Its spring and I am getting ready for some backpacking with my KX1 so I thought I would take the time to tweak/tune/analyze/hot rod my baby.
The rig is fully loaded. 4 bands, ATU and the SMD CW TUNING AID. I have several projects on the agenda. 1. Scope analysis 2. Dummy load construction with DVM RF measurement capabilities. Or just buy the Elecraft dummy load! 3. Possible tweaking of the existing hardware. 4. Exploring the possibility of increasing the power output to a full 5 watts. Just for the record, the KX1 is working FB on all bands and the readings on the rig are all within specs! Well, one thing at a time. I have hooked up my scope a dummy load consisting of six, 5 watt Milwaukee 300 ohm sand resistors in parallel. These resistors were given to attendees at hands on session of my local radio club. I was dubious about the resistor choice as I understand that these are wire wound and that is not appropriate for a dummy load. Sure enough, when comparing the SWR of the homemade dummy load, my MFJ-9895 and a BNC ½ watt 50 ohm terminator I found that the homemade load showed different SWR readings at 80, 40, 30 and 20 meters. While the MFJ and BNC terminator showed 1.0 SWR on the rig. The MFJ also showed the 1.0 on all four bands its SWR meter. Well, for convenience sake made I made my first scope connection on the homemade dummy load at 3.550 MHz. BATTERY NO LOAD = 12 VDC ON DVM. CONNECTED TO KX1 11.9 VDC ON DVM KX1 BAT FUNCTION = 11.7 VDC ON RECEIVE SCOPE PPV RIG WATTS RIG SWR CALCULATED WATTS 32 2.9-3.0 1.1 2.559 I calculated the power out by this formula. ((32 x .3535) (32 x .3535)) / 50 11.312 x 11.312 = 127.961 127.961 / 49.2 = 2.6.00 My DVM and the scope both show the same frequency! The scope had been calibrated when I bought it. The self calibration function shows the same measurements as when I bought it. So, I have two questions for the group at this point! 1. Are my measurements consistent with what a KX1 would be likely to put out? 2. Am I correct in thinking that the resistors in the homemade load are not the best choice? For what it is worth, I have found several articles on the web re: dummy loads and also looked at the schematic for the Elecraft dummy load and all indications are that sand style, rectangular, wire round resistors are not appropriate! It is true that my measurements confirm this, but as my construction technique was rushed, I do not want to assume anything! If my measurements pass the smell test I am going to trace the RF path of the KX1 end to end in order to establish a baseline! At that point, I will decide whether to try tweaking the KX1 or to continue home brewing a dummy load with power metering capabilities like the Elecraft dummy load! Thanks in advance for all your expert advice/admonitions! Jack, AE6GC, KX1 #1403, K3-100 #1433 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
