(note: Also see "Stacking 40-2CD and Tribander #2" on this web page) ANTENNA STACKING FIRST, THE ORIGINAL QUESTION: Date: 94-01-31 18:00:35 EST From: price@cod.nosc.mil Subj: Antenna stack problems To: KA9FOX As most of you know, I put up a 60' tower a few weeks ago which now sprouts a 40-2CD, WARC dipole, and TH-7, in that order, from top to bottom, all oriented the same direction. After 2 weeks of on-the-air time, here are my impressions: 1) The 2-el on 40 works ***very*** well. I can hear and work stuff I only imagined before. 2) The WARC dipole works *very* well on 30, but seems dead on 17 and 12. I did a side-by-side with another ham in the area who also has a WARC dipole, lower than mine, and signals to him on 17 were consistently a few S units louder than to me (same rig). 3) The TH-7 "works" in that signals get louder in the right direction, but overall it sounds rather dead--not much noise, a bunch of weak signals. Kinda like listening to 15 mtrs on a 40 meter dipole. Again, the side-by-side on 15 meters had same results--his 3-el tri-bander at 50 feet was "hearing" better than my TH-7 at 60 feet. (And my location is, if anything, better than his). Also, I failed miserably in trying to crack a small pileup on 20 SSB last night to work VP8CPC while several other 6s got thru in one call. So, I seem to have some severe interaction. Any specific experiences with a combination like this? Should I turn the TH-7 and WARC dipole 90 degrees to the 2-el 40? Should I reverse the order of the stack (perish the thought)? Tnx in advance, 73--Jim, K6ZH price@nosc.mil ----- NOW THE ANSWER SUMMARY: Date: 94-01-31 17:07:34 EST From: price@cod.nosc.mil Subj: More on ant. stacking problem To: KA9FOX I appreciate the large number of responses I've already gotten on this subject. So far the votes seem to be running in favor of mounting the 40-2CD and TH-7 booms at right angles to each other, except for the following comment from Bruce, AA5B: "My experience has been that antennas of the all-grounded variety (like TH6 and TH7) need to be in line with the 40m beam. That is to say, pointed in the same direction. Antennas that have elements insulated from the boom (like KT34XA and DX engineering antennas) need to be perpendicular to the 40m beam." which contradicts the above. Another particularly sobering comment from Jim, AD1C is: Jim, there are definite interaction problems between the 40-2CD and the WARC dipole. My father W1JR found this (even before he worked for Cushcraft) with a 40-2CD and the A3WS tribander (you should have the same problem). The problem is the 40-2CD shortened elements resonate around 9 MHz, 1/2 of the 18 MHz of the WARC antenna. He eventually had to take one antenna off the tower to use the other, and when he moved to NH, only put up the WARC tribander, and the 40 meter beam is still on the ground. And finally, another person pointed out to me that the boom on the 40-2CD is resonant on 15 meters! (argh) In any case, several of you asked about the ant. spacing, an issue I forgot to include in my original posting. I have a 15 foot mast in my rotator, so about 12 feet of it sticks out above the tower. The 40-2CD is as close to the top as the brace allows. The WARC dipole is about 2 to 3 feet below the 40 boom, in parallel with the 40-2CD elements. The TH-7 is as close to the tower as we could get it, so about 8 feet below the 40. Again, all elements are parallel. Keep those cards and letters coming, folks--Jim, K6ZH