[TowerTalk] EFHW

Jim Brown jim at audiosystemsgroup.com
Sat Jul 15 15:51:21 EDT 2017

On 7/15/2017 9:20 AM, Tom Osborne wrote:
> I built 3 UNUN's for some EFHW antennas I plan to use.  On 2 of them, I
> used 1 FT-240 mix 43 core (will be running these as portable antennas on
> LP) and one one of them I used 2 of the same cores.

#31 and #43 are poor choices for transformers that must handle power 
because they are lossy -- that's why they work for common mode chokes. 
#61 is a far better choice for a TX transformer -- much lower loss at 
HF, which is why it's also lousy for chokes. #31 and #43 ARE just fine 
for RX antenna transformers below 20M.

73, Jim K9YC

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