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KX3 connection to doublet question

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stan levandowski

KX3 connection to doublet question

For several years, I've been using my multiband non-resonant 94'
doublet, fed with a short run of 450 ohm window line, to a remotely
mounted SG234 autocoupler and then a 25 foot run of 50 ohm coax to my
KX3.

Has been working with perfection; no complaints, except I cannot operate
QRP below 3 watts because that's the minimum RF required for the
autocoupler.

Now, if I wanted to extend my 450 ohm line and connect it directly to
the KX3 and use the KX3's internal tuner, would there be any benefit in
a 1:1 isolation balun at the KX3?

I can't think of any reason this would be necessary except as a
transition from the window line to a convenient coax output to the KX3.

What would the KX3 prefer??

Thanks,
Stan WB2LQF
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Rick WA6NHC

Re: KX3 connection to doublet question

It's ALWAYS a good idea to use a common mode choke (not a voltage balun). In your case, like mine, it transitions window line to coax, but more importantly it helps keep the noise down and RF out of the shack.

73,
Rick wa6nhc

Tiny iPhone 5 keypad, typos are inevitable

> On Apr 20, 2015, at 8:42 AM, stan levandowski <[hidden email]> wrote:
>
> For several years, I've been using my multiband non-resonant 94' doublet, fed with a short run of 450 ohm window line, to a remotely mounted SG234 autocoupler and then a 25 foot run of 50 ohm coax to my KX3.
>
> Has been working with perfection; no complaints, except I cannot operate QRP below 3 watts because that's the minimum RF required for the autocoupler.
>
>
> Now, if I wanted to extend my 450 ohm line and connect it directly to the KX3 and use the KX3's internal tuner, would there be any benefit in a 1:1 isolation balun at the KX3?
>
>
> I can't think of any reason this would be necessary except as a transition from the window line to a convenient coax output to the KX3.
>
>
> What would the KX3 prefer??
>
>
> Thanks,
> Stan WB2LQF
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

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Wes (N7WS)

Re: KX3 connection to doublet question

In reply to this post by stan levandowski

I think you answered your own question.

On 4/20/2015 8:42 AM, stan levandowski wrote:

> [snip]
>
> I can't think of any reason this would be necessary except as a transition
> from the window line to a convenient coax output to the KX3.
>
>
> What would the KX3 prefer??
>
>
> Thanks,
> Stan WB2LQF
> ______________________________________________________________
>

stan levandowski

Re: KX3 connection to doublet question

Yeah, I think so ;-). I'm using "real" (read "stiff") window line so
trying to connect it directly to the KX3 via a dual BNC just sounds like
more springy trouble than it's worth. This installation is in my home,
not in the field. So I can get a good clean run through the wall and
away from metal, wire, etc. right to my rig. BalunDesigns sells a very
nice QRP isolation balun Model 1110 (actually good to 200 watts) which I
can mount on the wall and then just run a 2 foot PL259 to BNC jumper to
my rig. So I guess Problem Solved!

Thanks,
Stan WB2LQF

On Mon, Apr 20, 2015 at 02:24 PM, Wes (N7WS) wrote:

> I think you answered your own question.
>
> On 4/20/2015 8:42 AM, stan levandowski wrote:
>> [snip]
>>
>> I can't think of any reason this would be necessary except as a
>> transition from the window line to a convenient coax output to the
>> KX3.
>>
>>
>> What would the KX3 prefer??
>>
>>
>> Thanks,
>> Stan WB2LQF
>> ______________________________________________________________
>>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

Don Wilhelm-4

Re: KX3 connection to doublet question

In reply to this post by stan levandowski

Stan,

The transmission line acts as an impedance transformer, so no one else
can duplicate the performance and matching capability of your antenna
unless you specify the feedline length.

For the same reason, if you extend your 450 ohm line, you may create
some impedances that could be difficult to match.
A few sessions with the TLW software (see www.ARRL.org) will allow you
to experiment if you know the impedance at the antenna feedpoint.

A common mode choke at the end of the feedline will help with balance
and keeping RF out of the KX3.

73,
Don W3FPR

On 4/20/2015 11:42 AM, stan levandowski wrote:

> For several years, I've been using my multiband non-resonant 94'
> doublet, fed with a short run of 450 ohm window line, to a remotely
> mounted SG234 autocoupler and then a 25 foot run of 50 ohm coax to my
> KX3.
>
> Has been working with perfection; no complaints, except I cannot
> operate QRP below 3 watts because that's the minimum RF required for
> the autocoupler.
>
>
> Now, if I wanted to extend my 450 ohm line and connect it directly to
> the KX3 and use the KX3's internal tuner, would there be any benefit
> in a 1:1 isolation balun at the KX3?
>
>
> I can't think of any reason this would be necessary except as a
> transition from the window line to a convenient coax output to the KX3.
>