KPA100 SSB power control
Locked
 
|
I have just installed a recently constructed KPA100 (including the latest upgrades)
and appear to have run into the erratic power control problem. Using Tune + Display and an external LP100 meter, if I request 5w I get 5w out. Increasing power to 11w so as to engage the pa I also get 11w out - so all seems fine. Switching to SSB, and speaking steadily into the mic, at a requested 5w I get approximately 5-7w out on each band. However increasing the power to 11w I get the following: 80m Req 11 Get 45 40m Req 11 Get 80 20m Req 11 Get 25 15m Req 11 Get 30 10m Req 11 Get 20 Reading back through the archive I see that others have encountered the same problem but cannot see a definitive answer to the problem. Anyone have any thoughts as to where to start looking. 73 to all Trevor G0KTN _______________________________________________ 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 |
|
|
Trevor,
That behavior may be indicitive of a BIG oscillation in the KPA100, and the KPA100 throttles the power back to protect itself. In other words, it may not be a power control problem after all - check carefully to determine the real cause. OTOH, it COULD be a power control problem, but check the following first. One thing to look at first is the presence of a high SWR condition reported - if that occurs, it is confirmation that the KPA100 is oscillating out of band (it will not be seen when working into a dummy load). If you do find a Hi Refl situation, first check the orientation of Q6 and Q7 in the KPA100. Then check to be certain you have the latest upgrade to your KPA100, If there is no R12 resistor mounted and L15 is not installed, then you have the latest upgrade. Change C31 to a .22 uF capacitor (you can obtain one from mailto:[hidden email]). CAUTION: If you have a KPA100 without these latest upgrades, DO NOT change C31 to this new capacitor - the older design requires a 200 volt or greater capacitor and the new capacitor from Elecraft is only rated at 100 volts. The change of C31 is only to go with the new upgrade, it is not for unupgraded KPA100s. 73, Don W3FPR > -----Original Message----- > > I have just installed a recently constructed KPA100 (including > the latest upgrades) > and appear to have run into the erratic power control problem. > > Using Tune + Display and an external LP100 meter, if I request 5w > I get 5w out. > Increasing power to 11w so as to engage the pa I also get 11w out > - so all seems > fine. > > Switching to SSB, and speaking steadily into the mic, at a > requested 5w I get > approximately 5-7w out on each band. > However increasing the power to 11w I get the following: > > 80m Req 11 Get 45 > 40m Req 11 Get 80 > 20m Req 11 Get 25 > 15m Req 11 Get 30 > 10m Req 11 Get 20 > > Reading back through the archive I see that others have > encountered the same > problem but cannot see a definitive answer to the problem. Anyone > have any > thoughts as to where to start looking. > > 73 to all > Trevor G0KTN > No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.446 / Virus Database: 268.18.5/707 - Release Date: 3/1/2007 2:43 PM _______________________________________________ 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 |
|
|
In reply to this post by Trevor Smithers
I think you are seeing the attack spike of the ALC, Trevor. The LP-100
responds to very short peaks, apparently faster than the ALC in the rig can respond. If you go to www.telepostinc.com/K2_ALC.html you can see examples of this. There is a picture I took of CW keying and one Jack, K8ZOA took of the response to a tone burst in SSB. There are two things you can do. One is to back off the requested power just a tad, and the other is to look at the value of C36 in your meter. If it's not 330pF, then you might want to replace it. That's the filter cap in the detector circuit. Earlier meters used 100pF as I recall. I increased the value to slow down the response a little. You might also want to update the firmware if you haven't recently. You can email off-list if you need more info. 73, Larry N8LP Trevor Smithers wrote: > I have just installed a recently constructed KPA100 (including the latest upgrades) > and appear to have run into the erratic power control problem. > > Using Tune + Display and an external LP100 meter, if I request 5w I get 5w out. > Increasing power to 11w so as to engage the pa I also get 11w out - so all seems > fine. > > Switching to SSB, and speaking steadily into the mic, at a requested 5w I get > approximately 5-7w out on each band. > However increasing the power to 11w I get the following: > > 80m Req 11 Get 45 > 40m Req 11 Get 80 > 20m Req 11 Get 25 > 15m Req 11 Get 30 > 10m Req 11 Get 20 > > Reading back through the archive I see that others have encountered the same > problem but cannot see a definitive answer to the problem. Anyone have any > thoughts as to where to start looking. > > 73 to all > Trevor G0KTN > _______________________________________________ > 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 |
|
|
In reply to this post by Trevor Smithers
I think you are seeing the attack spike of the ALC, Trevor. The LP-100
responds to very short peaks, apparently faster than the ALC in the rig can respond. If you go to www.telepostinc.com/K2_ALC.html you can see examples of this. There is a picture I took of CW keying and one Jack, K8ZOA took of the response to a tone burst in SSB. There are two things you can do. One is to back off the requested power just a tad, and the other is to look at the value of C36 in your meter. If it's not 330pF, then you might want to replace it. That's the filter cap in the detector circuit. Earlier meters used 100pF as I recall. I increased the value to slow down the response a little. You might also want to update the firmware if you haven't recently. You can email off-list if you need more info. 73, Larry N8LP Trevor Smithers wrote: > I have just installed a recently constructed KPA100 (including the latest upgrades) > and appear to have run into the erratic power control problem. > > Using Tune + Display and an external LP100 meter, if I request 5w I get 5w out. > Increasing power to 11w so as to engage the pa I also get 11w out - so all seems > fine. > > Switching to SSB, and speaking steadily into the mic, at a requested 5w I get > approximately 5-7w out on each band. > However increasing the power to 11w I get the following: > > 80m Req 11 Get 45 > 40m Req 11 Get 80 > 20m Req 11 Get 25 > 15m Req 11 Get 30 > 10m Req 11 Get 20 > > Reading back through the archive I see that others have encountered the same > problem but cannot see a definitive answer to the problem. Anyone have any > thoughts as to where to start looking. > > 73 to all > Trevor G0KTN > _______________________________________________ > 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 |
|
|
In reply to this post by Don Wilhelm-3
Thanks for the reply Don, much appreciated.
Just to clarify, I built up the amp last year but never got around to installing it. So around December 06 I obtained the upgrade kit and installed that as well and that's how things stand at the moment. However your reply and mention of the new C31 had me looking around the Elecraft site and I see that there is an errata dated 4 December 06 which stresses the importance of changing R19 & R20 even though the correct values may already be installed - needless to say when I did the upgrade I followed the original instructions which basically says (on page 4) if the correct value components are already installed go to the next section. So, the upshot is, that I need to strip down the amp, replace R19 & 20 with the low inductance type, check the other components in accordance with the latest errata and install a new C31. At which point I should be in a position to check out the amp properly. 73 to all Trevor G0KTN _______________________________________________ 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 |
|
|
Trevor,
If your R19 and R20 resistors have a reddish/brown body, you can leave them in place - those are the good ones. The potentially bad ones are the light blue bodied resistors, and not all of those are inductive, but it is easier to just call for replacing them than to explain which ones might be bad. Inductive resistors were shipped with KPA100s and upgrade kits during the summer of 2006 - the resistor vendor changed to an inductive design without notifying Elecraft. 73, Don W3FPR > -----Original Message----- > > Thanks for the reply Don, much appreciated. > > Just to clarify, I built up the amp last year but never got > around to installing it. So > around December 06 I obtained the upgrade kit and installed that > as well and that's > how things stand at the moment. > > However your reply and mention of the new C31 had me looking around the > Elecraft site and I see that there is an errata dated 4 December > 06 which stresses > the importance of changing R19 & R20 even though the correct > values may already > be installed - needless to say when I did the upgrade I followed > the original > instructions which basically says (on page 4) if the correct > value components are > already installed go to the next section. > > So, the upshot is, that I need to strip down the amp, replace R19 > & 20 with the low > inductance type, check the other components in accordance with > the latest errata > and install a new C31. At which point I should be in a position > to check out the amp > properly. > > 73 to all > Trevor G0KTN > > > _______________________________________________ > 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 Free Edition. > Version: 7.5.446 / Virus Database: 268.18.6/709 - Release Date: > 3/3/2007 8:12 AM > No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.446 / Virus Database: 268.18.6/709 - Release Date: 3/3/2007 8:12 AM _______________________________________________ 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 |
«
Return to Elecraft
|
1 view|%1 views
| Free forum by Nabble | Edit this page |