16 May 2017
Good to hear from you, thanks for the reply. I have remade the
combiner's output transformer using 3 stacked 78 material toroids of
the same size, and wound it with 180 strand speaker wire, pure copper,
with an inner conductor of about 2mm diamter. I wound 3 times as many
turns, 15 on the primary, 21 turns on the secondary. It now runs about
40 degrees Celcius with no fan cooling, and the drain wave forms are a
lot less spiky. I saw fair-Rite now list a 98 compound, and it's
advertised as a big improvement for the frequency than the 78
material, but there's an error on their web site and 98 compound is
not available in toroidal form, unfortunately. I did see this beast in
78 compound though, a lot bigger than the FT-240 cores, and wondered
if the fairly high cost is worth it?
> I guess there is a little misstyping in the calculation performed from
> Clemens on the DJ5IL tool....
> he entered 2.5 instead of 25 in the impedance box: the primary
> winding after the combiner should work on 25 ohms. If you enter 25 ohm
> the flux rise a lot beyond the saturation of the 3 stacked cores and
> therefore they have all the rights to warmup!
> On the other hand if you apply the Bmax formula given from Andy, the 3
> stacked cores have A of 471mm²
> and with 2kW of power on 25 ohms the minimum number of turns on the
> primary should be 8 not 5.
> So one more turn to keep B below 0,1T and you should run more
> confortable with N1/N2=9/13
> 73 de Marco, IK1HSS
Chris mailto:[email protected]