[Elecraft] KPA-1500 wish list

[N4ZR]

I hope that the amp guys at Elecraft will reply to this thread.  I've 
been working with them for several weeks trying to address just this 
problem.  The latest beta firmware seems to handle it pretty well, so 
long as I make sure I've trained the ATU on every band segment.

I'd love to have 50-ohm resonant antennas on every band.  Short of that, 
there does not appear to be any way around the ATU's need  to identify 
which antenna is selected by the external switch, before it can decide 
which stored setting to apply.  This takes a measurable amount of time, 
as much as one character of 30 WPM CW, and I'm told that until this 
process is completed, the amplifier is bypassed.  I've observed, for 
example, that when I pounce on a CQer significantly far away from the 
frequency of my last QSO, the "N" in my call becomes "E", or goes away 
entirely, as heard by the other station.

73, Pete N4ZR
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On 11/19/2019 3:56 PM, K9MA wrote:
> Bill is touching on an issue I've raised before: A way to select 
> multiple ATU settings for the same frequency and antenna output. I had 
> to build a tri-band tuner to switch between my two tribanders so they 
> would both present the amplifier with the same impedance. The internal 
> ATU would have been able to do that, if only there were a way to store 
> and recall two different sets of settings. In the case of automated 
> antenna switching systems like mine, there also has to be a way to 
> electronically tell the amplifier which settings to use: Having to 
> press a front panel switch is not acceptable, as that would require 
> two operations to switch antennas, which is way too slow. (I sometimes 
> have to flip the antenna switch several times during a call to 
> determine which antenna to use.)
>
> 73,
> Scott K9MA
>
>
>
> On 11/19/2019 13:02, K8TE wrote:
>> Another issue not explicitly mentioned is using an external antenna 
>> switch
>> with different conjugate matches already trained withing the KPA1500 
>> ATU.
>> Those different matches mean when one selects a "new" (different) 
>> antenna
>> than already selected on a particular frequency (same band or not), the
>> KPA1500 doesn't know this fact until power is applied.  Then, due to 
>> a high
>> VSWR, the amplifier faults.
>>
>> With just two antenna ports on the KPA1500, there are only two quickly
>> accessible tuning solutions per frequency if using both ports. If using
>> only one port and an external antenna switch, a common choice in many
>> stations, finding the correct tuning solutions can't be done fast 
>> enough to
>> prevent a fault.
>>
>> As alluded to in previous messages on this topic, perhaps the solution,
>> unfortunately, is an external box that could contain the appropriate 
>> data so
>> that, when a new frequency/antenna combination, that has a previously 
>> tuning
>> solution, is selected, the external box will tell both the KPA1500 
>> ATU to
>> select the appropriate solution and transceiver to make appropriate 
>> power
>> level adjustments, both PRIOR to actually transmitting.
>>
>> This is done (approximately, but with no power level changes) by the 
>> KAT500
>> in selecting one of the three antenna ports and the appropriate tuning
>> solution.  This assumes no other antenna choices on each of the three 
>> ports
>> for the same frequency.  The KPA1500/K3S combination is (currently) not
>> sufficiently "smart" to accomplish this.
>>
>> Of course, if we had "perfect" antennas that provided resonant 
>> matches on
>> all bands/frequencies, we wouldn't be discussing this.  If we had 
>> those, we
>> wouldn't need the KPA1500 ATU either.  73, Bill, K8TE
>>
>>
>>
>> -- 
>> Sent from: http://elecraft.365791.n2.nabble.com/
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>
>