EUDX 2026

I participated in the EUDX 2026 just for practice and for testing a new power amplifier vintage, just finished to rebuilt and refurbished a few days before the contest.

It’s a fiftyes american PA with the power supply and other circuits burned. I bough it, as a wreak, in an radioamateur flea market several years ago and slowly rebuilt.

I rebuilt completely the power supply with new components. A transformer of about 1200 VA with secondary 850 V. The rectifier circuit with diodes connected type multiplier, give 1950 V of HT and 500 mA. Originally it was designed for two 3-500z tubes, but I used a pair of Eimac 4-250A, that I already had, with the screen grids to ground together with the control grids. They give me an output of 300 W on 10 metres and a little more on others. Also the two instruments and the front panel, are the originals one.

I add completely a new system of receive/transmit change over with the relay on the rear of amplifier and 12 cc suply on the power compartment. The relay coil current in compatible with my RTX’s contacts.

In line with its original design , I installed, as plate capacitor, an american A-27, see the pictures, and as bands switch another american switch with 4 kV isolation and 20 A contacts, see pictures. Instead as catodes supply I left its original one, not damaged by fire.

I rebuilt the Pi tank inductance circuit in an plexiglas support separating the inductance for 10 metres from the the other bands inductance. I rebuilt the RF chokes too, in an ceramic support, taking care of no resonate in one of the five PA working bands.

I poted the vintage PA insaid an empty old FM PA container. I had to add a small front panel to fill in the whole container, so I take advantage of this more space to move all service connector to the front panell in order to facilitates the use of amplifier.

With this amplifier I participated at the EUDX 2026, single operator CW mode all bands, the 7 and 8 febbruary 2026, performing 470 qso. This this the summary by QARTest

And this is the rate graph

I’m completely satisfied about the work in the vintage amplifier because it’s stable and performing a good job in all bands.

I add more picture about the amplifier to see the details.

And now two pictures with the electric diagrams:

The HT suplier

The general schematic

If you need more information, please write me using the form at the end of this article or via email that you can found on my page of qrz.com using the mouse to view.

73 and I’ll see you in the next contest de Fiorino/I3FDZ/IP3U