KPA100 - 80m poor quality SSB

classic Classic list List threaded Threaded
11 messages Options
Reply | Threaded
Open this post in threaded view
|

KPA100 - 80m poor quality SSB

Stewart Baker
The guests having departed - the Turkey finally disposed of - the booze consumed
- thoughts turned to "Playing radio".

I have been getting reports on 80m that my SSB signal had some "edge" to it.
At first I put it down to RF feedback, but that was not the problem.

I used my FT1000MP to listen to the 2nd harmonic of the 80m signal.
Having read recent mails I first monitored the 3.5MHz signal and found the
"Buzz" that others had reported.

I then tried the following frequencies on 80 and noticed that as I increased the
power control on the K2 the power output would suddenly jump, then when the
control was turned ACW the power would reduce smoothly and then suddenly drop.
It was also observable on the FT1000MP S-meter, accompanied by a click.
It was like a form of hysteresis. All other bands gave smooth power control.

The results were as follows:-

3.8MHz Low point=20W High point=70W Hysteresis=50W
3.7MHz Low point=25W High point=70W Hysteresis=45W
3.6MHz Low point=35W High point=70W Hysteresis=35W
3.5MHz Low point=40W High point=70W Hysteresis=30W

Very unsatisfactory...

I substituted a 1k resistor for RFC3, and all the 80m problems went away.
Smooth power control on all bands and a better SSB signal on 80m.

Many thanks to those who found/cured this problem that first showed itself on
CW, I would certainly have spent a lot of time tracking this one down !

I would suggest that owners of K2/100's check to see that their rig does not
exhibit these symptoms as it can make quite a big difference to transmitted
signal quality.

I, like a previous correspondent think that Elecraft should make some comment on
this design problem, and it's solution.

73
Stewart G3RXQ


_______________________________________________
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

Reply | Threaded
Open this post in threaded view
|

Re: KPA100 - 80m poor quality SSB

Don Ehrlich-2
Stewart,

I have been in contact with Gary intermittantly since first coming across
this problem in October.  He assures me that Elecraft is working on a
solution and will have something to say soon.  Both the "12 pF" fix and the
"1000 ohm resistor" fix have proved effective but are probably not the most
elegant or foolproof ways of solving the problem.  For instance, the 1000
ohm resistor alters the reverse bias on  D14 in a way that makes the T/R
switch marginal at high power levels.  I suspect that Elecraft is taking
their time and checking out all of the possible effects of design changes
and mods before committing to a final solution.

We will just have to be patient.

Don  K7FJ



The guests having departed - the Turkey finally disposed of - the booze
consumed
- thoughts turned to "Playing radio".

I have been getting reports on 80m that my SSB signal had some "edge" to it.
At first I put it down to RF feedback, but that was not the problem.

I used my FT1000MP to listen to the 2nd harmonic of the 80m signal.
Having read recent mails I first monitored the 3.5MHz signal and found the
"Buzz" that others had reported.

I then tried the following frequencies on 80 and noticed that as I increased
the
power control on the K2 the power output would suddenly jump, then when the
control was turned ACW the power would reduce smoothly and then suddenly
drop.
It was also observable on the FT1000MP S-meter, accompanied by a click.
It was like a form of hysteresis. All other bands gave smooth power control.

The results were as follows:-

3.8MHz Low point=20W High point=70W Hysteresis=50W
3.7MHz Low point=25W High point=70W Hysteresis=45W
3.6MHz Low point=35W High point=70W Hysteresis=35W
3.5MHz Low point=40W High point=70W Hysteresis=30W

Very unsatisfactory...

I substituted a 1k resistor for RFC3, and all the 80m problems went away.
Smooth power control on all bands and a better SSB signal on 80m.

Many thanks to those who found/cured this problem that first showed itself
on
CW, I would certainly have spent a lot of time tracking this one down !

I would suggest that owners of K2/100's check to see that their rig does not
exhibit these symptoms as it can make quite a big difference to transmitted
signal quality.

I, like a previous correspondent think that Elecraft should make some
comment on
this design problem, and it's solution.

73
Stewart G3RXQ


_______________________________________________
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

Reply | Threaded
Open this post in threaded view
|

Re: KPA100 - 80m poor quality SSB

Stewart Baker
On Tue, 28 Dec 2004 09:36:00 -0800, Don wrote:

> Stewart,
>
> I have been in contact with Gary intermittantly since first coming across
> this problem in October.  He assures me that Elecraft is working on a
> solution and will have something to say soon.  Both the "12 pF" fix and the
> "1000 ohm resistor" fix have proved effective but are probably not the most
> elegant or foolproof ways of solving the problem.  For instance, the 1000
> ohm resistor alters the reverse bias on  D14 in a way that makes the T/R
> switch marginal at high power levels.  I suspect that Elecraft is taking
> their time and checking out all of the possible effects of design changes
> and mods before committing to a final solution.
>
> We will just have to be patient.
>
> Don  K7FJ
>
>
> The guests having departed - the Turkey finally disposed of - the booze
> consumed
> - thoughts turned to "Playing radio".
>
> I have been getting reports on 80m that my SSB signal had some "edge" to it.
> At first I put it down to RF feedback, but that was not the problem.
>
> I used my FT1000MP to listen to the 2nd harmonic of the 80m signal.
> Having read recent mails I first monitored the 3.5MHz signal and found the
> "Buzz" that others had reported.
>
> I then tried the following frequencies on 80 and noticed that as I increased
> the
> power control on the K2 the power output would suddenly jump, then when the
> control was turned ACW the power would reduce smoothly and then suddenly
> drop.
> It was also observable on the FT1000MP S-meter, accompanied by a click.
> It was like a form of hysteresis. All other bands gave smooth power control.
>
> The results were as follows:-
>
> 3.8MHz Low point=20W High point=70W Hysteresis=50W
> 3.7MHz Low point=25W High point=70W Hysteresis=45W
> 3.6MHz Low point=35W High point=70W Hysteresis=35W
> 3.5MHz Low point=40W High point=70W Hysteresis=30W
>
> Very unsatisfactory...
>
> I substituted a 1k resistor for RFC3, and all the 80m problems went away.
> Smooth power control on all bands and a better SSB signal on 80m.
>
> Many thanks to those who found/cured this problem that first showed itself
> on
> CW, I would certainly have spent a lot of time tracking this one down !
>
> I would suggest that owners of K2/100's check to see that their rig does not
> exhibit these symptoms as it can make quite a big difference to transmitted
> signal quality.
>
> I, like a previous correspondent think that Elecraft should make some
> comment on
> this design problem, and it's solution.
>
> 73
> Stewart G3RXQ

Thanks for the "Heads up" Don.
I will look forward to the official modification when it is released.

73
Stewart G3RXQ


_______________________________________________
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

Reply | Threaded
Open this post in threaded view
|

Re: KPA100 - 80m poor quality SSB

Stewart Baker
>>> Although the 1k resistor mod seems to work there is a noticeable drop in
>>> received signals.
>>> Modeling the KPA100 T/R switching showed this additional loss.
>>> As a temporary measure until the official Elecraft modification comes out
>>> I have replaced RFC3 (100uH) with a 1mH RFC.
>>> My simulations show that the circuit resonance is now around 1.2MHz- maybe
>>> lower. Tried all bands, can't find a problem.

>>> 73
>>> Stewart G3RXQ

On Tue, 28 Dec 2004 18:11:15 GMT, Stewart Baker wrote:

> On Tue, 28 Dec 2004 09:36:00 -0800, Don wrote:
>
>> Stewart,
>>
>> I have been in contact with Gary intermittantly since first coming across
>> this problem in October.  He assures me that Elecraft is working on a
>> solution and will have something to say soon.  Both the "12 pF" fix and the
>> "1000 ohm resistor" fix have proved effective but are probably not the most
>> elegant or foolproof ways of solving the problem.  For instance, the 1000
>> ohm resistor alters the reverse bias on  D14 in a way that makes the T/R
>> switch marginal at high power levels.  I suspect that Elecraft is taking
>> their time and checking out all of the possible effects of design changes
>> and mods before committing to a final solution.
>>
>> We will just have to be patient.
>>
>> Don  K7FJ
>>
>>
>> The guests having departed - the Turkey finally disposed of - the booze
>> consumed
>> - thoughts turned to "Playing radio".
>>
>> I have been getting reports on 80m that my SSB signal had some "edge" to it.
>> At first I put it down to RF feedback, but that was not the problem.
>>
>> I used my FT1000MP to listen to the 2nd harmonic of the 80m signal.
>> Having read recent mails I first monitored the 3.5MHz signal and found the
>> "Buzz" that others had reported.
>>
>> I then tried the following frequencies on 80 and noticed that as I increased
>> the
>> power control on the K2 the power output would suddenly jump, then when the
>> control was turned ACW the power would reduce smoothly and then suddenly
>> drop.
>> It was also observable on the FT1000MP S-meter, accompanied by a click.
>> It was like a form of hysteresis. All other bands gave smooth power control.
>>
>> The results were as follows:-
>>
>> 3.8MHz Low point=20W High point=70W Hysteresis=50W
>> 3.7MHz Low point=25W High point=70W Hysteresis=45W
>> 3.6MHz Low point=35W High point=70W Hysteresis=35W
>> 3.5MHz Low point=40W High point=70W Hysteresis=30W
>>
>> Very unsatisfactory...
>>
>> I substituted a 1k resistor for RFC3, and all the 80m problems went away.
>> Smooth power control on all bands and a better SSB signal on 80m.
>>
>> Many thanks to those who found/cured this problem that first showed itself
>> on
>> CW, I would certainly have spent a lot of time tracking this one down !
>>
>> I would suggest that owners of K2/100's check to see that their rig does not
>> exhibit these symptoms as it can make quite a big difference to transmitted
>> signal quality.
>>
>> I, like a previous correspondent think that Elecraft should make some
>> comment on
>> this design problem, and it's solution.
>>
>> 73
>> Stewart G3RXQ
>>
> Thanks for the "Heads up" Don.
> I will look forward to the official modification when it is released.
>
> 73
> Stewart G3RXQ



_______________________________________________
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

Reply | Threaded
Open this post in threaded view
|

KPA100 - 80m poor quality SSB

S55M
So K2 Gentelmans...one question..

To fix RF switching problem in KPA100 there are 3 way's available (posted)

1. 12pF to ground from 1n4007's junction (just mooves a problem arround)

2. 1K resistor instead of RFC3 (affects RX preformance and marginal
switching at high power levels)

3. Change RFC3 100uH with 1mH choke (dont know abt side effects but shure
want to know the current rating of choke, cause i suppose must be at least
150mA or more?)

Which way is the best for now?

All kind of Help is Wellcome!
Thanks in advance!

S55M-Adi
K2-3204



----- Original Message -----
From: "Stewart Baker" <[hidden email]>
To: "Don" <[hidden email]>; "Elecraft Reflector"
<[hidden email]>
Sent: Wednesday, December 29, 2004 7:29 PM
Subject: Re: [Elecraft] KPA100 - 80m poor quality SSB


>>> Although the 1k resistor mod seems to work there is a noticeable drop in
>>> received signals.
>>> Modeling the KPA100 T/R switching showed this additional loss.
>>> As a temporary measure until the official Elecraft modification comes
out
>>> I have replaced RFC3 (100uH) with a 1mH RFC.
>>> My simulations show that the circuit resonance is now around 1.2MHz-
maybe
>>> lower. Tried all bands, can't find a problem.

>>> 73
>>> Stewart G3RXQ

On Tue, 28 Dec 2004 18:11:15 GMT, Stewart Baker wrote:
> On Tue, 28 Dec 2004 09:36:00 -0800, Don wrote:
>
>> Stewart,
>>
>> I have been in contact with Gary intermittantly since first coming across
>> this problem in October.  He assures me that Elecraft is working on a
>> solution and will have something to say soon.  Both the "12 pF" fix and
the
>> "1000 ohm resistor" fix have proved effective but are probably not the
most

>> elegant or foolproof ways of solving the problem.  For instance, the 1000
>> ohm resistor alters the reverse bias on  D14 in a way that makes the T/R
>> switch marginal at high power levels.  I suspect that Elecraft is taking
>> their time and checking out all of the possible effects of design changes
>> and mods before committing to a final solution.
>>
>> We will just have to be patient.
>>
>> Don  K7FJ
>>
>>
>> The guests having departed - the Turkey finally disposed of - the booze
>> consumed
>> - thoughts turned to "Playing radio".
>>
>> I have been getting reports on 80m that my SSB signal had some "edge" to
it.
>> At first I put it down to RF feedback, but that was not the problem.
>>
>> I used my FT1000MP to listen to the 2nd harmonic of the 80m signal.
>> Having read recent mails I first monitored the 3.5MHz signal and found
the
>> "Buzz" that others had reported.
>>
>> I then tried the following frequencies on 80 and noticed that as I
increased
>> the
>> power control on the K2 the power output would suddenly jump, then when
the
>> control was turned ACW the power would reduce smoothly and then suddenly
>> drop.
>> It was also observable on the FT1000MP S-meter, accompanied by a click.
>> It was like a form of hysteresis. All other bands gave smooth power
control.

>>
>> The results were as follows:-
>>
>> 3.8MHz Low point=20W High point=70W Hysteresis=50W
>> 3.7MHz Low point=25W High point=70W Hysteresis=45W
>> 3.6MHz Low point=35W High point=70W Hysteresis=35W
>> 3.5MHz Low point=40W High point=70W Hysteresis=30W
>>
>> Very unsatisfactory...
>>
>> I substituted a 1k resistor for RFC3, and all the 80m problems went away.
>> Smooth power control on all bands and a better SSB signal on 80m.
>>
>> Many thanks to those who found/cured this problem that first showed
itself
>> on
>> CW, I would certainly have spent a lot of time tracking this one down !
>>
>> I would suggest that owners of K2/100's check to see that their rig does
not
>> exhibit these symptoms as it can make quite a big difference to
transmitted

>> signal quality.
>>
>> I, like a previous correspondent think that Elecraft should make some
>> comment on
>> this design problem, and it's solution.
>>
>> 73
>> Stewart G3RXQ
>>
> Thanks for the "Heads up" Don.
> I will look forward to the official modification when it is released.
>
> 73
> Stewart G3RXQ



_______________________________________________
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

_______________________________________________
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

Reply | Threaded
Open this post in threaded view
|

Re: KPA100 - 80m poor quality SSB

Stewart Baker
On Thu, 13 Jan 2005 15:16:53 +0100, S55M wrote:

> So K2 Gentelmans...one question..
>
> To fix RF switching problem in KPA100 there are 3 way's available (posted)
>
> 1. 12pF to ground from 1n4007's junction (just mooves a problem arround)
>
> 2. 1K resistor instead of RFC3 (affects RX preformance and marginal
> switching at high power levels)
>
> 3. Change RFC3 100uH with 1mH choke (dont know abt side effects but shure
> want to know the current rating of choke, cause i suppose must be at least
> 150mA or more?)
>
> Which way is the best for now?
>
> All kind of Help is Wellcome!
> Thanks in advance!
>
> S55M-Adi
> K2-3204
>
Adi,

There is an Errata from Elecraft which does not appeared to have made it onto
their Web site yet. It is:-
-----------------------------------------------------------
 K2/100 MANUAL (Appendix G) ERRATA
 Rev. C-3, December 14, 2004
-----------------------------------------------------------
a) A 1k resistor is fitted across RFC3.

b) R4 in the HV bias supply is changed from 100k to 39k.

The 1k resistor damps out the resonance on 80m in my KPA100, and I no longer
experience the problem.

73
Stewart G3RXQ



_______________________________________________
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

Reply | Threaded
Open this post in threaded view
|

Re: KPA100 - 80m poor quality SSB

Don Ehrlich-2
In reply to this post by S55M
Adi,

Stewart Baker G3RXQ has also been fighting this problem and he sent me a
note a week or so ago saying that he understood that on Dec 14th Eleraft
issued an Errata for the KPA100 which changed R4 in the HV osc from 100k to
39k and ** added a 1k resistor in parallel with RFC3 ***.  There was no
reason given in the errata.   Stewart put these changes into his KPA100 and
so have I.  Our 80 meter performance is now normal.  These two changes are
obviously aimed at fixing the T/R instability in some KPA100's caused by
resonance in or near the 80 meter band involving RFC3 and the junction
capacitance of D14.  The 1k resistor spoils the Q of the resonant circuit
without affecting receiver sensitivity or bias voltages and the change in R4
is probably to increase the design margin of the HV bias in some units with
a 'lazy' oscillator.

I had been waiting for an official Elecraft recommendation to the list but I
finally got tired of waiting.  In my opinion the 1k resistor across RFC3 is
a very good solution.  The change in R4 is not necessary if your bias
voltage is already within the range recommended in the instructions.

Don  K7FJ

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

> So K2 Gentelmans...one question..
>
> To fix RF switching problem in KPA100 there are 3 way's available (posted)
>
> 1. 12pF to ground from 1n4007's junction (just mooves a problem arround)
>
> 2. 1K resistor instead of RFC3 (affects RX preformance and marginal
> switching at high power levels)
>
> 3. Change RFC3 100uH with 1mH choke (dont know abt side effects but shure
> want to know the current rating of choke, cause i suppose must be at least
> 150mA or more?)
>
> Which way is the best for now?
>
> All kind of Help is Wellcome!
> Thanks in advance!
>
> S55M-Adi
> K2-3204
>
>
>
> ----- Original Message -----
> From: "Stewart Baker" <[hidden email]>
> To: "Don" <[hidden email]>; "Elecraft Reflector"
> <[hidden email]>
> Sent: Wednesday, December 29, 2004 7:29 PM
> Subject: Re: [Elecraft] KPA100 - 80m poor quality SSB
>
>
>>>> Although the 1k resistor mod seems to work there is a noticeable drop
>>>> in
>>>> received signals.
>>>> Modeling the KPA100 T/R switching showed this additional loss.
>>>> As a temporary measure until the official Elecraft modification comes
> out
>>>> I have replaced RFC3 (100uH) with a 1mH RFC.
>>>> My simulations show that the circuit resonance is now around 1.2MHz-
> maybe
>>>> lower. Tried all bands, can't find a problem.
>
>>>> 73
>>>> Stewart G3RXQ
>
> On Tue, 28 Dec 2004 18:11:15 GMT, Stewart Baker wrote:
>> On Tue, 28 Dec 2004 09:36:00 -0800, Don wrote:
>>
>>> Stewart,
>>>
>>> I have been in contact with Gary intermittantly since first coming
>>> across
>>> this problem in October.  He assures me that Elecraft is working on a
>>> solution and will have something to say soon.  Both the "12 pF" fix and
> the
>>> "1000 ohm resistor" fix have proved effective but are probably not the
> most
>>> elegant or foolproof ways of solving the problem.  For instance, the
>>> 1000
>>> ohm resistor alters the reverse bias on  D14 in a way that makes the T/R
>>> switch marginal at high power levels.  I suspect that Elecraft is taking
>>> their time and checking out all of the possible effects of design
>>> changes
>>> and mods before committing to a final solution.
>>>
>>> We will just have to be patient.
>>>
>>> Don  K7FJ
>>>
>>>
>>> The guests having departed - the Turkey finally disposed of - the booze
>>> consumed
>>> - thoughts turned to "Playing radio".
>>>
>>> I have been getting reports on 80m that my SSB signal had some "edge" to
> it.
>>> At first I put it down to RF feedback, but that was not the problem.
>>>
>>> I used my FT1000MP to listen to the 2nd harmonic of the 80m signal.
>>> Having read recent mails I first monitored the 3.5MHz signal and found
> the
>>> "Buzz" that others had reported.
>>>
>>> I then tried the following frequencies on 80 and noticed that as I
> increased
>>> the
>>> power control on the K2 the power output would suddenly jump, then when
> the
>>> control was turned ACW the power would reduce smoothly and then suddenly
>>> drop.
>>> It was also observable on the FT1000MP S-meter, accompanied by a click.
>>> It was like a form of hysteresis. All other bands gave smooth power
> control.
>>>
>>> The results were as follows:-
>>>
>>> 3.8MHz Low point=20W High point=70W Hysteresis=50W
>>> 3.7MHz Low point=25W High point=70W Hysteresis=45W
>>> 3.6MHz Low point=35W High point=70W Hysteresis=35W
>>> 3.5MHz Low point=40W High point=70W Hysteresis=30W
>>>
>>> Very unsatisfactory...
>>>
>>> I substituted a 1k resistor for RFC3, and all the 80m problems went
>>> away.
>>> Smooth power control on all bands and a better SSB signal on 80m.
>>>
>>> Many thanks to those who found/cured this problem that first showed
> itself
>>> on
>>> CW, I would certainly have spent a lot of time tracking this one down !
>>>
>>> I would suggest that owners of K2/100's check to see that their rig does
> not
>>> exhibit these symptoms as it can make quite a big difference to
> transmitted
>>> signal quality.
>>>
>>> I, like a previous correspondent think that Elecraft should make some
>>> comment on
>>> this design problem, and it's solution.
>>>
>>> 73
>>> Stewart G3RXQ
>>>
>> Thanks for the "Heads up" Don.
>> I will look forward to the official modification when it is released.
>>
>> 73
>> Stewart G3RXQ
>
>
>
> _______________________________________________
> 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
>
> _______________________________________________
> 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 

_______________________________________________
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

Reply | Threaded
Open this post in threaded view
|

Re: KPA100 - 80m poor quality SSB

John Huffman
In reply to this post by Stewart Baker
However, my 80M SSB distortion turned out to be a different solution.

Like Stewart, I saw the jumpy power output on 80M as I varied the output from 11
to 100+ watts.  It was not smooth and either was my SSB signal.  The problem
persisted through the implementation of the solution listed below.

> a) A 1k resistor is fitted across RFC3.
>
> b) R4 in the HV bias supply is changed from 100k to 39k.

I also, with Gary's help, modified the KSB2 ALC -

"If the SSB RF output goes as high as 150-200w, there is a problem with the
ALC on the KSB2 and I know just what to do to correct that. R9 should be
changed to 1.5K, and the trace to Q1 is cut and a 1K resistor is inserted
across the trace. The 1K resistor should be a small 1/8w or SMD type, or cut
the leads really short to fit in the limited space between Q1's base and pin
6 of the KSB2 where the base circuit normally goes.  This gives the ALC the
extra control it needs to hold the SSB PEP RF output in check."

It was better, but not completely gone.

The cure, for me, was the Power Control Mod on the Elecraft web site -
www.elecraft.com/Apps/Power_Control_Mod.html

1.6K ohms looked best when I tested, but used a 1.3k because that was what I
had.  Locals have pronounced my 80M SSB distortion cured.

Hope that helps...

73 de NA8M
John

_______________________________________________
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

Reply | Threaded
Open this post in threaded view
|

RE: KPA100 - 80m poor quality SSB

Sverre Holm
In reply to this post by Stewart Baker
-----Original Message-----
There is an Errata from Elecraft which does not appeared to have made it
onto their Web site yet. It is:-
-----------------------------------------------------------
 K2/100 MANUAL (Appendix G) ERRATA
 Rev. C-3, December 14, 2004
-----------------------------------------------------------



The errata is there now, see

http://www.elecraft.com/manual/E740035E%20KPA100%20errata%20rev%20C-3.pdf 


73

Sverre
LA3ZA
http://www.qsl.net/la3za/
 



_______________________________________________
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

Reply | Threaded
Open this post in threaded view
|

RE: KPA100 - 80m poor quality SSB

Stewart Baker
On Thu, 13 Jan 2005 20:20:05 +0100, Sverre Holm wrote:

> -----Original Message-----
>
> There is an Errata from Elecraft which does not appeared to have made it
> onto their Web site yet. It is:-
> -----------------------------------------------------------
> K2/100 MANUAL (Appendix G) ERRATA
> Rev. C-3, December 14, 2004
> -----------------------------------------------------------
> The errata is there now, see
> http://www.elecraft.com/manual/E740035E%20KPA100%20errata%20rev%20C-3.pdf
>
> 73
> Sverre
> LA3ZA
> http://www.qsl.net/la3za/

Thanks for the information Sverre.

Unfortunately:-
a) The Errata is under the manual section, with no reference to it from the
builders notes or elsewhere as far as I can see.
b) The description in the Errata only mentions the changes to the KPA100 SWR
foldback,  nothing about curing the RFC3 resonance on 80m.

I think that this is where your excellent index of modification takes over.

73
Stewart G3RXQ



_______________________________________________
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

Reply | Threaded
Open this post in threaded view
|

RE: KPA100 - 80m poor quality SSB

srife
        You must have looked at a different errata sheet than I have. Item 3
talks about RFC3 and the resistor across it. The sheet is dated 12/14/2004


Stan Rife
W5EWA
Houston, TX
K2 S/N 4216
 
Thanks for the information Sverre.

Unfortunately:-
a) The Errata is under the manual section, with no reference to it from the
builders notes or elsewhere as far as I can see.
b) The description in the Errata only mentions the changes to the KPA100 SWR

foldback,  nothing about curing the RFC3 resonance on 80m.

I think that this is where your excellent index of modification takes over.

73
Stewart G3RXQ



_______________________________________________
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