Topband: 1:2 UNUN

[Kenneth Silverman]

Thanks for all the replies on and off the reflector.  My antenna, now a 90'
top loaded vertical with 60 x 100' radials, was not transmitting well.
While trying to fix it, I changed from an inverted L to the top loaded
configuration, and I stripped off the hairpin coil (1/4" copper tubing) and
the choke.  The antenna is working better, but it's likely due to the new
top loaded configuration rather than the hairpin/choke.  With the antenna
tuned without the hairpin, I thought it would be easier to put on an UNUN
rather than retuning the antenna and putting the hairpin back on, which
will lower the frequency.

73, and I hope to CU in the 160 CW contest in 2 weeks.  Kenny K2KW

On Mon, Jan 17, 2022 at 3:18 PM Mike Furrey <mikefurrey at att.net> wrote:

> Perhaps a "hair pin" match? I used a hair pin coil at the base of a
> vertical that was 35 ohms.
>
> 73, Mike WA5POK
>
>
> On Monday, January 17, 2022, 01:36:12 PM EST, Tim Duffy <k3lr at k3lr.com>
> wrote:
>
>
> I match my 26 ohm feed point with a simple L network. One series coil then
> a
> shunt capacitor. Steps up to 50 ohms perfectly.
>
> 73
> Tim K3LR
>
> -----Original Message-----
> From: Topband [mailto:topband-bounces+k3lr=k3lr.com at contesting.com] On
> Behalf Of Richard (Rick) Karlquist
> Sent: Monday, January 17, 2022 1:10 PM
> To: Kenny Silverman; TopBand List
> Subject: Re: Topband: 1:2 UNUN
>
> Maybe this will help:
>
> I use a 1:2.25 Unun (3 to 2 turns ratio).  It will match 22.2 ohms
> to 50 ohms.  It is wound on a single 2.4 inch diameter core of 77
> material.  A pair of RG-58 coax cables are wound around it in
> tandem.  I put on as many turns as would fit ... about 10 turns.
> The shields of the two coax cables are wired in parallel.
>
> This results in essentially a trifilar winding (1.  The shields;
> 2.  One of the center conductors  3. The other center conductor)
> This trifilar winding can then be connected in the usual way to
> get a 3 to 2 turns ratio autotransformer).  The order of the
> connections is:  center conductor #1, then the shields, then
> the #2 center conductor, in series.  The radio drives
> the 3 windings in series, and the antenna is tapped down to
> utilize only 2 of them.  I run this at 1,500 watts in
> contests with no problems at all.
>
> The concept is extensible to a quadfilar winding constructed
> from 3 coax cables in tandem (shields in parallel).  This can
> be wired with a 4 to 3 turns ratio resulting in a 1:1.77 UNUN.
> This matches 28.125 ohms to 50 ohms.  An alternate modality
> I have used is to use two coax cables as in the 1:2.25 UNUN,
> but make one of the coax cables from tri-ax.
>
> I can highly recommend UNUN's for the convenience factor if
> your drive impedance is compatible with the available ratios.
> They are broadband, no tuning.
>
> 73
> Rick N6RK
>
> On 1/17/2022 6:18 AM, Kenny Silverman wrote:
> > Does anyone have a drawing on how to wind a 1500w 1:2 UNUN?  And what
> type
> of core is needed?
> >
> > This is for my 160m vertical which is about 28 ohms.
> >
> > Regards , Kenny K2KW
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