an outward slant into two opposite spreader sockets.
These should be drilled at about a 45 degree slant beginning about ½” out from the center. A ten meter dipole requires no extenders. Longer wavelengths require extenders, and the 20 meter dipole may require wire extending slightly beyond the extended spreaders.
In general, feed the wire through the extender first, then into the ½” tubing, then slide the extender into the half inch tubing and push the wire beyond the end of the spreader about 4″. Feed the wire into the hub and up through the access holes that you drilled. Then push the spreader into the hub.
Now, from the tip of the spreader pull the wire until there remains just enough wire at the hub to make the connections to the feeder. Adjust the length of the spreader extenders, and tighten the hose clamps.
Leave about a foot of extra wire beyond the extender. You will then need to trim this to get proper resonance once the structure is in the air. In the case of ten meters, you are done, simply mount the hub on the mast and put it up. No guy lines are needed if you don’t mind a bit of droop. In the case of 20 meters, there is much more to do. Here, the length of the spreader will be about 15′ if you have a 1′ overlap with the extender.
So you will need a central guy post 6′ long, i.e., use a full 8′ section of 1″ tubing with 2′ below the hub. You will need guys to both the inner spreader at 8′ and the outer extender at 15′ up to the central hub for both spreaders. You also may need rotational stability if you want this to settle down after rotation or gusts of wind.
The two unused socket holes are there for a reason, so, fit two 6′ or 8′ (if you have room) ½” spreaders in these sockets and guy them in the same manner as before at the 8′ and 15′ locations. Always set the guys from the inside first, then add the outer ones. This is still a fairly loose structure since only gravity holds it in the downward direction. If this structure is still not stiff enough, you can guy downward to the mast as well. The limiting tension is set by the point where the extenders begin to buckle. That turns out not to be a whole lot of tension, because a 7′ section of the ¼” tubing sets the limit.
The second procedure is to make an inverted V dipole, where the antenna is the upper guy lines from the center pole out to the spreader tips.
For the ten meter case, this is nearly identical to the ground/counterpoise discussed in the Quick Vertical section. In that case, there are no extenders, so the construction is very simple. In the 20 meter case, all the same problems are encountered as above except that the wire load is acting as the upper guy lines rather than being in the spreaders. We also suggest using light wire for the 20 meter version. In fact, # 18 or # 20 hook-up wire works well, and the insulation should be left on.
We prefer the un-tinned type that is commonly available at Radio Shack. Using, the 6′ center pole, the length to the tip should be just about correct, however, the insulation slightly reduces the velocity factor, so you can shorten the extender or use a small length of Nylon fish line to extend the wire.
Note, the 17 and 20 meter versions of these dipoles are fairly large structures and can not be built up in small spaces. They are also rather flimsy, and go through lots of distortion when being tipped up. These are better erected from a push-up mast with the rotator near the top of the mast. This Dipole antenna gives the same gain as all other dipoles, however, the Half Square is a much better DX antenna for a given elevation and may be worth the extra effort. All parts used for the construction of the dipole can be used to construct the Half Square, so there is no loss in investment if you decide to switch. Note that 6 and 10 meters require no extenders, but we do recommend that you use guys from the tips to the center post. The post should extend about 3′ above the hub.
Parts required for all 6 and 10 meters versions:
| Item | Quantity | Description |
| 1 | 1 | HUB 4-050-100, Central Quad Hub (RFJ) |
| 2 | 2 | 8′ 1/2″ OD fiberglass tubing, spreaders (MGS) |
| 3 | 1 | 8′ 1″ OD fiberglass tubing, boom (MGS) |
| 4 | 2 | GT 4-050 1/2″ Guy Ties, for tips of spreaders (RFJ) |
| 5 | 2 | GT 4-100 1″ Guy Ties, for tips of boom (RFJ) |
Extenders are required for 12 , 15, and 20 meters.
To determine how much 1/4″ fiberglass to buy, you need to calculate the approximate length required for the dipole. If the wire is to be inside the fiberglass, the velocity factor is slightly less than 90%.
The size of a typical dipole is given approximately by 468/fMHz. This formula has a small correction factor for finite wire diameter and end effects.
When the wire is inside the fiberglass tubing, the appropriate factor is about 435/fMHz, so the lengths of the spreaders require for 12, 15, 17, and 20 meters is roughly as 8.72′, 10.25′, 12.02′, and 15.33′.
Assuming 6″ overlap and 8′ lengths of 1/2″ OD spreaders, the extenders will have to be 1.22′, 2.75′, 4.52′, and 7.83′.
Obviously, there is no compelling reason to cut the 8′ of 1/4″ OD tubing for the 20 meter spreaders.
You can get both a 15 and 17 meter extender our of a single 8′ length of tubing. 15, 17 and 20 meters require lateral guys to increase the stability. This requires two 4′ lengths of 1/2″ OD tubing inserted in the two remaining sockets.
Guys should be run to the tips of both the 8′ dipole tips and the extended tips. This is also true from the central Guy post. The guys can be either 50 lb. test Nylon fishing line or Kevlar thread.
The photos associated with the Half Square antenna show structures built with both fiberglass and PVC.
Article by KQ6RH
originally available at http://www.antenna-magic.com/antenna/dipole.htm
Please feel free to build or distribute the information on these antennas. G4DHF retain the copyright to the designs and ask that they are not manufactured for commercial gain.
This is a design for a 5 element 2 Metre beam with a forward gain of 8dBD and a front to back ratio of over 24dB. As with my fishing pole yagis, it has a feed impedance of around 50 ohm and so the Driven Element only requires a simple unbalanced to balanced feed. The antenna utilises flexible plastic coated wire for the elements, which are supported by fibre spreaders and kite flying cord. When assembled the antenna forms a rectangle of only 1 x 1.51 Metres. When not in use the antenna collapses into a very small package, which can be carried in a medium sized pocket or small bag making it ideal for backpacking. I have successfully carried these antennas as hand luggage during air travel and worked some quite remarkable DX.
The inclusion of the 30cm ruler is for visual reference only
This yagi is designed using highly flexible 16g plastic coated wire with an outer diameter of 3mm and a stranded inner conductor of 1.5mm and is of the type readily available from most electrical retailers. The plastic coating has a significant effect on the resonant length of the elements due to changes in the velocity factor when compared to free space values. The value of the velocity factor was determined by trail and error over a period of many weeks and several yagis. A correction factor of around 7% to 5% from the free space values gave repeatedly good results and a value of 5% has been applied in this design. If a different wire diameter is used or the wire is non-insulated changes to the length of each element will be required to compensate. As the elements are very thin it was expected that the operating bandwidth would be limited to around a few hundred kHz at 144MHz. As the operating frequency was designed around 144.1 MHz this should be of little concern to those operating in the European DX section of the band. In fact, the beam will give creditable performance up to around 144.6 MHz after which the 50 ohm feed impedance, gain and front to back ratio rapidly begins to deteriorate.
Cut the element lengths to these dimensions
The elements are held in position along a string frame, supported by four 6mm fibre spreaders. A number of string types were tried, ranging from 1.5mm polypropylene line to the more conventional household twine. Almost all exhibited an unacceptable memory affect, which turned the beam into tangled wire when the supports were removed. The ideal material was found during a visit to a kite shop when 2mm flying line was purchased. This consists of hundreds of fine nylon strands bound together in a woven cotton outer sheath. This cord is highly resilient to stretching, has minimal memory affect and is extremely strong. Once used there was no going back to the types used in the prototypes.
The end of each element is secured into lengths of 5mm plastic hollow tubing, obtained from model and craft shops. Each element end support has a different length in order to preserve the shape of the supporting frame. After the tips have been drilled each element is threaded along the length of the cord to their correct position. The end of each element is at a high RF voltage potential so care needs to be taken to ensure that surrounding objects and materials due not exhibit detuning effects. Four small lengths of 2mm plastic rod terminate each of the supporting frame by providing tie points for the cord.
The Driven Element consists of a simple dipole. The feed impedance for a conventional yagi is usually considerably lower than the desired 50 ohm feed and requires some form of matching network to compensate. This design sacrifices a few tenths of a dB of forward gain so that by careful attention to the length and position of the first director in relation to the dipole the feed impedance is raised to the desired value. This concept is not new. Indeed, at least one well-known commercial manufacturer of V/UHF antennas has used this technique successfully over many years, including matching UHF folded dipoles directly with 50 ohm cable. These parameters are, however, quite critical and so careful attention should be given to ensuring that the recommended dimensions are followed. The centre of the dipole passes through a small plastic support and is terminated with standard spade connectors, as weight at this point needs to be kept as light a possible to reduce element sag. The dipole requires an unbalanced to balanced balun, which is described below.
This balun serves to provide an unbalanced to balanced 50 ohm match, which helps reduce RF currents on the outer of the feed. Omit this balun at your peril as the antenna may exhibit false resonance at the desired frequency or high SWR due to the presence of circulating currents. For RG-58U coax with a velocity factor of 0.66, cut a 34cm length and trim back the braid 5mm at en end. Note that the two lengths run parallel to each other and that the braid and inner are isolated at opposite ends.
The end of each element is cut to the corrected length and secured into plastic element spacers, which are drilled 5mm from the tip and threaded onto the two outer lengths of kite cord. The element positions are marked out onto a length of wood and the cord stretched between two sets of panel pins. Thread one end of the Reflector element first, followed by the plastic end cap that holds the fibre support. When the beam is assembled these caps hold the Reflector and 2nd Director tight against the end supports. Next thread the Driven element, Director 1, another end cap and finally Director 2. Repeat the process for the opposite side. When the fibre supports are inserted into the end caps the beam assumes it’s physical dimensions. The element ends can be glued along the cord, but leave Director 1 free until adjustments are complete.
The shape of the yagi is created when the four fibre supports are inserted into a central hub and the four plastic end caps at each corner of the beam. Lengths of 6mm fibre rod are available from a DIY stores and kite retailers. I have even successfully used the types that support bicycle flags. The total length of each support is around 865cm, which I cut into three sections for portability. There is an additional 4cm of “hidden” length to be added when they are fitted into the central hub. I placed small lengths of 8mm (6mm ID) aluminium tubing on each end of all the second sections to enable the rods to be compression fitted together. A word of caution is necessary when handling and cutting these rods as fibres can easily become embedded in the skin causing irritation so gloves must be worn. When the rods have been cut each end should be dipped in “Super Glue” to prevent the fibres from peeling. Furthermore, the addition of heat shrink sleeving makes for safer handling. It is not recommended to use wooden dowel for the supports as the tension required to form the structure is quite high and this will either distort or snap the wood.
This yagi has to be lightweight, strong and portable. Metal fixings are almost eliminated. The supporting plates consist of two 9cm x 7cm sheets of 3mm acrylic. The geometry of the structure is scored on one of the sheets to determine the centre. Mark the 67-degree angle created by the fibre supports. The sheets are held together with the markings on top so the centre-supporting hole can be drilled. If two stacked antennas are planned, supported by a 6 metre to 9 metre fibre pole, the top antenna has a hole diameter of 2.5cm while the second, located some two metres lower has a cut out of 3.5cm. The four 4cm lengths of 8mm aluminium tube that house the fibre spreaders are then pop riveted in place. Turn the support over and secure the reverse. Two small “L” shaped aluminium brackets (or square open section) are formed and secured either side of the plates. These support a length of ribbed rubber matting, which, with the additional of cable ties, increases the grip between the central support and the mast support. There may be concerns regarding the effect of sunlight on acrylic over time but because the yagi is intended for temporary use the trade off in weight, strength and ease of assembly more than compensates for this potential problem.
Attach the antenna to an insulated mast at a comfortable working height of between five to six feet above ground in a clear environment. Attach the ends of the coaxial balun to the Driven Element and connect a length of 50 ohm cable to either an antenna analyser or SWR meter connected to a low level (1 watt max) 2 Metre signal source. Note the impedance or amount of reflected power. If the dimensions of the beam have been followed closely these will be reasonably low and close to 50 ohm. Moving only the position of the first director in 2mm steps, usually towards the Driven Element, note the change in impedance until the desired match is achieved. The antenna can now be raised to a more suitable operating height to confirm alignment. When complete, the position of D1 is marked and secured. Lengths of lightweight plastic placed either side of the dipole centre help to maintain this distance, which is critical, when the elements sag slightly in operation. Once aligned and the distance between D1 and the Driven Element has been secured power levels of up to 300W have been used successfully.
As has been previously suggested, stacking two or more of these beams is perfectly viable due to their low weight. Stacking two antennas at a distance of one wavelength (6′) should yield a forward gain of about 11dBD, which makes for quite a potent one-person system.
Readers may be interested to know just how effectively this type of antenna can perform. While testing one of the prototypes in the garden of my QTH near Spalding (IO92UU) in May 2005 we had a Sporadic “E” event late in the afternoon. I worked CN8LI (IM63) at a distance of 2163Km, EA9IB (IM85) 1966Km and several EA7’s running only 20W. Given the high QRM levels and the number of G stations who were active, these results speak for themselves and should encourage potential builders to “get busy”. I would be interested in receiving comments and details of your operating experiences using this type of antenna.
Author G4DHF
Icom IC706 User Review
by T. Kirby 1996, 1997
I wrote the following article for publication in the journal of the First Class CW Operators’ Club (FOC), FOCUS, in 1996.
In case you have not seen the adverts, the IC706 is a miniature 11 band transceiver, covering all amateur bands between 1.8 and 200MHz (excluding 70MHz in the UK – more of this later). On all bands except 144MHz, the power output is 100 watts. On 144MHz, output is 10 watts. Since I already had a reasonable quality HF rig, I was not too concerned about the HF performance of the rig and expected this to be mediocre. I was more concerned about the VHF performance on 50 and 144MHz, where I enjoy DXing on CW and SSB. After some discussions on the HAMNET – Icom Support forum on Compuserve and an exchange of e-mail with Geoff, GJ4ICD I was satisfied that the VHF performance would satisfy my needs.
Front panel of the IC706
As many members will know, I had the opportunity to take a “permanent” job here in Toronto earlier on this year which I was pleased to accept. This necessitated a rethink of what radio equipment I should keep in the UK and what I should take to Canada. I had a considerable number of items “surplus” to requirements, so I decided to trade those in against an IC706.
When the rig arrived, I thought there had been some mistake, as the packaging and box were VERY small. But a flurry of bubble wrap later, I confirmed I was indeed the proud owner of an IC706 rather than the latest tri-band handheld. The rig measures just 167W x 58H x 200D mm and weighs 2.5kg. There are options to have filters installed. I decided on the 500Hz filter. If you fit this yourself, note that physical installation is not enough ! You also have to enable the filter in the software – not difficult, as long as you know to do this.
A number of reviews I had read of the rig complained of a noisy fan. I am not sure whether Icom addressed this issue, or whether the reviewers were being super sensitive. Either way, I can report that fan noise is barely noticeable on receive and “normal” on transmit.
My first tests of the rig were on 50 and 144MHz CW and SSB. With the preamp switched on, I found the receiver sensitive. I was able to hear the 144MHz GB3ANG beacon quite consistently over a path of some 450kms using a small 8el yagi mounted at about 30 feet. Reports on SSB were good – and the processor got particularly good reports, increasing average “talk power” without introducing any distortion. I then tried CW and was pleased to have good reports of the keying from local stations on both semi and full break-in. I tend to use semi break-in on this rig as the chattering relays annoys me a little when using full break-in. Mobile on 144MHz with a 1/4 wave, I was able to make some good SSB contacts from the Cotswolds area to North Wales and the Isle of Man (distances of 150 to 200 miles). Another entertaining “testing” QSO was a cross band between 50 and 70MHz with my friend Evan, G3CJ. I discovered one minor annoyance at this stage, it is not possible to transmit on one band and receive on another. Normally this would not be an issue, but would make life difficult if you wanted to use the RS-12 satellite (21MHz uplink and 29MHz down) for example.
Gradually I was finding my way around the rig. The “menu” system of selecting functions does take a little getting used to, but after some initial hesitancy I find it quite simple. Most often used functions (RF Output, CW Speed etc) are towards the top of the “menu structure” and can be accessed using a Quick Set feature. Yes, the rig has a built in keyer. It has dot and dash memories and I find the timing pleasant and easy to use. It is a little off-putting not to be able to control the CW speed without diving in to the “menu”. This is only a problem when you need to adjust the speed, perhaps either at the beginning or end of a QSO as someone of differing CW ability calls you. I am beginning to perfect the technique of sending with right hand whilst pressing buttons and selecting options with my left. It’s not easy, I assure you ! I do think that some people might find the menu system confusing, but if you are used to computers – you’ll have no bother.
A number of friends were keen to see the IC706 and since I don’t have any real decent HF antennas at present, this afforded some opportunities to try the rig in some challenging conditions. Many of you will be familiar with the mega-station at VE3EJ. John has been kind enough to invite me to his house on a number of occasions and one day I took the IC706 for us to play with. John immediately suggested we try it on 7MHz. With a full-size beam at 175 feet, I was concerned that this would be embarrassing. Not at all ! Whereas with my poor antennas at home, I can generally operate on HF with the preamp selected, this HAD to be turned off to prevent overloading. However, with the preamp switched out and the CW filter selected, the rig was soon pulling in Europeans and the occasional Asiatic station. We then hooked up some rudimentary switching so that we could compare the ‘706 with John’s IC765. To our enormous surprise, the 706 put up a great show and there was nothing that we could hear on the 765 that we couldn’t on the 706. We both had a sneaking suspicion that the 706 might even have been better – but there certainly wasn’t much in it. I don’t think the ergonomics of the rig commend it as a contest radio – BUT if you find yourself in some DX hot-spot with a serious pile-up, you can feel confident that the 706 will not let you down.
On the higher bands, performance is good too. I enjoy the Quick Split function. If a dx station is working up a couple or so, you can hit the Split button and your second VFO will be placed a user defined offset, up or down (eg +3kHz). This saves a second or so from conventional arrangements. In a pile-up situation you can do all the usual good stuff like reverse the VFOs quickly so that you can listen on your transmit frequency and find out what’s happening.
I was not able to try the 50MHz DX performance until I got to Canada and the Sporadic E season got underway. In some casual operating this summer I have worked around 100 grid squares, including the West Coast and Caribbean using the IC706 and a small whip antenna on the balcony of the apartment here in downtown Toronto. So if you fancy trying out six metres this could be a great way to do it. You’d be surprised at the FOC members that you find there too !
In the UK, there is also 70MHz to be considered. The rig does not have transmit on that band (although several people are reported to have modified the rig in the UK), but I was keen to see how it performed on receive. Derek, G3NKS kindly allowed me to connect the rig to his 4m beam in Cheltenham. Performance was good, slightly inferior, I felt to Derek’s transverter and HF rig combo. But we were still able to hear the 70MHz version of GB3ANG consistently and a number of other closer beacons. If transmit mods do become widely available for the rig, this could revolutionise four metre activity in the UK. It also affords some possibilities for good crossband QSOs during, perhaps Es openings or even the peak of Cycle 23 !
The rig has general coverage receive up to 200MHz. Above 150MHz I have not heard a single station – even the weather station on the CN tower some 3 miles away (I can see the tower from my apartment, dammit!). Common “wisdom” on the Internet suggests that there is a problem with the way some of the filters are wired causing out of band VHF performance to be severely impared. I haven’t pursued this as yet – but it would be nice to be able to use the rig to listen to the Aircraft and Marine bands, for example. Wide band FM is available, so you can listen to your favourite FM station in Band II if you get bored of listening to amateurs! At HF, general coverage works just fine – though I have tried little other than listening to the BBC World Service in the evenings here.
In summary then, I am delighted with the rig. It exceeds my expectations of performance at HF and VHF. I believe it will satisfy the needs of many amateurs as a very small, yet high-performance radio. The menu to control the rig’s functions will not be intuitive to everyone – so try to play with a rig before you buy to see how you feel. My guess is that most people will get used to it. It’s a small price to pay for the convenience of having so much powerful functionality in a small package. I was disappointed with the extended receive performance at VHF, but feel sure that this can be addressed – so that the rig will work outside the amateur bands. That was hardly the reason I bought the rig in the first place. And hopefully, you’ll get a chance to hear my 706 on the air from some interesting location before long !
Article originally available at
http://ourworld.compuserve.com/homepages/timkirby/ic706.htm
| 15m | 7050KHz | 20.59m | 21.80m | 19.18m |
| 20m | 7050KHz | 20.68m | 22.15m | 19.38m |
| 25m | 7050KHz | 20.82m | 22.70m | 19.49m |
| 30m | 7050KHz | 20.85m | 22.80m | 19.60m |
Here is a copy of an article on a full wave horizontal loop antenna, feeded with a balanced line.
This article was originally published at k4qky web site, but seems has been lost. I keep here a copy for public reference.
W3DZZ Antenna
Moonraker supply a whole range of wire trap dipoles covering from 2 to 5 HF bands (MTD1; MTD2; MTD3; MTD4; MTD5; MTD6). Diamond also produce trapped wire antennas, the W-721, W-728 and W735. Comet and Diamond each produce similar interesting 5 band wire dipoles that utilize both traps and a fan arrangement – the Diamond W8010 and the Comet CWA-1000. If space really is limited then look out for KZJ Communications (dongo1950 on ebay) – he produces ‘Limited Space Inductive Dipoles’. These are inductively loaded and shortened dipoles so they will have reduced efficiency, of course, but are very nicely made, so might be very useful in a tight spot.
To obtain good efficiency and achieve a low angle of radiation, desirable for longer distance DX, a horizontal dipole needs to be installed at a good height – over 20 feet would be desirable and it is quite common to install horizontal dipoles at around 30 to 40 feet above ground level. This might be a problem at some QTH’s, it certainly is at mine!
Allan Copland, GM1SXX comments: “The dipole will operate well on the band it has been sized for , if placed at a suitable height, but will also operate as a’ three-half-wave’ aerial at three times the frequency and so on, so it’s not strictly a single band aerial. An 80M dipole (132 feet typical) will work nicely on 30 metres (three half waves) but not on 40m (two half waves)… because on 40M the feed-point is at a voltage node and not at a current node, for easy feeding. Most aerials are current fed.
The radiation pattern changes when a dipole is not used on its design frequency. The pattern will break up into multiple ‘petals’. This can be either a disadvantage or an advantage depending on what you expect from it. Since most of us use co-ax, an UN-BAL should really be used to connect the unbalanced feeder to the balanced aerial, but how many people actually bother? Not many I suspect. It’s possible of course to use a balanced feed-line system instead with a dipole and just have a delta match (no centre insulator… none needed). There are many choices and permutations, but in general, dipoles are centre fed at a point of current maximum (and minimum voltage).
A normal dipole is current fed but of course can be voltage fed instead. This is what’s done in the EFHWA or Fuchs aerial where a resonant half wave wire is fed at one end (max voltage / min current) from an L/C tank, against a very short counterpoise wire.
Original article is :W3DZZ Dipole Aerial design by the Maidstone Amateur Radio Society
http://www.btinternet.com/~shaun.scannell/club/w3dzz.htm
Here we are with the new toy recently purchased via Amazon witn case, wifi dongle, and cables, as my yearly christmas present for myself.
The idea is to setup a WSPR beacon for 40 meters. This will be my first project to complete.
I know this toy is easy to be used for many other usages, but I’ve decided to focus my attention to this first goal.
I’m collecting now documentation to better understand how to setup the Raspberry and the WSPR software.
https://github.com/JamesP6000/WsprryPi – this souds like to be the preferred client to be installed.
I’m accepting suggestions and other ideas or examples of raspberry usage within the ham radio world.
Anyone ?
|
Construction: I made and put this antenna up the Friday afternoon before the ARRL RTTY Roundup (1999)! It took me about 3 hours to make and install on the tower. Most of that time seem to be used untangling the wire..hi hi I made the antenna 142 feet long. Use tiewraps at each of the three points to form a small loop at each end so that A 3/16″ rope could be used to support the antenna. I used a center insulator (Budwig HQ-1) that I had left over from an old dipole. The feed point was 12′ from the bottom of one leg. This antenna requires a matching element of feedline made out RG-59 (75ohm) coax. The formula or the length is a 1/4 wavelength at the operating frequency times the velocity of the RG-59. It is pretty easy to figure, a 1/4 wavelength at 7.050 (234/7.050) = 33.19′ times 66 percent equal 21.9. I had RG-59 with the polyprolene dialectric therefore the length turned out to be approximately 22 Feet. |
. |  |
Since I had the Budwig HQ-1 with the SO-239 moulded in the unit, I put PL-259s on each end of the matching coax and then used a barrow splicer to put the regular 52ohm coax feedline to the antenna.. A little weather proofing and this setup has worked well for many years.
My mounting point was only about 45′ above ground, which is insulated from the tower by a 3′ fiberglass pole. The legs of the antenna were secured East and West, and North and South is broadside to the antenna. Because the mounting points was so low, the bottome portion of the antenna was sloped out several feets to help provide space under the antennea for cutting grass.. hi
Results: Actually, the antenna played better than anything that I have had previously. The SWR was flat from 7.0 to 7.1 only rising to 1.5 at 7.3. This was perfect because I wanted it to play RTTY and CW… I did find that the antenna appeared to be less effective broadside, to the North. Stations in New England were difficult to get, however, the Europeans and Western USA were answering on the first call. Also, a few days after the contest, I talked to K4HXW/Mr Tucker, he indicated that he thought the antenna was playing much better than the inverted Vee that I had previously.
Added 31 Aug 2002 Update: I put this antenna back up recently and found that the correct length was a little off on my original antenna. According to ON4UN’s Low Band DXing book, the proper length for a delta loop should be 1.05% to 1.06% wavelength. I used 1.05% and the correct formula to calculate this length in feet is to divide 982.8 by the frequency in Mega Hertz (982.8/7.150=137.45′). I also have changed where the antenna is feed to horizontal by feeding the antenna in the middle of the bottom. This is so that I could have better effectiveness in domestic contest. After several days testing, the antenna seem to work well. Only time will tell… hi hi
Added 17 Oct 2011: Been living in Alabama since 2005 and installed the Delta Loop with the apex at 65′ and the bottom slightly kicked out a bit (not more than 5 degrees). I also changed back to the feed point to 12′ from one of the bottom corners. I really have not been able to see any difference in it performace based on changing the feedpoint. It has worked marvelously both for DX and Domestic contacts. I truly think that it is the best single wire antenna I have ever had on 40m.
I am probably going to put one up for 80m when the WX permits.
Article by KC4HW originally available at http://kc4hw.net/deltaloo.htm
1. Introduction
Sooner or later every Shortwave Listener will hear them, the Number Stations: rarely letter-groups are read by a synthezised male or female voice, are keyed in Morse code or are sent in digital mode.
All transmissions start with an identifier/call, usually a 3-figure group, repeated several times. The following figure-groups specify the decryption key/group-count of the message which ends, for example, with a series of “Zero”s (or “out” if spoken).
Every network has its own “fingerprint”: transmission schedule, modulation and format are typical for a specific network and will help the listener assigning it to a certain country. An increasing number of utility listener are into the hunt for Number Stations.