[amsat-bb] Exciting Coax

[Alan]

No question, the original 9913 could be a water hose.  It  had an air gap
between the center conductor and the foam dielectric with a spiral winding
of Teflon (?) to keep the spacing constant.  A friend and operator of a
repeater went up to determine why the performance was deteriorating.  He
found water running out of the feedline into the utility building.  My first
satellite station, circa 1986, used 9913 to the preamps at the tower, and
then RG-213 (later LMR-400UF) to the antennas.  I put some additional
sealing at the preamps, and never had a problem with water.   Perhaps I was
lucky;  I certainly was not good.  :)

However, 9913 has evolved over the last 30 years in all versions.  After my
tower and antennas were destroyed, I rebuilt the system using LMR to the
preamps, and hardline for the 24 cm feed.   I had never been satisfied with
the actual flexibility of the 400UF.  9913F7 is the loss equivalent and far
more flexible.  It lacks the air gap of the original, so no water.  With
some trepidation, I ordered some for the "rotator loop."  After 5 years,
based on performance and loss measurements, they are as good as new. 

FWIW,

Alan
WA4SCA