I used my new KX3 (SN 2282) in the recent WAE RTTY test as part of an SO3R setup with 2 K3s, and wanted to record my impressions. The KX3 at 5W was driving an amp to 100 watts, and contributed 298 q's to my total. The KX3 had the per band sideband nulling and the roofing filter.
I took the headphone output and ran it through transformers, one channel directly to the computer sound card, and the other through a separate audio amp, to my headphones. This way, the decoder audio could be at a fixed level but still allow me to use the external amp to adjust the headphone level. The KX3 was set for AFSK A and of course I used AFSK from the sound card, which was also transformer isolated, and run to the MIC input. RX I/Q was run into another sound card to provide a spectral display using CW Skimmer (yes I know it doesn't decode RTTY, but I just like the way it looks). AFSK A uses a center frequency of 1Khz, which is good since I used high tones on the other two rigs, and it helps me to discriminate between what's going on between the rigs. Now AFSK A purports to use LSB, but is actually inverted, so I had to use the REV setting on MMTTY to get things to work. (this is on the list at Elecraft). It also meant manual fine tuning by ear or scope was reversed. Also AFSK A only allows the twin peaking filter, which I found I really don't like in a contest. Band noise is peaked up at the tone frequencies and I found that that made it harder to tell when a weak station was calling on a noisy band. I used MMTTY in non AFC mode, and found that the tuning was more touchy. 2-Tone, running in it's native AFC and AGC mode was better at decoding. Also in AFSK mode, it's necessary to set an offset in the N1MM logging software to get the frequency to net up with FSK packet spots. As others have noted, having a band scope is a great thing, and with the KX3 is pretty easy to implement. However, I found that with all the extra stuff in the shack going, the 'zero freq' portion of the display got what seemed to be progressively noisier. I did have transformer isolation on the I/Q output but more attention is needed. I also saw that on 40M, where my antenna is uncomfortably close to the house, that there was noise induced on the I/Q output. I don't think this was radiated on the transmitter, but will need to investigate more. I did not use the 8Khz offset in the KX3 to move the noise from 0 since I wanted the roofing filter action for the contest congestion. Also the image rejection of CW Skimmer degraded significantly during the contest. I think this was because I left the it in learn mode, and it was learning from the transmit signal sent out over the RX I/Q as well as very strong local signals (including my own 40M harmonic as heard on 20M). Turning off learning mode would help this I'm sure. I had a fan blowing on the back of the kx3, and PA temperature rise was minimal, toping out in the mid 40's, even with the extended duty cycle of exchanging QTCs. As others have noted, the KX3 should be mounted securely or it wants to wander off when pressing buttons. So how's it compare to a K3? I/O is limited (no separate fixed audio out, FSK in, or band outputs) RIT is harder to use (and reset) And if the rig isn't mounted well, it moves when you hit the buttons. Fewer options for center frequency setting In AFSK A, only twin peaking filter available No FSK transmit No fixed audio output No band dependent power out setting (my amp was pretty flat so not an issue for me) I don’t think I missed any contacts due to using the KX3 vs. a K3. The limiting factor on receive was more the clicks and splatter from other stations rather than any receiver performance. I do think the K3 is better, but not by leaps and bounds. Hi SIG detect seems to be more sensitive to an on frequency signal, rather than the K3 responding to on/off frequency signals equally. Wishes Add FSK transmit (Elecraft says the I/O is wrong to allow this) Allow other rx filtering selections Fix the sideband selection in AFSK A Mute the RX I/Q output on TX SO not bad for a 2 pound trail ready radio! Mark n2qt/we4m ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
