[Elecraft] KPA1500 ATU band/bin operation

[Dick Dievendorff]

Gary:

If the Xcvr provides freq info (a K3 menu enable is required), the KPA1500 selects new ATU settings as the K3 Tx VFO changes (a bit after VFO motion ceases), without waiting for a transmission.  The KPA1500 chooses the most recently stored ATU setting in the new “bin”.  On transmission, if SWR exceeds a threshold, and a KPA1500 config choice for HiSWR retune is enabled, other ATU settings in the bin are evaluated. This requires a bit of RF. Once the best ATU setting is found, the bin is reordered and stored, so when you return to this frequency, the most recent setting is tried first.

If you mostly use your three antennas on the obvious bands, there should be one or two ATU settings per bin.  If you train your 80 meter dipole on 20 and your 40 meter beam on 15, there may be more ATU settings per bin.   I’d consider putting the HyTower on the second ant port so that it can be used on all bands without having to search thru settings for the “other” antenna.

If there are any ATU settings in the bin, only those settings will be tried, so tune in every bin if you have multiple antennas.

It takes on the the order of 20 milliseconds of stable RF per ATU setting, which has to do with relay settle delay and reevaluating SWR.  A CW dit at 30 WPM is 40 mSec. ATU relays are changed after bypassing the PA momentarily, and that also takes a few mSec.  

73 de Dick, K6KR

> On Nov 15, 2020, at 08:51, Gary Slagel via Elecraft <elecraft at mailman.qth.net> wrote:
> 
> I'm thinking of replacing an old SPE amp with a KPA1500.
> I have 4 antennas: 10/15/20 yagi, 40M yagi, 80/160 dipole and an all band hytower vertical so will probably have 3 switched antennas to one antenna port on the KPA1500 and 1 antenna to the 2nd antenna port.
> After 'training' on all freq/antenna combinations I'll tend to have 2 or 3 settings for each freq/bin.   When I tune from one frequency to the next and one bin to the next bin, the tuner will have to select one of the 2 or 3 settings for the bin.  Does it wait until I transmit (a dit with the key) to select the new setting or will it track with the k3 and make changes as I move from freq to freq.   Will I notice the tuner trying each setting (lights flashing, relay noise) until it finds the correct setting? 
> My older SPE has a similar freq/bin concept but has 4 antenna ports and 1 set of band/bins per antenna port.   This allows it to know exactly setting to use which is nice.   But... maybe not as durable as the KPA1500.
> Thanks for any advice.
> Gary SlagelKT0A
>  
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