Given the fact that band data pullup resistors are included in the K3,
the only certain way to assure you are going to "get what you want"
would be to disconnect the K3 to KPA500 cable when using another
transceiver.
There may be a possibility of leaving the K3 powered on with the cable
connected, but that sounds 'iffy' to me because the K3 would be
determining the band that the KPA500 selects.
73,
Don W3FPR
On 4/23/2014 9:58 AM, Cady, Fred wrote:
Good morning all.
Sorry I haven't chipped in before.
I think Jack's comment "...something else going on..." is right on.
The band line pull-ups in the K3 are somewhat problematic. They weren't there
in the first placed (which was good design) but were added to the K3 early on
to compensate for band decoders that didn't have pull ups (not good design).
So that explains why the KPA500 shows 5.3 MHZ when the K3 is turned off.
However, neither of the key lines from the K3 (KEY OUT and KEYOUT_LP in ACC, K3
schematic of June 2010) are pulled up. One is an open drain and one an open
collector. These two lines are wire-ORed together in the KPA500. Wire-OR means
either KEY OUT or KEYOUT_LP or both can key the KPA500. So I don't think that
is what is causing the behavior you see.
I don't have the KX3 in the mix here at the moment but I tried the following:
K3 on 15 m, KPA on in Operate mode showing 21 MHZ.
Turn K3 off. KPA switches to Standby immediately and then shows 5.3 MHZ a
second or two later (significant delay there).
K3 still off. KPA switch from Standby to Operate and back and forth no problem.
K3 still off, KPA in Standby. Ground the KPA keying line PA KEY. KPA can
switch to operate and back and forth no problem. When in Operate the * shows
on the display as expected (saying the amp key line is low).
Another culprit might be DIGOUT1, although that too is an open collector
output. I wouldn't expect that to be doing anything when the K3 is off but if
you see a _ in the KPA display, that means the amp is inhibited when you try to
key because INHIBIT in enabled and DIGOUT1 is low.
Firmware: K3 4.83, KPA 1.38
What is your firmware? There was a firmware change in the KPA a while ago that
fixed a power up problem.
Cheers,
Fred
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