The Swedish 30K1, Part 2

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 The Swedish 30K1, exciter part 2.

The exciter had it's transformer missing. I got a lead on a suitable transformer from a ham in the south of Sweden, and an agreement was set. He would bring it to Eskilstuna hamfest, where Erik, SM2CLY, would pick it up and bring it north, to me.

Eskilstuna hamfest takes place in May on a saturday. Erik called me on sunday a, and told me he was in Umeå. I then drove out to meet up with him, and I got my transformer.




Unfortunately, it was about 3/8" too large to fit the space available.

I contemplated rewinding another transformer, or possibly ordering a new, custom transformer. I also considered cutting out the back panel of the ecxiter, having the transformer protrude out the back. But all of a sudden, I figured, why not mill the transformer to fit? Being cheap, I decided to go with the last option.

Said and done, a visit was paid to Mike, SJ2W. The transformer was rigged in his mill, and successfully hogged down 8mm. It now fits. Tight, but it fits. New mounting feet was fabricated and installed. 

The wiring harness was remade to fit the new transformer. A three conductor power cord was installed, filter capacitors was replaced.

Setbacks

When tested, I noticed that the note from the exciter was rough. It hummed badly. I hooked it to an antenna, and listened to it on a local sdr; the trace in the spectrum showed 50 and 100 Hz sidebands.

After a lot of diagnosing, I pinpointed the issue being magnetic coupling from the transformer, to the PTO. With the PTO being powered from an external power supply, the signal was clean. As soon as I flipped the power switch on the exciter, the sidebands appeared.







A metal shield helped some; it cut down the 100 Hz component by 35 dB, and the 50 Hz by a few dB.

Right now, I'll take a break from this, and see if I can find some Mu-metal (high permeability metal), or maybe I'll relocate the transformer to the transmitter.. 


To be continued

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