Your suggestion of a hairpin is a high-pass. Herb's suggestion for a
series-L shunt-C L-network is a low-pass. Sometimes you might prefer one
over the other.
Or choice might be entirely driven by parts on hand.
I happen to have some big old variable capacitors so all my tuners use them.
But a younger ham probably wouldn't and might rediscover the variometer or
other solution.
Tim N3QE
On Wed, Sep 19, 2018 at 1:46 PM Clive GM3POI <clive@gm3poi.com> wrote:
> What I don't understand is why would you use more components than needed.
> Why a capacitor (possibly vacuum). What is wrong in using a hairpin which
> also DC shorts the vertical to ground. A combination of hairpin size and
> top loading will give you 1:1 at your favourite 1.825 or anywhere else.
> Perhaps WX0B's article needs a reprint in the NCJ. It really is simple just
> a few microhenries of inductance and you are done.
> 73 Clive GM3POI
>
> -----Original Message-----
> From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of Don
> Kirk
> Sent: 19 September 2018 17:29
> To: Herbert Schoenbohm
> Cc: topband; ash.kf5eyy@gmail.com
> Subject: Re: Topband: Toploaded vertical - SWR
>
> >
> > Herb (KV4FZ) mentioned an L network, and that is what I always use. Very
> > simple, and you just plug you're measured complex impedance values (at
> the
> > frequency you want to be resonant) into one of the many online L network
> > calculators to determine the amount of inductance and capacitance
> required
> > for the L network. I normally just wind my own coil for the inductance,
> > and use high voltage silver mica caps for the capacitor.
> >
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