Where have these things been all my life and why didn't I use them in lieu of termination resistors (Rt) previously is what I must ask! With some good weather today and a drying antenna field I did some work on two DKAZ's today and reinstalled the Vactrol setup. I have only one setup from a friend who makes his own for his DKAZ DXpeds. I will stress that having a multi turn pot or a smaller pot in series for fine tuning is very useful. No one setting is going to be optimal for every frequency or deviation from 180 degrees from beampeak but I have found a setting that seems better than anything I ever could obtain using and manually fine tuning fixed resistor combos.
Here's some examples from daytime DX today. Locals on 1330 and 1430 are both at about 102 deg and 13 miles away. My DKAZ aims due west 270 deg so 90 deg should the spot of best back null per theory. 1330 WKTA's ethnic is so clobbered that I cannot hear a trace of it under WNTA. Without touching the Vactrol pot 1430 WEEF's ethnic is also inaudible under WCMY which isn't strong and has two more stations under it. I've never had nulls this good or stable on those two before even with phasing! With the same pot setting, WHFB 1060 at 94 deg is also crushed and WRHL is basically alone. WLW and WJR aren't strong here days, but they are gone with the same pot setting and WKZO 590 is basically lost under Omaha's KXSP. Yes you can get Nebraska in the daytime in NE IL thanx to good ground conductivity. Note also that Chcago's WRTO 1200 at 140 deg while not gone is deeply nulled with that setting. Fun also to have Clinton IA's GYer KROS 1340 dominant. I'll break out the ohm meter and measure what Rt the Vactrol is providing tomorrow and likely move the setup to my other west DKAZ as I've been having trouble getting deep back nulls since repairing it after severe storm damage. I'd recommend that anyone considering a terminated loop type of antenna strongly consider using a Vactrol as it is much faster and easier than walking back and forth manually adjusting resistances. My Vactrol is connected to the control unit with two separate wires about 250 ft long and clearly nulls aren't spoiled. A nice pure resistance is created by the Vactrol and applied to the termination end. 73 KAZ Barrington IL (35 miles NW of Chicago) _______________________________________________ IRCA mailing list IRCA@hard-core-dx.com http://montreal.kotalampi.com/mailman/listinfo/irca Be sure to register now for the Joint DX Convention Kansas City, September 9 to 11. Hotel space is filling up. Registration info: http://www.nrcdxas.org 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: irca@hard-core-dx.com