ANTENNAS
ANTENNAS USED AT K5DZE
AND SOME ANTENNA IDEAS FOR YOUR OPERATIONS
Circa 1973-74 - OSCAR 6 Antenna - K5DZE
A 4x4 - 16 element Homebrew AZ-EL mounted 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!
THE HORIZONTAL LOOP - If you have the space and can do so, I highly recommend a Full Horizontal Loop antenna (also known as the All Band Loop) 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 the necessary wire, a 4:1 balun, some insulators and 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 build!) When installing a loop, you are looking for the maximum area inside the loop so a square shape is normally used. A circle would be the best design for the most area, but that shape is harder to set up in most cases so the square design is an excellent compromise. 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 as to how make a Full Wave Loop to include...open wire or coax feed line...balun or no balun... 4:1 or 1:1 balun...balun placement on the antenna or on the transmitter... making the loop vertical or horizontal... making it as a square, triangle, circle, odd shape design... copper wire only or ???, etc. The combination that I use really works well and I have no reservations about recommending it to anyone.
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. The wire centers were about 17' high 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 what I considered an effective commercial 80m G5RV that I had 30' high in an inverted Vee configuration. The results of the loop 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 the very high end of 75 SSB were also excellent, but this antenna would not load up on 80m CW with my rig's internal tuner without a balun coil. Without a balun coil, there were some spots on the upper bands where my SWR was a bit higher than I like it to be, but the addition of a 4:1 balun fixed this issue. While an 80m Loop works well all the way to 6m, you need to design your Loop for the lowest frequency you intend to use as the cut off frequency is pretty sharp below its design frequency. (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 to be honest I personally doubted it would work very well. Just for fun I gave it a try 'up there' and once again, I was very surprised at how well it worked on an area 6 meter net. The big loop was as good or better than my full-size 6m copper "J Pole" antenna at 30'! When the 6m band opened a bit, I worked all up and down the east coast from my Alabama QTH using the Loop.
My current Horizontal 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 with a Buxcomm 4:1 balun at the antenna's feed point which is at one corner of the loop. The antenna corners are about 30' off the ground and I put small pulleys on each corner of the suspended antenna 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 and once to repair a broken wire on the balun caused by a severe wind storm. Installation was simple...I just put the loop up, let the rig's antenna tuner tune the antenna flat on all bands, and signals BOOMED in. It works particularly well for my PSK31 QRP efforts and let me work all states and 60+ countries in less than 120 days using 5 watts or less. This antenna also works very nicely for general HF receiving even down into the range below 500 KHz where I like to hunt for aeronautical LF beacons.
KF4ZR, Ken, (Features Editor of Monitoring Times Magazine) built a 750 ft(!) version of this antenna and reported excellent results in an article in June 2011 edition of MT, pg 30. Use his article and the one I wrote for OCT 2010 edition as noted below, and you can easily build an all band loop that is sure to delight you!
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 my article on this antenna in the 2010 OCT edition of Monitoring Times magazine, pg 16. Also look for an article about the building and use of this antenna by the Monitoring Times Feature Editor, Ken Reitz KS4ZR in the 2011 JUN edition, pg 30. )
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 to 4 ground radials that you can roll out and place on the ground. I use three 16 ft. long steel tape measures that I got from eBay for less than $10 total cost. I soldered a heavy wire with a large gator clip to each tape measure and I connect these to the antenna base when I operate. I just roll them in/out when needed. It makes a very fast to deploy, compact radial system. If you don't use at least one or two radials of some kind, my experience is that you will probably be talking to yourself!
If you need an antenna 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 40-10 Meter End-Fed Dipole
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 one that ultimately it must work well! Good company support (if needed) is certainly close behind these attributes. With these in mind, I chose one of the PAR ENDFEDZ antennas when I was living in a condo for a while. I now use it for portable QRP operations at the lake and as one of my emergency use antennas. 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 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 rigs like the Ten Tec R4020). It also rolls up nicely into a small package. It is so small that it fits in a Zip-Lock gallon 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 said to be made to the same standard according. 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 an issue for us QRP ops anyway. Note: Single band ENDFEDZ models can operate at up to 100 watts.
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 had a perfect score of 5 out of 5 for 201 reviews on one version of the antenna, and a perfect score for 70 reviews on the 3 band model! (As of the time I am writing this.) Now that's about the best ratings I have ever seen for any antenna! It also tells me that me the guys that use them must also think these antennas must work pretty well too! Check the eHam reviews to learn more if you need a small, effective antenna. For more details on PAR antennas, go to http://www.lnrprecision.com/endfedz.htm.
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 (works up to 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 for 144/440 MHz use. I made several of these while in the Army for use with projects as needed and of course I used this antenna in Ham Radio, always with good success. It works very nicely in an attic as a stealthy scanner and Ham antenna... plus 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 normally operating radios on the ground, I took particular interest when I heard about NVIS not only because I also worked in communications, but because I was a Ham and was of course interested in such things. A few years later while studying at Ft. Leavenworth, I was doing some research on German communications during the Battle for Stalingrad in WWII and I again ran across NVIS. I learned that the German Army was using NVIS techniques in their operations back in the war years of the '40's as were the Allies. In more recent years, I used antennas configured to work as NVIS antennas in Army MARS and for some State Defense Force operations to see how these techniques worked. Such configurations worked very well. NVIS is a big subject to cover and I only want to mention 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, NVIS techniques should be a natural for your consideration and investigation.
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 vertically 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 where normal communications are difficult, but it does not propagate the signal over long ranges. This lack of propagation could 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 well at a great distance for whatever reason such as Homeland Security needs.
For Amateur Radio use, NVIS techniques are typically practical on 160, 80/75, 60, 40, and perhaps on rare occasions in the 20 meter band. A critical factor for successful operation is to select a frequency that will allow vertical radio signals to reflect down from the ionosphere for the time of day or evening that you are using. The Maximum Usable Frequency (MUF) is the max frequency you can reasonably expect to reflect your signals. Choose a frequency of no more than 80% of the MUF and better yet, choose a frequency of no more than 50% of the MUF for reliable results. This means that in the daytime, the frequency is usually below 10 MHz, and at night it is usually below 5 MHz. Based on the frequencies available to Amateurs, we can expect 40 meters to work most of the time in daylight hours, and 160/80 meters to work well at night. This should tell you that if you tried to use 10, 6, or 2 meters for NVIS, you will strike out. Your signals would propagate up and out into space because they won't reflect back at these frequencies.
For many of our regular amateur antennas to be operated in an NVIS mode, we don't have to do anything except place the antenna very 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 can all 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 HF dead spots close to your QTH, it can lower your noise floor so the frequency is quieter and the signals you do hear sound stronger. Does it sound to good to be true? Well, it works and it works very well, but as good as it is, there are some limitations. This all works best when both stations are using NVIS techniques, although this not an absolute requirement for success. You should also understand that working DX is normally not much of an option with an NVIS setup...NVIS installations work super for area coverage, but do not do well for DX which may be a down side for Amateurs who can only put up one antenna. Another limitation for Amateur use is that really 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 can be overcome by using pulleys to raise your antenna for DX and then to 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 maximize its strengths and work with its limitations. As mentioned, I have had some very good results using NVIS techniques and you can too. 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
(Also look for my article on NVIS Techniques in the 2012 JAN edition of Monitoring Times magazine.)
(Boy, this antenna stuff is hard work! It's time for a coffee break!)