Posted by
Vic Rosenthal on
Dec 08, 2011; 5:22pm
URL: http://elecraft.85.s1.nabble.com/KAT500-update-tp7072932p7075088.html
I t's been shown conclusively that an unbalanced 'floating' tuner with a balun on the
input does not provide better balance than one with the balun on the output. Yes, I know
that there is such a tuner in the ARRL handbook and Alpha is manufacturing one. But the
math doesn't lie. So unless Elecraft wanted to use a balanced network -- which would make
the tuner MUCH more expensive -- I would prefer one without a balun. Then those who do not
use balanced lines would not have to pay for the balun.
On 12/8/2011 8:58 AM, Oliver Johns wrote:
> Wayne,
>
> When I talked to you briefly at the 2010 Pacificon, you seemed to say that the KAT500 would be a "floating-L" design. That is, it would contain an unbalanced L network, but that network and its circuit board would be floating and not connected to the metal enclosure. You said a balun would be put at the 50 ohm end, feeding a SO239 connector for the coax to the rig. The floating-L could then be connected to balanced lines, or to unbalanced ones by tying one side of it to the case at the antenna end.
>
> Now it seems that you are talking about a totally unbalanced tuner, with no provision for balanced antenna feeders. Do you mean to add an external balun on the *antenna* side of the tuner? Surely not. That seems an inherently bad idea for many balanced lines. The impedance there will be unpredictable, hence the need for the tuner. Not a good place for a balun IMHO. But if you put the balun on the 50 ohm end where it belongs, then the whole enclosure will be tied to one side of the "balanced" line, which will likely unbalance it.
>
> What happened? I had hoped to put the KAT500 in a weatherproof box of my own fabrication and use it between a balanced line to the antenna and a coax feed back to the rig. It could live out near the antenna, where it belongs.
>
> 73,
>
> Oliver Johns
> W6ODJ
>
>
> On Dec 7, 2011, at 5:22 PM, Wayne Burdick wrote:
>
>> We originally had two antenna jacks on the KAT500, with one of them
>> switchable between balanced and unbalanced.
>>
>> Recently we decided that a third antenna jack would provide greater
>> utility overall. (In my case, I'll be keeping a dummy load on the
>> third jack.) All three jacks will be unbalanced (SO239).
>>
>> We're hoping to add a high-power, high-performance balun to our
>> product line sometime next year that will serve the needs of those
>> using balanced lines.
>>
>> 73,
>> Wayne
>> N6KR
>>
--
Vic, K2VCO
Fresno CA
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