http://elecraft.85.s1.nabble.com/KAT-500-and-open-wire-tp7647776p7647811.html
lines. Unless you have a folded dipole, you probably don't have a match
> I should probably know this, but what is the old dual air coil Heathkit B-1
> balun, a current or voltage type?
> If I remember correctly, they are 4:1 ratio.
> Would this be a better choice for open-wire feed to a dipole intended for
> use on several bands?
>
> 73, Charlie k3ICH
>
>
>
>
> -----Original Message-----
> From:
[hidden email] <
[hidden email]> On
> Behalf Of K9MA
> Sent: Sunday, January 06, 2019 10:24 PM
> To:
[hidden email]
> Subject: Re: [Elecraft] KAT 500 and open wire
>
> On 1/6/2019 20:12, Jim Brown wrote:
>> We add one or more common mode chokes to minimize the effect if the
>> common mode circuit, which is radiation and reception, and to do that,
>> a very good choke must be AT THE FEEDPOINT. I don't know of a way to
>> EFFECTIVELY choke a feedline that is not matched to the antenna. Yes,
>> you can put something there, but if it did anything useful it would
>> fry (unless yo only ran QRP to the antena), and a choke that wouldn't
>> fry with TX power won't do anything useful!
> I have to respectfully disagree a little here. A choke specifically designed
> for the antenna impedance at the feed point could effectively eliminate the
> common mode current. The problem is, we often use balanced line with
> antennas which have a large range of impedances over frequency range at
> which they are used. (Think G5RV.) It may be impossible to design a single
> choke which can work over the whole range. However, feeding balanced line
> with a balanced tuner can work pretty well, even though the feedline may
> radiate a bit due to common mode current. I've only attempted this with
> link-coupled tuners. I'm not sure it works as well with the double T-network
> tuners with a choke at the input, like the MFJ-976, but it may.
>
> For years, I've used a warped, lop-sided, short, 80 meter "dipole" fed with
> window line and the balanced tuner. I never bothered to try to figure out
> the impedance at either the feedpoint or the tuner, but the tuner matches it
> on several bands. I don't use it much on 80, though, as it's so close to the
> roof of my house that the RF gets into everything.
> I'm sure the feedline radiates some, but that's not where the RFI is coming
> from.
>
> 73,
>
> Scott K9MA
>
> --
> Scott K9MA
>
>
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