Telamon wrote:

That depends on the core. Some are no good for 3 to 30 MHz. TV operates
at 50MHz.
--------------------------
And this post by Mr. Doty should put this argument to rest.
----------------
John Doty Feb 18 1999, 9:00 am
Newsgroups: rec.radio.shortwave
From: John Doty
Date: 1999/02/18
Subject: Buiding Matching Transformer

J W Schermerhorn wrote:

2/18/99

The TV torroid is probably not suitable for winding a balun transformer
for shortwave (HF) frequencies. It's formulated for VHF/UHF and doesn't
work well below about 10-Mhz.

Works fine if you use enough turns. For a 30:10 turn version, I've
measured a lower 3 dB cutoff of 330 kHz. A higher permeability material
optimized for HF would let you use fewer turns, but otherwise doesn't
perform better at HF, assuming the core is small.

The ICE model 180 transformer uses an HF core with only one turn on the
low impedance side. At HF its performance is nearly identical to 30:10
transformer on the TV core, but its lower 3 dB cutoff is 1 MHz, so it
isn't as good at MF and LF (needs more turns).

--
John Doty
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To sum it up, the "correct" ferrite core will require fewer turns.
But, a VHF material will work fine, if you can get anough turns
without exceeding the "5% of wavelength" rule.

Terry