Elecraft

KPA-1500 issues

Classic

List

Threaded

28 messages Options

Don Wilhelm

Re: KPA-1500 issues

Randy,

That indicates that you do not have your KAT500 and amplifier properly
connected.

The KEYOUT line from the transceiver should go first to the KAT500, and
then from the KAT500 to the amplifier.
When the KAT500 needs to tune, the amplifier will not be keyed and
tuning will take place at the power output of the transceiver.
After tuning, the amplifier will be engaged.

73,
Don W3FPR

On 11/29/2018 7:42 PM, Randy Farmer wrote:

> I've had difficulties with my KAT500 / KPA500 combo (only) on 160
> meters, apparently due to the tuner relying on RF sensing. I've
> carefully "trained" my KAT500 all across the 160 meter band. Since the
> manual states that the tuning bins are 10 kHz wide below 3 MHz, I do a
> tune at 1805, 1815 ... up to about 1895. My antenna is an impossible
> load above 1900 kHz, so I don't try to tune up there. Since I don't have
> exactly a great antenna system, I almost always stick to S&P operation
> in 160 meter contests. As I tune across the band I can hear the relays
> selecting the appropriate tuning solutions. But... every once in awhile,
> as soon as I key the transmitter I hear the relays in the KAT500 switch,
> presumably out of the commanded tuning bin due to frequency measurement
> error in the RF detection circuit. This shouldn't be a problem, since
> the tuning doesn't change significantly between adjacent bins. However,
> since the amp is being keyed while the tuner is changing presets, the
> amp immediately faults and goes off line. This is very annoying, and
> probably not so good for either the amp or the tuner. If the RF
> measurement resolution is really as poor as 8kHz, I don't see why
> there's any point in providing for 10 kHz wide tuning bins on the low
> bands. I would also strongly agree that if good frequency information is
> available to the tuner via the serial bus that's what it should use to
> select tuning bins. The RF sensing information should be a backup
> source, to be relied on only in the absence of such data.
>

______________________________________________________________
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

Re: KPA-1500 issues

Need to have recent firmware in both the KAT500 and KPA500 also. The KPA500 for this was updated shortly after the KAT500 was created. In any case, the latest firmware for both devices is strongly recommended.

73!
Jack, W6FB

> On Nov 29, 2018, at 6:48 PM, Don Wilhelm <[hidden email]> wrote:
>
> Randy,
>
> That indicates that you do not have your KAT500 and amplifier properly connected.
>
> The KEYOUT line from the transceiver should go first to the KAT500, and then from the KAT500 to the amplifier.
> When the KAT500 needs to tune, the amplifier will not be keyed and tuning will take place at the power output of the transceiver.
> After tuning, the amplifier will be engaged.
>
> 73,
> Don W3FPR
>
> On 11/29/2018 7:42 PM, Randy Farmer wrote:
>> I've had difficulties with my KAT500 / KPA500 combo (only) on 160 meters, apparently due to the tuner relying on RF sensing. I've carefully "trained" my KAT500 all across the 160 meter band. Since the manual states that the tuning bins are 10 kHz wide below 3 MHz, I do a tune at 1805, 1815 ... up to about 1895. My antenna is an impossible load above 1900 kHz, so I don't try to tune up there. Since I don't have exactly a great antenna system, I almost always stick to S&P operation in 160 meter contests. As I tune across the band I can hear the relays selecting the appropriate tuning solutions. But... every once in awhile, as soon as I key the transmitter I hear the relays in the KAT500 switch, presumably out of the commanded tuning bin due to frequency measurement error in the RF detection circuit. This shouldn't be a problem, since the tuning doesn't change significantly between adjacent bins. However, since the amp is being keyed while the tuner is changing presets, the a

mp immediately faults and goes off line. This is very annoying, and probably not so good for either the amp or the tuner. If the RF measurement resolution is really as poor as 8kHz, I don't see why there's any point in providing for 10 kHz wide tuning bins on the low bands. I would also strongly agree that if good frequency information is available to the tuner via the serial bus that's what it should use to select tuning bins. The RF sensing information should be a backup source, to be relied on only in the absence of such data.
> ______________________________________________________________
> 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
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]

ANDY DURBIN

Re: KPA-1500 issues

In reply to this post by ANDY DURBIN

"However, since the amp is being keyed while the tuner is changing presets, the amp immediately faults and goes off line. This is very annoying, and probably not so good for either the amp or the tuner."

That should not happen. The KAT500 should open the amp keying line before changing the LC selections. If it is happening to you it suggests that you are not running the amp keying line though the KAT500, or the KAT500 is not performing as intended. The interrupt is monitored by the KAT500 utiliity but the update rate is too slow to catch a typical keying interrupt. E.g. a single step change in the value of C shows a 167 ms interrupt in keying when viewed on a 'scope.

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]

Randy Farmer

Re: KPA-1500 issues

In reply to this post by Don Wilhelm

Now that you mention it, that sounds right. I SHOULD have the key line
set up properly; I did at one time. Guess it's time to accept the pain
of pushing the radio desk out from the wall and seeing what's really
there. I might have accidentally screwed things up the last time I did
some station rewiring. Thanks for the reminder.

73...
Randy, W8FN

On 11/29/2018 8:48 PM, Don Wilhelm wrote:

> Randy,
>
> That indicates that you do not have your KAT500 and amplifier properly
> connected.
>
> The KEYOUT line from the transceiver should go first to the KAT500,
> and then from the KAT500 to the amplifier.
> When the KAT500 needs to tune, the amplifier will not be keyed and
> tuning will take place at the power output of the transceiver.
> After tuning, the amplifier will be engaged.
>
> 73,
> Don W3FPR

Vic Rosenthal

Re: KPA-1500 issues

In reply to this post by Don Wilhelm

There IS a reason to be fanatical about a 1:1 SWR, although it doesn't
apply to an amp like the KPA1500.

If you are running a tube amplifier that requires tuning, and the tuner
always provides the identical load, you can tune the amplifier once,
record the dial settings, and quickly reset the amplifier tuning "by the
numbers" when you change bands.

But even a small change in load impedance might require manual touch-up
of the amp tuning. So it is nice to be able to preset the tuner exactly.

Of course, you lucky guys with KPA1500s don't have to worry about that!

73,
Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5
http://www.qsl.net/k2vco/
On 30 Nov 2018 00:57, Don Wilhelm wrote:

> Andy and all,
>
> The KAT500 and KAT1500 tuner band segments are divided into frequency
> band segments - 25kHz wide on the lower bands and 50kHz wide on the
> upper bands if I recall correctly, so an 8kHz shift will not be
> significant unless the frequency shift moves the tuning into the
> adjacent segment.
>
> There is also a limit to how far the firmware will go to reducing SWR.
> In the interest of minimizing tuning time (and relay wear and tear). If
> the match is less than 1.3:1 or so, tuning will be declared adequate and
> will be stopped.
>
> Since the typical driving transceiver can tolerate an SWR of at least
> 2:1 without power foldback or damage, setting that 1.3:1 limit is
> reasonable - unless you are a 'purest' and mentally can only tolerate a
> 1:1 SWR (big grin).
>
> 73,
> Don W3FPR

K9MA

Re: KPA-1500 issues

That is exactly why it's important that the ATU of a solid state
amplifier maintain a low SWR.

Scott K9MA

On 11/29/2018 21:59, Victor Rosenthal 4X6GP wrote:

> There IS a reason to be fanatical about a 1:1 SWR, although it doesn't
> apply to an amp like the KPA1500.
>
> If you are running a tube amplifier that requires tuning, and the
> tuner always provides the identical load, you can tune the amplifier
> once, record the dial settings, and quickly reset the amplifier tuning
> "by the numbers" when you change bands.
>
> But even a small change in load impedance might require manual
> touch-up of the amp tuning. So it is nice to be able to preset the
> tuner exactly.

--
Scott K9MA

[hidden email]

______________________________________________________________
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]

Randy Farmer

KAT500 investigation results (WAS KPA-1500 issues)

In reply to this post by Randy Farmer

First things first: My key line connections are correct. A little bit of
trial and error with the amp on on 160 meters shows that the
intermittent high VSWR faults I was encountering were due to a "feature"
of my antenna system. Apparently there is water in the FCP transformer
box or a bad coax cable that was causing an intermittent arc or other
breakdown at high power. The problem is much worse at the high end of
the band, where the antenna VSWR is higher (imagine that!).

All of this led me to spend a couple of hours investigating what the
KAT500 was actually doing on 160 meters. It turns out that, despite what
the manual says, the tuning bins on 160, and presumably everywhere below
3 MHz, are actually 8 kHz wide, not 10 kHz. This was verified by slowly
tuning the radio and listening to the presets changing. My 160 antenna
has a VSWR that changes rapidly enough as a function of frequency that
most every bin had a slightly different tuning solution. This made it
possible to see the bin boundaries across most of the band. The bins
start at 1800 kHz and are spaced exactly every 8 kHz. Tuning slowly with
fine tuning engaged it can be seen that, for example, when the radio is
tuned from 1807.999 to 1808.000 kHz the KAT will change to the next
preset. I re-trained the tuner by tuning to the center of each bin:
1804, 1812, 1816... all across the band and executing a "Tune" operation
at each frequency.

I had always wondered why the KAT utility reported frequency values that
were frequently quite different from the actual transmit frequency. It
turns out that the "Observed Frequency" value displayed in the utility
Operate window is the low end of the particular tuning bin that has been
selected by the selection algorithm. 1836 reports as 1832, for example.
Since my antennas for 80 meters and higher are not extremely high Q, it
would be difficult to do a similar experiment to determine what the
actual tuning bin widths are on the higher frequency ranges.

I realize this behavior may be of academic interest only, since the
firmware does seem to do a good job of selecting the appropriate tuning
solution, but for a very high Q antenna such as is frequently found on
160 and/or highly compromised shortened antennas for other HF bands it
could be important. It would be nice if the Elecraft folks would correct
the manual to show what the actual tuning bin widths are for each range.

73...
Randy, W8FN

> On 11/29/2018 8:48 PM, Don Wilhelm wrote:
>> Randy,
>>
>> That indicates that you do not have your KAT500 and amplifier
>> properly connected.
>>
>> The KEYOUT line from the transceiver should go first to the KAT500,
>> and then from the KAT500 to the amplifier.
>> When the KAT500 needs to tune, the amplifier will not be keyed and
>> tuning will take place at the power output of the transceiver.
>> After tuning, the amplifier will be engaged.
>>
>> 73,
>> Don W3FPR

Elecraft mailing list

Re: KAT500 investigation results (WAS KPA-1500 issues)

Randy;

The resolution of the frequency being reported from the K3 to the KAT500 is 8 KHz. This probably does a better job explaining why the relays switch every 8 KHz than bin size. I would bet that once in a while you will find two adjacent frequency segments that fall in the same bin, and no change occurs.
I also suspect that the RF frequency count resolution is 8 KHz (as it is in the KPA500), which will show similar frequencies when transmitting. When operating the KAT500 with the K3/K3S, we usually have the K3 tell the KAT its current frequency, which is why it switches during receive and on 8 KHz boundaries.

I sympathize with you on the water issues. We see a lot of that kind of problem. My “favorite” is the right-angle coax adapter (this one bit me). The cheaper ones do a poor job of constraining the inner conductor, and at high power will arc to ground. I changed out all my adapters for good ones (read: more expensive), and no longer have the issue. Figuring out the problem is usually rather difficult since you can’t actually see the arc results because they are inside an enclosure. You are lucky to find your issue so easily, but then water intrusion is a bit more obvious.

As far as calculating bin size, I suspect that K3WYC’s solution of sending FA; response frequencies into the KAT500’s serial port might actually yield a better solution since those frequencies can have 1KHz (or better) resolution. In this case the relays should switch very close to the actual boundary instead of at 8KHz boundaries. What I don’t know is if the KAT500 uses RF counted frequency for its bin determination or if it can use the externally reported frequency. I suspect it is the former.

Glad you found the issue. Perhaps you now might find a way to lower the antenna Q to require fewer bins (and perhaps wider bandwidth), but it is good to know the KAT is providing a solution for your antenna the way it is (well, without the water).

73!
Jack, W6FB

> On Nov 30, 2018, at 11:01 AM, Randy Farmer <[hidden email]> wrote:
>
> First things first: My key line connections are correct. A little bit of trial and error with the amp on on 160 meters shows that the intermittent high VSWR faults I was encountering were due to a "feature" of my antenna system. Apparently there is water in the FCP transformer box or a bad coax cable that was causing an intermittent arc or other breakdown at high power. The problem is much worse at the high end of the band, where the antenna VSWR is higher (imagine that!).
>
> All of this led me to spend a couple of hours investigating what the KAT500 was actually doing on 160 meters. It turns out that, despite what the manual says, the tuning bins on 160, and presumably everywhere below 3 MHz, are actually 8 kHz wide, not 10 kHz. This was verified by slowly tuning the radio and listening to the presets changing. My 160 antenna has a VSWR that changes rapidly enough as a function of frequency that most every bin had a slightly different tuning solution. This made it possible to see the bin boundaries across most of the band. The bins start at 1800 kHz and are spaced exactly every 8 kHz. Tuning slowly with fine tuning engaged it can be seen that, for example, when the radio is tuned from 1807.999 to 1808.000 kHz the KAT will change to the next preset. I re-trained the tuner by tuning to the center of each bin: 1804, 1812, 1816... all across the band and executing a "Tune" operation at each frequency.
>
> I had always wondered why the KAT utility reported frequency values that were frequently quite different from the actual transmit frequency. It turns out that the "Observed Frequency" value displayed in the utility Operate window is the low end of the particular tuning bin that has been selected by the selection algorithm. 1836 reports as 1832, for example. Since my antennas for 80 meters and higher are not extremely high Q, it would be difficult to do a similar experiment to determine what the actual tuning bin widths are on the higher frequency ranges.
>
> I realize this behavior may be of academic interest only, since the firmware does seem to do a good job of selecting the appropriate tuning solution, but for a very high Q antenna such as is frequently found on 160 and/or highly compromised shortened antennas for other HF bands it could be important. It would be nice if the Elecraft folks would correct the manual to show what the actual tuning bin widths are for each range.
>
> 73...
> Randy, W8FN
>
>> On 11/29/2018 8:48 PM, Don Wilhelm wrote:
>>> Randy,
>>>
>>> That indicates that you do not have your KAT500 and amplifier properly connected.
>>>
>>> The KEYOUT line from the transceiver should go first to the KAT500, and then from the KAT500 to the amplifier.
>>> When the KAT500 needs to tune, the amplifier will not be keyed and tuning will take place at the power output of the transceiver.
>>> After tuning, the amplifier will be engaged.
>>>
>>> 73,
>>> Don W3FPR
>
> ______________________________________________________________
> 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]