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PA4EME

Dutch Amateur Radio Station

Frank Veldhuijsen

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144 MHz amplifier with russian GS35b

When the Iron Curtain was demolished in 1989 Russian tubes came available in quantities. These tubes were very rugged and cheap compared to the Eimac tubes. So it became cheap to use “Russian QRO” and I purcheased some GS35b’s as well. Various designs are around but the first was from UV1AS/RX1AS. I decided not to invent the wheel again and started to build an amplifier based on the design of DL4MEA. It’s a W6PO style amplifier and likes to run on 4200 Volts and at maximum output it takes 1.2 Amperes of anodecurrent. It’s capable of delivering 65.5 dBm which equals 3.5 kW. It really needs a lowpass filter. Günther, DL4MEA, has written a building manual. There are some errors in it but those who are willing to build it will find them out soon. This manual can be found on his homepage: www.qsl.net/dl4mea .

On the photo you can see the amplifier in “service mode”; the top can slide up as the cavity is mounted on top of the HV-supply. Total weight is aprox. 200 kg.

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144 MHz amplifier with 2x4CX250b

This amplifier was my first project and build 1979/1980. In QST from February 1971 new ideas for a 2-Meter Kilowatt were described by W1QVF and W1HDQ. With almost no experience I started building this amplifier and I’m still proud of it. It has been in service for many years and in those days it was one of the few kilowatt amplifiers existing. With this amplifier I made my first EME-QSOs together with 4x15 element Que-Dee antennas.

It was completely build with surplus materials exept the HV-transformer that was winded myself at 3600V. I took it out of service in 2002 but it is still in my shack. It has not been powered up for many years now so the capacitors in the powersupllies will be dryed out now and the tubes will have lost their vacuüm. Surprisingly I still have every designing note...the QST articles, notes during the design, slip from the calculator when calculating the meterscales, the calculations of the transformer etcetera.

When you look at pictures from my shack you can see that even today I am using the topsection of the 19-inch racks with the power– and SWR-meters.

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144 MHz amplifier with GS35b

This is a GS35b amplifier designed by DJ5RE. To be honest the cavity was not completly build by me. I bought it from PA3CMC who got it from an unknown person. It was not working well and investigating the problem I found that the circuit was not working on 144 MHz at all but somewhere around 133 MHz. It turned out to be a fault in the design, or maybe better said, in the published design. The output resonator turned out to be to long. Probably due to the fact that the original design was using a GS31 tube which has a smaller cooler. Searching the internet showed me that I was not alone with this problem. So the interiour of the cavity was modified as well the chimey, the fan and coaxrelays were added. So I think it is fair to say it is homemade. In daily use it is a very nice compact amplifier so it is the one that is doing most of the work in the shack. Also it is very easy to swapp tubes so this one is also used to recondition NOS (new old stock) tubes. Output is typical 63 dBm (1.5 kW)

On the shelf above you can see that the in 1979/1980 builded topsection of the above mentioned power– and SWR-meter is still used.

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144 MHz amplifier with GS35b

Another design. This one is looking more like the first published design for a 144 MHz amplifier with a GS35b from UV1AS/RX1AS. This amplifier was intended to be used at the remote EME-QTH. However, meanwhile very nice TV amplifiers are available so there is no need anymore to play with HV at a remote location.

The anodeline is 650 mm long and made of standard 100 mm copper rain gutter pipe (0.6 mm wall thickness) which represents a 72 Ohm anodeline. The box is 308x308 3mm aluminium Ag3. Rest of the design is straight forward. Output somewhere in the 64 dBm/65 dBm range (2-2.5 kW). Franck, F1CXX, has a document how to build this amplifier. You can you can go to the following URL .

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DF9GR rotor controller

Building kit purchased in Friedrichshafen 2011. Nice design, well written manual. This controller allows me to make remote use of my home station. It can autotrack any source if needed.

More info can be found on the ERC-webpage.

OE5JFL antenna controller

Stand alone antenna controller. Works without PC. Accuracy about 0.2 degrees. Good quality PCB from Alex, HB9DRI. Very good manual can be found on the webpage of OE5JFL and there you can download driacs.doc ; the building manu-al.

Absolute BCD-encoder

Just builded for fun...an absolute BCD (binary coded decimal) encoder. Just to show that is was possible to use Gray-code combined with 7-segment LED-displays. The Gray-code was printed on transparent sheet and a reader was build. Good stuff to learn about encoding and decoding.

More hembrew stuff...preamplifier box, MGF-1302 build 1990, ATF-54143, sequencer, 70 MHz transverter etcetera. More of those will show up on my homepage soon….

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