For the past couple seasons here my desired western antenna system here in Barrington IL has been a broadside array of two DKAZ antennas aimed due west. Each antenna is 120' x 21' using 23' masts with the bottom wires 2' above ground. Broadside array means side by side and there was 265' between the two DKAZ. I'd prefer to have about 340' spacing but don't have that much land here aimed E-W. Anyhow, 265' spacing provided a nice narrowing of the main beam aimed West (or east if I wanted to swap feeds and termination resistors (Rt). However, the DKAZ along the southern edge of my field was only 20 ft away from parallel power lines running down my street. I knew these lines were making a mess of the pattern and adding noise as well, but could often make do anyhow. Empirically I noted that I could get reasonable termination on quite a few freqs using 470 ohms, but there were still quite a few freqs that weren't well terminated and sometimes backend stations leaking thru.
EZNEC modelling showed me three things, 1) that // wires 20 ft away mess up the back nulls in a big way. 2) That, indeed the lower Rt is needed for better termination due to coupling from the wires. 3) That if I move about 50 ft further from the power lines, they'll have almost no effect on the pattern. (Even moving 30 ft would help lots). Therefore, I moved the one DKAZ further into my property yesterday. I'll take it down in April once mowing starts but we have no use for the field other than DX in the winter. Since the new location is aimed right at my house I decided to stagger it in relation to the other DKAZ and install it 40 ft further east hoping to pick up less household QRN. This results in a 6 degree beamshift to 264 degrees rather than due west at 270 when both antennas are connected in phase. Given the constant semi-AU cx this season I don't mind riding with that cx and aiming a bit south of west. The older DKAZ terminates well with 690 ohms, I installed a 690 ohm resistor at the end of the new DKAZ and was quite happy with the results, indicating little in any coupling from power lines. Both antennas might benefit from a little Rt tweaking (maybe +/- 20 ohms) but the time to do that is not late afternoon this time of the year when skip from the east is starting as levels change to much for acurately measuring deep nulls. Note that my south DKAZ terminates with 875 ohms and that each one of these antennas is a different animal with regards to best Rt to get good nulls across the band. With it being warmer than usual and rather windy here, the new DKAZ was still getting lots of intermittant buzzing QRM from another bad powerline but that buzz isn't constant and I can usually DX past it. However, I may test moving that antenna closer to my house which will put that buzz spot (SE direction) further away and more into the termination null. With spacing of 214 ft, this is basically an upper band antenna as the two elements are too close to provide much beam narrowing on the low end. I tried some beam steering with phasing in the afternoon. The Wellbrook Array Controller's phasing is time delay. I easily nulled out SS from WJTI 1460 and I don't think that I've ever heard WIXN that well during the day. It was clear to me that I was also steering the main beam more towards the SSW than 264 deg and that effect was noted all over the upper half of the band. OK evening came, and I decided to go with the cx and steer the main beam further towards the SW by nulling down KSTP 1500 from my NW. EZNEC shows that I probably had the high end main beam aimed about 240 deg and with beamwidths from about 60-75 degrees. (60 at the extreme high end where 214 ft is a decent spacing). Stuff from KS, OK, MO, AR and even further south was clearly better with phasing than on a single antenna. 1570 XERF was often loud, but when I'd reverse the phase (aiming the main beam somewhat north of west, they'd be gone. KRJO 1680 was in a huge null and gone when I reversed phase, leaving Iowa DOT TIS's basically alone. With the beam aimed about 235-240 deg, I noted bits of a TIS on 1610 occ. (maybe 1% of the time) getting thru CHHA nuisance. CHHA is reduced by termination but not killed. I managed to hear "happened on Aug 3, 1837". Hmm..time for google but I strike out. Hmm cx and high band logs are all basically from near my SW... so what tourism is there SW of the Chicago area? OK Springfield and Abe Lincoln. Aha... on Aug 3, 1837 Lincoln was at a dinner in Athens IL called the Long Nine Banquet and toasted the moving of the state capitol from Vandalia to Springfield. Careful and repeated listening to my Perseus recordings indeed has enough mentions for me to be sure that I logged WPQZ702. Callsign: WPQZ702 Licensee: MENARD, COUNTY OF Radio Service: Public Safety Pool, Conventional (PW) City: PETERSBURG, IL Status: Active Grant Date: 12/15/2005 Expiration: 12/19/2015 Site: 1 Address: 1/4 MI E OF THE SR 97 AND COAL MINE RD INTERCHANGE City: PETERSBURG, IL County: MENARD Coordinates: 39° 57' 54.2" N, 89° 50' 22.4" W http://www.visitmenardcounty.com/styled-9/ http://abrahamlincolnonline.org/lincoln/sites/longnine.htm Hmm DXing and history all together! Note that of course, with the two antennas side by side and not staggered I could also steer the main due west beam about +/- 20-25 deg and sometimes did. 73 KAZ _______________________________________________ IRCA mailing list [email protected] http://montreal.kotalampi.com/mailman/listinfo/irca Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers For more information: http://www.ircaonline.org To Post a message: [email protected]
