[KPA500] stuck on TX when AUXBUS attached

[WD6DBM]

Tonight I tried to use my KX3 with my KPA500, but when I turn off the K3 that it is attached to via AUXBUS, then put the KPA500 into OPERATE mode, the asterisk comes on and it is in TX, which means that the receiver of the KX3 goes deaf.  Is this the way it is supposed to work, or have I messed up a setting?  Will I have to remove the AUXBUS cable from the K3--even though the K3 is turned off--whenever I want to use the KPA500 with another rig?

Thanks,

Eric WD6DBM
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[Jack Brindle-2]

Yes. It must be disconnected. The K3 is loading the band and PTT inputs to the KPA, pulling them low. This has two effects - it will cause the KPA to change to 60 meters, and the KPA will transition into transmit. If you wish to use the KPA500 with another transmitter, you will need to first disconnect it from the K3.

Jack Brindle, W6FB
Elecraft Engineering


On Sep 14, 2012, at 12:26 AM, eric norris <[hidden email]> wrote:

> Tonight I tried to use my KX3 with my KPA500, but when I turn off the K3 that it is attached to via AUXBUS, then put the KPA500 into OPERATE mode, the asterisk comes on and it is in TX, which means that the receiver of the KX3 goes deaf.  Is this the way it is supposed to work, or have I messed up a setting?  Will I have to remove the AUXBUS cable from the K3--even though the K3 is turned off--whenever I want to use the KPA500 with another rig?
>
> Thanks,
>
> Eric WD6DBM
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Uh - oh...

Then perhaps what I'm doing is not 'best-practice'. I just leave the K3
connected and --powered on--, and I can drive the KPA500 from another
radio and the KPA500 follows it and works perfectly. I even have the PTT
connections from both radios paralleled (the other radio is a
FLEX-5000A), so the only thing I need to do is change the source of the
rf drive to the KPA500.

73, Dale
WA8SRA


On 9/14/2012 6:39 AM, Jack Brindle wrote:

> Yes. It must be disconnected. The K3 is loading the band and PTT inputs to the KPA, pulling them low. This has two effects - it will cause the KPA to change to 60 meters, and the KPA will transition into transmit. If you wish to use the KPA500 with another transmitter, you will need to first disconnect it from the K3.
>
> Jack Brindle, W6FB
> Elecraft Engineering
>
>
> On Sep 14, 2012, at 12:26 AM, eric norris <[hidden email]> wrote:
>
>> Tonight I tried to use my KX3 with my KPA500, but when I turn off the K3 that it is attached to via AUXBUS, then put the KPA500 into OPERATE mode, the asterisk comes on and it is in TX, which means that the receiver of the KX3 goes deaf.  Is this the way it is supposed to work, or have I messed up a setting?  Will I have to remove the AUXBUS cable from the K3--even though the K3 is turned off--whenever I want to use the KPA500 with another rig?
>>
>> Thanks,
>>
>> Eric WD6DBM
>> ______________________________________________________________
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[Arthur Nienhouse]

It would be nice if the function of the AUXBUS cable could be disabled
from a menu choice on the KPA500 instead of disconnecting of the cable
between the K3 and the KPA500.

Would this be something that could be done in the KPA500 software?

Regards
Art
ka9zap
> Tonight I tried to use my KX3 with my KPA500, but when I turn off the
> K3 that it is attached to via AUXBUS, then put the KPA500 into OPERATE
> mode, the asterisk comes on and it is in TX, which means that the
> receiver of the KX3 goes deaf.  Is this the way it is supposed to
> work, or have I messed up a setting?  Will I have to remove the AUXBUS
> cable from the K3--even though the K3 is turned off--whenever I want
> to use the KPA500 with another rig?
>
>
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[Gary Gregory]

*Art

The Auxbus cable without the adapter carries the PTT function also so maybe
that is also an issue that FW may not be able to change?

With the addition of the KAT500 into the K-Line this may become even more
difficult as the Auxbus cable will run from the K3 to the KAT500 and then
to the KPA500 to enable really tight integration of the K-Line and this may
also make a FW option in the KPA500 difficult.

Just thinking.......Jack may jump back in and comment?

73
*
On 14 September 2012 23:16, Art Nienhouse <[hidden email]> wrote:

> It would be nice if the function of the AUXBUS cable could be disabled
> from a menu choice on the KPA500 instead of disconnecting of the cable
> between the K3 and the KPA500.
>
> Would this be something that could be done in the KPA500 software?
>
> Regards
> Art
> ka9zap
> > Tonight I tried to use my KX3 with my KPA500, but when I turn off the
> > K3 that it is attached to via AUXBUS, then put the KPA500 into OPERATE
> > mode, the asterisk comes on and it is in TX, which means that the
> > receiver of the KX3 goes deaf.  Is this the way it is supposed to
> > work, or have I messed up a setting?  Will I have to remove the AUXBUS
> > cable from the K3--even though the K3 is turned off--whenever I want
> > to use the KPA500 with another rig?
> >
> >
> ______________________________________________________________
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--
*Gary*
*Start the day off slow, then taper off.........*
K3 #679
KPA500FT #18
KAT500FT 007
P3 #1629
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[vk4tux]

An  ABB RXMA2-RK211-191  relay would do the job nicely powered from K3 '12v
out'

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Art Nienhouse
Sent: Friday, 14 September 2012 11:16 PM
To: [hidden email]
Subject: Re: [Elecraft] [KPA500] stuck on TX when AUXBUS attached

It would be nice if the function of the AUXBUS cable could be disabled from
a menu choice on the KPA500 instead of disconnecting of the cable between
the K3 and the KPA500.

Would this be something that could be done in the KPA500 software?

Regards
Art
ka9zap
> Tonight I tried to use my KX3 with my KPA500, but when I turn off the
> K3 that it is attached to via AUXBUS, then put the KPA500 into OPERATE
> mode, the asterisk comes on and it is in TX, which means that the
> receiver of the KX3 goes deaf.  Is this the way it is supposed to
> work, or have I messed up a setting?  Will I have to remove the AUXBUS
> cable from the K3--even though the K3 is turned off--whenever I want
> to use the KPA500 with another rig?
>
>
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[Jim Brown-10]

On 9/14/2012 3:39 AM, Jack Brindle wrote:
> Yes. It must be disconnected.

FWIW, I've never used an AUXBUS connection to my KPA500, nor have I felt
the need for one. I have only the AMP KEY line (PTT) between the K3 and
the KPA500. When I change bands, I hit a dit or tap my mic, the KPA
reads the frequency, changes bands, and is all set to go by the time
I've found someone to TX to.  I'm beta-testing a KAT500, and I'm using
it in the same manner.  With the KAT500, the AMP KEY line is "looped
through" the KAT500 -- that is, K3 to KAT500, KAT500 to KPA500. There
are two RCA jacks on the KAT500 that make this easy.

The only thing I use the AUX bus for is to drive a KRC2 that switches
bandpass filters.

73, Jim K9YC
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[Jim Brown-10]

On 9/14/2012 5:42 AM, Dale Boresz wrote:
> I even have the PTT
> connections from both radios paralleled (the other radio is a
> FLEX-5000A),

Right.  During the week, I use the KPA500, but for big contests, I use a
Titan.  My AMP KEY line goes in parallel to both amps, I select between
them with ANT1 or ANT2, and switch the amp outputs through a Top Ten
relay box.

73, Jim K9YC
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[Jack Brindle-2]

This is a matter of physics. A driver pulls its output to a power  
rail, either power or ground. In the case of the drivers used in the  
K3 for the AUX signals, pullups are used, to the positive rail to  
provide the pullup function. This means that when the driver is off,  
its output will be pulled to whatever voltage the power rail is  
sitting at. When the K3 is powered off, this voltage goes to zero,  
thus causing devices connected to the driver to see a zero value at  
their inputs. Thus the KPA sees a 60 meter input, and the key line  
appears to be active. Note that the Auxbus signal itself is only an  
output from the KPA, and has a diode block on the input. Thus it is  
_not_ part of this situation.

There is another, potentially bigger problem that occurs when you  
parallel two devices in this way. When one device is powered, and the  
other off, the powered device can actually inject power into the  
"unpowered" device through the IO lines. This will actually power up  
the device, at least partially. The device is in a dangerous state at  
this point, with transistor junctions improperly biased and processors  
running in very strange situations. It is actually possible to blow  
ICs in this situation. Beyond this, it is sucking power from the other  
device. This scenario is called "incidental power," and is a major  
problem in the telco co-processing arena where we specifically design  
to protect against it from happening.

Now, with all this going on, do you _really_ want to parallel the K3  
and KX3 control signals to the KPA, or even leave one connected while  
the other is driving the amplifier? By far the best thing to do is to  
pull the plug from the K3 when you use the other transceiver, then  
plug it back in when you use the K3 with the KPA. Why risk damage to  
any of this precious gear we have invested in?

Jack Brindle, W6FB


On Sep 14, 2012, at 6:25 AM, Gary Gregory wrote:

> *Art
>
> The Auxbus cable without the adapter carries the PTT function also  
> so maybe
> that is also an issue that FW may not be able to change?
>
> With the addition of the KAT500 into the K-Line this may become even  
> more
> difficult as the Auxbus cable will run from the K3 to the KAT500 and  
> then
> to the KPA500 to enable really tight integration of the K-Line and  
> this may
> also make a FW option in the KPA500 difficult.
>
> Just thinking.......Jack may jump back in and comment?
>
> 73
> *
> On 14 September 2012 23:16, Art Nienhouse <[hidden email]> wrote:
>
>> It would be nice if the function of the AUXBUS cable could be  
>> disabled
>> from a menu choice on the KPA500 instead of disconnecting of the  
>> cable
>> between the K3 and the KPA500.
>>
>> Would this be something that could be done in the KPA500 software?
>>
>> Regards
>> Art
>> ka9zap
>>> Tonight I tried to use my KX3 with my KPA500, but when I turn off  
>>> the
>>> K3 that it is attached to via AUXBUS, then put the KPA500 into  
>>> OPERATE
>>> mode, the asterisk comes on and it is in TX, which means that the
>>> receiver of the KX3 goes deaf.  Is this the way it is supposed to
>>> work, or have I messed up a setting?  Will I have to remove the  
>>> AUXBUS
>>> cable from the K3--even though the K3 is turned off--whenever I want
>>> to use the KPA500 with another rig?
>>>
>>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>>
>
>
>
> --
> *Gary*
> *Start the day off slow, then taper off.........*
> K3 #679
> KPA500FT #18
> KAT500FT 007
> P3 #1629
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[David Christ]

I'm puzzled.  Why not just buy an A-B switch box?  DB-9 DB-15 DB-25
Centronics RJ-11 RJ-45  Whatever you want.  $10 to $15 normally.

Might take a gender changer, but so what.

David K0LUM



At 11:08 AM -0700 9/14/12, Jack Brindle wrote:
>
>
>Now, with all this going on, do you _really_ want to parallel the K3
>and KX3 control signals to the KPA, or even leave one connected while
>the other is driving the amplifier? By far the best thing to do is to
>pull the plug from the K3 when you use the other transceiver, then
>plug it back in when you use the K3 with the KPA. Why risk damage to
>any of this precious gear we have invested in?
>
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