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Antennas and Output Power - KPA-1500

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N4ZR

Antennas and Output Power - KPA-1500

I have two antennas for 40M, a Carolina Windom and a full-wave parasitic
sloper, the latter fed through a 4:1 balun. The 1500's tuner handles
both antennas nicely, and I have trained it on both of them, but when I
switch from the Windom to the sloper (on an external antenna switch),
the output power changes from ~1400 watts to nearly 1700, often
triggering a high current fault. Any way around that?

--
73, Pete N4ZR
Check out the Reverse Beacon Network
at <http://reversebeacon.net>, now
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Don Wilhelm

Re: Antennas and Output Power - KPA-1500

Pete,

I would say re-tune after switching with the external antenna switch.
If you have tuned to one antenna (on a single port), and then change the
load slightly (by switching to the other antenna), a re-tune is necessary.

73,
Don W3FPR

On 10/15/2020 3:17 PM, N4ZR wrote:
> I have two antennas for 40M, a Carolina Windom and a full-wave parasitic
> sloper, the latter fed through a 4:1 balun. The 1500's tuner handles
> both antennas nicely, and I have trained it on both of them, but when I
> switch from the Windom to the sloper (on an external antenna switch),
> the output power changes from ~1400 watts to nearly 1700, often
> triggering a high current fault. Any way around that?
>
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Elecraft mailing list

Re: Antennas and Output Power - KPA-1500

See p.25 of the manual. Then p.30 set ATU HiSWR RETUNE to ON for 40m.

GL - Steve WB6RSE

> On Oct 15, 2020, at 1:00 PM, Don Wilhelm <[hidden email]> wrote:
>
> Pete,
>
> I would say re-tune after switching with the external antenna switch.
> If you have tuned to one antenna (on a single port), and then change the load slightly (by switching to the other antenna), a re-tune is necessary.
>
> 73,
> Don W3FPR
>
> On 10/15/2020 3:17 PM, N4ZR wrote:
>> I have two antennas for 40M, a Carolina Windom and a full-wave parasitic sloper, the latter fed through a 4:1 balun. The 1500's tuner handles both antennas nicely, and I have trained it on both of them, but when I switch from the Windom to the sloper (on an external antenna switch), the output power changes from ~1400 watts to nearly 1700, often triggering a high current fault. Any way around that?
> ______________________________________________________________
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N4ZR

Re: Antennas and Output Power - KPA-1500

In reply to this post by N4ZR

I guess I wasn't clear - when I see this overpower/fault combination,
the sloper is matched around 1.2:1, it's just that output power and
current draw jump up to fault levels, so a retune wouldn't help

73, Pete N4ZR
Check out the Reverse Beacon Network
at <http://reversebeacon.net>, now
spotting RTTY activity worldwide.
For spots, please use your favorite
"retail" DX cluster.

On 10/15/2020 3:40 PM, [hidden email] wrote:

> See p.25 of the manual. Then p.30 set ATU HiSWR RETUNE to ON for 40m.
>
> GL - Steve WB6RSE
>
>> On Oct 15, 2020, at 12:17 PM, N4ZR <[hidden email]> wrote:
>>
>> I have two antennas for 40M, a Carolina Windom and a full-wave parasitic sloper, the latter fed through a 4:1 balun. The 1500's tuner handles both antennas nicely, and I have trained it on both of them, but when I switch from the Windom to the sloper (on an external antenna switch), the output power changes from ~1400 watts to nearly 1700, often triggering a high current fault. Any way around that?
>>
>> --
>> 73, Pete N4ZR
>> Check out the Reverse Beacon Network
>> at <http://reversebeacon.net>, now
>> spotting RTTY activity worldwide.
>> For spots, please use your favorite
>> "retail" DX cluster.
>>
>> ______________________________________________________________
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N4ZR

Re: Antennas and Output Power - KPA-1500

I don't think so. After I've switched to the sloper, the ATU switches
properly to the parameters for it. The only thing that is unexpected is
that the correct level of driving power for one antenna pushes the amp
to 1700 watts on the other. If the ATU also remembered the driving
power level for each set of parameters, that would solve the problem, I
think, but that may not be practical.

73, Pete N4ZR
Check out the Reverse Beacon Network
at <http://reversebeacon.net>, now
spotting RTTY activity worldwide.
For spots, please use your favorite
"retail" DX cluster.

On 10/15/2020 4:35 PM, [hidden email] wrote:

> That's because the ATU is set for the previous antenna vs the sloper. If you've trained the ATU for both then those parameters are not the same. GL
>
>> On Oct 15, 2020, at 1:24 PM, N4ZR <[hidden email]> wrote:
>>
>> I guess I wasn't clear - when I see this overpower/fault combination, the sloper is matched around 1.2:1, it's just that output power and current draw jump up to fault levels, so a retune wouldn't help
>>
>> 73, Pete N4ZR
>> Check out the Reverse Beacon Network
>> at <http://reversebeacon.net>, now
>> spotting RTTY activity worldwide.
>> For spots, please use your favorite
>> "retail" DX cluster.
>>
>> On 10/15/2020 3:40 PM, [hidden email] wrote:
>>> See p.25 of the manual. Then p.30 set ATU HiSWR RETUNE to ON for 40m.
>>>
>>> GL - Steve WB6RSE
>>>
>>>> On Oct 15, 2020, at 12:17 PM, N4ZR <[hidden email]> wrote:
>>>>
>>>> I have two antennas for 40M, a Carolina Windom and a full-wave parasitic sloper, the latter fed through a 4:1 balun. The 1500's tuner handles both antennas nicely, and I have trained it on both of them, but when I switch from the Windom to the sloper (on an external antenna switch), the output power changes from ~1400 watts to nearly 1700, often triggering a high current fault. Any way around that?
>>>>
>>>> --
>>>> 73, Pete N4ZR
>>>> Check out the Reverse Beacon Network
>>>> at <http://reversebeacon.net>, now
>>>> spotting RTTY activity worldwide.
>>>> For spots, please use your favorite
>>>> "retail" DX cluster.
>>>>
>>>> ______________________________________________________________
>>>> 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

Antennas and Output Power - KPA-1500

In reply to this post by N4ZR

"The 1500's tuner handles both antennas nicely, and I have trained it on both of them, but when I switch from the Windom to the sloper (on an external antenna switch), the output power changes from ~1400 watts to nearly 1700, often triggering a high current fault. Any way around that?"

I suspect an effective solution would require the KPA1500, or a smart external controller, to have an interface with the external antenna switch. On sensing a switch change the key line should be inhibited and not re-enabled until the appropriate tuning solution has been selected and verified and the drive power has also been set and verified.

I face a similar problem with my KAT500/KPA500 combo as I have a manual antenna select switch in the back yard. My smart controller doesn't help because it doesn't know the switch selection (yet).

A solution that requires the bin stack to remember power for each solution is probably doomed to failure until it's possible to "reserve" tuning solutions to stop them being pushed off the stack.

73,
Andy, k3wyc
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john@kk9a.com

Re: Antennas and Output Power - KPA-1500

In reply to this post by N4ZR

Do you use both antennas on the same frequency? I do not have a KPA1500 but
I am curious how the tuner can remember the two different settings and know
which trained setting to use when you switch antennas. (assuming that you're
not also changing frequency).

John KK9A

N4ZR wrote:

I have two antennas for 40M, a Carolina Windom and a full-wave parasitic
sloper, the latter fed through a 4:1 balun. The 1500's tuner handles
both antennas nicely, and I have trained it on both of them, but when I
switch from the Windom to the sloper (on an external antenna switch),
the output power changes from ~1400 watts to nearly 1700, often
triggering a high current fault.

--
73, Pete N4ZR

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Dick Dievendorff-4

Re: Antennas and Output Power - KPA-1500

It's demonstrated around the last third of this K6XX video, where K6XX shows
matches on antennas on the same frequency.

73 de Dick, K6KR

-----Original Message-----
From: [hidden email] <[hidden email]> On
Behalf Of [hidden email]
Sent: Thursday, October 15, 2020 17:07
To: [hidden email]
Subject: Re: [Elecraft] Antennas and Output Power - KPA-1500

Do you use both antennas on the same frequency? I do not have a KPA1500 but
I am curious how the tuner can remember the two different settings and know
which trained setting to use when you switch antennas. (assuming that you're
not also changing frequency).

John KK9A

N4ZR wrote:

I have two antennas for 40M, a Carolina Windom and a full-wave parasitic
sloper, the latter fed through a 4:1 balun. The 1500's tuner handles both
antennas nicely, and I have trained it on both of them, but when I switch
from the Windom to the sloper (on an external antenna switch), the output
power changes from ~1400 watts to nearly 1700, often triggering a high
current fault.

--
73, Pete N4ZR

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N4ZR

Re: Antennas and Output Power - KPA-1500

No link, Dick.

73, Pete N4ZR
Check out the Reverse Beacon Network
at <http://reversebeacon.net>, now
spotting RTTY activity worldwide.
For spots, please use your favorite
"retail" DX cluster.

On 10/15/2020 8:19 PM, Dick Dievendorff wrote:

> It's demonstrated around the last third of this K6XX video, where K6XX shows
> matches on antennas on the same frequency.
>
> 73 de Dick, K6KR
>
>
> -----Original Message-----
> From: [hidden email] <[hidden email]> On
> Behalf Of [hidden email]
> Sent: Thursday, October 15, 2020 17:07
> To: [hidden email]
> Subject: Re: [Elecraft] Antennas and Output Power - KPA-1500
>
> Do you use both antennas on the same frequency? I do not have a KPA1500 but
> I am curious how the tuner can remember the two different settings and know
> which trained setting to use when you switch antennas. (assuming that you're
> not also changing frequency).
>
> John KK9A
>
> N4ZR wrote:
>
> I have two antennas for 40M, a Carolina Windom and a full-wave parasitic
> sloper, the latter fed through a 4:1 balun. The 1500's tuner handles both
> antennas nicely, and I have trained it on both of them, but when I switch
> from the Windom to the sloper (on an external antenna switch), the output
> power changes from ~1400 watts to nearly 1700, often triggering a high
> current fault.
>
> --
> 73, Pete N4ZR
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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>
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Dick Dievendorff-4

Re: Antennas and Output Power - KPA-1500

Oops!

https://youtu.be/mDZQK7OopIE

73 de Dick, K6KR

> On Oct 15, 2020, at 18:40, N4ZR <[hidden email]> wrote:
>
> No link, Dick.
>
> 73, Pete N4ZR
> Check out the Reverse Beacon Network
> at <http://reversebeacon.net>, now
> spotting RTTY activity worldwide.
> For spots, please use your favorite
> "retail" DX cluster.
>
>> On 10/15/2020 8:19 PM, Dick Dievendorff wrote:
>> It's demonstrated around the last third of this K6XX video, where K6XX shows
>> matches on antennas on the same frequency.
>>
>> 73 de Dick, K6KR
>>
>>
>> -----Original Message-----
>> From: [hidden email] <[hidden email]> On
>> Behalf Of [hidden email]
>> Sent: Thursday, October 15, 2020 17:07
>> To: [hidden email]
>> Subject: Re: [Elecraft] Antennas and Output Power - KPA-1500
>>
>> Do you use both antennas on the same frequency? I do not have a KPA1500 but
>> I am curious how the tuner can remember the two different settings and know
>> which trained setting to use when you switch antennas. (assuming that you're
>> not also changing frequency).
>>
>> John KK9A
>>
>> N4ZR wrote:
>>
>> I have two antennas for 40M, a Carolina Windom and a full-wave parasitic
>> sloper, the latter fed through a 4:1 balun. The 1500's tuner handles both
>> antennas nicely, and I have trained it on both of them, but when I switch
>> from the Windom to the sloper (on an external antenna switch), the output
>> power changes from ~1400 watts to nearly 1700, often triggering a high
>> current fault.
>>
>> --
>> 73, Pete N4ZR
>>
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>>
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N4ZR

Re: Antennas and Output Power - KPA-1500

In reply to this post by Dick Dievendorff-4

Thanks, Dick. That video squares with what I've been doing, but it
doesn't address my original question, which is:

When I have set the drive to give me ~1450 watts on the Carolina Windom,
and I need to switch to the sloper on the same frequency, I find that
the drive level that produced this output on is too high, resulting in
excessive output power - well over the legal limit. To get legal again,
I have to manually turn down the output power on my K3. If I then
switch back to the Windom, I'm suddenly only running ~1000 watts out.
Is there any way to have the drive level not only set band by band, but
antenna by antenna? K6XX's video seems to demonstrate 6 widely
different antennas with very different matching solutions required, all
producing the same power output for the same drive (unless, of course,
the K4 is better in this respect).

73, Pete N4ZR
Check out the Reverse Beacon Network
at <http://reversebeacon.net>, now
spotting RTTY activity worldwide.
For spots, please use your favorite
"retail" DX cluster.

On 10/15/2020 8:19 PM, Dick Dievendorff wrote:

K8TE

Re: Antennas and Output Power - KPA-1500

In reply to this post by Elecraft mailing list

No. This is not the solution for what Pete describes and for what I and
others also experience. Switching antennas, even antenna ports, often gives
very different power output numbers for the same drive levels from the
K3/K3S, even when appropriate and acceptable tuning solutions are found.

Using an external antenna switch on a single KPA1500 antenna port can be
problematic with the KPA1500 in cases where different tuning solutions are
necessary for different antennas. Currently, there is no means to tell the
KPA1500 to use a different solution other than "trial and error" which means
providing RF on the "new" antenna, allowing the KPA1500 to find the proper
(trained) solution, change to that solution, and proceed. At full power,
this process can result in an alarm which disables the amplifier,
inconvenient in the heat of battle (contest).

I have also noted that after not using the KPA1500 for a "long time" which
could be 15-30 minutes, power output can exceed alarm settings (well over
1500 Watts). And when used some more, the power output decreases to 1500
without any exciter adjustments. This means the KPA1500 gain figure seems
to increase after "resting" and decreases with use.

"Perfect" antennas that are always 50 Ohms and non-reactive won't cause
these symptoms. I hope someday to have those.

73, Bill, K8TE

--
Sent from: http://elecraft.365791.n2.nabble.com/
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Rick Bates, NK7I

Re: Antennas and Output Power - KPA-1500

This happens due to heating of the finals (network); typically 1500
watts when cold (15-25C in my shack), drops to 1400 watts once warmed up
(50-60C). One can either adjust as needed or just accept 1500 cold and
the drop (much less than one dB); but of course one should pay attention
in all cases, should the limit exceed the permitted levels.

True gain values should include the temp of the amp; it matters.

90% of the time, when I use the amp, I'll run <1200 watts out, even
though there is already plenty of headroom in the amp. It's rare that
the few hundred more watts makes any real difference (but it's nice to
have!).

Now that winter is starting (North Idaho), it also takes the chill off
the shack!

73,
Rick NK7I

On 10/31/2020 10:34 AM, K8TE wrote:
> I have also noted that after not using the KPA1500 for a "long time" which
> could be 15-30 minutes, power output can exceed alarm settings (well over
> 1500 Watts). And when used some more, the power output decreases to 1500
> without any exciter adjustments. This means the KPA1500 gain figure seems
> to increase after "resting" and decreases with use.
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David Smith

Re: Antennas and Output Power - KPA-1500

Have been reading all the threads on this issue is you (and others) are right on with the issue. I operate contests here (both cw and ssb) and have many multiple antennas for the same band.

What I have dome is train the AL1500 ATU for the main antenna I will probably use on that band, and unfortunately (the cost) I purchased a Palstar ATU for a new JK 403 I put up and trained it for that antenna and when I switch to the JK403. I turn off the AL1500 ATU and switch over to the Palstar and visa versa.
This is done for the other bands/antennas also. I know it’s a pain (and an expense) but it works for me.

73 David ND4Y

Sent from Mail for Windows 10

From: Rick Bates, NK7I
Sent: Saturday, October 31, 2020 2:46 PM
To: [hidden email]
Subject: Re: [Elecraft] Antennas and Output Power - KPA-1500

T

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