Gang: I'm finally off for the weekend. Just curious, what is the
easiest way to check the low pass filter relays to see if they are working????? I've already checked U2 and pins 13 -18 are going low as they should. I'm just not sure what I should be looking for to determine if the relays are working. Thanks and 73 Jerry N0JRN ______________________________________________________________ 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 |
Jerry,
I assume you are working on a KPA100 - if not, please ignore. The easiest way to check the relays and the LPF of the KPA100 is with an antenna analyzer. Put the KPA100 to the right of the K2 (upside down on a book or other support) with the ribbon cable connected to the K2. Power only the base K2 through the coaxial jack. Put the leads of a 50 (ok, 51 will do fine) ohm resistor into the connector that normally connects to the AUX RF header. Power the K2 on and select each band in turn. For each band, scan through the frequency range of the antenna analyzer to determine the cutoff frequency for the LPF - it should be higher than the band edge, but lower than the 2nd harmonic. If all bands meet that criteria, the relays and LPF are correct - assemble the KPA100 to the base K2 and go. 73, Don W3FPR n0jrn wrote: > Gang: I'm finally off for the weekend. Just curious, what is the > easiest way to check the low pass filter relays to see if they are > working????? > > I've already checked U2 and pins 13 -18 are going low as they should. I'm > just not sure what I should be looking for to determine if the relays are > working. > > Thanks and 73 > > Jerry N0JRN > > ______________________________________________________________ > 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 > ------------------------------------------------------------------------ > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 9.0.717 / Virus Database: 270.14.114/2575 - Release Date: 12/19/09 03:33:00 > > 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 |
In reply to this post by n0jrn
Thanks Don:
Easy enough ! I appreciate that very much. Yes I am working with my KPA100. I'm looking for why the K2 drops out of TX when I try to adjust output above 35 watts. A couple of the bands are also showing excessive current draw and high reflected. Just wanted to check the relays and make sure everything in the LPF first. I've spent a good part of the evening reading the archives for similar issues. Your comments in most cases take folks back to the SWR bridge and related components. BUT first things first ! Have a great evening Jerry > I assume you are working on a KPA100 - if not, please ignore. > The easiest way to check the relays and the LPF of the KPA100 is with an > antenna analyzer. > Put the KPA100 to the right of the K2 (upside down on a book or other > support) with the ribbon cable connected to the K2. Power only the base > K2 through the coaxial jack. > Put the leads of a 50 (ok, 51 will do fine) ohm resistor into the > connector that normally connects to the AUX RF header. > Power the K2 on and select each band in turn. For each band, scan > through the frequency range of the antenna analyzer to determine the > cutoff frequency for the LPF - it should be higher than the band edge, > but lower than the 2nd harmonic. > If all bands meet that criteria, the relays and LPF are correct - > assemble the KPA100 to the base K2 and go. ______________________________________________________________ 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 |
Jerry,
Yes, do check the LPF and relays first just as a 'confidence builder'. If that is all working fine, then I would first direct you to the wattmeter section. Check with an external wattmeter in-line. If the output power is in excess of 100 watts no matter what the requested power setting, then the KPA100 wattmeter is not working (D16 and D17 usually is the problem). Once you obtain proper power level control, then other problems can be addressed if necessary. 73, Don W3FPR n0jrn wrote: > Thanks Don: > > Easy enough ! I appreciate that very much. > > Yes I am working with my KPA100. I'm looking for why the K2 drops out of TX > when I try to adjust output above 35 watts. > > A couple of the bands are also showing excessive current draw and high > reflected. > > Just wanted to check the relays and make sure everything in the LPF first. > > I've spent a good part of the evening reading the archives for similar > issues. Your comments in most cases take folks back to the SWR bridge and > related components. > > BUT first things first ! > > Have a great evening > > Jerry > > >> I assume you are working on a KPA100 - if not, please ignore. >> The easiest way to check the relays and the LPF of the KPA100 is with an >> antenna analyzer. >> Put the KPA100 to the right of the K2 (upside down on a book or other >> support) with the ribbon cable connected to the K2. Power only the base >> K2 through the coaxial jack. >> Put the leads of a 50 (ok, 51 will do fine) ohm resistor into the >> connector that normally connects to the AUX RF header. >> Power the K2 on and select each band in turn. For each band, scan >> through the frequency range of the antenna analyzer to determine the >> cutoff frequency for the LPF - it should be higher than the band edge, >> but lower than the 2nd harmonic. >> If all bands meet that criteria, the relays and LPF are correct - >> assemble the KPA100 to the base K2 and go. >> > > ______________________________________________________________ > 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 > ------------------------------------------------------------------------ > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 9.0.717 / Virus Database: 270.14.114/2575 - Release Date: 12/19/09 03:33:00 > > 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 |
In reply to this post by n0jrn
OK, Back in the shack and checking the LPF of my KPA100. Per
Don's direction, I disconnected the amps RF line from the main board of the K2 and installed a 50 ohm resistor in the plug end of the RF line. ( resistor measure 50.5 ohms per my DMM ) Hooked my MFJ 259B to the PL259 on the KPA100 and checked results of the low pass filter set up on each band. Results as follows: 160 Mtr 1.8 1.2-1 45 ohms 2.0 1.2-1 49 ohms 80 Mtr 3.5 1.3-1 53 ohms 4.0 1.3-1 49 ohms 40 Mtr 7.0 1.2-1 41 ohms 7.4 1.2-1 41 ohms 30 Mtr 10.1 1.4-1 50 ohms 10.150 1.4-1 50 ohms 20 Mtr 14.0 1.2-1 40 ohms 14.4 1.1-1 40 ohms 17 Mtr 18.065 1.2-1 37 ohms 18.2 1.2-1 37 ohms 15 Mtr 21.100 1.3-1 35 ohms 21.4 1.3-1 34 ohms 12 Mtr 24.890 1.2-1 35 ohms 24.990 1.2-1 35 ohms 10 Mtr 28.0 1.3-1 33 ohms 28.3 1.3-1 33 ohms 28.9 1.3-1 33 ohms Becomes obvious that K3 - K12 are switching and the filters are intact. Just a quick recap on the problem I have with my KPA100, while trying to do the Transmit tests on page 50 of the KPA manual, something is causing the KPA100 and / or the K2 to drop out of TX around the 35 watt level on all bands. I've read as much as can be found in the archives on this and similar issues. I know I've got to go back and reset the bias of the amp to insure it is correct. I'll retest the output from there and see if I've gained anything. FWIW, I am using a quality watt meter in line with my dummy load. The watt meter agrees with the K2's displayed results relative to the amount of output and reflected power. I have reset C1 a couple of times and I've been working with R26 to see if I can gain any improvement with it's adjustment. ( I can get to around 50 watts on the lower bands by working with R26 but my requested power and actual output are off quite a bit when I do that ) SO, for tonight's activity ! I'll recheck the bias settings, check voltages at D11 through D14 and recheck T4. Any other suggestions would be great. I'll let you know what I come up with. 73 Jerry N0JRN ______________________________________________________________ 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 |
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