Wednesday, July 17, 2013

"Re-Stringing" the delta loop


My 10 and 15M two-element delta loop uses wire for the top elements.  Unfortunately, the 15M wire element failed at the connector this spring.

Then this loose element cleverly wrapped itself around the 10M reflector (and later the driven element), rendering the entire antenna almost useless.  Sigh.


After some thought, I decided that the soldered connection was an error on my part and elected to replace all of the wire elements with much stronger stranded wire attached with a mechanical - unsoldered - connection.  Taking the advice of those who know better, I selected The Wireman #531: insulated 13 AWG, 19 strand 40% Cu-clad steel 400# breaking strength (No affiliation with The Wireman, just a satisfied customer, etc.) 

Fortunately I had carefully measured the lengths of the elements before the original went up in 2010.  Here's my assembly technique for the wire terminations:

 


Note that I am depending on the clamping force of the stainless steel hardware at the ends of the tubular elements (not shown) with the crimp of the ring terminal for additional security.

I made up all four wire elements and then again contacted AB5K, Terry, who originally stacked the tower and mounted my antenna:
 



This time the antenna came down smoothly (note the reflector wire tangled around several elements):





It took about a half-hour to install the new wire elements and the antenna went back up much easier than in 2010.  It may not be obvious, but delta loops of this design are very difficult to handle as the center of gravity is nowhere near any metal.  This antenna was difficult to handle even on the ground - and AB5K and K9MBB are credited with a very clever way of stabilizing the antenna for re-mounting.  The second image shows a better view of the counterweight they devised (AB5K on the tower): 












Elapsed time:  ~3.5 hours.  Temperature 104F.   Antenna performance:  good as new.  Thank you AB5K and K9MBB.

Now for some sunspots...