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KPA-1500 ATU operation

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charles-2

KPA-1500 ATU operation

After saving my KPA-1500 ATU impedance matching parameters on 80M at 20
Kc intervals (3.510, 3.530, 3.550, 3.570, etc, etc), I expected that the
KPA-1500 ATU would automatically switch to the next set of L/C values at
the midpoint of the 20 Kc segments (like 3.520, 3.540, 3.560, etc, etc),
but I find that it switches randomly, sometimes just 2 Kc away from the
main tuning frequencies. Does anyone have information on how the ATU is
supposed to work when it is polling the xcvr for frequency?

Thanks, K5UA
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Dick Dievendorff-4

Re: KPA-1500 ATU operation

On 160 and 80 meters, the KPA1500 ATU has 10 kHz "step size" between "bins".

Consider tuning at 3505, 3515, 3525, 3535, 3545.... thru 3995. There's a
table on page 52 of the KPA1500 owner's manual that lists the suggested
tuning frequencies on all bands.

73 de Dick, K6KR

-----Original Message-----
From: [hidden email] <[hidden email]> On
Behalf Of [hidden email]
Sent: Tuesday, December 10, 2019 15:04
To: [hidden email]
Subject: [Elecraft] KPA-1500 ATU operation

After saving my KPA-1500 ATU impedance matching parameters on 80M at 20 Kc
intervals (3.510, 3.530, 3.550, 3.570, etc, etc), I expected that the
KPA-1500 ATU would automatically switch to the next set of L/C values at the
midpoint of the 20 Kc segments (like 3.520, 3.540, 3.560, etc, etc), but I
find that it switches randomly, sometimes just 2 Kc away from the main
tuning frequencies. Does anyone have information on how the ATU is supposed
to work when it is polling the xcvr for frequency?

Thanks, K5UA
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K9MA

Re: KPA-1500 ATU operation

In reply to this post by charles-2

I understand that the ATU uses 10 kHz segments on 80, which was at some
point changed from 20 kHz. That means the center points are 3505, 3515,
etc. There is some hysteresis when tuning, but I'm not sure that
consistently explains where it switches. It also won't switch until you
stop tuning for 1/2 second, or so.

Another factor is that the ATU only measure frequency to, I think, 8
kHz. The net result may be that sometimes it's not in the frequency
segment you think it should be in. Unless you have a very narrow band
antenna, it shouldn't make much difference.

73,
Scott K9MA

On 12/10/2019 17:03, [hidden email] wrote:

> After saving my KPA-1500 ATU impedance matching parameters on 80M at
> 20 Kc intervals (3.510, 3.530, 3.550, 3.570, etc, etc), I expected
> that the KPA-1500 ATU would automatically switch to the next set of
> L/C values at the midpoint of the 20 Kc segments (like 3.520, 3.540,
> 3.560, etc, etc), but I find that it switches randomly, sometimes just
> 2 Kc away from the main tuning frequencies. Does anyone have
> information on how the ATU is supposed to work when it is polling the
> xcvr for frequency?
>
> Thanks, K5UA
> ______________________________________________________________
> 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]

--
Scott K9MA

[hidden email]

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Paul Baldock

Re: KPA-1500 ATU operation

In reply to this post by charles-2

At 03:03 PM 12/10/2019, [hidden email] wrote:
> Does anyone have information on how the ATU is supposed to work
> when it is polling the xcvr for frequency?

If you are polling the transceiver and have fairly recent version of
firmware, the ATU will change frequency at the boundary of the
segment, with no hysteresis. Twiddle your VFO knob in standby and you
will here the relays clicking right at the edges.

- Paul KW7Y
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Bob McGraw - K4TAX

Re: KPA-1500 ATU operation

In reply to this post by K9MA

The ATU uses 10 kHz segments below 3 MHz. And then 20 kHz segments 3
MHz through 26 MHz. And 100 kHz segments from 38 MHz through 30 MHz.
And 200 kHz segments 38 MHz through 60 MHz.

The understanding regarding 80M would then be the segments are 20 kHz
wide and not 10 kHz wide.

73

Bob, K4TAX

On 12/10/2019 5:56 PM, K9MA wrote:

> I understand that the ATU uses 10 kHz segments on 80, which was at
> some point changed from 20 kHz. That means the center points are 3505,
> 3515, etc. There is some hysteresis when tuning, but I'm not sure that
> consistently explains where it switches. It also won't switch until
> you stop tuning for 1/2 second, or so.
>
> Another factor is that the ATU only measure frequency to, I think, 8
> kHz. The net result may be that sometimes it's not in the frequency
> segment you think it should be in. Unless you have a very narrow band
> antenna, it shouldn't make much difference.
>
> 73,
> Scott K9MA
>
>
>
> On 12/10/2019 17:03, [hidden email] wrote:
>> After saving my KPA-1500 ATU impedance matching parameters on 80M at
>> 20 Kc intervals (3.510, 3.530, 3.550, 3.570, etc, etc), I expected
>> that the KPA-1500 ATU would automatically switch to the next set of
>> L/C values at the midpoint of the 20 Kc segments (like 3.520, 3.540,
>> 3.560, etc, etc), but I find that it switches randomly, sometimes
>> just 2 Kc away from the main tuning frequencies. Does anyone have
>> information on how the ATU is supposed to work when it is polling the
>> xcvr for frequency?
>>
>> Thanks, K5UA
>> ______________________________________________________________
>> 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]
>
>

markmusick

Re: KPA-1500 ATU operation

From page 24 of the KPA1500 manual:

Re-tuning to maintain a low SWR is normally required over a narrower frequency range on the lower frequencies. Band segments are:
• Below 4.8 MHz the segments are 10 kHz wide.
• From 4.8 MHz through 26 MHz the segments are 20 kHz wide.
• From 26 MHz to 38 MHz the segments are 100 kHz wide.
• Above 38 MHz the segments are 200 kHz wide.

Mark, WB9CIF

-----Original Message-----
From: [hidden email] <[hidden email]> On Behalf Of Bob McGraw K4TAX
Sent: Wednesday, December 11, 2019 02:08
To: [hidden email]
Subject: Re: [Elecraft] KPA-1500 ATU operation

The ATU uses 10 kHz segments below 3 MHz. And then 20 kHz segments 3 MHz through 26 MHz. And 100 kHz segments from 38 MHz through 30 MHz. And 200 kHz segments 38 MHz through 60 MHz.

The understanding regarding 80M would then be the segments are 20 kHz wide and not 10 kHz wide.

73

Bob, K4TAX

On 12/10/2019 5:56 PM, K9MA wrote:

> I understand that the ATU uses 10 kHz segments on 80, which was at
> some point changed from 20 kHz. That means the center points are 3505,
> 3515, etc. There is some hysteresis when tuning, but I'm not sure that
> consistently explains where it switches. It also won't switch until
> you stop tuning for 1/2 second, or so.
>
> Another factor is that the ATU only measure frequency to, I think, 8
> kHz. The net result may be that sometimes it's not in the frequency
> segment you think it should be in. Unless you have a very narrow band
> antenna, it shouldn't make much difference.
>
> 73,
> Scott K9MA
>
>
>
> On 12/10/2019 17:03, [hidden email] wrote:
>> After saving my KPA-1500 ATU impedance matching parameters on 80M at
>> 20 Kc intervals (3.510, 3.530, 3.550, 3.570, etc, etc), I expected
>> that the KPA-1500 ATU would automatically switch to the next set of
>> L/C values at the midpoint of the 20 Kc segments (like 3.520, 3.540,
>> 3.560, etc, etc), but I find that it switches randomly, sometimes
>> just 2 Kc away from the main tuning frequencies. Does anyone have
>> information on how the ATU is supposed to work when it is polling the
>> xcvr for frequency?
>>
>> Thanks, K5UA
>> ______________________________________________________________
>> 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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markmusick

Re: KPA-1500 ATU operation

In reply to this post by Bob McGraw - K4TAX

Everyone,
The following is from page 24 of the KPA1500 manual dated February 12, 2019. This is the latest I have. Is there a later one that differs from this on the ATU segments?

Re-tuning to maintain a low SWR is normally required over a narrower frequency range on the lower frequencies. Band segments are:
• Below 4.8 MHz the segments are 10 kHz wide.
• From 4.8 MHz through 26 MHz the segments are 20 kHz wide.
• From 26 MHz to 38 MHz the segments are 100 kHz wide.
• Above 38 MHz the segments are 200 kHz wide.

73,
Mark, WB9CIF

-----Original Message-----
From: [hidden email] <[hidden email]> On Behalf Of Bob McGraw K4TAX
Sent: Wednesday, December 11, 2019 02:08
To: [hidden email]
Subject: Re: [Elecraft] KPA-1500 ATU operation

The ATU uses 10 kHz segments below 3 MHz. And then 20 kHz segments 3 MHz through 26 MHz. And 100 kHz segments from 38 MHz through 30 MHz. And 200 kHz segments 38 MHz through 60 MHz.

The understanding regarding 80M would then be the segments are 20 kHz wide and not 10 kHz wide.

73

Bob, K4TAX

On 12/10/2019 5:56 PM, K9MA wrote:

> I understand that the ATU uses 10 kHz segments on 80, which was at
> some point changed from 20 kHz. That means the center points are 3505,
> 3515, etc. There is some hysteresis when tuning, but I'm not sure that
> consistently explains where it switches. It also won't switch until
> you stop tuning for 1/2 second, or so.
>
> Another factor is that the ATU only measure frequency to, I think, 8
> kHz. The net result may be that sometimes it's not in the frequency
> segment you think it should be in. Unless you have a very narrow band
> antenna, it shouldn't make much difference.
>
> 73,
> Scott K9MA
>
>
>
> On 12/10/2019 17:03, [hidden email] wrote:
>> After saving my KPA-1500 ATU impedance matching parameters on 80M at
>> 20 Kc intervals (3.510, 3.530, 3.550, 3.570, etc, etc), I expected
>> that the KPA-1500 ATU would automatically switch to the next set of
>> L/C values at the midpoint of the 20 Kc segments (like 3.520, 3.540,
>> 3.560, etc, etc), but I find that it switches randomly, sometimes
>> just 2 Kc away from the main tuning frequencies. Does anyone have
>> information on how the ATU is supposed to work when it is polling the
>> xcvr for frequency?
>>
>> Thanks, K5UA
>> ______________________________________________________________
>> 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

KPA-1500 ATU operation

In reply to this post by charles-2

"If you are polling the transceiver and have fairly recent version of firmware, the ATU will change frequency at the boundary of the segment, with no hysteresis. Twiddle your VFO knob in standby and you will here the relays clicking right at the edges."

An explanation of how the tuner follows VFO frequency is probably incomplete without understanding how RF detected frequency can override the VFO frequency. Someone familiar with KPA1500 may provide the details. I'm only familiar with KAT500 and I don't find the same tailoring parameters (FCCS and FCMD) in the KPA1500 programming reference.

Andy, k3wyc
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ANDY DURBIN

Re: KPA-1500 ATU operation

"If it were up to me, I would not allow the counter to have priority unless the frequency difference is at least several bin's worth. That way, transmission wouldn't be needlessly interrupted because of the low counter resolution, but the amp would still be protected against erroneous data from the radio"

The same issue exists for the KAT500 and I have proposed that, when CAT tuning is present, that RF frequency override should be based on a time magnitude monitor. That would mean small differences between RF and CAT frequency would have to exist for a long time before RF took priority and that a large difference would result in immediate correction of a gross VAT frequency error. The constants time and magnitude would be adjustable by the user.

I got so annoyed with RF freq taking priority that I have defeated RF tuning for my KAT500.

Andy, k3wyc
________________________________

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