Elecraft

KPA 100 Low power on 160M

Classic

List

Threaded

10 messages Options

Andrew UK

KPA 100 Low power on 160M

HI,

I have just fitted the DSP board and it works fine, on
putting the K2 back together, I fond that 160M will not go
above 50 Watts and I get a high current warning, All other
bands are 111 Watts no problem. I am using Rohde & Schwarz
power probe and a 40dB attenuator, to the match is close to
50 OHMS. I have also used my bird through line and get the
same results. I suspected the band pass filter in the KPA
100, I did find what looked a poor joint on L1, but re
soldering has not cured the problem. I do not like
disturbing the PCB and power transistor mounts so need to
pinpoint quickly. In QRP mode the K2 works fine. ( 6 Watts
1800 to 2.000 with 11 watts at 1900 I have never had 10
Watts + on this band). I will sweep the low pass filter
tonight, if I find this in order, I will then connect the
Watt meter directly to input to the low pass filter and see
if everything is fine at this point. Has any one had this
before and can give some pointers it would be appreciated?
The SWR circuit gives 1:1 into the dummy load so is metering
correctly. Has anyone know C2A, C2B, C2C, C2C, C2D, or CDE
to fail or indeed L1 and L2

73

Andrew

_________________________________________

Check your Email accounts at http://www.MyEmail.com

Login from home, work, school. Anywhere!

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

Don Wilhelm-4

Re: KPA 100 Low power on 160M

Andrew,

If you cannot get at least 10 watts out of the base K2 over all the 160
meter band you have a problem in either the 160/80 meter bandpass filter
or the 160m low pass filter. I encourage you to look there first.
You will likely have to compromise the bandpass filter settings between
160 and 80 meters. Set the filter inductors midway between the peak at
3700 kHz and 1850 kHz for your initial trial and make slight adjustments
from there. Check the coupling inductor to be certin it is the right
value - your report indicates that the bandpass filter may be more
narrow than normal.

That being said, low power combined with high current warnings do
indicate a problem with the low pass filter for that band - be certain
the capacitors are the correct value and the number of turns on the
toroids are correct.

If you had not already discovered, the limited power out of the base K2
is what is likely causing the reduce power from the KPA100.

73,
Don W3FPR

[hidden email] wrote:

> HI,
>
> I have just fitted the DSP board and it works fine, on
> putting the K2 back together, I fond that 160M will not go
> above 50 Watts and I get a high current warning, All other
> bands are 111 Watts no problem. I am using Rohde & Schwarz
> power probe and a 40dB attenuator, to the match is close to
> 50 OHMS. I have also used my bird through line and get the
> same results. I suspected the band pass filter in the KPA
> 100, I did find what looked a poor joint on L1, but re
> soldering has not cured the problem. I do not like
> disturbing the PCB and power transistor mounts so need to
> pinpoint quickly. In QRP mode the K2 works fine. ( 6 Watts
> 1800 to 2.000 with 11 watts at 1900 I have never had 10
> Watts + on this band). I will sweep the low pass filter
> tonight, if I find this in order, I will then connect the
> Watt meter directly to input to the low pass filter and see
> if everything is fine at this point. Has any one had this
> before and can give some pointers it would be appreciated?
> The SWR circuit gives 1:1 into the dummy load so is metering
> correctly. Has anyone know C2A, C2B, C2C, C2C, C2D, or CDE
> to fail or indeed L1 and L2
>
> 73
>
>

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

Andrew UK

RE: KPA 100 Low power on 160M

Hi Don,

Thanks for that, Putting aside the K2's low power on 160, which no doubt has
a component error value somewhere, the KPA 100 has been working at 111 Watts
for two years until I disturbed the PA last week to make way for the DSP
board. So something has happened to the KPA100. I only get a high current
warning when the KPA100 is in use. 80 to 10 Metres is fine 11 watts no
warnings! I think something has happened to the high power low pass filter,
any thoughts?

73

Andrew G8UUG

-----Original Message-----
From: Don Wilhelm [mailto:[hidden email]]
Sent: 24 October 2008 23:57
To: [hidden email]
Cc: [hidden email]
Subject: Re: [Elecraft] KPA 100 Low power on 160M

Andrew,

If you cannot get at least 10 watts out of the base K2 over all the 160
meter band you have a problem in either the 160/80 meter bandpass filter
or the 160m low pass filter. I encourage you to look there first.
You will likely have to compromise the bandpass filter settings between
160 and 80 meters. Set the filter inductors midway between the peak at
3700 kHz and 1850 kHz for your initial trial and make slight adjustments
from there. Check the coupling inductor to be certin it is the right
value - your report indicates that the bandpass filter may be more
narrow than normal.

That being said, low power combined with high current warnings do
indicate a problem with the low pass filter for that band - be certain
the capacitors are the correct value and the number of turns on the
toroids are correct.

If you had not already discovered, the limited power out of the base K2
is what is likely causing the reduce power from the KPA100.

73,
Don W3FPR

[hidden email] wrote:

I use BullGuard to keep my computer clean.
Try BullGuard for free: www.bullguard.com

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

Don Wilhelm-4

Re: KPA 100 Low power on 160M

Andrew,

If the KPA100 low pass filter were a problem it would misbehave at both
the low and high power ranges because it is always in the circuit with
the KPA100 connected.

A "Hi Cur" message means the *base K2* is drawing current in excess of
the CAL CUR setting, and the power will be reduced to control the current.

If the HI CUR message only shows up when driving the KPA100, then I
would look for a problem in the input of the KPA100, or mis-calibration
of the wattmeter in the KPA100. If you bumped the setting for R26 while
working on the KPA100, that in itself may be sufficient to explain the
HI CUR indication. Did you measure the actual power output with an
external wattmeter or are you depending on the K2 display? If the
internal wattmeter is not properly calibrated, the actual power output
can be much greater than indicated by the K2.

73,
Don W3FPR

Andrew Lenton wrote:

> Hi Don,
>
> Thanks for that, Putting aside the K2's low power on 160, which no doubt has
> a component error value somewhere, the KPA 100 has been working at 111 Watts
> for two years until I disturbed the PA last week to make way for the DSP
> board. So something has happened to the KPA100. I only get a high current
> warning when the KPA100 is in use. 80 to 10 Metres is fine 11 watts no
> warnings! I think something has happened to the high power low pass filter,
> any thoughts?
>
> 73
>
> Andrew G8UUG
>
>

Andrew UK

Re: KPA 100 Low power on 160M

Hi Don,

Ah very good point this rules out the low pass filter on the KPA 100, as low power is OK. I only have this problem on 160, as 80 to 10 are fine

Th High current only show up on 160 M, the display on the K2 reads the same on the external watt meter Bird through line. SO! symptoms below are:

1 Power on display matches Watt meter from 160 to 10 ( all be it 160 is 60 Watts Max)
2 Power from 80 to 10 max 111 Watts on display and meter, no high current warning
3, Power after 60 watts on 160 I get high current warning
4, I did not disturbed R 26 it was covered by metal plate when I removed the KPA100 to make way for the DSP, and the setting of R26 would also affect other bands

The Bird meter was calibrated this year with all its elements, also I have more than one Watt meter, all say the same low power on 160 and high current

Something must have been disturbed somewhere!! I guess?

73's

Andrew

On Sun, 2008-10-26 at 10:43 -0400, Don Wilhelm wrote:

Andrew,

If the KPA100 low pass filter were a problem it would misbehave at both 
the low and high power ranges because it is always in the circuit with 
the KPA100 connected.

A "Hi Cur" message means the *base K2* is drawing current in excess of 
the CAL CUR setting, and the power will be reduced to control the current.

If the HI CUR message only shows up when driving the KPA100, then I 
would look for a problem in the input of the KPA100, or mis-calibration 
of the wattmeter in the KPA100.  If you bumped the setting for R26 while 
working on the KPA100, that in itself may be sufficient to explain the 
HI CUR indication.  Did you measure the actual power output with an 
external wattmeter or are you depending on the K2 display?  If the 
internal wattmeter is not properly calibrated, the actual power output 
can be much greater than indicated by the K2.

73,
Don W3FPR

Andrew Lenton wrote:
> Hi Don,
>
> Thanks for that, Putting aside the K2's low power on 160, which no doubt has
> a component error value somewhere, the KPA 100 has been working at 111 Watts
> for two years until I disturbed the PA last week to make way for the DSP
> board. So something has happened to the KPA100. I only get a high current
> warning when the KPA100 is in use. 80 to 10 Metres is fine 11 watts no
> warnings! I think something has happened to the high power low pass filter,
> any thoughts?
>
> 73
>
> Andrew G8UUG
>   
>

Don Wilhelm-4

Re: KPA 100 Low power on 160M

Andrew,

FB on all of that.
Before doing anything else, remove the KPA100 and run the base K2 into a
dummy load. With the power at maximum, note the current draw during a
TUNE (press DISPLAY to see the voltage and current). Do that on 160 as
well as on 80 and 40 (to compare the current per band). If you receive
a HI CUR message, increase the CAL CUR setting (up to 4 amps) to see if
it goes away.

If the 160 meter power output and current draw is similar to the other
bands, then you can say the base K2 is OK and look for a problem in the
KPA100. (the current draw at max power will normally be lower on 40
meters). The problem can actually be in the base K2 160 meter LPF - the
above test will reveal it if present.

73,
Don W3FPR.

Andrew Lenton (Linux account) wrote:

>
> Hi Don,
>
> Ah very good point this rules out the low pass filter on the KPA 100,
> as low power is OK. I only have this problem on 160, as 80 to 10 are fine
>
> Th High current only show up on 160 M, the display on the K2 reads the
> same on the external watt meter Bird through line. SO! symptoms below are:
>
>
> 1 Power on display matches Watt meter from 160 to 10 ( all be it
> 160 is 60 Watts Max)
> 2 Power from 80 to 10 max 111 Watts on display and meter, no high
> current warning
> 3, Power after 60 watts on 160 I get high current warning
> 4, I did not disturbed R 26 it was covered by metal plate when I
> removed the KPA100 to make way for the DSP, and the setting of R26
> would also affect other bands
>
> The Bird meter was calibrated this year with all its elements,
> also I have more than one Watt meter, all say the same low power
> on 160 and high current
>
> Something must have been disturbed somewhere!! I guess?
>
> 73's
>
> Andrew
>
>
> On Sun, 2008-10-26 at 10:43 -0400, Don Wilhelm wrote:
>> Andrew,
>>
>> If the KPA100 low pass filter were a problem it would misbehave at both
>> the low and high power ranges because it is always in the circuit with
>> the KPA100 connected.
>>
>> A "Hi Cur" message means the *base K2* is drawing current in excess of
>> the CAL CUR setting, and the power will be reduced to control the current.
>>
>> If the HI CUR message only shows up when driving the KPA100, then I
>> would look for a problem in the input of the KPA100, or mis-calibration
>> of the wattmeter in the KPA100. If you bumped the setting for R26 while
>> working on the KPA100, that in itself may be sufficient to explain the
>> HI CUR indication. Did you measure the actual power output with an
>> external wattmeter or are you depending on the K2 display? If the
>> internal wattmeter is not properly calibrated, the actual power output
>> can be much greater than indicated by the K2.
>>
>> 73,
>> Don W3FPR
>>
>>
>> Andrew Lenton wrote:
>> > Hi Don,
>> >
>> > Thanks for that, Putting aside the K2's low power on 160, which no doubt has
>> > a component error value somewhere, the KPA 100 has been working at 111 Watts
>> > for two years until I disturbed the PA last week to make way for the DSP
>> > board. So something has happened to the KPA100. I only get a high current
>> > warning when the KPA100 is in use. 80 to 10 Metres is fine 11 watts no
>> > warnings! I think something has happened to the high power low pass filter,
>> > any thoughts?
>> >
>> > 73
>> >
>> > Andrew G8UUG
>> >
>> >
>>
> ------------------------------------------------------------------------
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
> ------------------------------------------------------------------------
>
>
> No virus found in this incoming message.
> Checked by AVG - http://www.avg.com
> Version: 8.0.175 / Virus Database: 270.8.3/1747 - Release Date: 10/26/2008 9:27 AM
>
>

Andrew UK

Re: KPA 100 Low power on 160M

In reply to this post by Andrew UK

Hi Don,

I am sorry I should have said:

The K2 with the KPA100 removed behaves normally, current
does not exceed 2.5A on any band at full power (between
10-17 Watts depending on band 40M I get the most power)

I have retuned 80 and 160M and I have checked all the
components for correct value C11,12,13,14,15 + 16, L34 +5,
160M board checked C1,2 and 3 and L1 and L2 for 21 turns.

Now UK band is 3.5 to 3.8Mhz 300 KHZ wide 80 Metre gives
full power where ever I centre tune 3.6, 3.65, 3.7 or 3.75
MHz, now top band I get 15 Watts if I tune at 1.9 MHz drops
off a bit at 1970 upwards, and also 1840 downwards, however,
in dB terms lest than 1.5dB across the band, looks worse in
watts when you see 15 drop to 10! I have compromised top
band to give the max output between 1900 and 2000. It is
better than it was.

With your help, I am beginning to think that the input match
to the KPA 100 is not 50 OHMS on top band, hence the high
current warning( High return loss). I will replace the
co-ax, as a start, and measure S11 and S12 form my network
analyser, and check the match into the KPA100 and report
back, it is odd the other bands seem happy with the match. I
must of damaged something somewhere removing the KPA100.

73's

Andrew

> Andrew,
>
> FB on all of that.
> Before doing anything else, remove the KPA100 and run the
> base K2 into a dummy load. With the power at maximum,
> note the current draw during a TUNE (press DISPLAY to see
> the voltage and current). Do that on 160 as well as on
> 80 and 40 (to compare the current per band). If you
> receive a HI CUR message, increase the CAL CUR setting
> (up to 4 amps) to see if it goes away.
>
> If the 160 meter power output and current draw is similar
> to the other bands, then you can say the base K2 is OK
> and look for a problem in the KPA100. (the current draw
> at max power will normally be lower on 40 meters). The
> problem can actually be in the base K2 160 meter LPF - the
> above test will reveal it if present.
>
> 73,
> Don W3FPR.
>
> Andrew Lenton (Linux account) wrote:
> >
> > Hi Don,
> >
> > Ah very good point this rules out the low pass filter on
> > the KPA 100, as low power is OK. I only have this
> problem on 160, as 80 to 10 are fine >
> > Th High current only show up on 160 M, the display on
> > the K2 reads the same on the external watt meter Bird
> through line. SO! symptoms below are: >
> >
> > 1 Power on display matches Watt meter from 160 to 10
> > ( all be it 160 is 60 Watts Max)
> > 2 Power from 80 to 10 max 111 Watts on display and
> > meter, no high current warning
> > 3, Power after 60 watts on 160 I get high current
> > warning 4, I did not disturbed R 26 it was covered
> > by metal plate when I removed the KPA100 to make way
> > for the DSP, and the setting of R26 would also
> affect other bands >
> > The Bird meter was calibrated this year with all its
> > elements, also I have more than one Watt meter, all
> > say the same low power on 160 and high current
> >
> > Something must have been disturbed somewhere!! I
> guess? >
> > 73's
> >
> > Andrew
> >
> >
> > On Sun, 2008-10-26 at 10:43 -0400, Don Wilhelm wrote:
> >> Andrew,
> >>
> >> If the KPA100 low pass filter were a problem it would
> misbehave at both >> the low and high power ranges
> because it is always in the circuit with >> the KPA100
> connected. >>
> >> A "Hi Cur" message means the *base K2* is drawing
> current in excess of >> the CAL CUR setting, and the
> power will be reduced to control the current. >>
> >> If the HI CUR message only shows up when driving the
> KPA100, then I >> would look for a problem in the input
> of the KPA100, or mis-calibration >> of the wattmeter in
> the KPA100. If you bumped the setting for R26 while >>
> working on the KPA100, that in itself may be sufficient to
> explain the >> HI CUR indication. Did you measure the
> actual power output with an >> external wattmeter or are
> you depending on the K2 display? If the >> internal
> wattmeter is not properly calibrated, the actual power
> output >> can be much greater than indicated by the K2.
> >>
> >> 73,
> >> Don W3FPR
> >>
> >>
> >> Andrew Lenton wrote:
> >> > Hi Don,
> >> >
> >> > Thanks for that, Putting aside the K2's low power on
> 160, which no doubt has >> > a component error value
> somewhere, the KPA 100 has been working at 111 Watts >> >
> for two years until I disturbed the PA last week to make
> way for the DSP >> > board. So something has happened to
> the KPA100. I only get a high current >> > warning when
> the KPA100 is in use. 80 to 10 Metres is fine 11 watts no
> >> > warnings! I think something has happened to the high
> power low pass filter, >> > any thoughts?
> >> >
> >> > 73
> >> >
> >> > Andrew G8UUG
> >> >
> >> >
> >>
> >
> ----------------------------------------------------------
> -------------- >
> > _______________________________________________
> > Elecraft mailing list
> > Post to: [hidden email]
> > You must be a subscriber to post to the list.
> > Subscriber Info (Addr. Change, sub, unsub etc.):
> > http://mailman.qth.net/mailman/listinfo/elecraft
> >
> > Help: http://mailman.qth.net/subscribers.htm
> > Elecraft web page: http://www.elecraft.com
> >
> ----------------------------------------------------------
> -------------- >
> >
> > No virus found in this incoming message.
> > Checked by AVG - http://www.avg.com
> > Version: 8.0.175 / Virus Database: 270.8.3/1747 -
> Release Date: 10/26/2008 9:27 AM >
> >

_________________________________________

Check your Email accounts at http://www.MyEmail.com

Login from home, work, school. Anywhere!

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

Don Wilhelm-4

Re: KPA 100 Low power on 160M

Andrew,

OK, sorry for the 'dumb' response, but I had to check it out so there
would be no 'tail chasing' in a non-problem area.
Yes, it would seem that the input to the KPA100 is nowhere near 50 ohms
on 160m.
I don't know the vintage of your KPA100, but if it does not have blue
toroids at RFC1 and L16, now would be a good time to install
KPA100UPKT. That change was mostly to the T/R switch area, but still
can impact the input circuit response.

You can check out the KPA100 LPF easily with an antenna analyzer - put
the base K2 into CW TEST just to be safe, and set the power less than 11
watts. Pull the input coax from the RF Board and insert a 51 ohm
resistor. Switch to 160 meters and connect the analyzer to the SO-239
connector. The K2 and KPA100 must be powered (and the ribbon cable
connected) because the KPA100 relays are not latching types. The SWR
should be less than 1.5 over the entire 160 meter band.

You could try running the antenna analyzer into the KPA100 input
(connect the output to a dummy load since some power may be developed at
the KPA100 output). If you set the K2 power to less than 11 watts, you
will be reading only the KPA100 LPF, but when the power is set at
greater than 11 watts, you should read the input impedance of the
KPA100. I have never actually done this measurement, so I don't know
what is normal, but you could compare with the results on 80 and 40
meters as a sanity check.

73,
Don W3FPR

[hidden email] wrote:

> Hi Don,
>
> I am sorry I should have said:
>
> The K2 with the KPA100 removed behaves normally, current
> does not exceed 2.5A on any band at full power (between
> 10-17 Watts depending on band 40M I get the most power)
>
> I have retuned 80 and 160M and I have checked all the
> components for correct value C11,12,13,14,15 + 16, L34 +5,
> 160M board checked C1,2 and 3 and L1 and L2 for 21 turns.
>
> Now UK band is 3.5 to 3.8Mhz 300 KHZ wide 80 Metre gives
> full power where ever I centre tune 3.6, 3.65, 3.7 or 3.75
> MHz, now top band I get 15 Watts if I tune at 1.9 MHz drops
> off a bit at 1970 upwards, and also 1840 downwards, however,
> in dB terms lest than 1.5dB across the band, looks worse in
> watts when you see 15 drop to 10! I have compromised top
> band to give the max output between 1900 and 2000. It is
> better than it was.
>
> With your help, I am beginning to think that the input match
> to the KPA 100 is not 50 OHMS on top band, hence the high
> current warning( High return loss). I will replace the
> co-ax, as a start, and measure S11 and S12 form my network
> analyser, and check the match into the KPA100 and report
> back, it is odd the other bands seem happy with the match. I
> must of damaged something somewhere removing the KPA100.
>
> 73's
>
> Andrew
>
>
>
>
>

Andrew UK

Re: KPA 100 Low power on 160M

In reply to this post by Andrew UK

Hi Don,

Set up: KPA100 powered up connected to K2 only the Aux RF
plug disconnected. 50 ohm load connected to RF O/P

Ok I measured the return loss into the KPA100, the loss is
6-7dB on 1.9 MHz, so an SWR of 2.5 to 1! on 3.5 to 24 MHz
less then 1.3 to 1 and rises a bit towards 29MHz. I did not
have a lot of time last night as it was a club meeting, so
will make some more measurements tonight and get back.

73

Andrew

Hi Don,

I am sorry I should have said:

The K2 with the KPA100 removed behaves normally, current
does not exceed 2.5A on any band at full power (between
10-17 Watts depending on band 40M I get the most power)

I have retuned 80 and 160M and I have checked all the
components for correct value C11,12,13,14,15 + 16, L34 +5,
160M board checked C1,2 and 3 and L1 and L2 for 21 turns.

Now UK band is 3.5 to 3.8Mhz 300 KHZ wide 80 Metre gives
full power where ever I centre tune 3.6, 3.65, 3.7 or 3.75
MHz, now top band I get 15 Watts if I tune at 1.9 MHz drops
off a bit at 1970 upwards, and also 1840 downwards, however,
in dB terms lest than 1.5dB across the band, looks worse in
watts when you see 15 drop to 10! I have compromised top
band to give the max output between 1900 and 2000. It is
better than it was.

With your help, I am beginning to think that the input match
to the KPA 100 is not 50 OHMS on top band, hence the high
current warning( High return loss). I will replace the
co-ax, as a start, and measure S11 and S12 form my network
analyser, and check the match into the KPA100 and report
back, it is odd the other bands seem happy with the match. I
must of damaged something somewhere removing the KPA100.

73's

Andrew

_________________________________________

Check your Email accounts at http://www.MyEmail.com

Login from home, work, school. Anywhere!

------------------------------

Message: 3
Date: Mon, 27 Oct 2008 08:25:10 -0400
From: Don Wilhelm <[hidden email]>
Subject: Re: [Elecraft] KPA 100 Low power on 160M
To: [hidden email]
Cc: [hidden email], [hidden email]
Message-ID: <[hidden email]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Andrew,

OK, sorry for the 'dumb' response, but I had to check it out
so there
would be no 'tail chasing' in a non-problem area.
Yes, it would seem that the input to the KPA100 is nowhere
near 50 ohms
on 160m.
I don't know the vintage of your KPA100, but if it does not
have blue
toroids at RFC1 and L16, now would be a good time to install
KPA100UPKT. That change was mostly to the T/R switch area,
but still
can impact the input circuit response.

You can check out the KPA100 LPF easily with an antenna
analyzer - put
the base K2 into CW TEST just to be safe, and set the power
less than 11
watts. Pull the input coax from the RF Board and insert a
51 ohm
resistor. Switch to 160 meters and connect the analyzer to
the SO-239
connector. The K2 and KPA100 must be powered (and the
ribbon cable
connected) because the KPA100 relays are not latching types.
The SWR
should be less than 1.5 over the entire 160 meter band.

You could try running the antenna analyzer into the KPA100
input
(connect the output to a dummy load since some power may be
developed at
the KPA100 output). If you set the K2 power to less than 11
watts, you
will be reading only the KPA100 LPF, but when the power is
set at
greater than 11 watts, you should read the input impedance
of the
KPA100. I have never actually done this measurement, so I
don't know
what is normal, but you could compare with the results on 80
and 40
meters as a sanity check.

73,
Don W3FPR

[hidden email] wrote:

drops
> off a bit at 1970 upwards, and also 1840 downwards,
however,
> in dB terms lest than 1.5dB across the band, looks worse
in
> watts when you see 15 drop to 10! I have compromised top
> band to give the max output between 1900 and 2000. It is
> better than it was.
>
> With your help, I am beginning to think that the input
match
> to the KPA 100 is not 50 OHMS on top band, hence the high
> current warning( High return loss). I will replace the
> co-ax, as a start, and measure S11 and S12 form my network
> analyser, and check the match into the KPA100 and report
> back, it is odd the other bands seem happy with the match.
I
> must of damaged something somewhere removing the KPA100.
>
> 73's
>
> Andrew

_________________________________________

Check your Email accounts at http://www.MyEmail.com

Login from home, work, school. Anywhere!

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

Andrew UK

Re: KPA 100 Low power on 160M

In reply to this post by Andrew UK

Hi Don,

Just to tie the ribbons, I completed the KPA 100 up grade, blue cores ect, and it made no difference, so I went back to basics, "what could cause a poor return loss on 160 only into the KPA 100?" I checked the following:

C86, C67, D11, R2,1 R22, C66, C60, C61, C62, C63 and R9 The fault was traced to D11. although it measured OK and the volt drop when forward biased was reasonable 0.65V, it did not like 160M and gave a poor reflection to the K2 ( high current warning). I had replaced it before to try and cure this fault, which threw me, however, the current replacement is from a different manufacture!! so maybe not all 1N4007's are the same!

Now I have brought the KPA up to reversion E the radio seems a lot more stable, I am currently adding the 60M and transverter board. Thanks for all your words of wisdom

73 and Merry Christmas

Andrew & Sue (M3UUG)

On Sun, 2008-10-26 at 16:41 +0000, Andrew Lenton (Linux account) wrote:

Hi Don,

Ah very good point this rules out the low pass filter on the KPA 100, as low power is OK. I only have this problem on 160, as 80 to 10 are fine

Th High current only show up on 160 M, the display on the K2 reads the same on the external watt meter Bird through line. SO! symptoms below are:

1 Power on display matches Watt meter from 160 to 10 ( all be it 160 is 60 Watts Max)
2 Power from 80 to 10 max 111 Watts on display and meter, no high current warning
3, Power after 60 watts on 160 I get high current warning
4, I did not disturbed R 26 it was covered by metal plate when I removed the KPA100 to make way for the DSP, and the setting of R26 would also affect other bands

The Bird meter was calibrated this year with all its elements, also I have more than one Watt meter, all say the same low power on 160 and high current

Something must have been disturbed somewhere!! I guess?

73's

Andrew

On Sun, 2008-10-26 at 10:43 -0400, Don Wilhelm wrote:
Andrew,

If the KPA100 low pass filter were a problem it would misbehave at both 
the low and high power ranges because it is always in the circuit with 
the KPA100 connected.

A "Hi Cur" message means the *base K2* is drawing current in excess of 
the CAL CUR setting, and the power will be reduced to control the current.

If the HI CUR message only shows up when driving the KPA100, then I 
would look for a problem in the input of the KPA100, or mis-calibration 
of the wattmeter in the KPA100.  If you bumped the setting for R26 while 
working on the KPA100, that in itself may be sufficient to explain the 
HI CUR indication.  Did you measure the actual power output with an 
external wattmeter or are you depending on the K2 display?  If the 
internal wattmeter is not properly calibrated, the actual power output 
can be much greater than indicated by the K2.

73,
Don W3FPR


Andrew Lenton wrote:
> Hi Don,
>
> Thanks for that, Putting aside the K2's low power on 160, which no doubt has
> a component error value somewhere, the KPA 100 has been working at 111 Watts
> for two years until I disturbed the PA last week to make way for the DSP
> board. So something has happened to the KPA100. I only get a high current
> warning when the KPA100 is in use. 80 to 10 Metres is fine 11 watts no
> warnings! I think something has happened to the high power low pass filter,
> any thoughts?
>
> 73
>
> Andrew G8UUG
>   
>