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I've just finished installing a Sigma 80 and everything went by the book. It is an exceptionally well-made antenna and tuning was a cinch. I easily got a perfect match. Resonance is set for about 3520 kHz and the match is acceptable up to about 3560 or so. Since it is a physically short antenna, there is a tradeoff in bandwidth. I didn't use the shroud they provided; to do so with the one I got would require an extra slot be cut in the shroud to accommodate the balun support rod. If you stretch the coils out as Force12 recommends in their manual, it will be tuned for the high-end of the phone band. Both of my coils together wound up being only about 44" in length, about 10-12" shorter than Force 12 recommends for set-up. I have a half-sloper that I've been using on 80 m. Receive tests indicate that very close-in signals are down by about 10 dB, from S9+20 dB down to S9+10 dB on the Sigma 80 vs my half-sloper. Most other receive signals sound about the same between the two antennas. My first QSO was with 5R8FU during his dawn. My experience on the low bands is admittedly limited, but this is a nearly E-W path and, based on the reading I've done, sounded like a classic gray-line opening. I happened to be on his frequency when his CQ quickly appeared out of the noise and rose to an honest 579 RST. I tried once with 100 W, as did someone with an N1 call, but he heard neither of us. I then switched on the amp and got him on the first call, getting a 579 from him. Shortly afterwards, he faded back into the noise, and was gone. Using the Sigma 80 isn't like having a 3 element yagi up a couple of hundred feet, and I'm sure that the rx signals will still be characteristically crummy on 80 m compared to the higher bands, but this will be as good as it gets for me for awhile. Noise pickup is not significantly different between the two antennas. I live in a very quiet location, so my night-time noise levels right now run about S3-S5. In the day, the noise level is low enough that it doesn't move the S meter. I'd hoped to be able to load the antenna up on 160 m using my tuner, but had no luck. The Sigma 80 uses a hairpin match, and I'll bet that the hairpin coil helps generate a very low impedance at 160 m, preventing me from getting a match. All is not lost, however, because I turned up a pair of 80 m traps I'd made long ago for a trapped dipole for 40, 80 and 160 m. I'll add one to my half-sloper, along with some wire, and see if I can get a match on 160 m. While I can tune the half-sloper for 160 m, I go through a remote antenna switch to this antenna, and the antenna switch won't tolerate much power with a big mismatch. I did that once with disastrous results. See you in the pile-ups! 73, Kim Elmore, N5OP At 04:55 PM 1/29/2003 -0500, you wrote: >Hi >I have been thinking about purchasing a sigma-80 and I would like any >comments good or bad about this antenna. I live on Long island and wonder if >there is a local ham that has one. If not would appreciate any info. >Frank K2PWG > > > >-------------------------------------------- >Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. >Force12 Web Site: http://www.force12inc.com > >To Submit Message to the List: Force12Talk@qth.com >To unsubscribe and view the Message Archive: see http://qth.com/force12/list >For problems with the list: contact n4zr@qth.com Kim Elmore, Ph.D. University of Oklahoma Cooperative Institute for Mesoscale Meteorological Studies "All of weather is divided into three parts: Yes, No, and Maybe. The greatest of these is Maybe" The original Latin appears to be garbled. -------------------------------------------- Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. Force12 Web Site: http://www.force12inc.com To Submit Message to the List: Force12Talk@qth.com To unsubscribe and view the Message Archive: see http://qth.com/force12/list For problems with the list: contact n4zr@qth.com |
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