[Elecraft] K2 Antenna Tuner Question

[Ignacy (NO9E)]

 >It's done more than that! In a couple fits of extreme stoopidity (SIC),
 >I've actually managed to match an EMPTY SO-239.

Since coils (toroids) have limited Q, without the antenna, one matches
losses in the coil. This has some practical implications of what are the
losses in KAT2. If the best match without the antenna conected is SWR of
4, and with the antenna is 1.0, roughly at most 25% of power stays in
KAT2, or KAT2 is > 75% efficient. Any tuner will have high losses with
some Z, but whats good about KAT2 is that it does not get burned.

Recently I tested baluns by trying to have KAT2 match them without a
load. Mix 73 matches well without a problem especialy on 14 MHz and up. 
This
says that losses at high Z are high although at low Z may be very low. A
balun with mix 43 did not match as well but fooled KAT2 into temporary
SWR of 1.0 but with POUT like 4.0 3.8. It is now my mix of choice for K2.

Are toroids used in KAT2 ferrites or iron?

Ignacy, NO9E