[hfsig] Sidebands on Raspberry Pi WSPR carrier - how to build an ground isolation balun

Zoltan Doczi zoltan.doczi at gmail.com
Mon Sep 5 14:59:54 EDT 2016

Hopefully we hear some hints from software side too, for augmenting that
noise, as this coupling to the chain during the modulation phase possibly.

The problem with hand made parts, that this inexpensive module use commerce
mass production capable parts so not fitting the actual BOM.


On Mon, Sep 5, 2016 at 8:55 PM, Tom McDermott <tom.n5eg at gmail.com> wrote:

> Hi Ron, thanks for the pointer.
> For use at 14 MHz, winding the two transformer windings on opposite sides
> of the ferrite core
> could be an issue. That causes a lot of leakage inductance, and at 14 Mhz,
> depending on load
> Z may attenuate the desired signal. 30 turns might be a bit much at 20
> meters
> Forming a bifilar twisted pair of the two windings reduces the leakage
> inductance a lot.
> Minimizing the interwinding capacitance would not seem to be much of a
> consideration
> at 60 or 120 Hertz.
> -- Tom, N5EG
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