[Amps] Real time tests to see if an RF transformer is saturating?

[Manfred Mornhinweg]

Chris,

> I await the cores and wire patiently, 

I have a lot of practice in awaiting parts. Chilean customs is delaying 
everything by 2 to 3 months...

> in the meantime i am wondering
> if this transformer could be wound to negate the need for my separate
> impedance matching transformer outside, and its associated losses?

Probably. How long is your feedline? Probably just a tiny little 
fraction of one wave, at 136kHz! So the correct line impedance is 
irrelevant. You can run a 50 ohm coax at 20 or 100 ohm with little 
consequences. And you could probably use plain electrical installation 
wire without any more loss.

> The
> set up is Driver - Amps - Combiner - LPF bank- co-ax to outside -
> Impedance matching transformer comprising two FT-240 77 material
> stacked toroids in a box, with a separate primary and secondary
> winding, each with multiple taps that can be manually selected with
> banana plugs and flying leads - Loading coil with internal variometer
> ( BIG plastic bucket wound externally with 2.5mm insulated wire, with
> a variometer inside to load to operating frequency - Top hat loaded
> vertical antenna about 20 feet high with a horizontal quad loop of
> about 480 feet circumference as capacitive top hat.

Really the outside trafo seems superfluous. The bucket coil can be used 
to tune out any reactance, and the variometer to perform resistance 
matching to a wide range of values.

> The matching transformer outside only has a little impedance matching
> to do as I see a fairly close match even without it.

More reason to get rid of it.

> Could this extra
> loss be negated by winding your combiner transformer design
> differently?

I do think so.

> Now I am running more power the impedance matching
> transformer is running quite hot... I did build the impedance matching
> transformer as an autotransformer, but I had serious issues with RF
> setting the workshop and house alarms off, stopping or slowing my
> internet connection, and tripping the house mains panel RCD. When I
> changed to a "normal" transformer this immediately stopped. 

Hmm... In that case you might still need the transformer, even if it 
does no impedance matching at all, just as an isolation transformer. The 
alternative is a common mode choke on the line, having enough choking 
inductance. The other alternative, which is a better earth connection at 
the feedpoint, is probably impractical.

Manfred

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