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Author Topic: 1:1 Feritte Toroid Heating  (Read 355 times)
N2LK
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Posts: 71




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« on: October 19, 2011, 09:39:33 AM »

I have 2 Amidon FT cores, 2.25 or 2.40 inch diam. (I forget which) I have been experimenting with as a 1:1 tuner choke. Both bought at same time. This feeds my 52 ft. flat top dipole fed with 50 feet of Radio Shack twinlead. Choke is placed on output of my homebrew T-Tuner in shack, for tuning 40-10 meters. Tunes up just fine all bands as I would expect.

One choke is a single FT core with 10 bifilar turns of 14 gauge insulated wire pulled from some Romex.

Other choke is same model single FT core with 10 wraps of RG-8X instead.

I had RFI issues in shack with computer before on 20 meters, running 40-100 watts rtty or psk. I used either choke and both eliminated that problem easily.

However, I noticed some heating with the bililar wound choke. Using an infrared thermomenter and transmitting 35 watts psk31 early this AM, I measured the temp rise after calling cq at 35 watts. The bifilar choke would heat up to low - mid 80 deg F. vs. ambient temp of 68 F.

The coax choke was put on and same transmitting conditions (called cq 3 times at 35 watts) and just measured a 4-5 deg. F rise above 68 F ambient.

Any particular reason for this?

In all my reading it seems a bifilar wound choke would be a better choise for this application. But I dont like seeing heat issues. But then again, maybe that temp rise just represents a low single watt output lose??

Any thoughts appreciated and 73!
N2LK
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