http://elecraft.85.s1.nabble.com/KPA1500-in-the-IARU-Contest-Last-weekend-tp7663146p7663179.html
We're drifting off topic and you're pushing at an open door.
I accept that wire size has an influence, but in my experience on smaller cores (UK limit is 400W) wound with RG316 I have observed the core getting hotter than the wire.
BOK = Brick On Key. I think it was Alpha that used this in their advertising.
So, in the protagonist's system, if he finds his swr climbing for no apparent reason, rather than blaming the linear it might simply be the core of the choke getting too hot with continuous use. A bigger core (or doubling up) helped me and it might help him.
> On 16 July 2020 at 04:26 Jim Brown <
[hidden email]> wrote:
>
>
> On 7/15/2020 1:36 PM, CUTTER DAVID wrote:
> > It's all about size. Bigger core helps,
>
> Dave,
>
> No, it is NOT about size. It is about design of the entire antenna
> system, including the antenna, the feedline, and other parts needed to
> make the SYSTEM work. The principal characteristic of a common mode
> choke is the resistive component of its common mode impedance at the
> operating frequency(ies) where it will be used. Further, dissipation in
> the choke occurs at least as much in the WIRE that is wound around the
> core as in the core itself.
>
> There is another fundamental error in many antenna systems that ONLY
> looks at matching to the transmitter at the transmitter, ignoring the
> match between the antenna and the transmission line, using high
> impedance, parallel wire line, and using a random center-fed or
> off-center fed horizontal wire on all bands. Yes, the transmitter can be
> made to supply power to the feedline, yes, it will get to the antenna,
> and yes, it will radiate. But it may not receive all that well due to
> common mode current on the line from noise sources in our own homes and
> those of our neighbors. THAT is the problem with using a decades-old
> design for a world where there was 20 dB less noise than most of us face
> today.
>
> so a core that is OK for ssb
> > and cw might be undersized for AM or some data modes. Just like linear
> > amplifiers.
>
> So it is NOT the size of the core, it's the design of the antenna
> system. HFTA author and retired ARRL Antenna Book and Handbook editor
> Dean Straw, N6BV, published an excellent piece in QST 6-8 years ago
> called "Don't Blow Up Your Balun," in which he pointed out the
> differential mode dissipation in chokes, which can be extremely high if
> the choke is at a very high current point in a mismatched line. When he
> passed it to me for review, I noted that these losses were in addition
> to the common mode dissipation, and he revised the piece to reflect that.
>
> you can't
> > label something poorly designed because it doesn't pass the BOK test.
>
> BOK?
>
> 73, Jim K9YC
>
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