Amateur Radio news from Italy

IW5EDI Simone – Ham-Radio

eSoftAnywhere DSP & More

Posted in Ham Radio Software 2 Comments

This freeware software performs DSP (Digital Signal Processing) on audio signals received from an input line on your computer’s sound card. It is specifically intended for processing audio signals from short wave, amateur (ham) radios, or any other radio to “clean up” or improve the listening quality of radio signals. It can also improve radio signal quality before the signal is sent to a radio modem or TNC (Terminal Node Controller)

Offer audio recording functionalities.

A logbook feature is incorporated so that radio contacts and transmissions may be recorded (something practically mandatory for ham radio operators and often practiced by short wave listeners as well). There are a great many other features available, just browse through the help file.

To properly use eSoftAnywhere DSP & More you will generally need to run an audio cable from your radio audio output jack to the microphone or other input jack on your computer’s sound card. The Audio Wizard can then fine-tune your sound card audio levels for use by the audio processing features of the software.

By Konrad Byers VE1EXE (sk)

Download eSoftwAnywhere DSP & More  (3.8 Mb) 

The Stacked J-Pole

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First build a regular MonoBand J-Pole from the Copper Cactus plans for a 2-meter antenna, leaving off the top pipe cap.

Build a second J-Pole, which will look like an L-Pole, the vertical is 38-3/4 inches from the top of the antenna, down to the centerline of the horizontal member.


The lower leg of the L consists of two horizontal pipes spaced as close together as you can get them using standard 90 degree elbows.
From the centerline of the vertical, to the centerline of the fittings at the end of the horizontal members the distance is 18 inches for 2-meters.

I have not calculated the exact measurements for any antenna other than the 2-meter band. A final 90 degree elbow is placed directly under the vertical section and is soldered to the top of the existing J-Pole.

The finished product resembles an L on top of a J, of course the lower leg of the L is two pieces of horizontally positioned pipe.

The Adcock HF RDF Antenna

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The Adcock antenna has been used for a long time for RDF. It is basically an interferometer.

When both of the two dipoles see exactly the same signal strength and RF phase, no signal is delivered to the receiver. This condition happens only when the signal source is equal distance from the two dipoles.

As the antenna is rotated through 360 degrees, there will be two directions where the signal will drop to a very low strength. This can be a very deep and narrow null. The direction readout is then read, and the direction of the signal is then known, with an ambiguity; we don’t know which of the two null directions is the correct direction.

The directional ambiguity will be resolved when another station takes a bearing from some significant distance away. The two correct headings will cross, while the two incorrect ones will not cross.

Since this antenna only responds to vertically polarized components of signals, poor performance can occur when the signal is horizontal or nearly horizontal. Since purely horizontal signals are rare, it should function on most signals.


Construction

Construction is not critical. The only really important factors are electrical balance, and a lot of clearance distance to other objects. These factors may require the antenna be placed out in the open, away from the radio operating position.

The simplest arrangement would be a free-standing support with the vertical mast pivoted on a compass rose on the ground. This can be wood. Metal can be used for the support and for the cross-boom, as long as the two dipoles both always see the same capacitance from the structure. Symmetry is the name of the game here.

A remote speaker and remote S meter can be mounted at the antenna in a weatherproof box. The operator can tune in the suspect signal, and then go out to rotate the antenna and take the heading.

Detail of the Combiner circuit

The combiner circuit mounted on the cross boom is not critical for the antenna to DF. If a tiny toroid is used, use small diameter wire. If a large toroid is available, larger wire can be used. #30 wire would probably work for a 1/2 to 1 inch diameter toroid.

The number of turns is not critical, but slightly greater sensitivity for weak signals may be achieved through experimentation.

The feed line lengths on each side must be identical.

The length of the dipoles is not at all important, so long as they are not resonant at some frequency of major interest. Phase characteristics of a resonant antenna are strongly affected by very slight detunings. If the two dipoles are not exactly the same (they won’t be!) then the antenna will exhibit maximum error at the resonant frequency.

Because this is a broadband low-cost antenna, it is not possible to have good impedance match between the antenna and the feed line at all frequencies. Experimentation with turns ratio (bifiler turns versus coax feed turns) may provide an optimum match at some desired frequency, such as 20 meters. Mismatch on a receiving antenna is usually not important. Even with a poor antenna one can hear most of the signals on the band, because receivers today are so very sensitive.

We hope that some of the visitors to our page will try this antenna.
The writer has worked with interferometers on 2 meters. The results where truly impressive!

Copyright by K6BMG BMG Electronics. [members.aol.com/bmgenginc]

An Improved Multiband Trap Dipole Antenna

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You need this—traps with lower loss, higher Q, increased power-handling capability and four-band coverage!

trap

This improved multiband trap dipole introduces a new trap design and a change in trap location. The antenna features double-coaxial-cable-wound traps having lower reactance and a higher quality factor (Q) than earlier coax-cable traps. .

Article published on QST, author and copyright Al Buxton, W8NX

Trap-Dipole-AntennaDownload

available also at www.scribd.com/doc/24990781/Trap-Dipole

3 Element 28 MHz light weight Yagi

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Background:

In the solar maximum years 28 MHz is full of DX stations, that can be worked with very simple equipment. However the fun will be even greater with a proper antenna. So I decided to build a 3 elm. yagi and took the design from ARRL’s: “Yagi Antenna Design” by W2PV. But I also wanted to see, if it was possible to build it from the materials normally used for VHF (TV) antennas.
One reason was to have a real low cost design, where a couple of old Band l TV antennas would supply all the building material, another reason is that working for a TV-antenna producing company, I have easy access to building materials from the production left-overs.

The design:

The boom is made from square 18×24 mm aluminum. The elements from tapered aluminum tubing of 12mm, 10mm and 8mm diameter. The ø12mm center section is 2000mm long, two pieces of 1030mm ø10mm is inserted 30mm into the ø12mm piece and locked with a self tapping screw. This gives a very light 4 meter long element. Two pieces of ø8mm tubing are added to reach the final length of each element. The elements are mounted on top of the boom using metal brackets.
The gamma match is made from 800mm ø10 tubing mounted 60mm under the driven element. The series capacitor was found experimentally; remember to use a high voltage low loss type at this place! Because of the thin elements the resonance length must be recalculated

Results:

By adjusting the length of the Gamma match and the series capacitor, the VSWR can be adjusted to 1.1:1 at 28.4 MHz – the bandwidth is a bit narrow due to the thin elements, but for my TS820 that’s no problem.
On the air there was an immidiate difference of almost 2 S-units between the beam and my old 5/8 wavelength vertical. Instead of always having to call others, I could now call CQ – and get answers. And within two days of putting the beam up I worked VK9NS.

Mechanical strength:

This antenna is made from light materials. It will not be able to withstand a severe hurricane – the kind that hits me every 3 to 5 years. But being low cost and home build! I have simply prepared myself by stocking some alu tubes for new elements. If and when the antenna is damaged I can repair in an hour.
Until now it has survived storms having 20 m/s (72 km/h) average windspeed with 30 m/s (108 km/h) gusts. When expecting a storm it’s wise to turn the antenna so the windload on the elements is as low as possible.

By OZ2OE originally at hjem.get2net.dk/ole_nykjaer/oz2oe/28mhz/28mhz.html

WLAN antenna 2.4 GHz Do-It-Yourself

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Homebrew outdoor antenna to 2.4 GHz band.

Antenna gain is comparable to panel antennas including the Freedom Antenna Set sold in Finland. Comparing is made simple by connecting antennas to same computer with Orinoco WLAN card and indicating results in Link Test of the Client Manager. My antenna has been found about 2 dB better gain than the Freedom antenna, which is specified as 12 dBi antenna. And prices … Oh, I need not even mention this! In Europe there is a maximum allowable output power of 20 dBm (100 mW) because of the ETSI standard we use. While Orinoco “red” card is transmitting 8 dBm signal and my antenna gain is about 14 dBi there has to be only 2 dB cable and connector loss to keep output level below 20 dBm. The Orinoco Adapter Cable takes about 1 dB and H1000 antenna cable takes 2 dB/10m. So using 5 metres antenna cable there is no risk of exceeding the output power within the ETSI standard. This antenna can also be built without the Ring to decrease antenna gain if needed especially with very short antenna cable.

Dimensioning

The very first point in antenna dimensioning is to calculate the wavelength (the Lambda character has been replaced with letter L ):
L /mm = 300 / (f/GHz)   ->  at 2.45 GHz  L = 122 mm.



Main parts can been found even in mama’s dish cabinet but maybe safer to buy them from a department store. The Reflector is made from an aluminium cake pan and the Cover from a plastic microwave bulb, both 240–250 mm dia. The pan must be straight and smooth without profilations and the sides will be orthogonal with the bottom. If you find a pan made from stainless steel may be that may be  better. I used a pan from italo ottinetti code 140024 , whose sides were 60 mm and I cut them to 32 mm.

Other parts needed:

  • A piece of copper water conduit, internal dia 10 mm, length below 40 mm
  • A piece of brass rod, outer dia 4-4.5 mm, length < 40 mm
  • Copper wire about 2 mm dia, length < 70 mm
  • N-connector, panel socket
  • A couple pieces of tinned steel sheet  e.g. from tin can
  • A piece of PVC coated electric wire 1,5 mm2
  • Screws and bolts M3, solder tin etc.



Antenna construction:


The Reflector (aluminium pan) dia = L x 2, the height of the sides = L/4.
In the centre of the bottom there is the N connector to left and the dipole to right. A distance from bottom to the dipole is little more than L/4. The Dipole is mounted with an air-insulated coaxial type foot, whose impedance is 50 ohm and length L/4. Inner wire of the coaxial is made of 4 to 4.5 mm rod or conduit and shield made from split copper conduit which internal dia is 10 mm. To the right of the dipole there is a disc whose dia is L x 0.4 (= 49 mm) and distance from the dipole is again L/4. Disc material can be thin aluminium or tinned steel sheet.

At same distance as the disc, there is also a ring made from pvc-coated electric wire 1,5 mm2 by binding it to ring diameter about L x 2. It is not neccessary to short the ends of the ring, I left ~ 1 mm space. If you want you can short the ends together as well. PVC coating on the wire has no magic, you can use e.g 2 mm clear copper wire as well.

I mounted the Disc and the Ring to the plastic cover made from microwave oven bulb. A piece of plastic sheet and glue are needed to mount the disk. The ring I glued inside the cover, so the diameter of the ring becomes somewhat smaller than L/4.


Assembling:

Interior The sides of the reflector (cake pan) must be L/4 or 32 mm, so extra height must be cut away. In the centre of the pan there will be a hole 12 dia and four 3.5 mm holes according the N-connector. The feet of the dipole is made of split copper conduit and inside it a rod or a pipe. The impedance of the feet must be 50 ohm which actually means the ratio of inner dia of the outer conduit and dia of the inner rod be 2.3. It is quite near when inner rod or pipe has 4 to 4.5 mm outer dia and copper conduit has 10 mm inner dia. The exact equation of  Impedance versus Diameter ratio is:

Z = 138 * Log(D/d)
 
The table of Impedance and Diameter Ratio


D = inner diameter of the tube
d = outer dia of the rod
Z = impedance in free air

D / d    Z / Ohm
2.2       47.3
2.3       50
2.4       52.5
2.5       54.9


If the inner wire is made from rod it is good idea to drill axially a 3 mm hole on the end of it so the rod can be solder firmly to the inner tap of the N connector.
The length of the rod becomes about L/4, but it is better first to leave it longer and cut it later after the parts are first pre-assembled.

The copper conduit must be split with a metal saw as accurately as possible and deburred with a file. The end of the split conduit is then  fastened to the centre of the pan. It is not possible to solder it directly to aluminium but we made a flange from tinned steel sheet to same dimensions as the flange of the N connector. In the middle of the flange is drilled a hole equal the outer dia of the conduit and four 3.5 mm holes as in the N connector. The one end of the split conduit is then soldered in the centre hole of the flange while keeping the width of the slots between halves to 1-1.5 mm.

The split conduit is then cut so that the length of the open slots becomes a very accurate  L/4.

This is the most accurate point in the antenna construction. Among with many roles, the slot acts as a band pass filter which rejects other frequencies than nominal HF.

Now is good time to pre-assemble parts. With four 3 mm screws, the N connector with the centre rod and the flange with split conduit are assembled on opposite sides of the centre hole of the pan, N connector to the outer side. The centre rod is now cut to same length as the split conduit.

The Dipole was made from 2 mm enamelled wire. The one arm of the dipole is soldered both to the centre rod and to the half of the copper conduit. The second arm of the dipole is soldered only to the second half of the conduit.
The arms of the dipole are cut to L/4 from axle, so total width of the dipole becomes L/2.
Before soldering it is good idea to file grooves for dipole wire to the centre rod and the halves of the conduit.

To the right of the dipole there is the disc and the wire ring which can be assembled to the cover bulb so that their distance from dipole becomes to L/4.

The cover bulb can be locked with three 3 mm screws and sealed with silicone mass as well as the N connector joint.

On the very lowest point of the pan there must be drilled a small hole for condensed water exhaust.

Frequently asked details

 Detail 1

The most important dimension of the antenna is the length of the slot,
which must be 31 mm @2.45 GHz.
I don’t know the optimum width of the slot. I made it with metal handsaw inserting two blades parallel. So it becomes ca. 1.5 mm.

Detail 2

Yes really!

The one arm of the dipole is soldered both to the centre rod (2) and to the half of the copper conduit (1). The second arm of the dipole is soldered only to the second half of the conduit (3).

 It doesn’t mean a “short circuit”.  Remember the signal here is not direct current but high frequency !


 

Mast mounting of the antenna

Mast fasteners can be made from exhaust pipe clamps. See above some mounting ideas. Be careful not to mount clamps in the centre line otherwise the mast prevents connection of cable to the N connector. The rightmost picture is from back side.

Lightning protection

When the antenna is mounted above the roof there becomes a risk of lightning damage to the WLAN card.

The mast has to be grounded firmly e.g with 16 mm2 copper rope to a good earthing point. Lightning protection module is recommended between antenna cable at the  place where the cable enters the roof.

Antenna cable and connectors

Cable type Belden H1000 is found to be low loss on microwave band and it is not very expensive. All cable and connector impedances must be 50 ohm. Outdoor connections are not watertight enough as such. So called self vulcanizing tape is best choice to wind over connection and above all there have to be wound black electrical tape to protect the vulcanizing tape against ultraviolet light. See cabling details .

Sources

Antenna construction is from page  http://6mt.com/2304tech.htm where is found an item MICROWAVE ANTENNA YOU CAN BUILD (73 10-82) c56.zip . I have dimensioned it to 2.4 GHz band and made some additions.
 

Article by Martti Palomaki
Ilmajoki, Finland

Originally available at  saunalahti.fi/elepal/antenna1.html

2 meter mobile antenna

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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

Calculate your antenna gain

Posted in Homebrew 1 Comment

More than ten years ago a humorous article on antenna gain was published in the ham radio magazine “QRV.” The article stated that there are three kinds of gain:

1. the dB/d and dB/i gain based on CCIR regulations (the true and honest real gain!)
2. the “dB/ham radio gain,” which is 6dB higher than the real one.
3. the “dB/CB gain,” which is 10 dB higher than the real one.

Confused? Here is a little help so you can make your own calculations.

 The gain of an antenna A compared to an antenna B is equal to the capture area of antenna A compared to the capture area of antenna B.

The capture area of an antenna is determined by multiplying the antenna’s radiator length by 1/4 lambda. See Figures 1 and 2.

Example:

Antenna A Full-size 20m antenna (made from CU-wire 2mm/1/16″ O.D. +/-)
14 MHz dipole 1/2 lambda long: = 10m x 5m (1/4 lambda) = 50 sq meters

The capture area of a 20m dipole is 50 sq. meters or 540 sq. ft. The gain of this antenna is zero dB/d or 2.14 dB/i.

Antenna B Shortened 20m antenna (CU-wire 2mm/1/16″ O.D. w/big loading coils)
radiator length 5m/16.5ft., tuned by two loading coils to 14.2 MHz = 5m x 5m = 25 sq. meter.

The capture area of antenna B is 25sq. meters or 270 sq. ft. Note: Antenna B has only half the capture area of antenna A and is therefore able to “catch” only 50 percent of the electromagnetic field; e.g., 50mV, compared to 100 mV/50 Ohms. This means 6dB less gain for antenna B in comparison to antenna A.

These calculations require extremely low loss coils. Since there is no such thing as “no-loss coils,” an additional loss of typically 3 to 8 dB has to be taken into account.

Imagine how much power is wasted while using such antennas for receiving/transmitting.

The fact is, that only 250 Watts of the 1,000 Watts HF in your feedline are radiated — and this with “extremely-low-loss loading coils.”

These kinds of calculations can be found in all good antenna books, usually presented in the form of rather intimidating mathematical formulas. We hope the explanation above prove helpful to you.

Some Typical Examples

A typical vertical antenna with 0 (zero) dB/D gain in space is the Sleeven 1/2-wave dipole. Other 0 dB/D gain systems are 1/2-wave antennas such as the Zepp-Windom-Fuchs and vertical radiators such as Ground Plane-Discone (all in space).

Antennas shorter than 1/2-wavelength (tuned by a loading coil or traps) have much less gain. Typical: 1/2-wavelength = 1/4 $#34;power gain” ±loss of traps/coils. Following are some examples:

40 m GROUND PLANE 14 ft / 4.3 m high*, center loaded. Its efficiency is 7%. Its gain is -12 dB/D (compared to a full-size system without losses). This means that only 7 watts of a 100-watt signal will be radiated; 93 watts are wasted in this antenna.
See Ham Radio Magazine, Sept., 1982, P. 18 ff, by W1GV.

* A full-size 40 m 1/4 wavelength ground plane is 34.6 ft/10.5 m high; it has 0 dB/D gain.

160 m GROUND PLANE 33 ft / 10 m high*, 12-Ohm ground

        Configuration                    Gain        Efficiency
1. Top loaded (big capacitor)           -10 dB          10.0%
2. Center loaded coil                   -19 dB           1.2%
3. Base loaded coil                     -20 dB           1.0%


All the gains are compared to a full size* radiator and 0-Ohm ground. At #2 and #3, only 1 watt of a 100-watt signal will be radiated; 99 watts are wasted.

See Ham Radio Magazine, May, 1983, p. 36 ff, by W7DHD.
* A full-size 160 m 1/4 wavelength ground plane is 136 ft / 41 m high.; it has 0 dB/D gain.

20 ft / 6 m long MULTIBAND ANTENNA 10-12-15-17-20 m Half-wave Zepp system. Open wire feedline or matchbox on “F”

Configuration      Gain         Efficiency
A=10 m          -0.5 dB/D          ~90%
B=12 m          -2 dB/D            ~63%
C=15 m          -4 dB/D            ~25%
D=17 m          -6 dB/D            ~15%
E=20 m          -8 dB/D            ~15%

Note: The traps were air coils, made from #9 copper wire, with air capacitors.

article originally available and copyright at sommerantennas.com website

Halo antenna for 70Mhz

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Concepts

The halo is an omni-directional antenna with horizontal polarization. This is practically a horizontal loop, namely a half-wave folded dipole, with its endings slightly separated. The feeding is done through a system called gamma-match with the condenser obtained by inserting the central core of rg58 cable including the insulator, inside the aluminum tube that forms the gamma-match.

Assembling

Based on a commercial model, it was reproduced using aluminum tubes from 4 and 6 mm (sold in DIY stores). The boom (H) is made with an aluminum profile 10/10 mm square section. If you are using anodized aluminum, remember that it should be grinding to all points of contact for an improved electrical conduction.

The dimensions below can be modified during implementation to match the materials used in construction. But the important is to maintain unchanged the distance E-F and B-C. (Photo 4 and Photo 5)

The E-F segment is composed of an insulating material (PVC or wood) (Photo 5).

The dipole is connected to the boom in the A-B side, through a screw with an insulator between the boom and the dipole. (Photo 2)

The gamma-match (C-G) (photo 4) is electrically connected at the point C with the dipole and isolated in G by a distancer from the PVC boom. In this point it is connected the connector cable with the ground attached to the boom, while the central core is soldered the wire (rg58) with which the tuner-capacitor is done. (Photo 8)



Calibration:
For calibration can be used to a simple swr meter, find the lowest point of swr by inserting or removing the wire inside the tube (C- G gamma-match). With the above dimensions has been achieved swr values of 1:1 from 70,100 to 70,300.

IZ5HQB Site

Endfed 20/30 Mtr Antenna

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I’ve had good luck with an endfed antenna on 20 and 30 meters. Depending on available trees/supports I can arrange this antenna as an inverted vee, a sloper or a horizontal 1/2 wave. It functions an endfed zepp on 20 meters consisting of a 1/2 wave 20 meter wire (33′ 3″ long) endfed with a 1/4 wave x velocity factor of twin lead (14′ 3″ long). By disconnecting the grounded side of the twin lead it becomes an endfed  antenna  on 30 approximating 1/2 wave long. By being a 1/2 wave long I avoid the need for an extensive ground system. If RF in the “shack” is a problem, a connection to a convenient ground clears it up.



This antenna behaves very differently on 20 vs 30 meters. On 20 the twin line transforms the hign impedance of the endfed 1/2 wave 20 meter wire into a low impedance that is easily handled by many QRP rigs. On 30 meters this impedance transformation does not happen. The rig is connected directly to the high impedance feed point of the 30 meter antenna. In both cases, though, the K1 built-in automatic antenna tuner allows the rig to work fine.

 The endfed  20/30  meter antenna  “wired” for 20 meters. On 30 meters disconnect the short black wire from the binding post. If required, a ground may be connected to the black binding post.

A project by W0VLZ