Re: KAT500 Auto or Manual

[Jim Wilson]

This is a puzzle.You say the Amp sees infinite SWR ?

Do you have a dummy load?  With the Amp fed directly
to a dummy load with a known good coax, it should switch
to "operate" and feed power to the dummy at an SWR of 1.0:1

If this is true, seems to me you have a problem "downstream"
of the KPA500.

Jim - W4RKS
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[k4vd]

Hi Jim...

The radio sees infinite SWR when the amp is in operate mode. The radio sees
good SWR when the amp is in standby mode.


[FLEX] --> [AMP] --> [DUMMY LOAD]

When the amp is in standby the Flex shows good SWR. When I switch the amp
to operate the Flex shows infinite SWR. It's as if I just disconnected the
coax when I switch to operate. The amp shows no indication power is
reaching it yet it must be if it goes through the amp in standby mode. So I
think it has to be how it is switched within the amp. Same symptoms if I
replace the dummy load with:

[FLEX] --> [AMP] --> [TUNER] --> [ANTENNA]

As long as the amp is in standby the radio is happy and I can make QSOs
(Guinea-Bissau a few minutes ago). But when I switch the amp to operate,
the radio shows maximum deflection on the SWR meter and there's no
indication from the amp or tuner that RF is making it that far.

These symptoms persist even after replacing all the coax (jumpers between
equipment and between tuner and BALUN (tried each of DXE-BAL600H10A,
DXE-BAL200H11CT, DXE-BAL050H11CT). Also no help when I switch from the
dipole to the Hex on 20. Has to be the amp and it is like the amp switches
from standby to limbo (open). I considered tapping lightly with an 8 lb
hammer but maybe that's not a good technique. ;)

Someone had suggested checking the PIN diodes. I'm looking over the
schematics I could find on the Internet. They are a little help though the
don't seem to be consistent. On the LPF schematics there's a control
signal *[TR
Switch>* but I can't follow that back to the origin of the control signal.
The other obvious place to look is K23/K24 on the TR Switch schematic. The
control signal here is *[BYP> *but again I can't figure out the source of
the signal yet. The schematics were just found on the Internet and dated in
2011 so I can't even be sure I'm not using something too outdated.


73,
Kev K4VD


On Sat, Nov 18, 2017 at 3:30 PM, James Wilson <[hidden email]> wrote:

> This is a puzzle.You say the Amp sees infinite SWR ?
>
> Do you have a dummy load?  With the Amp fed directly
> to a dummy load with a known good coax, it should switch
> to "operate" and feed power to the dummy at an SWR of 1.0:1
>
> If this is true, seems to me you have a problem "downstream"
> of the KPA500.
>
> Jim - W4RKS
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

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