Pixie qrp BC and output filter

BC  interference is a major problem when operating a Pixie on a multiband antenna. This filter

is a great help and also improves the output. L is a mini choke type .Remove the original coil en final C to install this mod.

Iler qrp 20/40 power mod

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..

Adjustable bandwidth

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.

LM386 on steroids

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  (-:

Taurus QRP trx mods

The Taurus is a verry nice and easy to build 3.5 Watt qrp SSB transceiver designed by SP5DDJ.http://www.sp5ddj.pl/ Building the semi-kit causes no problems to a novice Ham if he respects the basic principles .Perfect boards are available here:sp5ddj@wa.home.pl .A parts kit is available at HaJe electronics http://www.haje.nl/index.php?cPath=30_41 However there are some points of improvement of the design

Both voltage stabilisers  78L06 are to weak to handle the current demand and has to be replaced by a larger 1A type.If not , frequency shifting will occur on Rx and Tx.

The position of the 2 drivers on the tx board is wrongly printed  , check EBC !

On the Rx board the IC is conected to the VFO output by a long path. At TX there is feedback into this lead and the frequency tends to shift. Cut the path as near as posible to the IC and make a coaxial conection to the TX board and the counter. 

The bandwith of the receiver frontend is to narrow to cover the complete 20m band and needs to be modified according to this plan:

 A bigger problem is the powertrain that tends to oscillate .

De-Qing the drviver stage takes care of the problem , place a 4K7-10K resistor over the first winding of TR as the plan shows:

Here's the correct way to wind the PA toroids:

Tuning your antenna can be difficult without a MOX.  Take great care by decoupling the wire to the resistor for it tends to pick up RF . This mod can also be used to perform cw on Taurus .

 Audio is fairly weak in Taurus . Replacing the 100R at pin 6 of the IC by a 10R type is the option.
Changing from RX to TX can cause audio popping due to the discharging of the 100uF capacitor at pin 6 of the IC. Replacing the part bij a 10uF type cures the problem. 

S-meter mod

Wim SP5DDJ wrote:
Here you have step by step alignment of VFO:

1.    Set both 47k pots in the middle of its range. They will be used for range setting later
2.    Set the multiturn pot in the left edge and check if you have minimum voltage on cathodes of varactors. This will result lower VFO  frequency i.e.
4150kHz after alignment. If the left edge doesn't  correspond to,  change cables soldered to multipot.
3.    Turn the VFO cap trimmer and find  signal in RX or measure around 4150kHz.
4.    Turning multipot to the right you should increase the frequency. Make a note what was the highest frequency in right edge of multipot.
5.    Now is the time to set the span and both edges of VFO range. Use pots 47k and find out which is increasing or decreasing span and edge frequencies.
This is a very nice job to do and feel free to make some experiments. If the range is to low unwind one turn from VFO coil.
After alignment check voltages on varactor cathodes. You should have approx. 1V in one edge and 6V on the other side. Remember not to go below 1V in the left edge of multipot ( this is set by one of the 47k pots) because signal of VFO will be distorted. Make an exercise with this

About the oscillating PA stage he wrote:
1.    Solder parallel resistor values between 1k to 10k to L5 ( driver circuit) pins 3 and 4
2.    Change value of capacitor linking collector of 2N2219 with TR1 transformer pin 1. Try 10nF or less
3.    Solder capacitor of 100pF between collector of 2SC2078 and ground on the bottom of PCB. Use shortest legs as possible
4.     Parallel to first 2N3904 collector choke of 22uH solder 300 ohms resistor
Good luck and 73'ss
Wim SP5DDJ

Antenna program Levy

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.
  Download site

Dipole 20m.

EXAMPLE ZS6BKW

 EXTENDED DOUBLE ZEPP  20M WITH 230 CM TWINLINE MATCHING SECTION

Multiband end fed antennas 3.5 - 30mHz

This is a 200 Watt PEP transformer for end fed full and half wave antennas without radials, designed as a 200 Watt PEP upgrade of the originaly Par Electronics designed 25 Watt HF endfedz multiband end fed. The coil has a total of 16 turns . 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 pusch against and in this case that's the coax , so don't forget a line choke near to your transceiver. 

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

Coaxial half wave antenna

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.

No ground antenna for backpackers, balconies or plastic car bodies

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.

Z-Match 100 and mini Z-Match

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

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

Travel loop antenna type 40-10 and 80-10

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.

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 .

Simple antenna analyzer 0.1 - 30 MHz

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

20m. end fed halfwave antenna

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.

Good DX !

Magnetic windowloop for 20m. no tuning ! Updated november 2011

1. A stealth solution for apartments ?
2. I made a wireloop on the inside of the wooden windowframe in my shack with a circumference of 6,20 meters. The tuning capacitor is made of 20 cm PVC coated copperwire. Feeding is done by a medium size Ferroxcube  4C65 toroid with 1 full turn at the antenna and 2 turns at the coax. For 100 Wats power use only a full size 4C65 or a FT140-61 and replace the tuning section by a pice of RG-213 that forms a high voltage capacitor. For 40 m use a pice of aprox 75 cm RG-213. You can even use a double switch to change bands.By means of 4 hand suckers this antenna can be placed on any medium size window.

First contact was made with Bari Itali with 5-7 report.This was followed that day by several qso's with HA, YT , and LZ . All made with 3.5 Watts SSB even S56EQC with a 5-9 report .  The antenna needs no tuning for the SWR is lower than 1:1.5 all over the band. This is not a wonder antenna but it gets you on the air for certain. Using 15 mm copper tubing drasticly improves efficiency.
When build as mini deltaloop whith the help of two 2m. fibreglass poles it becomes a nice small field antenna .
Give it a try !

You can find toroids and hamstuff at Haje Electronics

SEVERAL  TOROIDS WERE TESTED , THE 4C65 PERFORMS FB

LOOP DATA ALTHOUGH THE BANDWIDTH ( Q-FACTOR ) DOES NOT MATCH

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.

MINI 40 - 20m  SSB-CW  QRP TRX ( UNDER CONSTRUCTION )

TAURUS TRX VFO/RECEIVER SIDE

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