Re: End Fed antennas w/ uBITX #ubitx


iz oos
 

Thanks Allison for the feedback. The core I have used must be lossy for conventional transformers. I have just wired a 1:49 transformer using a small binocular core with 8uH at the input and 380uH at the output like the previous lossy transformer and wired in the way and this new one show not measurable SWR without any load which is a good thing. Of course using such small core I can't use it for TX probably even at qrp level. I have not the right cores in my drawer, so I will experiment with iron powder large cores (white, grey etc) maybe increasing the number of turns. Two turns with low permeability toroids at the primary seem to me too little especially below 10mhz.


Il 05/ago/2018 22:26, "ajparent1/KB1GMX" <kb1gmx@...> ha scritto:
Pretty good sign the core loss  is very high.  Its likely it does not match well at ~2500 ohms

I have never measured any for inductance as its like measuring it with a DC ohmeter,
not very informative.

Those I have tend be very high SWR no load high is greater than 20:1 at the low end
and at least 10:1 at the high end for a low power unit near me.  The problem is that's a
marginally informative as the loss can still be high or the ability to match is poor.

I can build a monoband L network in minutes and be far more sure it will be low
loss. 

Allison

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