[ARC5] Input impedance - BC-453-B - un-un

[Dennis Monticelli]

Guys,

Maybe we're over-thinking this input matching "problem."

If the input parallel tuned tank's parallel resistance at resonance is in
the neighborhood of 50K ohm (as Ian reports), then let's ask ourselves what
a 50 ohm antenna looks like after passing through the series 8.5pF input
coupling cap.  The series circuit of 50 ohms and 8.5pF need only be
transformed into its parallel equivalent circuit to answer that question.
Doing the mathematical conversion at 400KHz results in 44K ohm in parallel
with 8.5pF.  The capacitance will get absorbed by the antenna trimmer
leaving 44K of antenna source resistance.

I just don't see a need to be fiddling with input matching networks.  And
let's give the ARC-5 designers the credit they deserve.

Dennis AE6C



On Fri, Jan 30, 2015 at 1:37 PM, Kenneth G. Gordon <kgordon2006 at frontier.com
> wrote:

> On 31 Jan 2015 at 10:03, AKLDGUY . wrote:
>
> > Why not simply connect a standard antenna coupler backwards?
>
> Because most of those available will not match anywhere near 40K ohms to
> 50 ohms. I remember something like 1500 to ~5K being tops, depending on
> the coupler.
>
> Your idea would certainly be a major help for transmitting, of course...
>
> Ken W7EKB
>
>
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