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Topband: 300 ohm

To: "topband@contesting.com" <topband@contesting.com>
Subject: Topband: 300 ohm
From: "Rodman, David" <rodman@buffalo.edu>
Date: Sat, 29 Feb 2020 12:37:50 +0000
List-post: <mailto:topband@contesting.com>
Joe, I have had some trial with this bidirectional setup many years ago.  
Although having a NE and SW listening antenna is quite desirable for stations 
in the NE USA, I have experienced repetitive mechanical failure with this 
system.  In the wind, no matter what wire diameter twin lead selected, wind 
tends to create constant twisting of the antenna.  Perhaps, I chose distances 
between supports that was too long?  However, one can see the antenna 
constantly twisting and moving in any appreciable wind.  I did not get more 
than 8-9 months from each attempt.  I tried it for 2-3 years and gave up.  
Perhaps if supports were shortened to every 20 ft, this could be better 
managed?  Once the twinlead breaks, it may be hard to find the repair spot by 
observation as the antenna is so long.  For a decent length beverage, say 800 
ft, this is lots of supports and can be lots of maintenance.  For me, the 
failures were always in the winter when it was difficult to repair and when you 
needed the ante
 nna most.  I also tried the coaxial cable RG6 bidirectional and was not overly 
impressed with that either.  For bidirectionality, one needed two feed lines 
and lots of mechanical support to the antenna in order to keep the connectors 
from pulling off.   It worked for 2 years without repair.  I abandoned that 
antenna and used the two transmission lines for phased SAL-30 arrays which have 
been much more mechanically stable (and offer multiple directions) at my 
location.   Those tend to stay up for years without mechanical failure or 
needing any maintenance, although they may not play as well as a long beverage. 
 I hope this helps you.




---
David J Rodman MD
Assistant Clinical Professor
Department of Ophthalmology
SUNY/Buffalo

Office 716-857-8654
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