On Thu, 26 Aug 2010 13:38:22 +0300, KBa wrote:

On 16.06.2010 20:24, R.Scott wrote:
I see all kinds of crazy matching sections in posts about 6 meter
beams. How about direct connect.

Direct connect is used in a number of tribanders, but AFAIK it's not
used in larger than 3L beams due to the low impedance. It can also
distort the pattern, but with a 3L I doubt you'd notice. Just put 3
or 4 2.4", #32 mix toroids with 4 or 5 turns of feed line through
them. It'll give the isolation and balance needed as long as the
impedance at the feed point is correct.

I have an A4S that has major issues
in the traps and I cant find the problem (IE I opened them and cant

Problems in traps can be difficult to find. I had an ATB34 that
appeared to have a trap problem but it turned out to be the feed line
to driven element connection. They use 1/4-20 SS bolts through the
insulators. The bolts simply press on the element inside the
insulator. One was making a poor connection even though it felt
tight. Taking it apart and cleaning the ends of the bolts and
polishing the ends of the driven element where the bolts rested fixed
it even though I could see nothing wrong at the time.

find anything) SOOO I have a new A4S coming.

Has anyone taken an old 3 elem tribander and converted it to 6 meter
monobander using the direct connect.

Any Issues.

Spacing is generally far more than a little too wide.


Would a 4 elem be better since its a long boom ?

Long boom? Tribanders come in a wide variety of lengths. If it's the
typical 19 or 20', you are probably looking at around 5 elements.

Use one of the modeling programs, or get some to run it for you.


I'm pretty sure I know the answers. Just want to confirm and see if
there is any reason not to direct connect rather than through a
hairpin or a gamma match.

There's really nothing particularly complicated about a hairpin or
gamma match. There are probably lots of designs that could be copied.



Scotty W7PSK

Hi

Probably my comments are bit late... but OWA yagi's use direct feed to
driven element with a ferrite balun near the feedpoint.
OWA's give good impedance match in large bandwidth, this is based on
nearer driven element-first director spacing.
Otherwise gain, F/B etc. are very good.
I have constructed one 6m OWA yagi, with 20 ft boom as it was available,
using 7 elements in it, and finally with good match below

That's enough elements for a 30 foot boom.

S 1.2 between 50...51 MHz.
Nothing critical in it, element dimensions were taken from NW3Z & WA3FET
article in OWA yagis, their 21MHz desing was re-scaled to 50MHz.
At least waterproofing is less critical in direct feed.

Water proofing the coax is very important, particularly when you get
to 50 MHz.

73

Roger (K8RI)


73's Kari