Can you use a pipe cutter or a hack saw, can you solder – then here is how to build a SIMPLE ”J” antenna that will more than double your 2 meter (and even 440) performance! by Dale “Kuby” Kubichek, N6JSX
HF Receiving loop antenna
Receiving HF signals at my location is a compromise situation due to the antennas I use and the high noise environment in the city. Although my transceiver has good selectivity and excellent filters, I suffer from high noise conditions that at times make receiving a chore. This is true for both weak-signal DX as well as regional chats with friends in the Southwestern US.
I have often wondered whether a loop receiving antenna would be a good solution to my need for better reception but was hesitant to get involved with the typical preamplifiers and monstrous dimensions most of the designs I have seen require. This all changed when I came across a website that described an easy-to-build receiving loop that does not need a preamp.
This design does require an external antenna tuner to provide some preselection gain and uses your transceiver’s preamp. You simply connect the loop through the feeder to your antenna tuner and feed the tuner into your transceiver’s auxillary antenna input connector. You peak the external tuner for maximum signal strength. Remember: this is a RECEIVE only antenna – it is not intended for transmitting!
If your rig doesn’t have an internal antenna switchover relay you will need to exercise caution doing it manually. I built my first loop for 40/80m in order to improve reception of signals in the Southwest and inadvertently transmitted once on 75m. I was heard weakly, 150 miles away -pumping 300 watts into the loop – it didn’t damage anything but you don’t want to operate this way for long! I built this loop directly from the greertech.com website dimensions (see below) and added my own wooden support design made from 1/2X3/4 inch stock from Home Depot.
I first built the loops and supported them with a simple 1/2 inch PVC pipe mounting system to evaluate them. I liked this antenna so much that the final versions have a simple wood support built into my operating desk for hand rotation. I can remove the entire antenna system in a manner of minutes when I don’t want to use the loop.
The photos here show the basic parts and how small the 20m loop really is – each wooden frame piece is 22 inches long. The feeder from the loop to the antenna tuner is 34 inches long, and the loop itself is 5.9 feet in length, per the greertech.com dimensions for RG-58/U coax. If you use a different coax type, make sure you use the appropriate dimensions in the referenced material. Receiving HF signals at my location is a compromise situation due to the antennas I use and the high noise environment in the city.
Although my transceiver has good selectivity and excellent filters, I suffer from high noise conditions that at times make receiving a chore. This is true for both weak-signal DX as well as regional chats with friends in the Southwestern US. I have often wondered whether a loop receiving antenna would be a good solution to my need for better reception but was hesitant to get involved with the typical preamplifiers and monstrous dimensions most of the designs I have seen require. This all changed when I came across a website that described an easy-to-build receiving loop that does not need a preamp.
This design does require an external antenna tuner to provide some preselection gain and uses your transceiver’s preamp. You simply connect the loop through the feeder to your antenna tuner and feed the tuner into your transceiver’s auxillary antenna input connector. You peak the external tuner for maximum signal strength. Remember: this is a RECEIVE only antenna – it is not intended for transmitting! If your rig doesn’t have an internal antenna switchover relay you will need to exercise caution doing it manually. I built my first loop for 40/80m in order to improve reception of signals in the Southwest and inadvertently transmitted once on 75m. I was heard weakly, 150 miles away -pumping 300 watts into the loop – it didn’t damage anything but you don’t want to operate this way for long!
I built this loop directly from the greertech.com website dimensions (see below) and added my own wooden support design made from 1/2X3/4 inch stock from Home Depot. I first built the loops and supported them with a simple 1/2 inch PVC pipe mounting system to evaluate them. I liked this antenna so much that the final versions have a simple wood support built into my operating desk for hand rotation. I can remove the entire antenna system in a manner of minutes when I don’t want to use the loop. The photos here show the basic parts and how small the 20m loop really is – each wooden frame piece is 22 inches long.
The feeder from the loop to the antenna tuner is 34 inches long, and the loop itself is 5.9 feet in length, per the greertech.com dimensions for RG-58/U coax. If you use a different coax type, make sure you use the appropriate dimensions in the referenced material.
I pegged the pieces of the loop support together using dowels so as not to have any metal inside or close to the loop. I made the shorted end of the loop out of an old “blitz bug” lightning arrestor which was in my junk box that conveniently has female ‘259 connectors and a screwhole in the barrel. Make sure you short only the braid to the center conductor to the braid and don’t short out the center conductors! You could simplify things and skip the connector altogether – just solder the center conductor to the braid to the shield as greertech.com indicates on his website.
My first 40m loop was built this way and it took about 15 minutes to construct. Notice the very important gap in the shield braid on the side of the loop – this is one of the key features that makes this design work. See the greertech.com website referenced below for the electrical details and principles of operation – this is an excellent source of information for these simple, constant-current magnetic loop antennas. RESULTS This simple and inexpensive loop works remarkably well for something so cheap and simple. It has given me enhanced receive performance in three areas:
- Nulling noise sources and interference – Orienting the loop so that the plane of the loop is directly aimed at a noise source (and it works for noise sources either near or far, it doesn’t matter) allows you to essentially remove the noise. The nulls are sharp, meaning a slight rotation of the loop will pass through it if you’re not careful. Of course, if the noise source is in line with the bearing to the signal you want to receive this is not going to help – but in cases where the bearings are different it is a significant help. I am now able to eliminate some sources of noise that have plagued me for years.
- Peaking desired signals – Aim the plane of the loop to maximize the desired signal and other signals are reduced in strength (unless they are on the same bearing). This loop receives a bi-directional figure-8 pattern, where the peak is in the plane of the loop and the null is broadside to the loop. This little antenna has excellent directivity – I have enjoyed orienting the loop for peak signal strength on both DX as well as US stations and for the majority of cases I can determine the Great Circle Bearing within 5 degrees of the actual bearing. If you enjoy RDF (Radio Direction Finding) pursuits on HF, this is a neat way to do it. There are instances where signals don’t show much directivity – I have especially noticed this on Near Vertical Incidence Skywave signals.
- Lower noise floor – The loop delivers a lower strength signal than a conventional antenna so you need to compensate for this with your transceiver’s preamp (or use an external preamp after the antenna coupler and in to the receiver) to bring the signal back up. By doing this in combination with reducing your RF gain and using your AF gain to bring up the signal for comfortable listening you will have reduced the noise floor in your system and will enjoy quieter receive performance. Of course your S-meter won’t read like it normally does, but that’s a slight penalty to pay when you can hear signals without so much noise!
I am pleased with the improvement this loop has provided in my receive capability. I am able to copy some weak-signal DX I previously could not copy at all and I can now listen on the lower bands with the 40/80m loop and enjoy improved noise conditions.
Copyright pictures and text to K7ZB
2 Meter mobile antenna
Do you have trouble getting your mobile signal into the LEO satellites? Try this small 2 meter vertical antenna with your mobile rig or HT and enjoy more success in your uplink. I built this small vertical because I could not uplink very well at low elevations and I just could not bring myself to drill holes in the roof of my new truck to install a more substantial antenna. I had been using a very common 1/4 wl mag-mount with only marginal results.
Design:
This is a high-efficiency “gain” antenna. It is not mounted permanently: I have a magnet attached to it and “throw” it up on the roof when I want to work a LEO satellite.
The antenna is an atypical vertical: instead of the common 1/4 wl vertical monopole or 14/ wl ground plane with 1/4 wl radials, this design employs a 3/8 wl vertical section and short radials to complete the “ground plane.” Effectively, an off-center-fed vertical dipole that does not rely on the earth or, in my case the truck body, to complete the bottom half of the antenna.
This is an important point. The fact the antenna has a fully contained lower half, i.e., the ground plane, makes it very efficient. This is especially significant when compared to my mag-mount monopole antenna where the “ground plane” had to be completed through the coax, through the rig, then to the vehicle body. I suspect the mag-mount was not very efficient at all. The dipole is off-center-fed to get a better match to the feedline and the bottom “half” of the antenna is completed with capacitive reactance from the four shortened radials.
This design has an honest 3 dBi of gain at 6′ elevation (2 dBi free-space) with a suitable pattern for LEO communications–favoring the horizon. At 20′ high, the same antenna exhibits almost 6 dBi of gain. The feedpoint is a nominal 50 Ohms at 146.850 mHz.
Construction:
The antenna is built using a 3/4″ PVC tee, a cap for the top, and a plug (flat on the bottom) for the bottom. The tee is arranged vertically with the top cap drilled for connection of all 5 elements (I used 6-32 stainless steel botls/nuts/washers) and the bottom plug is drilled for connection of a magnet (optional).
The coax is fed thru the open side of the tee and connected directly to the elements via ring lugs. Alternately, a lower-profile version could be constructed substituting a coupling for the tee and drilling a hole in it for the coax to exit. I connected the center of the coax to the mast and the shield to one of the radials using crimp style ring terminals. I then wrapped some small gauge wire around the outside of the cap, connecting all four radials together, and covered the assembly with electrical tape and paint.
The figure at right shows the layout and dimensions (in cm) of the elements. A 25-3/16″ (64 cm) vertical section is combined with four 7-3/16″ (20 cm) radials. I recommend you make the elements slightly longer and then trim them based on SWR readings. I used 10 gauge insulated wire for all the elements, but 1/8″ or 3/16″ aluminum rod would be a suitable material–and likely more durable. When tuning for minimum SWR, I eventually pruned the mast to 24-3/4″ and the radials to 7″ to get a 1.2:1 SWR. That is much better than my mag-mount ever showed so I stopped fine-tuning and put it on the air.
The radials are angled down at about 30 degrees. This angle can be adjusted to get the SWR perfect once the vertical mast is trimmed for best SWR at the desired frequency, but I found the effect minimal. You could also “wind” a coil of a few turns in the center of the mast to lower the profile of the antenna without affecting feedpoint impedance drastically or performance too much. I did that to make it short enough to fit under my garage door header and note no significant difference in SWR or performance.
Performance:
Mission accomplished. I can now get “into” the birds at low elevations. On it’s maiden journey out of the garage, I worked four stations (one was marine mobile) on an 8 degree AO-27 pass. If I could hear the bird, I could work it (as long as a “big gun” station did not have the bird already captured). At high elevations I found I could run on low power (about 3 Watts) and capture the bird with little difficulty.
This antenna makes a nice companion to the 70 cm Handi-Tenna or can be used for any fixed, mobile, or portable service. Since the elements are flexible 10 gauge wire, they can be readily folded and unfolded for backpacking.
Aricle by K5OE originally availbale a http://members.aol.com/k5oejerry/vhf_vert.htm
4 Elelemt Yagi Beam Antenna for 20 meter
On picture 1 you can see the GK 4 element 20m yagi on a 40ft boom on the construction pedestal for the 20m stacks
All of the yagis were built on the pedestal you see under the beams.
Omega match on this new yagi for the 4X4 stacks has been adjusted using a TS-50 and a BIRD 43 watt meter.
The antennas installed, one at 95-ft and the other at 37-ft.
Top one on a 3in diameter boom, the bottom on a 4 in diameter boom.
Article and project by ve3gk
End Fed antenna
This end fed type of antenna was marketted in the UK and is a useful system for the portable set-up.
Being a half wave, no radials or counterpose wires are needed.
As the impedance will be high at the end of the wire, some form of matching unit is needed and a simple parallel tuned circuit housed in a plastic film container is fine (figure 1).
A hole in the container allows for tuning, by adjusting the ferrite core in the coil for maximum reading on a field strength meter nearby.
The inner of the coax goes to a tap about 1/4 of the way from the earthy end of the winding, to which the braid of the coax is soldered.
As a rough guide, a capacitor of 50pf across a winding of say 30 turns is a starting point for 40m. Some experimenting with turns and tapping point is necessary.
The coil former used was about 1/4 inches in diameter as found in old IF transformers.
The antenna wire (1/2 wave long) is soldered to the top of the coil as shown in figure 2.
The drawings illustrate the set up, I hope.
For portable use, throw the wire into a tree or whatever, using thin cord or rope onto the insulator (figure 1), tune for best filed strength reading and off you go!
Try it – it works!
Want to work two bands? Use a slightly bigger container with two tuned circuits which have some sort of terminal each, to which one of their respective wires can be connected.
Rough lengths of half wave wires:
80m – 132 feet, 40m – 66 feet, 20m – 33 feet.
Source: g3ycc
How To Make A High Power 4:1 Balun
How To Make A High Power 4:1 Balun Info
I built a homebrew 75 meter Double Extended Zepp Antenna,
And I needed a 4:1 Balun , so I decided to Homebrew the Balun also.
Here is how I did it!
I used a 5 inch long piece of PVC Plastic pipe about 5/8 ID and about 7/8 OD , 1 inch OD will work fine.
I wound 12 bifilar Turns using 10 Gauge Solid insulated copper wire, but you can use 12 or 14 Gauge.
I recommend using two different color wires.
I used Black and White from an old piece of 10 Gauge Romex house wire.
If you use 10 Gauge wire the Balun will handle the legal power limit!
Connect the top end of the black wire to the bottom end of the white wire.
This connection point will also connect to the coax shield and ground wire.
Optional – You can also connect a heavy wire as short as possible from this connection point to a ground rod and/or ground system,
A short piece of ½ inch coax with the center and shield connected together at each end would work great.
This puts the whole antenna system at DC ground potential.
Connect one side of your open wire feedline or 450 ohm ladder line etc. to the Top wire “white wire in picture below”
Connect the other side of your open wire feedline or 450 ohm ladder line etc. to the Coax Center and Bottom Wire “black wire in picture below”
After winding the coil I recommend coating it with several coats of clear spray paint “available at Wal-Mart for about $1.00 a can.
This 4:1 balun will work fine from 10 thru 160 meter bands.
NB: There is NO open wire feedline or 450 ohm ladder line etc. connected to the Balun in the picture.
I currently use a 75 Meter Full Wave Delta Loop on the 6 thru 75 Meter bands with a tuner.
I am very pleased with it!, I also currently use a 160 Meter 1/4 wave inverted L antenna.
It will also tune 6 thru 160 meter bands
Copyright by W2HT originally available at http://www.bloomington.in.us/~wh2t/balun.html
Web Shortware Receivers
I began dxing in 1986 with my old MARC II shortwave receiver. I used to wonder what it would be like to dx from distant points all over the world and country. I never would have imagined someday I would be using remote controlled receivers worldwide.
We can use Icom PCR 1000’s, AOR_AR 5000’s, Kenwoods, Drakes R-8’s,and other receivers.
We can use spectrum analyers, and rotors.
We have access to elaborate antenna systems.
Here is a list of popular online radio receivers:
N2JEU’s web controlled shortwave receiver
The W5UN 2 Meter QUAGI 97
The W5UN Quagi 97 is a computer optimized quagi derived from the original W5UN Quagi of the early 1980s. The length of the 1997 model has been deliberately shortened to allow it fit on a 24 foot boom. Performance is substantially higher than that of the original antenna. It now compares favorably with yagis of the same length. The two programs used to optimize the updated antenna were AO6 and NEC 2.
This antenna has not been verified by actual construction. Gain and front to back will be as stated below. The only component of the antenna that needs verification is the 50 ohm match. Who would like to be the FIRST to build the actual prototype model?? Full consultation will be available to the prototype builder during construction. Contact w5un@wt.net if you wish to be the first!
Antenna Characteristics: 23′ 9″
11 Element Gain: 13.56 dBd at 144.100 Mhz
F/B : 23 dB
Stacking:
Optimum: E Plane: 13.73′
Optimum: H Plane: 12.86′
Stacking can be reduced up to 90 percent of optimum and still achieve acceptable stacking gain.
Optimum stacking is recommended, however.
W5UN QUAGI 97 Dimensions in FREE SPACE:
Element Boom Pos. El. Length Material
Reflector 0.0000" 84.37" loop. #12 solid INSULATED copper wire *
Driven 16.2500" 82.43" loop. #12 solid INSULATED copper wire *
Dir 1 37.1875" 36.168" 3/16" aluminum rod
Dir 2 70.1875" 36.052" 3/16" aluminum rod
Dir 3 102.5000" 35.817" 3/16" aluminum rod
Dir 4 135.8125" 35.475" 3/16" aluminum rod
Dir 5 169.0625" 35.179" 3/16" aluminum rod
Dir 6 202.8125" 35.090" 3/16" aluminum rod
Dir 7 234.2500" 35.324" 3/16" aluminum rod
Dir 8 264.8750" 35.617" 3/16" aluminum rod
Dir 9 285.0000" 35.108" 3/16" aluminum rod
* #12 TW insulated solid copper wire is common house wire, found at most hardware and building supply stores. Do not strip the insulation.
The above dimensions may be used for non metallic booms like wood or fiberglass.
If you wish to use a metal boom with through the boom insulated elements, please apply the following correction to the directors only.
The reflector and driven quad elements must remain insulated from the boom.
Boom Diameter Correction Add
0.750" or 19.050MM 10.56% .0792" or 2.02MM
0.875" or 22.225MM 12.14% .1062" or 2.70MM
1.000" or 25.400MM 13.66% .1366" or 3.47MM
1.125 or 28.575MM 15.13% .1702" or 4.32MM
1.250" or 31.750MM 16.54% .2068" or 5.25MM
1.375" or 34.925MM 17.90% .2462" or 6.25MM
1.500" or 38.100MM 19.21% .2882" or 7.32MM
1.750" or 44.450MM 21.67% .3792" or 9.63MM
2.000" or 50.800MM 23.91% .4783" or 12.15MM
Further information concerning use of metallic booms with insulated ‘thru-the boom’ mounted elements follows:
PROVEN ACCURATE FOR BOOM DIAMETERS SMALLER THAN .055 WAVELENGTHS.
MEASUREMENTS BY DL6WU.FORMULA BY G3SEK.
FORMULA: C = 12.5975B – 114.5B^2
C = CORRECTION FACTOR AS A FRACTION OF THE BOOM DIA.
B = BOOM DIA IN WAVELENGTHS
B^2 MEANS B SQUARED
2 METERS BOOM DIAMETER CORRECTION ADD 2 METERS.
2 METERS BOOM DIAMETER CORRECTION ADD 2 METERS.
0.750" OR 19.050MM 10.56% .0792" OR 2.02MM
0.875" OR 22.225MM 12.14% .1062" OR 2.70MM
1.000" OR 25.400MM 13.66% .1366" OR 3.47MM
1.125 OR 28.575MM 15.13% .1702" OR 4.32MM
1.250" OR 31.750MM 16.54% .2068" OR 5.25MM
1.375" OR 34.925MM 17.90% .2462 OR 6.25MM
1.500" OR 38.100MM 19.21% .2882" OR 7.32MM
1.750" OR 44.450MM 21.67% .3792 OR 9.63MM
2.000" OR 50.800MM 23.91% .4783" OR 12.15MM
20.000MM 11.04% 2.21MM 28.000MM
14.87% 4.16MM 30.000MM
15.78% 4.73MM 32.000MM
16.66% 5.33MM 38.000MM
19.17% 7.29MM
Insulators can be commercial shoulder insulators and keepers or as simple asheat shrink tubing with the element held in place by hot melt glue or epoxy glue.
The RockLoop Antenna
W9SCH described this small loop in Sprat 60 and it has proved useful to the QRPer, especially where space is at a premium. It is basically a variant of the usual magnetic loop, using a toroid balun to get a reasonable match on the three bands.
A slow motion drive would prove useful on the tuning capacitor, which is a 100 pF airspaced variable. The lamp is used to tune the loop.
Depending on local environment, it may be necessary to experiment with the dimensions of 33″ square and the turns on the toroid.
Using this indoors, the author worked several thousands of miles with QRP.
Info and drawings by G3YCC and W9SCH
CobWebb 5 band antenna
I have a very small back garden and am limited with what type of antenna I can use. I built my first antenna in July 2004. If you are looking at this after speaking to me, you know it works. It is basically a 5 band antenna comprising of 5 full half wave dipoles for each band – between 10M & 20M. As an added bonus, the antenna is also resonant on 6M!! Each dipole leg is made from twin cable and fed with 50ohm coax. It is Omni directional and cost about £40.00 to build. I don’t know how much power it will take except to say it comfortably handles 400 watts, although I usually only use 50 watts. I used an MFJ-259B to help tune the antenna – this proved invaluable Below are some pictures that may help anyone considering building an antenna of this type. You are more than welcome to email me if you want more info.
Antenna Construction tips
| Band | Overall Loop (suggest you cut 15-20cm longer to allow for band adjustment.) | Each leg | Short point |
| 10M | 508cm | 254cm | 156cm |
| 12M | 586cm | 293cm | 179cm |
| 15M | 690cm | 345cm | 208cm |
| 17M | 812cm | 406cm | 222cm |
| 20M | 1030cm | 515cm | 272cm |
*(suggest you cut 15-20cm longer to allow for band adjustment.) Each loop is made from figure 8 speaker cable. The ends of each loop are folded back on themselves to adjust resonant frequency as well as providing an anchor point for the loop. The ends have been left approx. 3″ apart from each other, but are joined together using cable ties. Click here for a handdrawn diagram with additional fine tuning info (approx 254kb). Here are some of the countries I have reached using this antenna mounted approx. 15ft high over a 6 week period (between July and mid September 2004) using about 50 watts power. When next I get the time I will update this image to 2005 stats.
**Update July 2005**
I rebuilt the antenna using white fiberglass poles, white twin speaker wire and a white junction box. A good friend of mine, Pete – 2E0PRP, welded up the quad bracket.
The result is a much neater looking antenna on top of my push up mast. The antenna is resonant on the bands it has been designed for, and to my delight I also find that it is resonant on 6m. The table below shows the SWR / bandwidth with the antenna about 15ft high. As you will see its’ turned out quite well – but you have to decide what mode you want as the antenna has not got a wide bandwidth. The pictures below show the revised antenna.
| Band | Low Point SWR | Mid Point SWR | High Point SWR | Bandwidth | |||
| 20m | 14.024 | 1:1.6 | 14.090 | 1:1.0 | 14.151 | 1:1.6 | 125Khz |
| 17m | 18.081 | 1:1.6 | 18.115 | 1:1.3 | 18.190 | 1:1.6 | 110Khz |
| 15m | 21.000 | 1:1.6 | 21.044 | 1:1.0 | 21.099 | 1:1.6 | 99Khz |
| 12m | 24.872 | 1:1.6 | 24.931 | 1:1.1 | 25.000 | 1:1.6 | 125Khz |
| 10m | 28.484 | 1:1.6 | 28.406 | 1:1.0 | 28.325 | 1:1.6 | 160Khz |
| 6m | 50.110 | 1:1.5 | approx 100Khz |
Copyright MOMRR