More on Litz Wire

Elton & Nancy Sanders
Sat, 25 Apr 1998 16:16:43 -0400

 I think the tower guy said that the feed lines were attached to copper
strap that went 
from where the feed lines were attached to the tower to the top feeding the
3 panels of 
the antenna.

At 01:56 AM 4/24/98 -0400, Bob Bruhns wrote:
>The NSS antenna was reported to be a "modified Goliath" system
>copied from (gasp) a Russian system.  There were a few odd things
>about it...  For example, the brute-force parallel  splitting of
>the RF output to three feedlines of different lengths, fanning
>from the top of the Frankensteinian tuner building to the 300,
>600 and 900 foot levels of the 1200 foot tower, was strange.  It
>seems to me that at 21.4 KHz it would resemble an end loaded,
>crooked half-bowtie monopole leaning over toward the south. 
>Maybe I ought to model it on MiniNEC...
>  I think the use of so many large bundles of such finely divided
>Litz wire as feedline to a galvanized steel tower is
>questionable.  The magnetic properties of steel cause a severe
>skin effect, and the electrical resistance of steel and zinc are
>high compared to copper and silver...  Seems to me that if
>efficiency was that much of an issue, heavy copper lines should
>also have been run along each tower leg, and that the top hat,
>which was probably also galvanized steel, should have been
>heavily copper-clad.  But possibly the loss resistance was useful
>for bandwidth purposes, and simple galvanization was less
>expensive.  Could the total resistance budget of the design have
>been used up in the tower and tophat, requiring the use of a very
>low-loss feedline?  I wonder how this antenna's overall
>efficiency (840 000W in, 30 000W radiated) and bandwidth (very
>careful tuning required to accommodate 50 BPS, 50 Hz shift FSK)
>compared to the efficiencies and bandwidths of other VLF antenna
>systems around the world.
>  Bob Bruhns, WA3WDR
>  The transmit tuning arrangement was also strange, with so much
>back and forth interactive tuning going on.  But with 16% power
>loss, maybe it was better than a broadband iron-core transformer.
>Andre Kesteloot wrote:
>> One of my own  --possibly blasé--  theories is that, this 
>> being a huge Government contract, the fellow who wrote the 
>> original specs (against which the various manufacturers had to 
>> bid) did not know all about Litz wire, and decided that Litz
>> was better than no-Litz (based on the sound bureaucratic 
>> approach that "one never knows"), and that none of the bidders 
>> dared to question the Government document's wisdom. And 
>> anyway, it increased the cost of the contract...   ;-)
>> Also, the equipment, as I recall, was built circa 1937. hence 
>> the specs were probably written i 1935 or '36.  The quote I 
>> recently posted from the RCA book (and reprinted later in 
>> Langford-Smith) is dated 1941. Possibly they learned something 
>> between 1935 and 1941...
>> 73,
>> André N4ICK