[Elecraft] Tuning band segments with the KPA-1500

[Dick Dievendorff]

The intent is that the tuner does this already in normal practice. 

If you press the ATU tune button at a frequency where the antenna SWR, with the ATU bypassed, is “low enough”, the ATU setting stored and later recalled is “ATU bypassed”. Both ATU LEDs are lit when this happens. The relays for this situation are exactly the same as if you turn the ATU off.

You can influence the SWR for “good enough” with a KPA1500 utility function, edit configuration, SWR threshold for SWR bypass. It’s per band and defaults to 1.2 to 1.

The amp is rated at 1500w for a 3:1 or better antenna. At 10:1, you’ll need to dial back below 1500W to avoid damaging the ATU. This is what the power too high for bypass SWR fault is for. If the antenna is 10:1, figure on about 850W.

The amp does better if the SWR the PA sees is low.

73 de Dick, K6KR

Sent from my iPhone

> On Sep 7, 2018, at 10:41, Peter Dougherty <Peter at w2irt.net> wrote:
> 
> Is it possible (or might it be possible with a firmware upgrade) to selectively
> use the KPA-1500's tuner on only a portion of an individual band? 
> 
> As a contester I face my biggest SWR challenges are 40m and 80m SSB. 
> 
> On 40, my Yagi is resonant at 7045, and the KPA will give me a full-power match
> between 7000 and 7125 pretty easily. Anywhere north of there, however, I'm above
> 3:1, rising as high as about 7 or 8:1 at 7295. On 80, I could use the KPA from
> 3500 (resonant 3550) to about 3750, but would need to switch to the external
> tuner for anything above that (I only ever go as high as 3850, and extremely
> rarely at that. Maybe a dozen transmissions per year calling mults).
> 
> At the moment, I have a Palstar HF-Auto, which is bypassed everywhere except the
> phone portions of 40 and 80, and the internal tuner in the KPA that's bypassed
> only on those two bands. The freeware software for the HF-Auto is positively
> wretched, and the tuner itself is only RF-sensing, not commanded by band data,
> so obviously I'm looking for a better solution that will allow me to use full
> legal limit with fast, seamless switching. I would prefer to use the KPA-1500
> for as much of the tuning duties as possible, and only dropping to the HF-Auto
> when absolutely necessary, since quite frankly I don't trust the Palstar to not
> go rogue on me (a regular occurrence, sadly).
> 
> As it stands now, I can set the KPA's internal tuner to operate or bypass on
> full bands only, not in segments. It doesn't seem like a stretch to allow a user
> to put in limits within a band.
> 
> ----------------------------------------------------
> 
> Regards,
> Peter Dougherty
> 
> 
> 
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