[Elecraft] [K1] Question about antenna tuners that I should not have to ask but do.

[Byron Servies]

Sorry, I should have said "none" instead of "1:1".  You don't appear to need it.

I also have a very compromised installation, but better now than a
dipole. And, yes, a tidy installation does us a shocking amount of
coax!

Good luck,

73, Byron N6NUL

On Mon, Sep 28, 2015 at 5:02 PM, Byron Servies <byron at n6nul.org> wrote:
> On Mon, Sep 28, 2015 at 4:37 PM, Douglas Hagerman
> <douglas.hagerman at me.com> wrote:
>
>>
>> I have a space-limited dipole for 20 meters with drooping ends. The KAT-1 tuner
>> will tune it. What I want to know is whether to use a 4:1 or 1:1 balun, or no balun,
>> at the antenna.
>>
>
> Are you feeding the antenna with coax or ladder line?
>
> Even a low dipole will have a feed point impedance of roughly 75 ohm,
> so 1:1 would be fine with coax.  You may want to consider a current
> choke at the feed point, but that's up to you.
>
> With 450 or 300 ohm ladder line, a 4:1 would be more appropriate to
> match the feedline to the expected impedance of the K1 input.
>
>> If the tuner reports 24 “x10” pF, is that 240 pF or 2.4 pF? A straight reading
>> suggests that it’s 2.4 pF, but I don’t see how the tuner circuit can provide so
>> little capacitance. But C4 (82 pF) plus C5 (150 pF) gives 232 pF which could
>> 240 pF if you include some parasitic capacitance, maybe?
>
> Xc = 1/(2 * pi * 14 x 10^6 * 240 x 10^-12) ~~ 47.
>
> So, the tuner thinks it is seeing roughly 50 + j47 and needs -47 of
> capacitance to balance it out, right?  I'd go with the 1:1.

-- 
- Northern California Contest Club
- CU in the Cal QSO Party 3-4 Oct 2015
- www.cqp.org