[Elecraft] High power tuner

[Vic K2VCO]

The balanced output is not referenced to the case. So the balun is functional when feeding 
a balanced line, not shorted as you suggest. However, you are correct that it will not 
serve as a common mode choke with unbalanced output. And Paul's comments about the 
placement of the balun are correct. I was surprised to see this from Alpha, whom I would 
have expected to know better.

I suppose I'll have to wait for the KAT1500 (no, no such product has been announced or 
hinted at as far as I know!)

On 11/26/2011 8:55 AM, Joe Subich, W4TV wrote:
>
>> The new RF Concepts tuner would not work well for me. It's an
>> unbalanced C-L-C design with a CM choke input, similar in design
>> with several Palstar tuners, only with much more rugged components
>> than what Palstar provides. W9CF, W7EL, and W8JI have analyzed a
>> current choke placed at the input to a C-L-C tuner and have concluded
>> that placement at the input is not as effective for maintaining line
>> balance as a balun placed at the tuner's output.
> The common mode choke in the Alpha tuner will be completely ineffective
> with any of the coaxial fed antenna outputs in any case!  Since it is
> *inside* a metal box and the input as well as output connectors are all
> connected to the case, any common mode current will simply bypass the
> the choke on the case!
>
> The *only way* to make a common mode choke effective with an unbalanced
> tuner is to connect the case of the tuner to a low impedance "ground"
> and place the choke in the feedline between the rig/amplifier and the
> tuner - external to the tuner.
>
> 73,
>
>      ... Joe, W4TV
>
>

-- 
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/