[Amps] Fil transformer
Geert Jan de Groot
pe1hzg at xs4all.nl
Sun Aug 13 08:19:06 EDT 2017
> Just to be clear, I do not require a transformer for providing
> filament power: it's to fix a design flaw in the Clipperton L,
> which lacks a centre tap for the filament windings and instead
> feeds the filaments with RF on one side only, introducing hum.
> The fix is to parallel a centre-tapped 6v transformer secondary
> with the filament windings on the main transformer and move
> the RF input to the new centre tap.
I'm not sure if any kind of AC transformer is of any help?
The way I have seen this done is that there is an RF choke
between the AC transformer and the filament on both filement wires.
This de-couples the AC and the RF world as it provides a high
impedance to RF signals.
On AC, whether one side, or the middle, is grounded, should not matter
much to RF because the choke provides a high impedance to both
On RF, both filements are floating and isolated by the choke.
A capacitor is used to couple-in the RF to the filament,
both filament wires.
I don't think that your RF input signal passes the center tap of
an AC transformer irrespective of type or taps.
Geert Jan PE1HZG
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