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K3/KPA500 question

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Bob McGraw - K4TAX

K3/KPA500 question

Check to see that the AUX cable is properly seated at the amp and at the
the K3. If you have the KAT500, check the control cable is connected
as shown on page 5, Figure 1 in the KAT500 manual.

Always secure the plugs with the supplied connector screws. Just
plugging in the connector is and invitation for issues.

73

Bob, K4TAX

Message: 6
Date: Fri, 23 Apr 2021 21:17:02 -0400
From: "Joe K2UF"<[hidden email]>
To:<[hidden email]>
Subject: [Elecraft] K3/KPA500 question
Message-ID:<[hidden email]>
Content-Type: text/plain; charset="us-ascii"

I have my K3-KAT500-KPA500 working great. The amp is off to the left side
and I can't see the display easily. while working on building an auto
antenna switch I noticed that the band display on the amp does not synch
with the K3. It seems to be random. If I hit one dit on the key the amp
will synch the band with the K3. I am not sure if this has been working
like this right along and just did not notice.

Any ideas guys.

73 Joe K2UF

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Bob Wilson, N6TV

Re: K3/KPA500 question

Does your automatic antenna switch use the Unified Microsystems BCD-10 or
BCD-14 band decoders, or is your design similar to the 4O3A Antenna Genius?

These products all use opto-Isolators on the four Band Data lines in the
AUX cable. Wiring this type of decoder in parallel with the
K3/KAT500/KPA500 AUX cable via a 15-pin Y-cable or similar *will usually
cause automatic band changes on the KPA500 to stop working*, until you
disconnect the antenna switch's band decoder, or send some RF so that the
KPA500 frequency counter takes over. Not cool.

Opto-isolators draw too much current from the K3 ACC pins, leaving too
little voltage for the KPA500's band decoder to track properly. This is no
problem for the KPA1500, only the KPA500, with or without the KAT500.

The solution I discovered was to connect four 4.7K pull-up resistors to 12V
to each band data pin in the K3 ACC cable, assuming the band decoder in the
antenna switch can handle 12V instead of 5V (most can). The KAT500 and
KPA500 will have no problem with 12V on the band data lines.

The Y-BOX v3.0 (not pictured on my website because I have not had time to
update it) includes these four pull-up resistors. They can conveniently be
wired internally to the band data pins, and band switching should work
again when all the devices are connected in parallel to the K3 ACC via the
Y-BOX. This assumes your KPA500 "RADIO" menu is set to "K3" or to "BCD" so
it tracks properly when the automatic antenna switch is disconnected from
the ACC/AUX cables.

FYI, you can still tap the BAND buttons on the KPA500 to change bands on
the K3, because that uses the AUXBUS line (ACC Pin 2), not the BAND DATA
lines. Many folks may have never discovered this cool feature of the
KPA500 and KPA1500.

73,
Bob, N6TV
https://bit.ly/Y-BOX

On Fri, Apr 23, 2021 at 6:18 PM Joe K2UF <[hidden email]> wrote:

> I have my K3-KAT500-KPA500 working great. The amp is off to the left side
> and I can't see the display easily. while working on building an auto
> antenna switch I noticed that the band display on the amp does not synch
> with the K3. It seems to be random. If I hit one dit on the key the amp
> will synch the band with the K3. I am not sure if this has been working
> like this right along and just did not notice.
>
> Any ideas guys.
>
> 73 Joe K2UF
> ______________________________________________________________
> 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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ANDY DURBIN

K3/KPA500 question

In reply to this post by Bob McGraw - K4TAX

"FYI, you can still tap the BAND buttons on the KPA500 to change bands on the K3, because that uses the AUXBUS line (ACC Pin 2), not the BAND DATA lines. Many folks may have never discovered this cool feature of the KPA500 and KPA1500."

I had to write code to put the KPA500 back on the correct band if one of these band buttons was accidentally pressed. I wish there was a way to disable them completely. One person's cool feature is another's PITA.

Andy, k3wyc
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Lou Mecseri

Re: K3/KPA500 question

That also controls the KAT500 when connected.

73, Lou KE1F

On 4/25/2021 4:08 PM, Andy Durbin wrote:

> "FYI, you can still tap the BAND buttons on the KPA500 to change bands on the K3, because that uses the AUXBUS line (ACC Pin 2), not the BAND DATA lines. Many folks may have never discovered this cool feature of the KPA500 and KPA1500."
>
> I had to write code to put the KPA500 back on the correct band if one of these band buttons was accidentally pressed. I wish there was a way to disable them completely. One person's cool feature is another's PITA.
>
> Andy, k3wyc
> ______________________________________________________________
> Elecraft mailing list
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Bob Wilson, N6TV

Re: K3/KPA500 question

In reply to this post by ANDY DURBIN

It's not clear why this feature of the KPA500 is a "PITA," since the
majority of users want the rig and the amp. to always be locked to the same
band. However, I suppose it could be a problem in a station where antenna
switching is all manual rather than automatic.

In that case, one can change the KPA500 "RADIO" menu from "K3" to "BCD",
and now the band buttons will not change the band of the K3 anymore, but
the amp. will still follow band changes made by the K3.

Hope that helps.

73,
Bob, N6TV

On Sun, Apr 25, 2021 at 1:11 PM Andy Durbin <[hidden email]> wrote:

> "FYI, you can still tap the BAND buttons on the KPA500 to change bands on
> the K3, because that uses the AUXBUS line (ACC Pin 2), not the BAND DATA
> lines. Many folks may have never discovered this cool feature of the
> KPA500 and KPA1500."
>
> I had to write code to put the KPA500 back on the correct band if one of
> these band buttons was accidentally pressed. I wish there was a way to
> disable them completely. One person's cool feature is another's PITA.
>
> Andy, k3wyc
>

Bob Wilson, N6TV

Re: K3/KPA500 question

OTOH, if you change Radio type from K3 to BCD, and have set the K3
menu *CONFIG:PWR-SET
*to *PER-BAND*, the K3 will no longer be able to recognize when a KPA500 or
KPA1500 is switched from STBY to OPER, so there will effectively be just
one fixed drive power setting stored per band, instead of two power
settings (one for amp in OPER and a second for amp in STBY).

73,
Bob, N6TV

On Tue, Apr 27, 2021 at 8:19 PM Bob Wilson, N6TV <[hidden email]> wrote:

> It's not clear why this feature of the KPA500 is a "PITA," since the
> majority of users want the rig and the amp. to always be locked to the same
> band. However, I suppose it could be a problem in a station where antenna
> switching is all manual rather than automatic.
>
> In that case, one can change the KPA500 "RADIO" menu from "K3" to "BCD",
> and now the band buttons will not change the band of the K3 anymore, but
> the amp. will still follow band changes made by the K3.
>
> Hope that helps.
>
> 73,
> Bob, N6TV
>
> On Sun, Apr 25, 2021 at 1:11 PM Andy Durbin <[hidden email]> wrote:
>
>> "FYI, you can still tap the BAND buttons on the KPA500 to change bands on
>> the K3, because that uses the AUXBUS line (ACC Pin 2), not the BAND DATA
>> lines. Many folks may have never discovered this cool feature of the
>> KPA500 and KPA1500."
>>
>> I had to write code to put the KPA500 back on the correct band if one of
>> these band buttons was accidentally pressed. I wish there was a way to
>> disable them completely. One person's cool feature is another's PITA.
>>
>> Andy, k3wyc
>>
>

ANDY DURBIN

Re: K3/KPA500 question

In reply to this post by Bob Wilson, N6TV

"It's not clear why this feature of the KPA500 is a "PITA," since the majority of users want the rig and the amp. to always be locked to the same band. "

And that is exactly why the band buttons are a PITA - If pressed they would ensure that my KPA500 is NOT on the same band as my transmitter.

I don't have a K3 and the KPA500 band buttons control nothing except the KPA500 BPF selection. Yes I could make them change bands on my TS-590S but my station control is based on frequency not band. Also, if I want to select bands, I would do it with the TS-590 band buttons which each provide a 3 deep frequency/mode stack.

I don't need any help. I have effectively defeated the KPA500 band buttons but I only added that code after I realized the risk they presented.

Andy, k3wyc

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Bob Wilson, N6TV

Re: K3/KPA500 question

On Tue, Apr 27, 2021 at 8:34 PM Andy Durbin <[hidden email]> wrote:

> "It's not clear why this feature of the KPA500 is a "PITA," since the
> majority of users want the rig and the amp. to always be locked to the same
> band. "
>
> And that is exactly why the band buttons are a PITA - If pressed they
> would ensure that my KPA500 is NOT on the same band as my transmitter.
>

Well, a few milliseconds after you transmit, the KPA500's frequency counter
will automatically switch the KPA500 back to the right band.

> if I want to select bands, I would do it with the TS-590 band buttons
> which each provide a 3 deep frequency/mode stack.
> I don't need any help. I have effectively defeated the KPA500 band
> buttons but I only added that code after I realized the risk they presented.
>

OK, but for others who may be curious, the KPA500 can automatically track
the band of TS-590S with no computer and no custom code required. Just a
connect a straight serial cable from the KPA500 *XCVR (RS232)* jack to the
TS-590S *COM* port, and set the KPA500 MENU as follows:

RADIO to SERIAL
RS232X to the baud rate of the TS-590S COM port
SER POLL ON if the TS-590S is the only device connected to the TS-590S COM
PORT
-or-
SER POLL OFF if some other device like an RS232 band decoder is polling the
radio on the TS-590S COM port, in which case both KPA500 and the device can
be connected in parallel to the TS-590S COM port via an RS-232 Y-Cable or
S-BOX. SER POLL OFF uses a relay to open the TXD pin of the KPA500 RS232
connector, so the usual problems caused by connecting two RS232 devices in
parallel are no problem.

Now the KPA500 will automatically track the band of the TS-590S, as will
an RS232 band decoder or similar.

73,
Bob, N6TV
https://bit.ly/S-BOX
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Elecraft mailing list

Re: K3/KPA500 question

In reply to this post by Lou Mecseri

Actually, no. The KAT500 does not communicate with the KPA500, only the K3. In RADIO=K3 (on the KPA) changing bands on the KPA500 causes the KPA to send a special Auxbus message to the K3. The KAT500 cannot receive this message. The K3 does a band change, then sends data using normal Auxbus communications to the KAT500. Note that the KPA500 only sends data on the Auxbus (only the K3 can decode this), while the KAT500 only receives data, and only from the K3.

I _really_ wish the KAT500 and KPA500 could communicate, but unfortunately they cannot.

73!
Jack, W6FB

> On Apr 25, 2021, at 1:51 PM, Lou <[hidden email]> wrote:
>
> That also controls the KAT500 when connected.
>
> 73, Lou KE1F
>
> On 4/25/2021 4:08 PM, Andy Durbin wrote:
>> "FYI, you can still tap the BAND buttons on the KPA500 to change bands on the K3, because that uses the AUXBUS line (ACC Pin 2), not the BAND DATA lines. Many folks may have never discovered this cool feature of the KPA500 and KPA1500."
>>
>> I had to write code to put the KPA500 back on the correct band if one of these band buttons was accidentally pressed. I wish there was a way to disable them completely. One person's cool feature is another's PITA.
>>
>> Andy, k3wyc
>> ______________________________________________________________
>> 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]
> ______________________________________________________________
> Elecraft mailing list
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> 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]