SWR is slightly bumped up but only by 0.1 which is not worth a complaint. And the response directly up to the sky (90 degree) is about the same. The good is that the F/B is almost unaffected. The trace in BLUE is the 10m especially as it's pattern is affected (smeared you could say) by the interaction with the other two antennas around it. Here we can see both the 40m especially as well as the 17m elements are acting as unintended participants on the 10m band.īut how bad is this interaction? To answer that question we look at the elevation pattern in two cases, first is the 10m antenna alone, and then we look at the10m antenna with the top and bottom antennas present. In EZNEC, cranking up the current deflection on the wire frame view of the antenna shows you visually which elements are getting involved. Fortunately the array ended up looking pretty decent despite shortcomings of the top beam's location. I got lucky because that minimal but present interaction case is exactly what I have with top 10m.Īnd it's great that the result was good, because the only alternative other than an additional tower (which is not happening) is moving to a location at 30' up on the test tower. But if you are lucky, the interactions are minimal and while you take a small hit on each of these, the antenna can remain operational for the most part. Interactions in the worst case ruin patterns, kill gain and screw up SWR. This is hard to get around because as frequency goes up, even sub-features of surrounding and mostly non-interactive antennas can get into the interaction game. Unfortunately for the 10m beam especially, both antennas interact to an extent. The 10m beam sits between the 40m Moxon above and the 17/30m dual bander below. That leaves poor 10m as the last man standing and he's assigned the open spot on the 40m tower. So 20m gets it's own tower seperate from 40m and lives with the 15m stuff. If 20m and 40m were on the same tower, one would be a compromise from height at a minimum. Because 40m and 15m don't play well together, they must be on separate towers meaning 10m goes with one, and 20m with the other. Tower assignment depended on which combination yielded the least interference. All other antennas were put on at heights that were defined by what was available, rather than what would be optimal. The middle slots on the two towers are left for the unfortunates of the setup 10m and 6m.Ĥ0m and 20m are THE primary DX and contesting bands so the towers were literally built around getting the best possible result on those two bands. Lower: fixed-on-SA 5-element/24 foot yagi at 51' & 35', BIP stackedįixed-on-SA 10m 5-element/27' foot yagi at 35' ** Mid: fixed-on-EU 10m JK106 6-element/35 foot yagi at 114' Top: rotating 10m JK106 6-element/35 foot yagi at 133' 6-over-6 on 10m plus 6 elements fixed on SA
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |