Date: Tue, Aug 30, 1994 10:30 PM EDT From: gary.sutcliffe@mixcom.mixcom.com Subj: Stacking A3's - Summary To: KA9FOX A while back I asked if anyone has had any experience with stacking small tribanders such as the Cushcraft A3. Since the summary is fairly small and becase of the number of requests for a summary, I decided to post the summary here. As background, even a die-hard 10 meter fan as myself has come to the conclusion that my 4 over 4 ten meter stack will not be of much use for the next few years, and it is time to do something different on that tower. The tower in question is 60', on the edge of a hill overlooking a marsh and lake towards Europe, giving me a higher effective height. Currently there is a 2 el 40 at the top of the tower, a 4 element 10 about 8 feet above it, with the lower 4 element 10M at about 30'. Some changes would need to be done to convert to A3's, probably including adding another 10 feet of tower. I really became a believer in having multiple antennas on a band with it, along with a TH7 on another tower (with a feed system allowing me to feed 1, 2 or all 3 antennas at once on 10M). Hopefully even though a two stack of small tribanders is not optimum, it will prove to be worthwhile. The responses seem to indicate it is. I plan to go ahead with the project if time & money permit before the snow flies at this cold Wisconsin QTH. Thanks to everyone who responded. 73 - Gary W9XT **************************** ORIGINAL POSTING: Has any had experience stacking small tribanders such as the Cushcraft A3? What heights, spacing, matching system, etc. did you use? What were your results? Is it worthwhile? **** Sender: "AI7B" Try contacting Jay WX0B.. H makes a phasing system for this type of application. He is on Internet. 73'd de bravo **** From: Steve Miller WD8IXE Hi Gary, I have a 402CD about 3 feet above my TET tribander. I used to have TVI problems on 15m. Eventually I found the 40 was receiving a couple watts of 15m power. When on 15, the energy received from the 40 (which was grounded via a shorting B&W switch) was modulating my station ground. Once I started terminating the 40 into a dummy load, the TVI was substantially reduced (only my neighbors cheap TV is affected now). I know there is interaction on 15m but it didn't seem to affect the TX/RX performance to any significant degree. Just a little higher VSWR on 15. 10 and 20 seem to perform the same as when the 40 was not there. If you can increase the spacing, you should have less trouble but even with my close spacing, the situation is managable. The 402CD was a great improvement and well worth the "compromise" of the tribander. Hope this helps. 73, Steve WD8IXE millersg@dmapub.dma.org ***** From: Steve Merchant I've stacked the A4S and the 40-2CD with as little as 5.5 ft separation with no ill effects, Gary. You might want to consider the A4S for next up cycle (4th 10m element). Now that I'm back out here in 6-land I've reverted to being a KLM bigot -- we need the extra aluminum! Good luck. 73, Steve N4TQO merchant@crl.com ***** From n0bsh@aol.com Gary, Sounds like you just described the former station of Tony, KM0O (St. Paul) where I did Phone SS a couple times. Not being a technical guru type, I can't offer you any hardcore technical info on the setup but it was pretty straight-forward. And it worked!!! As best I can recall the tower was about 60' and the antennas were an A3 at 65', a 2 el 40 at ~60', another A3 at about 40', and a dipole of some sort for 80 close to the top. The top A3 and the 40 rotated, the bottom A3 was fixed ESE. >From what Tony told me, the ONLY thing he did when hooking the two A3s together was to feed them with equal lengths of feedline, brought together with a T-connector, and plugged into the radio. No fancy phasing harnesses or anything. I'm sure there was some interaction between top A3 and the 40 - probably more to the 40 - but Tony, like me, believes in just using what you have and getting on and operating. (IMHO, with all the modeling software out there these days, I think way too much time is spent trying to optimize stuff of which you will never actually notice the results - like trying to find some way to get one more .00013 dB out of an antenna. I'm all for it to get you as close as possible to where you want to be but...) The bottom line is that the station played well. The 40 was louder than I really felt it was (the first year) and I operated accordingly the second year. The A3s played exceptionally well. The only thing that I found bad was that I probably spent too much time using them in "stack configuration", ie. both pointed the same way. But I always got GREAT signal reports on 15 and 20 (10 was not a factor so I didn't use it much but Tony saw good results as well on this band.) I should have had the top A3 pointed west more but I think I kept it east because that was where 40 would then be pointed. Obviously, there are probably ways to optimize this setup but Tony made do with what he had available. Simple and effective!! Today, however, this setup is no longer in service. Tony replaced the top A3 with an optimized 204BA to better take advantage of 20 for SS, etc. in light of current condx. 73 Mike N0BSH n0bsh@aol.com **** Sender: "WX0B" Gary, call Dunestar Systems and get some literature on the Stack matching system SM-03. It makes stacking Tri-banders easy! Cu Jay WX0B Mr. SM-03 **** From: Victor Burns Not stacking small tri-banders, but the tri-bander 40M problem is a tough one and you will get 10 answers. YES they will interact, even with 12-15' spacing which I have. The thing to do is put them at 90 degree angles to each other as this seem to minimize the interaction, probably due to the 15 meter/40 meter resonances. GOOD LUCK! and hope you have a crank-down tilt-over or like ot climb a lot. **** From: "Fred Hopengarten" K1VR: I, of course, have stacked TH6's, which have a 24 foot boom. But in writing the feature article with N6BV which appeared in February QST, Dean and I both completely agree that stacking is advantageous even for small tribanders. It is even advantageous for stacking dipole above a dipole! Stacking distances are determined by the frequencies in use, not boom size, EXCEPT that if stacking too close, coupling between the antennas goes up and patterns go all to hell. -- Fred Hopengarten K1VR -- Gary Sutcliffe - W9XT Unified Microsystems (414) 644-9036 ppvvpp@MIXCOM.COM PO Box 133, Slinger WI 53086 OL-Member: ka9fox