[Elecraft] KPA-1500 wish list

[Paul Baldock]

By "manually tuning" I mean using KPA1500 Utility 
program to tweak the L and C. In most cases you 
can get closer to zero reflected power than the 
automatic routine can. Getting the SWR down as 
close as possibly to 1.0:1 at all frequencies 
most certainly flattens the gain/frequency response.

If you know how to use the Utility program try it. You might be surprised.

You should also investigate the ^PB command, very 
useful if you have a high Q antenna. The ^PB 
command chooses the stored setting for the lowest 
SWR within  a segment. I have this mapped to PF1 
on the front panel and use it on 160M where the 
tuning segments are wide compared to the fast 
changing SWR (high Q) of my antenna. I also have 
WET and DRY settings for one of my antennas that are selected by PF1 (^PB).

- Paul  KW7Y

at 07:19 PM 11/18/2019, K9MA wrote:
>There are a couple issues here. First, even if 
>the SWR is 1.2:1, about the best the KP1500 ATU 
>firmware can do, across the whole band, the 
>power can still vary a lot. It depends on the 
>actual load impedance, which, at 1.2:1 could be 
>anywhere from 42 to 60 Ohms. If you happened to 
>be at 42 Ohms when you set the power to 1500 W, 
>it could possibly go up to 2100 W elsewhere in 
>the band. (Except, of course, that the KPA1500 
>won't let you do that.) The other issue is the 
>temperature dependence: I find I have to reduce 
>drive by about 20 percent when the amplifier is 
>cold, or it will fault. Both of these problems 
>could be solved by a slow feedback mechanism 
>which adjusted the K3 output like we do 
>manually. It might even remember previous 
>settings as a function of PA temperature and 
>frequency. The second issue is that this is 
>nothing like conventional ALC, a relatively fast 
>feedback loop. ALC has proven to be highly 
>problematic, so let's not go into that again. 
>It's an entirely different issue. Yes, ALC that 
>really worked well with an amplifier would make 
>the above unnecessary, but I don't think anyone 
>has figured out how to do that. Until someone 
>does, a slow feedback loop adjusting drive power 
>would solve the problem above, not introduce any 
>distortion, and save us operators the bother of 
>riding the power control. 73, Scott K9MA On 
>11/18/2019 20:32, N4ZR wrote: > Jim, I think 
>Paul is talking about something different 
>here.  On Page > 18 of the manual it describes 
>tapping the ATU Tune button again within > 3 
>seconds of completing the initial tune, to get 
>closer yet.  I just > tried it, and it works 
>well so long as you have trained the tuner for > 
>both antennas on every segment. Unfortunately, 
>there appears to be no > way to actually 
>transmit the first character at full power 
>when > changing antennas or QSYing bigly.  I 
>understand the tuner bypasses > the amp until it 
>has determined which setting it should use, 
>which it > can only do by learning what the load 
>looks like by actually sending > power into 
>it. > > 73, Pete N4ZR > Check out the Reverse 
>Beacon Network > at <http://reversebeacon.net>, 
>now > spotting RTTY activity worldwide. > For 
>spots, please use your favorite > "retail" DX 
>cluster. > > On 11/18/2019 8:18 PM, Jim Brown 
>wrote: >> On 11/18/2019 11:34 AM, Paul Baldock 
>wrote: >>> I have manually tweaked (with amp in 
>standby and running 50W) my >>> auto learned atu 
>settings to get as close to 0W reflected power 
>as >>> possible. >> >> Yes, and this is exactly 
>what the manual says to do -- before using >> 
>the amp, train the tuner by tuning at multiple 
>frequencies in each >> band, AND for each 
>antenna that you use on that band. The tuner 
>is >> smart enough to select between multiple 
>"trainings" when you use more >> than one 
>antenna. >> >> 73, Jim K9YC >> 
>______________________________________________________________ 
>-- Scott  K9MA k9ma at sdellington.us 
>______________________________________________________________ 
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