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ANTENNAS
ANTENNAS USED AT K5DZE AND SOME ANTENNA IDEAS FOR YOUR OPERATIONS
Circa 1973-74 - OSCAR 6 Antenna - K5DZE & DA1EZ 4x4 - 16 element Homebrew AZ-EL mount Circular Quad for 144 MHz with 10 Meter Dipole [This antenna was eventually expanded to a 4x7 - 28 element version] (Click on thumbnail photos to view larger size)
Antennas are truly one of the fun areas of Ham Radio for me. Experimentation is fairly easy and the results can be dramatic (positive or negative!). On this page are some of the antennas I am using with comments on how they work and what I did to set them up and/or use them. Verticals, long and short wire antennas, fixed or portable, area wide or DX antennas...there is likely something of interest for you. Enjoy!
A FULL WAVE HORIZONTAL LOOP - If you have the space and can do so, I recommend a Full Wave Horizontal Loop antenna as one of the best HF antennas to consider for overall Amateur use. This version of an 80-6m Loop uses 52 ohm coax for the feed which simplifies a number of issues. Add to this some wire, a 4:1 balun, some insulators and some support lanyards and you have everything you need. At 284', it works really well for 80 CW and 75 SSB, and it works just as good on the upper bands all the way to 6m (using an antenna tuner). IMHO, it is simply the most effective, relatively simple wire antenna I have seen for HF and it is both inexpensive and easy to make. The main issue with this antenna is the space it takes to put it up. (It certainly is not complicated to make.) When installing a loop, you are looking for the maximum enclosed area inside the loop so a square shape is normally used. A circle would be the best design, but that shape is harder to set up in most cases. A triangle shape is also common and this is often referred to as a horizontal Delta Loop. To figure the length of the antenna and the space needed to put it up, use the formula Length = 1005/freq in MHz. Then divide this total length by 4 to get the length of each of the 4 sides of a square loop. If needed, an excellent calculator is provided by KA1FSB on his Loop Calculator webpage http://ka1fsb.home.att.net/loopcalc.html. There are a lot of recommendations on how to put up a Full Loop to include...balun or no balun... placement up high or down low... making it vertical or horizontal... square, triangle, circle, odd shape... etc. Described below is what I did when I built mine and I can tell you that it really works, but you might want to check out these and other Loop websites for more details: http://ka1fsb.home.att.net/loopcalc.html http://www.bloomington.in.us/~wh2t/loop.html http://www.radioworks.com/nloop.html http://www.antennasmore.com/omniloop.htm (A commercial version loop antenna, plus some loop info) Like all antennas, there are some limitations with a loop (though not many it would seem to me). One thing to note is that while it works well for the lowest frequency for which it is cut, it does not do very well when you go below that design frequency. (What antenna does?) The SWR quickly skyrockets and then your rig's internal tuner almost certainly won't handle it. This means you always need to cut your antenna for the lowest frequency you plan to use. As an example, cut a loop cut for the upper end of 75 meters and it likely will not be usable on 80 CW using your rig's built-in antenna tuner... so figure the length carefully for the frequency you want to maximize. Although these antennas cut off (stop operating) below the design frequency, they operate very well above the primary design frequency using an antenna tuner, thus a 75 meter loop works all the way to 6 meters! About the only limitation that might be a real consideration is again the size of the antenna. To give you an idea of what I mean, consider a loop cut for the low end of 80 meters (3.5 MHz). The length for this frequency is 287' in total length or ~72' for each of the 4 sides. (Equal to putting up four 40m dipoles!) If you design the antenna for 3.8 MHz, the length is ~ 264' or 66' per side. For best results on the average site, you need 4 supports to make a square if possible. Five supports will make a 5-sided pentagon shape and give more area inside the antenna loop. Support structures can be trees, poles, masts or whatever you decide to use. If you tie the corner insulators/supports to the antenna, they cannot slide along the antenna. I left mine untied so they could slide (see picture below) and this helps me adjust the insulator properly on the antenna in relation to the support that suspends it.
A corner insulator (Shown hanging loose for clarity)
To visualize this antenna, imagine a closed loop of wire laid out on the ground in a square shape with an insulator at each corner that will be used to support it when it's up. (See the antenna picture at http://www.bloomington.in.us/~wh2t/loop.html ). Open the loop at one corner (or any convenient place on the wire) and connect an insulator at this feed point between the wires to take the strain off the coax. Leave enough wire on the ends to let you tie the antenna to the two binding posts on the balun coil. Then using the 'eye bolt' on top of the balun coil, tie the balun to the support insulator. (Although not clearly shown in the photo below, the balun has an eyebolt on its top that lets you tie it to the insulator.) I completed this antenna/balun/coax connection by taking a 1 quart plastic Zip-Lock sandwich bag to seal up everything from the weather. Just split the sides and the bottom and place the whole connection inside and tape it all up. The Zip top bag will let you easily open the bag to change or check a balun connection. You could also use a piece of heavy black leaf bag to cover and tape all connections. It looks a bit odd, but experience shows that will keep water, ice, snow, etc from getting at the connections. When spring comes after a tough winter, it is very easy to remove the bag, clean the connections to the balun and replace the bag with a new one. Of course if you prefer, just drop the bag idea and simply tape all connections for weather protection.
4:1 Balun with strain insulator (Shown unprotected for clarity) I have found that while a balun is not absolutely required to make this antenna work (I tried it), a 4:1 balun greatly improves the design. Depending upon what you read, the impedance at the feed point is around 100 to 125 ohms, so a 4:1 balun a simple way to provide a better match for 52 ohm coax. This makes all band loading for the radio's antenna tuner very easy and lets me tune up on any band at or above the design frequency using. Bottom line... I recommend using a balun, but if you don't have one don't let this stop you from trying a loop antenna. You can also make a balun by coiling your coax at the feed point. Read up on balun coils with loop antennas and decide what you want to do on this. Run the coax from the balun directly to your rig's antenna tuner. For good area coverage (300-400 mi) you can place the antenna anywhere from 8' to 15' in height above the ground keeping it horizontal. When mounted really low to the ground (6' to 10') , this becomes an NVIS technique and it works surprisingly well for local area coverage on 80-40m although hi power on an antenna this low can be a definite RF hazard to people and animals. (See NVIS section below.) For improved range and DX coverage, raise the antenna to 30' - 40' elevation again keeping it horizontal. I bet you will surprised! RESULTS: When I first tried this antenna, I cut my wire to the length I needed, fed it directly with RG-8X coax (no balun) , and put it up only 20' high on the corners so the centers were about 17' due to sagging. This version was cut for use on Army MARS and was about 253' long or about 63' on a side. It replaced an effective commercial G5RV that had been at 30' high in an inverted Vee configuration. The results were striking and exceeded my expectations. During comment time on our state net the first time I used it, several stations that were at least 250 miles distant immediately commented without my asking that my signal was considerably stronger than usual. Results on 75 SSB were also excellent, but the antenna would not load up on 80m CW with my rig's internal tuner, so again you need to cut it for the lowest frequency you intend to use. (Incidentally, I highly recommend this antenna for MARS, state EMCOMM, or area NCS stations needing solid area coverage.) When I built this antenna, I understood the antenna would work on 6 meters, but I personally doubted it. Just for fun I gave it a try 'up there' and once again, I was most surprised at how well it worked on an area 6 meter net. The bit loop was as good or better than my full-size 6m copper "J Pole" antenna at 30'. When the 6m opened a bit, I worked all up the east coast from my Alabama QTH. My current Full Wave Loop is 284' long and uses aluminum electric fence wire for the antenna wire. I highly recommend this wire for this or any other wire antenna. (A 500' spool costs ~ $23 at an area Tractor Supply Company.) It is very strong, has a small diameter and is fairly stealthy. For a feed line, I use 35' of RG-8X feed line with a Buxcomm 4:1 balun at the feed point. Three of the antenna corners are about 30' off the ground and the fourth is about 20' high. I put small pulleys on each corner of the suspended antenna supports so I could easily lower the antenna to make make adjustments. So far, I have not had cause to make any adjustments and have lowered it only to check and clean connections after a tough winter. I just put the loop up, let the FT-920's antenna tuner tune the antenna flat on all bands, and signals BOOMED in. It works particularly well for my PSK31 QRP efforts letting me work all states and 60+ countries in less than 120 days all with 5 watts or less . For more info and more links concerning Full Wave Loops, start with these websites: http://www.antennasmore.com/omniloop.htm (Commercial version of the loop) http://ka1fsb.home.att.net/loopcalc.html http://www.bloomington.in.us/~wh2t/loop.html (Look for an article on this antenna in the 2010 OCT edition of Monitoring Times magazine.)
S9V VERTICAL - For a number of months, I had a section on this page devoted to the S9V 40-10 m vertical antenna. I had good success with it but had to take it down due to the radials and coax being destroyed by workmen who accidentally dug up and cut most of the underground radials and coax cable. I can say that the S9V was a very good antenna and mine worked well with 16 - 27' radials, the 1:1 unun, and a 50' run of RG-213 buried coax. I think is a good buy for the money and makes a very unobtrusive 31 ft vertical that will work well if a vertical is the antenna you wish to put up.
80-10 G5RV G5RV - Ever since its introduction in 1946 by UK Amateur Louis Varney, G5RV (SK), this antenna has been highly popular with Hams worldwide. For me, the G5RV has two big advantages going for it... First, it is only 102' for an 80-10 version, and.... secondly, it really works well! It is actually designed to be 1.5 wave length center fed antenna for 14 MHz and if you have used a G5RV, you know it will perform well on 20 meters. Despite advertisements of a number of designs of antennas that claim to be superior (and other antennas such as the Windom and Windom variants are indeed very good), the G5RV is a consistent excellent performer. Remember...it is only a single wire antenna and not a beam, so don't expect miracles, but my considerable experience with one has shown me it will indeed work well on multiple frequencies. It is fair to say that the general Amateur population also thinks pretty highly of this design. You can easily construct your own G5RV, and there are many websites with information in detail as to how to do this, so I won't duplicate those here. You can also purchase a number of versions of this antenna ready to go up. In the interest of time, I chose to purchase my G5RV antenna. I bought the 102' 80-10 version (there is a 160-10 and 40-10 version as well) from Antennas and More http://www.antennasmore.com/g5rv.htm. While I am not pushing this particular company's version, I personally like the quality of the materials used and have found it to be a very good performer. I particularly like the black insulated wire that will not easily kink and that is very hard to see when its up. One of the best ways to see what other Hams think of this antenna is to look at the reviews on eHam concerning this version http://www.eham.net/reviews/detail/2143. The reviews show a 4.9 out of 5.0 for an overall rating, so that speaks pretty well of it. Another highly rated version of the G5RV is the True Talk G5RV found on eBay. I am impressed that these antennas come with 70' of RG-8X coax attached! This seems to make this a great buy too. EHam Reviews has much to say about the high quality of this particular antenna as well. RESULTS: I have used many types of wire antennas, but the 102' G5RV has always worked well in a relatively small space. In one example during an ARRL DX Contest, I worked 23 countries in ~2 hours on 20 meters running QRP SSB (10 watts) with a G5RV. Not bad for a simple wire antenna up 25' in an inverted Vee configuration! It has also been great for general short wave and long wave listening. I logged 235 Low Frequency aviation NDBs from one QTH using a G5RV!
TRIPOD MOUNTED HAMSTICKS - I wanted an antenna that was easy to transport, easy to set up, and quick to take down that I could use for short duration, portable operations such as QRP CW while at the lake. To meet this need, I used a discarded photo tripod with a Lakeview # 081 Tri- Mount attached at the top of the tripod so I could mount a Hamstick antenna. To change bands, you simply change Hamsticks. (I use quick disconnects such as shown in the picture below for fast antenna change.)
While certainly not the best portable antenna set up you might use, this little antenna does work when you need a very fast, very small footprint system, or you don't have trees for supports where you need to operate. Of course this set up is extremely portable and rather stealthy too. I use an LDG Z-817 auto tuner to fine tune the antenna and this little tuner works nicely. NOTE: One key point to this antenna is to use 1-4 (or more) ground radials just rolled out and placed on the ground. I use 1/4" wide copper braid and it seems to work well. Simply attach the braid to the mount and roll it out. If you don't use at least one radial, my experience is that you will likely be talking to yourself! If you need something like this, see my PROJECTS page for ideas on how to construct one for your use.
HAMSTICK TRANSPORT TUBE - If you decide to use a Tripod Mounted Hamstick set up as noted above or you use something similar like an Outbacker antenna, you may want to consider making one or more carrying tubes/cases to protect your antenna as you move it around. A Hamstick Transport Tube offers a lot of protection and can be a great asset for anyone carrying Hamstick type antennas from place to place. Again, if you need something like this, see the PROJECTS page for details on how to construct one or more of these transport tubes for your for your use. (This idea appeared in OCT '09, pg 60, 'Hints and Kinks' section of QST).
PAR ENDFEDZ - PAR Electronics ENDFEDZ - Of particular interest to QRP operators that live in antenna restricted areas and/or who need a good portable antenna, is an antenna that has the attributes of stealth, small size, high quality construction and efficiency (ultimately it must work!). Good company support (if needed) is certainly close behind these attributes. With these in mind, I chose one of the PAR Electronics ENDFEDZ antennas when I was living in a condo for a while. I now use it for portable QRP operations at the lake. These half wave end fed dipoles make use of a small antenna mounted matchbox connected to your coax feed line. What particularly caught my eye was the fact that this antenna used coax rather than twin lead or parallel line for its end feed. Coax is not sensitive to nearby objects which could be a problem at many QTHs trying to get the feed line into the operating position. I also like the fact that this antenna is both visually stealthy and bit shorter than a regular dipole. My triband 40-20-10 model is only ~ 40' long and can be used as a sloper, a vertical or a horizontal antenna. It does not require an antenna tuner and in fact, the instructions say you should not use one... (It is great for portable work with my little Elecraft KX-1). It is so small that it fits in a Zip-Lock quart size bag and the black coated wire won't tangle or easily kink during repeated portable use. The PAR ENDFEDZ antennas are now being used by the military and our Amateur antennas are made to the same standard according to the company owner, W4OP. The 3 band model I use (shown in the picture below) limits operation to a maximum of 25 watts due to the little matchbox's power limitation, but that is not a big issue for QRP ops anyway. Note: Single band ENDFEDZ models can operate at up to 100 watts.
PAR 40-10 Meter End-Fed Dipole The other thing that is impressive about the PAR ENDFEDZ is that on eHam Reviews ( http://www.eham.net/reviews/detail/3632 and http://www.eham.net/reviews/detail/5105 ) these antennas have a perfect score of 5 out of 5 for 138 reviews on one version of the antenna, and 41 of 41 on the 3 band model! Now that's about the best ratings I have seen for any antenna and this told me the guys that use them must also think these antennas must work pretty well! Check the eHam reviews to learn more if you need a small, effective antenna. For more details on PAR antennas, go to http://www.parelectronics.com. Incidentally, antenna cost is ~ $55 to $70 depending on the band and version you select.
VHF/UHF Discone A VHF/UHF DISCONE ANTENNA - This is an inexpensive well functioning antenna made from "hardware cloth", aluminum window screen, or even card board and heavy aluminum foil (for inside use). It provides exceptionally wide frequency coverage (up 10x the design freq with an acceptable SWR). It has no gain, but its very wide frequency coverage makes it a great a scanner antenna while providing a transmitting antenna from 144/440 MHz use. I made several of these while in the Army for use with projects there and of course I used it in Ham Radio with good success. It works very nicely in an attic as a stealthy scanner and Ham antenna... you can just hang it from a rafter! This antenna was featured in the March 2003 'Antenna Issue' of QST. To get a copy of this article with measurements and details, go to the ARRL website http://www.arrl.org/ and select the QST Archive Search link or use this link: http://www.arrl.org/members-only/qqnsearch.html . To find the article, enter K5DZE in the call block and then enter 2003 in the date block. NOTE: you need to be an ARRL member to access this link. Non-members can order a copy of the article from the ARRL for $5 if you decide it meets your needs. Details for ordering are on the following ARRL website. You will find this antenna fairly easy to make, low cost, and very effective for an exceptionally wide band receiving/transmitting antenna.
NVIS ANTENNA - Near Vertical Incident Skywave (NVIS) is a term I first heard about while I was serving in Vietnam. Infantry units, teams and patrols used this technique to operate from deep in jungle areas or particularly from mountainous valley areas. Although I was a helicopter pilot and was not operating radios on the ground, I took particular interest when I heard about NVIS not only because I was in the military, but I was a Ham and was of course interested in such things. A few years later, while at Ft. Leavenworth I was doing some research on German communications during the Battle for Stalingrad in WWII and I again ran across NVIS. It seems the German Army and the US Army were using NVIS techniques in their operations back in the '40's. In more recent years, I used antennas configured to work as NVIS antennas in Army MARS and some State Defense Force operations to see how these techniques worked. In summary...such configurations worked very well. NVIS is a big subject to cover and I only want to mention it and provide some links for Amateurs who may be interested in trying such a technique for ENCOMM use or for improved area HF area net use. In rugged or mountainous country where VHF/UHF repeaters are stretched to provide coverage, NVIS techniques on HF may well get the job done for you without the need to use and maintain VHF or UHF repeaters. If you are involved in Homeland Security communications, this should be a natural for your consideration. As you will see when you research the subject, NVIS is not really an antenna at all, although we speak of it as such...it is actually a communications technique. Simply stated, the idea is to take low angle of radiation (such as we use to work DX) and direct it upwards at a very high angle (60-90 degrees) so it will go almost straight up and then reflect back down from the ionosphere to cover a large area under the reflection. The purpose of using NVIS is to communicate over a local or regional area (300-400 mile radius) using moderate power and simple antennas. This not only lets an operator work out of a rugged mountainous area or a heavily wooded/jungle area effectively, but it does not propagate the signal over long ranges. This lack of propagation may be important to avoid interference when there are two nets on the same HF frequency at the same time only in different states/areas. It also is a technique to use if you don't want your signal to be heard at a great distance for whatever reason (Homeland Security needs). For Amateur Radio use, NVIS techniques are typically used on 160, 80/75, 60, and 40-meter bands. A critical factor for successful operation is to select a frequency that will allow radio signals to reflect off the ionosphere, so you must choose a frequency that will reflect your radio signals back from the ionosphere for the time of day or evening that you are using. In the daytime, this frequency is usually below 10 MHz, and at night it is usually below 5 MHz, but 80 meters seems to work well most of the time. This should tell you that if you tried to use 10, 6, or 2 meters for NVIS, you would strike out. Your signals would propagate up and out into space because they won't reflect at these frequencies. For many of our regular antennas to be operated in an NVIS mode, we don't often have to do anything except place the antenna low over the ground. Imagine a dipole for 75 meters placed only 6' to 8' off the ground and making more reliable contacts out to 350 miles than it might if it was up at 30'! Dipoles, end feds, loops, L's...all can perform well for NVIS if you keep them low to the ground. Another technique is to use a counterpoise under the antenna. Not only will NVIS techniques overcome dead spots close to you, it lowers your noise floor so the frequency is quieter and signals you do hear sound stronger. Sound to good to be true? Well, it works and works very well, but as good as it is, there are again some limitations. This all works best when both stations are using NVIS techniques, but this not an absolute requirement for success. You should understand that working DX is normally not much of an option with an NVIS setup...such installations work super for area coverage, but are not for DX which may be a down side for Amateurs who can only put up one antenna. Another limitation for Amateur use is that low level antennas can also be a real hazard to people and animals due to entanglement or RF burns if touched while the rig is transmitting. This might be overcome by using pulleys to raise your antenna for DX and then lower it for NVIS area coverage as needed. Sounds like an interesting experiment! Overall, NVIS techniques have a lot to offer if you understand and can work with the limitations. I have had some very good results using NVIS techniques. Why not read up on the subject and take a look at what it might do for you? These links will get you started: http://www.athensarc.org/nvis.asp http://www.qsl.net/wb5ude/nvis/ http://www.lenoir-arc.org/Newsletters/050507/NVIS%20Experiment_NARRATIVE.pdf
www.arrl-sc.org/Tech%20Presentations/ http://home.centurytel.net/w9wis/NVIS.html
(Boy, this antenna stuff is hard work! Time for a coffee break!)
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