OZ2OE Technical Home Page - Equipment and Operation on HF/VHF/UHF

NEWS: Uploaded to new web site September 17'th 2009. Minor adjustments.

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My name is Ole Nykjær. I got my amateur license in 1966 and my interests has always been in designing, building/modifying equipment and to a lesser extent operating - especially on VHF and above frequencies.
On this place I would like to share with you some of my idea's and designs of equipment for radio amateurs.

New designs are added from time to time, so you may want to revisit this site.

Interference problems in contest

A note on interference, splatter etc. What can be expected from good and bad equipment. How to test for broadband noise from transmitters and phase noise in receivers.- see here.

Home building

Home building is what I enjoy most. To me it's always rewarding to build a new piece of equipment and have it perform to expectation. Or to improve on an old circuit.
It doesn't have to be "rocket science" everytime, making a simple piece of equipment work is also a challenge - because the simplest solution is often the most elegant!

Antennas

I like designing and building antennas. (-this is also what I do for a living). Here are a few designs:

Other designs that I plan to upload: 8 elm yagi for 144 MHz. 20 elm yagi for 432 MHz.

Mostly for the fun of it, I have made a curve of stacking distances for yagi's based only on the length of the boom. By combining already published formulas from Kraus W8JK, Bertelsmeier DJ9BV and Rothammel Y21BK, I arrived at one universal stacking graph.

Beacons

I built the OX3VHF combined 6 meter and 2 meter beacon. It was shipped to Greenland many years ago, and is now only active on 6 meter. There are new plans for a high power beacon from OX - land.
I also built and runs the OZ5SHF 10 GHz beacon.

Listning to beacons is very useful for checking out conditions. But "looking" at beacons using a PC with a suitable FFT program, can give you much more information.
See signals below the noise floor, discover different propagation mechanisems like rainscatter and aircraft reflections. With the right setup you can even measure the speed of vehicles at several miles distance.
Look here for some examples and explanations.

Filters and combiners

Antenna combiners for VHF/UHF. A study of calculation methods for deriving the caracteristic impeadance of a coaxial line with square outer conductor and round inner conductor.
Also on the importance of using bandpass filters to combat out-of-band interference.
And - when declassified - a real interference killer: A 144 MHz x-tal filter with 5 kHz BW for the contest station.

Preamplifiers

Now here is a topic to fill a book! I have designed many during the years, so here are descriptions of a few:

Testequipment

How I made a Power Meter from a surplus power sensor.

Transverters

Power Amplifiers

Here are descriptions of some Power Amplifiers I've build:

Other PA designs to be uploaded soon: 80W PA for 50 MHz with BLV38.

Modifying

I have commercially build equipment too. If I was to build everything from scratch, I should never have been QRV on all the bands from 1.8MHz to 24GHz. However most of it is quite old and heavily modified to add or increase performance.
So I'd rather spend my time and money on testequipment and components, than on new "black boxes". And it doesn't cost a lot, as you can get a good bargin on ham festivals and flee markets.

Modifying commercial equipment

Before starting any modification, you should ask yourself why you want to do the change? - and how you plan to do the job.
I've often wondered why people who just bought a new rig, immediately put out a request on packet: "Any mods for ICOM/YAESU/KENWOOD model xyz?" - as if they bought the wrong station and now wanted something else.

Still there is a lot you can do to older equipment to improve or add new performances, being old they are also easier to work with and the results are more marked. With all modifications, it is important that you are able to verify which improvements have really taken place.

Modifying a KENWOOD TS-820 to include the WARC bands.
Modifying the MFJ-940 VERSA TUNER II to improve bypass VSWR.

Living in a populated area

For me - as for many other amateurs - this is a fact of life. And with that comes the problems with TVI, interference to telephones and from computers - and the list goes on! This is really a two way street.
I shall have comments an experiences on this subject too.

Please write to me if you have comments or questions, and given the time I'll answer every E-mail that arrives in my mailbox oz2oe@mail.dk