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/hamradio/ - Electronics

For the discussion of electronics, tinkering, radio, amateur radio, and related electromagnetic phenomena and communications.

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 No.280

Sup hamfags

I'm in the process of building a WSPR transmitter based around an Arduino and an AD9850 DDS VFO. I'd like to add a PA (about 250mW or so) to the output (plus a LPF, of course), and I think I've found one whose design I can borrow: the BS170-based PA in the Ultimate3S WSPR/QRSS beacon: http://www.hanssummers.com/images/stories/ultimate3s/assembly.pdf

Now, L1 calls for an FT37-43 toroid with 25 turns of wire, but I have neither the toroid nor the magnet wire. I estimate that it's about 270uH, so could I take a pre-packaged 270uH inductor and use that?

Alternatively, are there any sub-1W broadband PAs that don't require any toroids? By broadband, I mean at least 40m thru 12m, but ideally all the way down to 600 meters.

 No.286

You should be able to use it.

Even the small molded one's should be able to survive 250mW.

And well, most wideband poweramps DO need torroids for the baluns. You could build a MMIC-style amplifier with BD139's or 2n4427's for the transitors and possibly get suitable broadband gain.

Most designs use toroids for the coils in the LPF, but you can replace them with air core coils, jsut keep all coils 90* to each other so that they don't couple.

Also, you could take a look at the schematics of FT-817 or xiegu X1M for the final and copy with with some low power transistors.



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