lørdag den 7. december 2013

New QRP Club

I received a mail containing an invitation to join QRP Club last week. The club's main activity is running a forum for QRP'ers. I liked the idea and decided to join (you have to register, and await approval by the admin).

The forum already contain many presentations. Here is mine:
Hello fellow members!
I have worked QRP for many years now, actually since 1985. 
I worked as a secondary school teacher in Greenland 1985-88, and held the call OX3XM. During that time, I worked approx. 500 QSO with 20W (almost real QRP...). It was easy to get contacts in cw, even though my signal was weak.
I work mostly cw and JT65 today, and QRP still fascinates me. My next goal is QRP DXCC.
72 from OZ1BXM Lars
Best wishes for a Merry Christmas, and a Happy new Year!

OZ1BXM Lars Petersen

A Tiny QRP Page by OZ1BXM

søndag den 17. november 2013

144 MHz EME antennas

Autumn is here, and the weather has become rainy. It is frequently blowing and occasionally we have storms. Antenna work is difficult now, especially when you only have weekends for this kind of job. I have decided to mount 2 x 8 element yagis for 144 MHz as my first EME antenna array. The yagis will be vertical polarized, and two rotators will turn the array.

Two 8-element yagis on the ground.
I have replaced the standard 200 W balun on both antennas with high-power baluns from Wimo. I intend to use 1 kW output for EME, and each antenna will be fed with 500 W RF.

73 from OZ1BXM Lars Petersen

tirsdag den 1. oktober 2013

Completing WAZ

I have been chasing WAZ for many years. Two years ago, I worked the last of the 40 zones. It was zone 6 (Mexico). You can read a short story on how I worked this zone.

Working 40 zones is not enough. You have to collect QSL in order to apply for the diploma. The most difficult QSL to obtain was 5R8Z (Madagascar) from zone 39. My first two snail-mail letters to Madagascar went unnoticed. Then 5R8Z got a QSL-manager in USA, and this gave me hope. The precious card arrived in the mail two weeks ago. I opened the envelope and held the card in my hands 2 years after the QSO took place! Oh yes, patience is a virtue.

My 40 QSL-cards were checked in Denmark by OZ1ACB, the award manager of EDR. The verified and signed list was then scanned and sent via email to the WAZ award manager N5FG. I transferred the award fee and postage for the paper award via PayPal. Two days later, I received a mail from N5FG: WAZ #9053 was granted to me! The paper award will follow in 5-6 months.

The end of this story: We had a WAZ celebration in our home. A delicious cake was bought, shared, and eaten with great delight. You have to celebrate your victories!

See you next month.

73 from OZ1BXM Lars Petersen
In pursuit of WAZ - done

søndag den 8. september 2013

Bringing order to chaos

The headline may be a bit grandiose, but there has been chaos for some time in my shack, mainly due to space limitations. I started to utilize the floor for larger objects like antenna rotor, HF-transceiver, power supplies, etc.

Component rack.
Two months ago, a new floor was laid down in the shack. This gave me the opportunity to rearrange things, and as I received two big component racks for my birthday, I can now say that chaos in the shack is under control. Saying that there is no chaos left would be an exaggeration!

Click this link to view another picture of the component racks.

See you next month!

73 from OZ1BXM Lars Petersen
My homepage: http://oz1bxm.dk

lørdag den 10. august 2013

New QSL-card

After 10 years I became tired of my old QSL-Card. I needed a new one. Since my main interest right now is EME, it was only natural for me to search for a front page theme related to Moonbounce. I visited several QSL-printer's homepages before I found what I wanted.

QSL by IT9EJW became my preferred source. As described in my eHam product review, the only obstacle when ordering was the Italian tax number SSN. Since I am not an Italian citizen, I had to enter a dummy number, and this is 123456. You can use that number as well, if you order from IT9EJW! Besides this kink, the process went smoothly. I received the cards in the mail about 3 weeks after the order was submitted.

The rear side of the card is almost blank. Since my logging program DXKeeper supports label printing, I'll start using labels for the QSO details.

OZ1BXM has got a new QSL card.
Vy 73 and see you next month!
OZ1BXM Lars Petersen

My homepage: http://oz1bxm.dk

mandag den 1. juli 2013

SSPA for 2 meters - Finished project

Finally! My SSPA for 2 meters is now finished. The building process has been long, but the learning experience was good. The picture below shows the SSPA as seen from the front:
On top of cabinet:
Two black 140 mm fans cool the radiator. The air is taken in below the radiator.
The black radiator exchange heat between the cooling water and the air.
The cabinet:
Upper row: Output meters (forward and reflected power).
Center: Voltage and Amps are monitored.
Lower row: Water and heatspread temperature are monitored.
The square to the left: Switches and control lamps for 12V, 48V, and PTT.

You can read the full SSPA story on my homepage, where more than 20 SSPA pictures are found, and where I've calculated the cost of the project.

73 from OZ1BXM Lars

SSPA for 2 meters with Freescale MRFE6VP61K25H

søndag den 2. juni 2013

Polar bears in Copenhagen Zoo

I went to Copenhagen last weekend together with my wife to visit our daughter and her husband. As my daughter lives near Copenhagen Zoo, it was an easy decision to go there and spend the afternoon looking at wild animals. We spent most of the time in the new facility called The arctic Ring, which specializes in animals from the Arctic.

The polar bears are busy eating fish.

Two polar bears caught our eyes. They were busy eating fish, but as the fish were frozen inside a block of ice, it was a tough job for the bears to get the food out. However, it seemed as if they were entertained by the chore. And so were we!

Next month I'll tell you more on the progress of my 144 MHz SSPA.

OZ1BXM Lars Petersen

Homepage: oz1bxm.dk

fredag den 10. maj 2013

Visiting Kennedy Space Center

This month I'll mention my journey to USA to visit my sister, who lives there. I also visited Kennedy Space Center's visitor complex, which is located near Cape Canaveral in Florida.

I have always loved space exploration, and being at the Kennedy Space Center feels like Heaven! There is so much to see and do. I went on a tour to visit the historic launch-pads at Cape Canaveral from where the different space missions and satellites have been launched. The highlight of the tour was visiting the control centre from where the first american flew into space. Allan Shepard's trip was a short one: he returned to Earth after just 15 minutes in space. However, the russian cosmonaut Yuri Gagarin was the first human in space - he went there just 23 days before Shepard!

I am in the control center with my fingers
on the launch button!

This Mercury-Redstone rocket launched
Alan Shepard into space in 1961.
 If you ever get the opportunity, do pay a visit to the Kennedy Space Center. I can heartily recommend it.

OZ1BXM, Lars Petersen, oz1bxm.dk

mandag den 1. april 2013

SSPA for 2 meters - project about to finish

Since last time, I have performed the SSPA smoke test. I adjusted the bias of the LDMOS transistor and set it to 3.5 A drain current at 48 V DC. Some heat was developed, but the cooling system could easily deal with it. Rf input and RF output were both connected to 50 ohms resistors. No oscillation was observed, which is good. Conclusion: so far, so good. Smoketest passed.

Many components, cables, relays, fuses, a sequencer, a high-current switch, and so on are used in the SSPA. It takes considerable time to mount them and connect the wires. As this is a prototype, some errors will happen in between. You learn from your errors - but they consume time. Today I can happily tell you, that the project is soon to be finished. The end is in sight!

One of the SSPA sidepanels seen from inside the cabinet.
The picture above shows how one of the side panels is equipped. Clicking the picture will make the text on the picture readable.

73 from OZ1BXM Lars Petersen  Visit my homepage: www.oz1bxm.dk

fredag den 1. marts 2013

SSPA for 2 meters - 1 kW module

If you want to explore more details of the amplifier project, I recommend an article by W6PQL: "Solid state 1 kW Linear Amplifier for 2 Meters". It appeared in QST October 2012.

I decided to buy the amplifier module as a kit from James Klitzing, W6PQL, where all components were included. The copper heat spreader, however, was purchased from PE1RKI Bert. I opted for the version prepared for watercooling.

The core of the SSPA is the 1 kW amplifier module. The module is built around the LDMOS transistor MRFE6VP61K25H from Freescale. This device can operate between 1.8 MHz and 600 MHz and delivers 1250 W output. In this application, the output is limited to 1000 W.

The photo below shows how small the 1 kW module is. Dimensions are 12 cm x 8 cm. But the copper heat spreader is 2 cm thick and weights 1.5 kg. This size is necessary, because the heat spreader must be able to transfer up to 400 W.

1 kW amplifier module for 2 meters.

A low-pass filter follows the amplifier module in order to suppress harmonics of 144 MHz. The physical size of the PCB is the same as the amplifier module. A directional coupler is included, which allows monitoring of forward and reverse power.

1 kW low-pass filter for 2 meters.

This project is still in progress and the 'smoke test' should be completed soon.

Lars Petersen, OZ1BXM

Homepage: http://oz1bxm.dk 

fredag den 1. februar 2013

SSPA for 2 meters - Watercooling

The primary advantage of watercooling is its ability to transport heat away from the source (a transistor) to a secondary cooling surface (a radiator). This allows for large, more optimally designed radiators rather than small fins mounted directly on the heat source.

The disadvantage of watercooling is higher cost and complexity when compared to air cooling.

The picture below shows the components in a watercooled system. In my project, the PA transistor is soldered directly to the copper water block. The radiator is mounted on top of the cabinet and cooled by two large 140 mm fans. The pump and the reservoir is one single unit making the system more compact.

The watercooling system for my SSPA project is about twice as expensive as conventional air cooling. In return, I expect a quiet system which allows high-power transmission and human conversation in the schack at the same time!

OZ1BXM Lars Petersen

Homepage: http://oz1bxm.dk/

tirsdag den 1. januar 2013

SSPA for 2 meters - Cabinet

Building a Solid State Power Amplifier (SSPA) is my project this winter. I have chosen the 1 kW SSPA for 144 MHz as described by F1JRD in DUBUS 4/2010. I'll attempt 2 meter EME later this year, and a powerfull SSPA will become a key component in the set-up.

I have decided to build the cabinet first. I have found DIY alu-frames that can be taylored to many sizes. The cabinet's alu-framework is 30 cm wide, 15 cm high, and 15 cm deep. Furthermore, 2 mm alu-sheets are available from another source, and these sheets fit exactly into the alu-framework. This means no cumbersome cutting and bending of cabinet parts!

The SSPA cabinet.

Another feature of my new SSPA is watercooling. This cooling method is known and used among PC freaks. But as far as I know, only few radio amateurs use that technique. More on watercooling next month.

OZ1BXM Lars Petersen

My homepage: oz1bxm.dk

My latest 10 QSO