In article , Richard Clark
writes:
On 10 Apr 2004 14:59:24 GMT, PAMNO (N2EY) wrote:
That's quite understandable, given that the original Lattin designed used
tubular Twin Lead and countd on a velocity factor of 0.8.
What sort of test gear and design methods did you folks use?
Hi Jim,
This hard to accept given the timelines offered by those who have
reported the references. For one, the antenna was invented in the
late 40's and patented 26 Dec. 1950, and reported in 1960. ALL such
dates precede the introduction of tubular Twin Lead in the mid 60s.
Hello again!
Direct quotes from the 1960 QST article:
"If open line with a velocity factor near unity is used for the stubs, the
over-all lenght for a two-band antenna would be nearly a full free-space
wavelength at the higher frequency and and the whole antenna would resonate at
something less than half that frequency. Very fortunately, the the velocity
factor of 300-ohm tubular Twin-Lead (0.8) gives such lenghts for the stubs that
that, in most cases, the adding the stub makes the antenna resonate at just
half the original frequency."
"Fig. 3 shows how tubular Twin-Lead can be used for the antenna itself as well
as the stubs and includes dimensions for 10- and 20-meter operation. The
foam-filled type of Twin-Lead is recommended to keep out moisture."
So it must have existed when W4JRW wrote the article, some time before the
December 1960 QST went to press.
In addition, my 1953-54 RESCO (Radio Electronic Service Company, once a great
source of all things radio and TV here in the Philly area) catalog lists
Amphenol "flat and tubular Twin Lead". The tubular stuff is number 14-271 and
was 5 cents a foot - less in quantities of 100, 500 or 1000 feet. And it wasn't
a new item.
All of this supports both your experiences and those of others. If the exact
characteristics of tubular Twin Lead are important to the design, it's no
wonder that the reported results cannot be obtained.
One more point. The SWR graphs shown for the 5 band version show quite narrow
SWR bandwidths. If anyone is interested I can report them in a future post.
73 de Jim, N2EY