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 > > > > > >
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