[ARC5] ARC-5 antenna match

[Mark K3MSB]

>From the April 1990 ER article by KJ4KV:

Series capacitor:
160M: 400-700 pf
80M: 200-300 pf
40M: 150-175 pf

The air variable is 200 pf

The coil is 30 turns #20 wire 16 turns per inch.  1" Diameter coil tapped
at 2 and 4 turns.

73 Mark K3MSB

Sent from my Android phone
On Jul 28, 2013 12:12 PM, "Kenneth G. Gordon" <kgordon2006 at frontier.com>
wrote:

> On 28 Jul 2013 at 19:49, neilb at ihug.co.nz wrote:
>
> > An antenna tuner can match a 50 ohm transmitter to a wide range
> > of antenna impedances.
> > I got to wondering whether one could be connected backwards to
> > match the unknown output impedance of an ARC-5 transmitter to
> > a 50 ohm antenna.
>
> Of course it can. I used this method many years ago to build what one
> could,
> I suppose, call a very simple antenna coupler.
>
> My reasoning at the time was that a parallel-tuned circuit with one end
> grounded is essentially a wide-range impedance auto-transformer, with the
> high-impedance end being at the "top", i.e., the end opposite "ground".
>
> Therefore, one should be able to find a point on the coil, somewhere, that
> matched fairly closely any impedance between "high" and "zero".
>
> Tapping the transmitter in at some point and the antenna in at another
> point
> would then result in a proper "match" to both.
>
> In practice this worked very well, although it took some experimentation to
> get the best results.
>
> Using a coil with as high "Q" (read, "lowest possible ohmic resistance") as
> possible, in combination with a fairly high value of tuning capacitor of a
> good
> design would result in an "antenna coupler" of fairly wide range, covering
> something like a 2:1 frequency range, at least.
>
> My favorite such unit used a roller coil from a defunct Command
> transmitter,
> and an old, but very well-built, BC tuning capacitor. Taps would always be
> made between the "roller" and the ground end, the "roller" determining the
> basic frequency range over which the "coupler" would be used.
>
> I also sometimes used a simple two-turn link around the "ground end" of the
> roller coil in lieu of a tap for the antenna IFF I was using a 50 ohm
> antenna.
> Otherwise, a second tap was used for the antenna.
>
> YMMV.
>
> Ken W7EKB
> ______________________________________________________________
> ARC5 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/arc5
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:ARC5 at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>