Max.loop size for 20m. and projects

October 11, 2010, 11:03 pm

15MM COPPER TUBING LOOP

Magnetic loopantenna calculator by KI6GD : http://www.standpipe.com/w2bri/software/loopcalc.exe
The prog. doesn't have an icon, just klick in the white square above it's name .

DO YOU LIKE TO EXPERIMENT WITH ANTENNAS ?
Here's all you ever wanted to know about VSWR :

http://www.amateurradio.org.za/VSWR%20John%20Fielding%20Final.pdf

SOME OF MY OTHER PROJECTS.

TAURUS 20M SSB TRX WITH PA 8WATTS

PIXIE 20M. CW QRP LINE WITH TUNER TOY TRX BUT FUN TO BUILD

BANDPASS FOR 20M. AT FIELDDAYS IT'S MANDATORY
http://www.arrl.org/files/file/Technology/tis/info/pdf/8809017.pdf

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20m. end fed halfwave antenna

June 1, 2011, 1:20 pm

≫ Next: Simple antenna analyzer 0.1 - 30 MHz

≪ Previous: Max.loop size for 20m. and projects

Working portable demands an easy setup of your antenna. The antenna also has to give enough punch at a low radiation angle without the need of radials.

The vertical end fed half wave antenna is my choice for it’s easy to employ and it's a perfect DX antenna . This antenna is grounded thus giving les static noise to your receiver.

A 20m. version is about 10 m. long and has aprox. 3000 Ohms at the feedpoint. So we need a simple tuner to reduce this to 50 Ohm .

Put 20 turns ( covers half of the toroid ) of 1 - 1.2 mm enamel wire on a T130-2 toroid with a tap at 3 turns from the ground .The first picture shows the first test setup with a 2.5 turn tap. You also need about 25 cm of thin Teflon coax (RG 178 b/u) that will act after tuning as a high voltage capacitor of about 22 pF.

The pictures explain the simple construction. The cabinet is a PVC type G302 made by Velleman.

TWISTED TAP FOR MORE STABILLETY

NOTE THE GROUNDSTRIP

ADDING THE CAPACITOR/COAX

HOT GLUE FIXATION

Tuning : The trick to tune this transformer is to find the working frequency first by tuning the capacitor. Then we look for the the 50 Ohm point on the coil . Connect a 3300 Ohm resistor from the top of the coil to the ground of the antenna plug.

Adjust the length of the open coax line until you reach the lowest VSWR in the centre of the band with an analyser. The coax will be about 23 cm in total resulting in 22pF .

Now remove the resistor and connect the antenna wire of aprox. 10 m. PVC coated copper wire. Tune the antenna for best VSWR by reducing it's length carefully. My antenna is 9.9m. long and is mounted on a 12.5 m. fishing pole. A near 1:1 VSWR on 14.200 MHz can always be achieved ! Before tuning , fix the toroid with some hot glue and wait fore it to cool off. Beware of the high voltage at the antenna feedpoint , this can rise up to almost 500V at 100 Watts.

My first DX contact with a vertical half wave end fed antenna was with VK6MV in SSB using the long path, over the north and south pole, with a 5-5 report.

I was also able to work Japan,Taiwan, Thailand, India, Indonesia, South-Africa, The Falklands ands. in SSB with good reports. Every end fed / vertical needs some kind of counterpoise to push against and in this case that's the coax , so don't forget a line choke near to your transceiver.

Good DX !

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Simple antenna analyzer 0.1 - 30 MHz

June 25, 2011, 11:30 am

≫ Next: Travel loop antenna type 40-10 and 80-10

≪ Previous: 20m. end fed halfwave antenna

This is a verry simple but good working swr analyzer based on the LTC 1799 smd generator . Tuning is easy: Connect your antenna to the analyser with the meter at full scale and look with the 100K potentiometer for a dip on the meter.
Disconnect the antenna and push the set switch. Now adjust the power for a 1:3 reading on the VSWR meter.Releasing the switch will make the meter jump in to the right corner, but that's normal due to the simple bridgeform . Connect the antenna and read the axact VSWR. The first model had a 6.5 V power suply but this caused the LTC 1799 to warm up and drift. At 5V the current is low and the IC is stable.
Most components are mounted on the back of a little pcb , the rest is soldered directly on to the meter and " point to point ". To expand the range downwards to about 0.1 MHz , just put a switch between pin 4 of the generator and the ground. If you want to use a counter , put a 1K resistor in series with the connector. Those who want to build in a counter can replace the 100 K potmeter by a 10 turns type and omit the presets.A verry small counter is available by Hendricks QRP Kits If you are not using a counter , a tuning scale can be made with the help of digital receiver. By lowering the value of C1 the amplitude can be reduced so a more equal power setting can be obtained over all the bands. The meter should have a 100-200 uA reading. PE1IWT did an interesting mod on this analyzer project , you can find it here .It's in Dutch but the pictures explain it all. This versatile instument offers the novice radio amateur a lot of help with his antenna and balun projects .

VFO TUNING OR PRESETS POSSIBLE

MINIMAL COMPONENTS

1:1 PCB

COMPONENTS ARE MOUNTED ON THE COPPER SIDE

NOTE THE GROUNDING OF THE REGULATOR BY A JUMPER

INSIDE VIEUW OF a SECOND MODEL ,MADE FOR AN OTHER HAM
THE PRESET POTENTIOMETERS ARE 10 TURNS TYPES

Not to scale alternative pcb suggesture made by carving with a steel scribe

Wil need 2 jumpers to complete

THE COUNTER BY HENDRICKS QRP KITS
http://www.qrpkits.com/freqcounter.html

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Travel loop antenna type 40-10 and 80-10

June 29, 2011, 5:57 am

≫ Next: Z-Match 100 and mini Z-Match

≪ Previous: Simple antenna analyzer 0.1 - 30 MHz

Haunted as many others by radio interference and noise I started looking for a wideband portable antenna . Soon I became focused on a magnetic loop antenna. The only catch was the method of feeding by a Faraday loop , it made the project hand sensitive …. In the Rothammel Antennabook I found a complete different way of feeding made by capacitors .

This was a big improvement and made a perfect match possible between 6.5 and 30 MHz.

Both tuning capacitors come from old AM radios and because their sections are switched in series , they can be used up to 30 Watts without arcing. They interact so it’s wise to make some markings on the front for fast tuning.

The loop is made of RG-213 coax and rests on a cross made of 6 mm. fibreglass rods( kite shop )

Inside the tuner is a shortcut between the centre and the braid of the coax loop to form a solid ring . By simply adding a second loop with a 5 cm.spacing and a switch to put the loop's in parallel or in series, the antenna becomes a 80-10 m. portable low power loop for travelling. The travelloop was born HI. It has been my travel companion for many years with many qso’s even far over the Atlantic.
Tuning capacitors : http://www.rfparts.com/old_site/caps_antennaload.html

6.5-30 MHz TRAVEL LOOP

6.5- 30MHz tuner

3.5- 30 MHz VERSION WITH BANDSWITCH

THE SWITCH SHOWN FROM BEHIND

CAUTION !
Magnetic loop antennas can produce a high voltage that may be harmfull to your health.
Tune your antenna at low power and take a safe distance while operating .

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Z-Match 100 and mini Z-Match

June 29, 2011, 2:37 pm

≫ Next: No ground antenna for backpackers, balconies or plastic car bodies

≪ Previous: Travel loop antenna type 40-10 and 80-10

FIRST TEST WITH A 4C65 TOROID

This is a one for all antenna tuner with wide range tuning on all the HF bands. The tuner is based on a G3WQW design. A T200-6 should give a better Q but the T200-2 was in stock and gives me sufficient tuning range. Being a high-pass type it contributes to less receiver noise. The capacitors are radio types and can be used up to 150 Watts. I used a plastic cabinet but a metal type would provide better HF isolation. Using a metal cabinet needs a "floating"mount of the input capacitor. More info about the Z-match design can be found here
Tuning capacitors :http://www.rfparts.com/old_site/caps_antennaload.html

EASY CONSTRUCTION

The QRP 160-6 m. mini Z-Match with a T130-2 toroid in a matal cabinet. Polyvaricons are used for tuning within qrp limits. By switching a 270-500 pF capacitor over the left side of C2 (2x 500pF) the tuning range can be extended. It's possible to tune a doublet antenna on all HF bands. Together with the FT-817 it makes a great qrp combo.

The mircro Z-Match with 12x5x3 cm ultra portable for 80-6 m. In this tuner a nr. 6 material toroid was used. There is still some room left for a tuning indicator....

QRP tuning indicator . A perfect match is indicated by a bright shining LED , suitible for QRP only. Can be mounted in any QRP tuner at the antenna output. Gives a better reading than the FT-817 internal swr meter.

THE TUNING AID IN MY MINI Z-MATCH

VELCRO MOUNTED MICRO Z-MATCH

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No ground antenna for backpackers, balconies or plastic car bodies

July 24, 2011, 5:20 am

≫ Next: Coaxial half wave antenna

≪ Previous: Z-Match 100 and mini Z-Match

A common problem with backpacker or balcony antennas is finding a good counterpoise. Also cars and caravans with a plasic body are a problem. Althow nothing beats a set of resonant radials, the shown solution offers a 1/4 wave stub that wil create an artificial counterpoise. The mobile antenna mount must be isolated from any metal by a epoxy or plastic plate and a normal T-Connector is used at the antenna feedpoint. Be shore to shortcut the end of the stub. The length of the stub in meters equals 1/4 Lambda x 0.66 (this is the velocity factor of 50 Ohm RG-58 ) or can be calculated by deviding 50 by the frequency .So if you need a stub for 14 MHz the outcome is 3.57 m. but this length is not critical. The setup can be easily mounted on top of a rucksack. On a balcony the stub can be layd on the floor.

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Coaxial half wave antenna

February 26, 2012, 4:08 am

≫ Next: Multiband end fed antennas 3.5 - 30mHz

≪ Previous: No ground antenna for backpackers, balconies or plastic car bodies

READY FOR FIELDWORK .USES A COAXIAL T- CONNECTOR

For those who don't like to wind transformers there is handy solution for making a have wave antenna for fieldwork on a 12m.fisching pole. Althow a coax stub is a little lossy , this antenna is easy to build and effective . My first contacts with VK and JA on 20m. were made with this antenna . The other half wave antenna further down on my page has more gain.
Other bands ( center freq. )
28.3 MHz : A 1.51m. B 25cm.
21.2 MHz : A 2.02m. B 33cm.

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Multiband end fed antennas 3.5 - 30mHz

April 19, 2012, 2:11 am

≫ Next: Antenna program Levy

≪ Previous: Coaxial half wave antenna

This is a 200 Watt PEP step up transformer for end fed full and half wave antennas without radials, designed as a 200 Watt PEP upgrade by PA0EJH for the originaly Par Electronics designed 25 Watt HF endfedz multiband end fed antenna.
The original design has a 27/3 turn ratio ( 1: 81 ) on a small 43 material toroid, but the larger toroid has more wire so the nr of turns had to be reduced for max.efficiency on 10m. The coil now has a 16/2 ratio ( 1: 64 ) For max. performance the 2 turns to ground must be twisted . The 100-150pF capacitor gives a better match on 10m.and both windings start at the ground side of the coil .Don't try to stack toroids for more power for this will increase overall inductance . This makes it impossible to tune the high bands. The best results are obtained with a small toroid.....The 3 band antenna has a length of 10.1m. followed by a coil of about 34 uH ( 90 turns 1mm enamel wire on a 19mm pvc tube ) and a endpiece of 1.85m , offering you a perfect vertical or horizontal antenna for fieldwork at 40 -20 and 10m. There is also a 5 band version with 20.35m wire followed by a 110 - 120uH coil ( about 260 turns 1 mm cul on a 19mm pvc tube ) and a 2.39m. endpiece. This antenna works on 80 - 40 - 20 -15 and 10m.without radials and has a verry low swr combined with a low noise level. Keep in mind that every end fed / vertical needs some kind of counterpoise to push against and in this case that's the coax , so don't forget a line choke near to your transceiver.

Tranformer with 150pF and 3K3 resistor to ground

Transformer made by Tony PA3GWO on a smaller FT140-43 toroid for max. 100 Watt pep

Update nov.23-2013
High power endfed for 80-40m designed by PA0EJH
Stack 2 FT240-43 toroids and add 3 primary and 21 secondary windings with 1.5mm enamelled wire to form a 500 Watt key down transformer.

Here is the well build transformer optimized for 80-40m. by Gus, VK6WB . You can clearly see the 2 toroids for high power use.

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Antenna program Levy

July 3, 2012, 4:09 am

≫ Next: LM386 on steroids

≪ Previous: Multiband end fed antennas 3.5 - 30mHz

There are not many simple antenna programs out there for free , but this is a welcome exeption.This program made by F5IMV wil calculate a dipole,extended double Zepp,G5RV, ZS6BKW and many other wire antennas the easy way. It shows one dipole leg on the left and the feedline on the right side .Even the radiation patern is included .You can pin point the antenna length by clicking A<..>B or selecting the feedpoint by clicking B<..>C .The light grey zone on the right top and bottom indicate a low Z , the centerline has a high Z. Just click on Lancer to start the simulation.As you can see it's the twin feedline that matches this antenna to an acceptable low Z, from where it switches to coax. All examples with bare copper wire. 0.97VF . Use 0.92 for plastic coated wire.
Download site

Dipole 20m.

EXAMPLE ZS6BKW

EXTENDED DOUBLE ZEPP 20M WITH 230 CM TWINLINE MATCHING SECTION with bare copper wire ( 0,97 )

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LM386 on steroids

December 11, 2012, 12:32 pm

≫ Next: Adjustable bandwidth

≪ Previous: Antenna program Levy

A problem with DC receivers is getting enough audio output. With a simple mod you can lift the gain of the LM386 to 34-74 dB .This is the ultimate mod for Pixie type transceivers. My Pixie needed a volume control after this mod (-:

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Adjustable bandwidth

December 20, 2012, 10:41 pm

≫ Next: Iler qrp 20/40 power mod

≪ Previous: LM386 on steroids

A MAX7400 is an 8^th order elliptical filter giving a 100 Hz to aprox. 3000 Hz tuning rate. It means much more selectivity in many homebrew receivers.

The output can drive a LM386 . This filter is a must have for cw operators with simple ssb receivers.

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Iler qrp 20/40 power mod

April 5, 2013, 11:16 pm

≫ Next: ILER 20 QRP MODS

≪ Previous: Adjustable bandwidth

The 2SC1945 has 2.5 dB more gain than the 2SC1969 .Without changing the drive train a full 8 - 10 Watt PEP qrp ssb should be possible. The emittor resistors should be changed to handle the current. The wire bridges in front of the transistor have to be changed for correct BEC. For best results only original Mitsubishi types must be used..

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ILER 20 QRP MODS

June 3, 2013, 9:34 am

≫ Next: End fed half wave high pass for 20m.

≪ Previous: Iler qrp 20/40 power mod

My Iler 20 is finally oparational. The IF has changed to 4.000 MHz and the vxo has 10.250 MHz cristals.(Ebay) The VXO coil now holds 64 turns no.26 (0.31mm) magnet wire and the tuning range with the polyvaricon is 14.129 - 14.246.4 MHz with a stable signal . 5 capacitors of 10 pF now serve in the 4 MHz cristal filter. As you can see, even the microphone was to bulky and was replaced by a home made model. Audio sounds verry good and the rf power is 6 Watts PEP at 13.8V. Also C28 was lowered to 33nF to get more high tones in the audio output, but that's a question of personal taste. I found a perfect little speaker named : Visaton K 50 WP , 3 Watt 8 Ohm art.nr.:2915 .In order to lift the microphone input, R6 was changed to 470K. The mini counter comes from Hendricks QRP and was chosen for it's low power consumption and small size . Some humming interference can be caused by the display multiplexer of the counter but a small filter takes care of that:

The cabinet was ordered from Qrp Project in Berlin http://www.qrp-shop.biz/epages/qrp-shop.sf/de_DE/?ObjectPath=/Shops/qrp-shop/Products/Kuehlr168x110x54 It fits the board like a glove . For smooth tuning a 1:10 ball drive is added. Because of the 180 degree tuning range of the polyvaricon, only a 1:5 reduction remains. A series 3000 Multiplex RC transmitter was the donor for the tilt stand, but US builders can find one here :http://www.budwig.com/collapsible-tilt-stands.html
Here is a tuning range video :

The latest boards have a litle bug causing a shortcut to ground of C37 and R22 .This prevents the noisefilter from doing his job. Before installing C37, take a mm drill and make a smal cone in the board surface to remove the ground connection .

I noticed that the noise filter even causes the noise levell to rise , so i desided to remove C37 and R22 permanently.

The Iler kits represent a modern and compact, easy to build alternative, to the Bitx and Taurus.
More info about this nice kit : http://ea3gcy.blogspot.nl/

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End fed half wave high pass for 20m.

September 24, 2013, 5:42 am

≫ Next: Broad band 1:1 current/choke balun

≪ Previous: ILER 20 QRP MODS

A common problem with qrp transceivers is a weak frontend . Most end fed antennas use low pass tuners causing high stress due to strong signals coming from BC stations .

The High pas tuner used here helps to reduce these problems. Put 19 turns 1mm transformer wire on a T130-6 torroid to form a 4.8 uH coil. The trimmer used is a 60pF type set to about 25pF . Put a 3.3K resistor between the antenna connector and the ground of the coax connector and tune the trimmer for resonance at 14.180 MHz. Keep in mind that a thin antenna wire has a higher Z.

After tuning the unit connect the half Lambda wire ( 10.15m PVC covered stranded copper wire) and cut it for lowest swr. A 1:1.2 swr is easily obtained with this unit. The cabinet is a PVC type G302 made by Velleman. Every end fed / vertical needs some kind of counterpoise to push against and in this case that's the coax , so don't forget a line choke near to your transceiver.

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Broad band 1:1 current/choke balun

October 16, 2013, 7:40 am

≫ Next: Traveltuner 3.5-30 MHz

≪ Previous: End fed half wave high pass for 20m.

In search of a no nonsence 1:1 balun i came up with this easy to build unit. It offeres a almost flat swr curve from 1 to 30 MHz as you can see in the plot. Use 10 turns of side by side1 mm enamelled copper wire on a 4C65 or FT140-61 toroid . Teflon tape was used on the toroid but this is not essential.

SWR plot of the balun bridged with a 50 Ohm resistor.

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Traveltuner 3.5-30 MHz

November 21, 2013, 2:50 am

≫ Next: Mini Travelloop for receivers

≪ Previous: Broad band 1:1 current/choke balun

There is no known qrp tuner for both small magnetic loops and longwire antennas for sale so here is an idea for your next holiday . A 2.5 m circumflex loop wil cover 6.5 - 30 MHz , a 5m loop wil cover 3.4 - 8 MHz. To tune a loop tune C1 for resonance and C2 for low swr . To tune a longwire switch to the coil for the desired band and tune C1B for best swr. The coil can be replaced by a T130-2 toroid with 50 turns 0.8mm enamelled wire on a 12 positions rotary switch. Use a plastic cabinet for this tuner.
Tuning capacitors :http://www.rfparts.com/old_site/caps_antennaload.html

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Mini Travelloop for receivers

February 3, 2014, 4:01 pm

≫ Next: Helical Loop Antenna for 20m. Window/Balconey use.

≪ Previous: Traveltuner 3.5-30 MHz

Portable shortwave receivers are normally equiped with short telescopic whip antennas producing a poor reception. This option has more selectivity and a better impedance (low Z) over the 5-21 MHz range. A 2-section capacitor can be used wit a larger loop aswell. Construction is easy and a plastic enclosure should be used. If you switch a 1200 pF capacitor over the loop base you can tune 80m. aswell (-:
Even a preamp with a low Z imput could be an option.

22 pF to the frame and 100+22pF in parallel to the coax

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Helical Loop Antenna for 20m. Window/Balconey use.

April 17, 2014, 1:43 am

≫ Next: Cheap 5A power supply for the FT-817

≪ Previous: Mini Travelloop for receivers

Always in surge for a better Window/Balconey antenna i found this nice Russian design by UA9JKW.
http://educypedia.karadimov.info/library/slinky8.pdf
My copy is a little smaller with a 70cm loop made from 19mm.PVC. It has 650 turns 1.5mm PVC isolated electrical wire .Coil value is 134.6 uH. There is no need for a tuning capacitor and the feedpoint has a low Z . Power handling is easy 100 Watts and the recieved signals have a verry low noise levell. This antenna radiates like a dipole , that makes it perfect for window use. I could make clean and loud contacts throughout Europe on my first attempt having bad conditions. At the feedpoint is a line choke made of a ferrite rod with 15 turns RG-58 , giving about 1000 Ohms at 20m. SWR is 1.7 ( 83 Ohm X=0 ) at 14.200MHz with a sharp second resonance at 37.485MHz .( 50 Ohm X=3 )This little Russian is a big performer an will stay at my apartment window for shure HI

The effective line choke

First results with bad conditions

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Cheap 5A power supply for the FT-817

August 1, 2014, 4:15 pm

≫ Next: Single knop Travelloop 6.5 - 31 MHz

≪ Previous: Helical Loop Antenna for 20m. Window/Balconey use.

The Toshiba PA3083U-1ACA laptop powersupply deliveres 15V at 5A.without any noise.
It has been my travell supply for more than 3 years now without any problem. They can be found on Ebay for fair prices and need oly a new Molex plug to match the set.

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Single knop Travelloop 6.5 - 31 MHz

August 22, 2014, 7:39 am

≫ Next: T-MAG ANTENNA 40-10m.

≪ Previous: Cheap 5A power supply for the FT-817

First attempt with a large space between the loops

This small loop can handle 20 Watts from 45-10m . Loop circumference is 2.5 m with a Faraday coupling loop of 50 cm . Sticks are 6 mm glass fibre ( kiteshop).The 2 vertical sticks are 41cm and the suports are 34cm long. A 2 x 500 Pf tuning capacitor with the sections put in series is used for tuning. Because of the high Q ( 328 on 14.200 MHz ) a 1:3 reduction is mandatory. The loop is made of RG-213 with the shield and centre soldered together. Highest SWR is 1:1.5 . Despite of bad conditions, contacts were made troughout Europ with 10 Watts SSB. The Faraday coupling loop is made of RG-58 and is bend to a slightly horizontal oval. Reducing the space between the loops leads to a drastic improvement of the swr and return loss.

Plot 14.200MHz after coupling loop modification.


Improved coupling by reducing the space between the loops . I used a piece of U-shaped plastic for the looprest.	.

Although fast tuning is a big plus with this loop, the overall efficiency is less than the twin capacitor Travelloop further down on this blog. The broadband coupling loop makes a perfect match impossible , especially on 10m.

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