I'd like to get the opinion of the IRCA brain trust on this. I just got a pa0rdt active mini-whip, mainly to use traveling with an Afedri SDR. I decided last night to use it to phase against my indoor Wellbrook. I had mixed results--I could knock down all of my locals, but in all cases but one I did not hear any usable audio from other stations. What I was doing was to orient the Wellbrook to null my local as much aspossible, then phase it against the mini-whip. Is this the right technique,or should I be aiming the directional antenna in some other fashion?
There are a number of ways to do that. One that I have done is a combination of a large 24" broadband ferrite rod loop and a 64" plain steel whip. I put the level of the loop at maximum and leave it there. Then put the level of the whip to zero. Phasing is set to the zero amount and left at that.
Turn the loop to null the unwanted local station. Then, turn up the whip level a bit and see if the null goes further down. If it doesn't, turn the loop 180 degrees and null again. Then bring up the whip slightly again. You should see the null improve. Slightly turn the loop for more null, and adjust the whip potentiometer. By doing that you can get a dramatic null.
The ferrite loop and whip is on my 1988 K5 Chevy Blazer, and a Palstar R-30CC receiver. The loop is inside because it has a fiberglass roof. I've parked about fifty feet from one of my broadcast clients tower. They are nondirectional daytime at 1000 watts on 550kHz near Providence, RI. I nulled it to the lowest level and could then hear the 540 station on Long Island, NY, and 560 station in Springfield, MA. I've done the same basic thing at other AM clients as well and equally good.
By combining any figure eight loop and whip does work well. Instead of a phaser, you'd simply need a potentiometer on the whip side of the combiner transformer. A regular phaser could also work, though most of it wouldn't need to be turned. Moving the loop seems the better way.
Hope that helps... Craig Healy NG1U Providemce, RI _______________________________________________ IRCA mailing list IRCA@xxxxxxxxxxxxxxxx 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: irca@xxxxxxxxxxxxxxxx