I ran my K3 in diversity mode during the ARRL 160 meter contest for the first time from this side of the country. It was a revelation. If you've never listened in diversity, you must do everything you can-- now that we're in the time of year that's favorable for the low bands-- to experience this for yourself. Top Band here in the Eastern Time Zone is a lot more fun that it was on the west coast.
The K3 Owner's Manual describes diversity mode like this: "True diversity requires a pair of identical receivers running from a common frequency reference and using two different antennas." Where you connect your two antennas depends on whether you have the antenna tuner and transverter board options, but you should configure the transceiver to accept the dedicated receiving antenna at the AUX input because there's a bit less loss at this input. You enter Diversity mode with a long press of the SUB button. Usually, your main (transmitting) antenna is fed to one ear and the receive antenna to the other ear by setting "L-MIX-R = A b" in the K3's CONFIG menu. It also helps to set "SUB AF = BALANCE" so that you can use the SUB audio control on the front panel to make the two antennas sound equally loud in your headphones, in conjunction with adjusting the RF gain of each antenna from the front panel. I believe the best practice is something like the following: * While listening to noise adjust the RF gain controls for 'an equal amount of noise' from the two antennas * Then listen to a signal and use the SUB (Balance) control to equalize the levels and place the signal in the center of your stereo headphones Who would have thought that an antenna laying on the ground would be useful, but this year I tried a loop on ground (LoG) antenna as the 2nd antenna. The LoG was a square only 20 feet (6.1 m) per side, made of insulated wire, in contact with the ground, and fed at a corner with a 9:1 transformer wound on a binocular #73 core. This is the common LoG design that you see all over the web ( http://kk5jy.net/LoG/ ). The LoG is somewhat bi-directional for low angles of arrival, so I oriented it northeast-southwest. I got the best results by: 1/ Using an antenna tuner to better match the LoG to the 50-ohm input of the K3. A LoG has very high loss, so everything you can do to conserve its signal power helps. I noticed an S-unit of LoG receive improvement when using the tuner. 2/ Turn the preamp on for the LoG, but the attenuator on for your main antenna. 3/ Route the main ant to your left ear and the LoG to your right, as discussed earlier. 4/ Because my LoG was directly under the transmit antenna, and even though I possibly could have done without one, I was more comfortable with a PIN diode switch to protect the AUX input (which is where the receive ant enters the K3). I built a circuit that takes the KEY OUT of the K3 and switches a bias voltage to the PIN switch: +12 V on receive and -12 V on transmit. This switch has a measured isolation of > 60 dB... good enough for transmitting at 100 W and probably much more. However, this might have been overkill and a simple diode limiter probably works just as well. Using the RF gain and Balance controls, you can center a signal in your headphones as discussed earlier. Pretty soon you'll have a soundstage between your ears where signals seem to float from left to right and back again as fading and polarization occur. It's as if your head is inside the band. It's a very powerful psychoacoustic experience that gives you a visceral feel for what propagation is doing. Instead of fading in and out, signals move from left to right and back again, sometimes slowly, sometimes abruptly, always randomly. My main ant being a horizontal dipole, I was pleased that when a signal would fade *out* on the main, it tended to fade *in* on the LoG, and vice-versa. The end effect of this is that you largely mitigate QSB. Signals stubbornly hang in as the band does its fading thing. Since the contest, I've tried the LoG on 80 and 40 and it works even better on those bands. Since your main ant's RF gain is cranked way down to match the LoG's output, everything sounds quieter. I found myself wondering why my noise level was so low. But don't worry, you'll still have enough sensitivity. The noise floor is so low that you feel as though you can copy signals down to negative infinity. The effect is addicting! If your K3 or K4 has a subreceiver, I urge you to try diversity mode. I think you'll be delighted at what you hear. Al W6LX/4 ______________________________________________________________ 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 Message delivered to arch...@mail-archive.com
