[TowerTalk] Beverage Interaction?

[Michael Tope]

I did some topband operating in the CQ WW 160 contest this past weekend courtesy
of an invite from Paul, N6LL to his sight on Mt Wilson, Ca. The sight which overlooks the 
L.A. Basin, consists of several slopers hung off a 270'  tower and a number of beverages 
which were erected by one of Paul's colleagues who works with him at the site. Although 
the site is very quite relative to the buzz of the city, I am beginning to suspect that the beverages
could stand to be improved. 

I still don't have a complete picture of how and where all the beverages at the site are situated, 
but I was able to explore the site a little with Paul on Saturday afternoon at which time I was 
able to find and follow several of the beverage wires. Additionally, Paul and I were able to repair 
the northeast and east wires which previously hadn't been working.  Although it was a good feeling 
to have a couple more antennas to choose from, I found  strangely enough, that only three of the 
half dozen receive antennas at the site seemed to work effectively. On Friday night the beverage 
labelled NE/SW seemed to provide the best signal/noise for most of the signals I was trying to 
copy. Aside from the label on the switchbox, I have no clue as to how long this antenna is, how 
its fed or terminated, or even what direction it actually runs. Oddly enough it seemed to work 
equally well (or equally poorly perhaps) to both the east coast, the carribean, and JA. The beverage 
labelled NW did work better to the northwestern US and Canada and Alaska, but was less effective 
than the NE/SW antenna to JA. On Saturday night the North antenna seemed to outperform the 
NE/SW antenna to the east coast, but the NE/SW antenna still excelled toward JA. On Saturday night,
the trasmit antenna provided the best signal to noise while I was listening to YV5JDP. Needless to say,
I was a little perplexed and disapointed with the beverages. 

At any rate, either we were experiencing some very strange skew path propagation, or these beverages 
weren't really working properly. One thought that came to mind was the close proximity of the 1000'
TV trasmitting tower present at the site with its long conductive guys. In fact two of the beverages (the north 
and east I believe) are fed from the northwest guy pier of the tower (they share their ground connection
with the pier's ground). Does anyone have a good feel for how much interaction their would be between these
beverages and the tower guys? Or how far away they would need to be to achieve good performance (clean
pattern, good F/B). The other question I have is what effect will the irregular mountain terrain have on the 
beverage performance. Seems that this might cause the characteristic Z of the beverage to vary considerably
which might in turn make it hard to achieve a good F/B ratio (due to structural reflections). Anyone have any 
thoughts on this? 

This is really a great site, and if possible I would like to invest some time in improving these receive antennas 
(proper terminations and matching), but if the big tower guys can't be effectively decoupled, it might not be 
possible to ever get them to work really well. If this is the case, perhaps I might be better off to investigate 
alternative receive antennas (probe arrays, EWE's, etc). 

Thanks,

Mike, W4EF (opr W6UE/p Mt Wilson, Ca)



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