This halo antenna by KB1DIGÂ is made with a true Gamma Section this time and is fashioned from aluminum.
Most of the parts are leftovers from old car projects. The best part is it’s omnidirectional!
The 3/8″ fuel-line I used came from Summit Racing Equipment: http://store.summitracing.com #SUM-G2538,
and a 25′ section costs only about $20.oo.
Frank NG1I and Steve N1TYH used aluminum fuel line from a NAPA auto parts supply store.
Welded the elements to the aluminum plate with some of that “Alumaloy” stuff advertised on television.
Alumaloy Sample auctionÂ 1/10 pound or 2 rods of alumaloy aluminum repair rods.
Go to eBay: http://www.ebay.com/Â Key words for search: (SAMPLE) Aluminum REPAIR Rods ALUMALOY
I drilled a small hole in one of the elements to allow condensation to evaporate.
Capped off the end of the gamma arm with a plug to keep the weather out. The plug was an automotive type used to block off a PCV line from a carburetor.
After mounting horizontally to a 10′ mast I added a support system made from 2 thin 3′ fiberglass rods and some wire-ties.
Also, remember to hot-glue the wire-ties to the fiberglass rod.
Both 54″ elements are bolted and welded to the mounting plate.
Use galvanized or some other type of corrosion resistant bolts.
The size of the bolts is not so important other then that they fit snugly into the ends of the 3/8″ fule-line and hold the elements in place while welding the elements to the mounting plate.
This “Alumalloy” product is great for this purpose and is more like soldering than welding.
After the 2 elements are welded, leave the 2 bolts in place for added support.
The so-239 connector is pop-riveted to the mounting plate.Â Face the pop-rivets out and away from the gamma section.
Cut back and expose about 1/4″ of the center conductor of the RG-8 section for soldering to so-239 connector.
Position the 1″ wide aluminum bracket on the Gamma arm, inward about 3 1/2″.
Expose about 3″ of the RG-8 coax center section.
This is just a starting point for matching this antenna.
I was lucky and didn’t need to make any further adjustment for lowering the SWR.Â The SWR on this design seen here, just the way it is, was 1.2 to 1 at 50.125Mhz.
This halo design is intended to be mounted parallel to the ground.
It should work well for base or mobile operation.
I presently use this antenna at my home QTH and it has proven itself to be quite successful for SSB work.Â It is presently up on the roof, mounted to a 10′ mast section in a 3′ tripod stand.
It can also be modified to work on the FM portion of the 6-meter band by shortening the length of the 2 main elements a little at a time.Â I have not done this.Â No change to the gamma arm will be required if this antenna is altered for 6-meter FM.
This article originally available at http://home.comcast.net/~buck0/6m_halo.htm
(C) 1998, 1999, 2000
Â Cubic Quads
Â The cubic quad is a very popular way to get reasonably high gain and excellent front to back ratios as well as low angles of radiation for without going to extreme heights. Here I present several designs that that achieve the great performance that hams have associated with this antenna for years. Data are presented for 2 and 6 meter quads and a combined 2 and 6 meter quad that is optimized. The 2 meter 3 element design gets a great 9.5 dBi gain coupled with a F/B ratio of 23 dB.
Â Light weight portable cubic quads can be constructed rather easily from fiberglass tubes supported by central hubs. You should be familiar with the material presented in the Quad Loop and Pfeiffer Quad sections of the Antenna Magic page. Cubic quads for wavelengths shorter than 15 meters are easily constructed, however, you should be aware that the weight of these structures is larger by a factor of about 3 relative to most of the planar designs presented in the main menu. Because of this, a heavier mast must be used to support the structure in most cases. Also, be aware that the space needed to assemble and raise a full cubic quad is larger than for the planar designs, and this may be a significant limitation imposed in some locations. In my own case, the backyard associated with my town house is barely large enough to assemble a cubic quad with spreaders of 8′ in length. Wires and guy cords get tangled in the fruit trees, and spreaders hang over into neighbor’s yards. Anything larger 8′ with extended spreaders is essentially impossible to assemble without working above the level of the fence and fruit trees. For that reason, I shall present only two designs which are more or less typical of what can be done easily. The two designs presented are for HF and VHF and should be useful to a wide audience. The HF design is a two element quad for 10, 12, and 15 meters while the VHF design is a two element design for 6 meters with three elements for two meters. A specific advantage of the standard quad design is that multi-band operation is easily accommodated.
I was trying to increase the overall performance of the J-pole, in this design.Â The diagram provided is a more simplified version of the one I did.Â These are a few of the modifications I came up with.Â I added a cap on the top end of the PVC.Â Mounted a so-239 to a split piece of copper tubing, that took the place of the #14 copper wire.Â And, I also added a short aluminum mast that fit into the lower end of the PVC.Â Â I mounted the antenna to a 10′ antenna mast and a small tripod on the roof.Â I tried to add some type of a ground plain but everything I did made the antenna perform poorly.Â After all my efforts the end result was an antenna that out performs the 1/2-wave colinear copper version, with only one exception.Â The working model is somewhat narrow banded and still requires more experimentation.Â Some of the elements must be a little long.
Article originally available at http://home.comcast.net/~buck0/5-8thx2j.htm
This is the antenna for you guys who want to get on HF effectively, and haven’t too much space or cash to throw around. Actually, it’s a design from ZS6BKW (aka G0GSF), similar to the G5RV, but it actually resonates on five bands, (well 6, actually) and doesn’t rely on a tuner (ATU) to make it work. The design appeared in TT (RadCom) Jan & Feb 1993, but is also in Pat Hawker’s “Antenna Topics” (publ. RSGB 2002) It’s only 90 ft long (27.51 metres), with a 40 ft (12.2 m) downlead.
So, it’s a cousin to the G5RV (which only resonates on 14 & 24 MHz), but better as it needs no ATU on 40, 20, 17, 12, 10 and 6 metres.
The following diagrams and tables show some simple 1:1 and 4:1 baluns for use between 1.8 and 30 MHz using twin transmission lines made from enamelled copper wire (ecw). The bifilar windings have been adjusted (spacing) to produce transmission lines with Zo of 50 or 75 ohms as required for best matching. These designs should be suitable for 100-200 Watt operation.
RF transformers should always operate within safe limits of temperature and linearity. The following designs which use toroid cores can be checked for safe operating conditions with the programs included in Programs.
- Ferrite Core: Select either rod or toroid core as detailed below
- Core insulation: 1 layer of ptfe tape (plumbers thread sealing tape); plumbing and hardware suppliers
- Wire: 1.0 or 1.25mm enamelled copper wire (ecw) as specified; electronics shops
- Spacing material: Kinnears 540 TEX colourfil twine; product code K 069048; newsagents, craft suppliers
- Note: This spacing material is polypropylene; other material is probably suitable, but ensure it will not absorb moisture.
Article by Charles Greene, W1CG
My 4:1 current-type balun is wound on a FT-114-43 core. The FT-140-43 is a little easier to
work with, and maybe the FT-140-77 would cover 160-10. This one is reasonably flat from 4.5
to 35 MHz but drops off a little at 3.5, 40-ohms with a 200 ohm resistor on the high side instead
of the 50-ohms I get on the higher bands.
The reason I used the R/S speaker wire is that last summer Wayne (N6KR) reported his
double Zepp with a R/S speaker wire feed line, and someone at ARRL lab measured the
impedance and came up with around 120 ohms. You are supposed to use something that has
an impedance of approximately 2X the input impedance, and this was close.
Now, to the construction instructions:
Refer to the schematic (or figure 2-1A on page 18 of Jerry Sevick’s book “Building and Using
Baluns and Ununs”).
A plan for HF Log Periodic Antenna working 10-20 meters band by VA2PHI
Pictures originally available at http://hb9tmw.free.fr/EuroNet/HTML/loghf.html
A Mississippi Style 40 Meter Magnetic Loop
Ken Holland, K9FV
Edited by Brian Levy, W2BRI
It all starts with my friend Leon, K5BUL. Well, he’s a new ham of about 3 years who lives in Aberdeen, MS. He got into ham radio because he wanted to use it as part of cruising on his 35â€™ Fantasia sailboat. His life took a different turn after he bought a new â€™99 Goldwing motorcycle. Heâ€™s now a biker. He has even mounted a screwdriver antenna to his bike and has worked HF using his ICOM 706MKIIG on the motorcycle.
Iâ€™ve myself have been a ham since the mid-70â€™s (â€™75 I think) with the original call of WA4UBD, which I kept until a couple of years ago when I got the vanity call K9FV. Iâ€™ve used ham radio on my sailboat for years. In â€™99 when the XYL and I took an extended honeymoon for 6 months to the Bahamian Islands, ham radio stood us in good stead.
We had been in the Islands only a few weeks when Hurricane Dennis decided to visit. We found a protected place and rode out the hurricane. The first night out after Dennis, we headed out of the cove. We decided we wanted some something good for supper so we dove for lobsters. What was most unfortunate, however, is that while I was cleaning lobster, my XYL took a shower, slipped, and broke her pelvic bone! The next morning as the Intercoastal Waterway Net came on I reported my emergency traffic. Dr Jim of Miami came on the air and discussed my wife’s symptoms with me. We agreed that it did in fact sound like a broken bone, and she would surely need more medical attention. Needless to say, we needed more medical support than the island could provide. Another ham got on the air and did a phone patch, we were still anchored out, to my insurance company and to DAN (Divers Alert Network). I then upped anchor to the closest marina where we could access the island’s nurse and a pay phone. DANâ€™s staff doctor talked to the local nurse at the island, then the DAN doctor talked to my insurance company. The insurance company authorized a Lear jet ambulance to transport us to Fort Lauderdale for medical treatment.
Since that fateful experience, my XLY does not complain about any radio purchases I make. These days I just say â€œItâ€™s for safety on the boatâ€. She even bothered getting her Technician license â€“ KG4TIN.
From time to time, I also install a screwdriver antenna on my motorcycle. It’s an old â€™92 goldwing and it works just fine for HF mobile.
Let’s get back to the topic of Magnetic Loops. Leon and I both share an enjoyment for building things, and antennas are certainly included. Since I live on a 40â€™ sailboat, and he has the land for antennas â€“ we do most of our antenna work at his QTH. After reading Brainâ€™s post (W2BRI) on QRZ and eham.net, I visited his webpage and liked what I read. I spoke to Leon and sold him on the idea of a magnetic antenna before Christmas of 2002. By Christmas Leon had the basic loop built using electrical 3 inch aluminum conduit. This is a fairly heavy walled soft aluminum pipe that bends easy. Leon constructed the loop using â€œfactory 90â€™s.â€ These are pre threaded pipe which is bent into a 90 degree pieces. The loop is a 10 foot by 10 foot square with a 3 inch gap at the top of one side â€“ like we saw in Brian’s antenna plans on this site.
Leon and I got the Magnetic loop tuned and tested Dec 30th, 2002. Leon had the loop all made up and ready to be completed when I got there on Monday morning. We hung the 10 ft square loop from a tree limb putting the bottom about three feet off the ground. We added the feed and the capacitor and got the loop tuned up to forty meters.
We turned on the radio, and got ready to do our on the air comparison. We were located just north of Columbus, MS. We were able to test the antenna with a station in Talladega, Alabama against Leon’s permanent forty meter full wave loop at 30 feet. The gentleman in Talladega was located about 200 miles ESE of our location. WA4FMR near Knoxsville, TN was our second contact, who was located perhaps 400 miles NE of us. Both stations gave good reports on the magnetic loop, but did say the full wave 40 meter loop was better by about 1 or 2 S units. That was about the same results we saw on the S-meter when receiving the two test stations. This performance confirms what Brian had expressed to me earlier on the phone. The one major advantage with the loop however, is its small size. Leon liked the loop so much, he is now planning a 20 meter version. He hopes to compare it to his 20 meter bazooka one day.
Ken Holland, K9FV
Build a Motor Driven Magnetic Loop AntennaÂ 1.5 Meters Square for 3.5-10MHZ
By Neil Lowson, GM4XRF
- 4 1.5 mtrs 22mm copper pipe
- 4 22mm copper 90 degree bends
- 1 500pf 6kv capacitor
- 1 12 volt 4 RPM geared motor
- 2 flexible couplings
- 1 insulated if possible
- 1 6-1 or 10-1 reduction gear
- 2 small micro switches
- 1 5 pin SIN SKT@plug
- 1 400mm 4â€plastic pipe
- 1 4â€plug insert for bottom of pipe they have a rubber seal on (B)
- 1 4â€seal for top this a screwed on cover for access to the capacitor (A)
- 1 60mm *350mm *4mm paxolin for motor/capacitor
- 1 75*75 4mm paxolin plate for fixing mast to loop at bottom with saddles
- 2 12volt leds 1green 1 red
- 1 25mm PVC coupling
- 1 25mm broom handle
Assembly first starts with the capacitor and motor, this is the important part of the magnetic loop. Get the strip of paxolin and mount the capacitor at one end (top). Fit the insulated coupling to the capacitor shaft and then fit the reduction gear. The brackets will need to be made from 4mm aluminium. Then make up a bracket for the 2 micro switches.
They have to be set as to use the flexible coupling with a long 4mm screw in one of the holes for switching at min/max capacitance, see photo and wiring diagram. Next the 100mm /300mm plastic drain pipe (length to suit cap/motor) fits the bottom section of top plug with pvc. Glue and drill 2* 25 mm + holes 30mm down from top of pipe with the holes opposite one another for the 25mm copper pipe to be inserted in about 25mm. Then bolt cap/motor assembly into pipe. Connect capacitor to copper pipe with coax braiding and 6nmm brass bolts. Get the bottom plug fit the 25 mm coupling and the din socket connect to motor and fit with self-tapping screws and sealant on main pipe. Assembly of capacitor is now complete. Fit broom handle to coupling, I use this as the mast, also to attach the coupling loop with cable ties.
Assembly of the Loop:
4*1.5 mtrs 22mm copper pipe. Take 1 length cut 30mm of the length the pipet in half — this is the top portion ofÂ the loop. Clean the pipe and bends with wire wool and add flux. Then fit bends to pipe. Do this on flat surface and fix bends with self-tapping screws till you solder. You now have a square loop. Paint if required.
Coupling the Loop:
Coupling loop should be about a 1/5th size of main loop made from RG58U COAX but I always make it bigger. Then trim it by 15mm at each end till you get a 1-1 match (see photo). Then solder And seal with rubber tape.
I use small power supply unit you can buy for calculators/portable radios 3/4.5/6/9/12/volt at 1 amp — they are ideal for the small 12V motor. I built mine into a small box with the switches and the LEDs work well. There are more sophisticated control circuits that can be used but this was the easiest.
This article was available at http://www.standpipe.com/w2bri/article2.htm