[Elecraft] [KPA500] K3S/KPA500/KAT500 - Adjusting TX Power

[David Bunte]

Bret -

I recall hearing that as well. That has not been my experience. My antenna
presents a real challenge on some bands, but right now, for example, on
14.019 I have  1.34:1 indicated SWR in the shack at about 20 watts tune
power. Key down with the KPA500 in line, showing power of 585 watts and the
SWR holding steady at 1.34:1.

If I put my remote tuner in ByPass, and use my KAT500, I am seeing the SWR
at 1.28:1, whether at 20 watts, or at 500 watts. But, I will gladly use the
remote tuner which is right at the base of my 30' Flag Pole Vertical. It is
not a big deal on some bands, but with 125' of LMR400 coax, there is more
loss on a few bands than I want to give away. I cannot tune this antenna on
160 with the KAT500, because impedance is WAY too low, and the native SWR
is 'out of sight'. The KAT500 is an awesome tuner, but nowhere near up to
that task.

My remote tuner will make the rig happy on 160, but my antenna is so short
for 160 that many folks think I am crazy to even try it, but I never
claimed to not be crazy... I just keep on having fun.

Best of luck,

Dave - K9FN





On Mon, Sep 4, 2017 at 6:36 PM, Charles <cbjesseenh at comcast.net> wrote:

> You are very likely right David. If my rATU gets me down below 1.5 I will
> bypass the KAT500. I do recall reading somewhere that a near 1:1 SWR at low
> tune-up power can be higher at TX levels but I'm not sure about by how much
> higher.
>
> Best regards,
>
> Bret
>
> aka Charles Jessee N4SRN
>
>
> ------ Original Message ------
>
> *From: *David Bunte
> *To: *Charles Bret Jessee
> *Cc: *elecraft at mailman.qth.net
> *Sent: *September 4, 2017 at 12:36 PM
> *Subject: *Re: [Elecraft] [KPA500] K3S/KPA500/KAT500 - Adjusting TX Power
>
> Bret -
>
> W6FB - Jack, was spot on with his information regarding the differing
> readings... but I have an added question. If your SGC-235 gives an
> acceptable match, then why use the KAT500 at all? I think that it is seldom
> a good idea to use two antenna tuners in series... at least that has been
> my thinking for the past 60 years. Am I missing something.
>
> I have a K3, P3, KPA500 & KAT500... but also have a hi power remote tuner
> at the base of my vertical. My KAT500 is bypassed, UNLESS I have a failure
> in my remote tuner, in which case I can bypass it, and quickly switch to
> the KAT500.
>
> If there is a compelling reason to run both tuners I could try that, but
> thought that was ill advised.
>
>
> Very 73 de Dave - K9FN
>
>
>
> On Mon, Sep 4, 2017 at 8:06 AM, MaverickNH <cbjesseeNH at comcast.net> wrote:
>
>> I'm learning about a new KPA500/KAT500 installed with my K3S. When I have
>> the
>> K3S power knob set, in this case, to show 420-440W peak-hold as read on
>> the
>> KPA500 LED screen, I see the KPA500 SWR showing 1-3 LEDs lit (it may stay
>> at
>> 1 LED or climb from 1 to 3 LEDs over 15sec TX, always below 1.5), the
>> KAT500
>> with SWR 1.2 LED lit, and P3TXMON indicating SWR 1.00 (it might start at
>> 1.15 and settle back to 1.00 over 15sec TX). But PEP on the P3TXMON can
>> range from 10-15W up to ~400W on successive 15sec periods of TX using
>> WSJT-X
>> FT8 (going for very distant CQs). Adjusting the K3S power knob down may
>> bring P3TXMON displayed power up if its 10-15W. If the P3TXMON shows 200W
>> adjusting the K3S power knob up may bring the P3TXMON power shown down.
>>
>> Is that how it's supposed to work?
>>
>> I have a P3TXMON 2000W 1.8-54MHz unit installed on my feedline at the rig
>> as
>> follows:  KAT500 to Common Mode Choke to P3TXMON to Bias-T to SG-235
>> remote
>> ATU at antenna base to 43ft Vertical antenna, with some Lightning GDTs
>> between at antenna base and home feedline entrance. My tuning practice is
>> to
>> change Frequency, turn KAT500 to BYP, tune the remote ATU, then set KAT500
>> to AUTO and let it adjust on 1st TX.
>>
>> Bret/N4SRN
>>
>>
>>
>> --
>> Sent from: http://elecraft.365791.n2.nabble.com/
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>
>