Hi All,
Thanks again for the posts re stacking 15m 4el and 10m 4el yagis.
I think I may have a clew as to what is happening re the drop in absolute
gain of the 10m antenna. The general feeling is that a forward director on
the 15m acts like a poor reflector to the 10m yagi. This happens more when
the 15m is above the 10m, the season being that the 15m boom is likely to be
50% longer than the 10m and therefore "gets in the way"of the main lobe of
the 10m yagi.
With the 10m yagi uppermost it gets a clearer shot ahead and the 15m 4el
with its physically longer boom has its main lobe clearing more of the 10m
yagi.
So far the improvement by putting the 10m above the 15m is about 0.75db over
the other way around and they still need a separation of at least 16ft not
to get degradation. The answers to the problem are therefore 1. large
separation. 2. Have 15 above 10m. Turn the yagis at 90 deg to each other.
3.Try to optimise gain or F/B with closer separation. 4. Go Full size
duo/Tri bander. 5. Live with up to a loss in GAIN not F/B of at least 2db.
Any comments. And anyone capable of optimising two 4els for GAIN at say 10ft
spacing given there 7/8" equivalent dimensions?. 73 Clive GM3POI
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