On Jun 20, 10:03*am, John Ferrell wrote:
On Sun, 20 Jun 2010 03:27:52 -0700 (PDT), K1TTT
wrote:





On Jun 16, 5:24 pm, "R.Scott" wrote:
I see all kinds of crazy matching sections in posts about 6 meter
beams. How about direct connect. I have an A4S that has major issues
in the traps and I cant find the problem (IE I opened them and cant
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.

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

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.

Scotty W7PSK

There are at least 3 reasons to use some kind of a matching network.
1. impedance transformation - usually the feedpoint impedance of a
simple dipole in a yagi is not near 50 ohms so the matching system
gives you an easy way to adjust that.
2. it is often easier to build an aluminum element without a center
insulator and feed it with something like a gamma or T match.
3. to keep current off the feedline shield you need to go from the
unbalanced coax to a balanced dipole feedpoint. *gamma matches and
others do that transformation for you.

I am in agreement with all your points. [Not that I am any kind of
authority!]

Many years back I purchased and installed a Cushcraft A3S tri band
beam with the 40 Meter option. The decision was based on past
experience with Cushcraft products.

When I assembled it I was disappointed to find it did not have a gamma
match! Instead it got by with a direct connection to the driven
element with the 50 ohm line. Then it used a jury rig device called a
"choke balun" to keep the RF where it ought to be... It reminded me of
the Gotham Vertical (Google it!) that so many of us fell for way back
when. I assembled and installed it according to the instructions any
way. Much to my surprise, it worked great! I have been very happy with
it.

That led to my taking the ARRL Antenna course and buying the EZNEC
program. *

Some things I model I can make work and some I cannot.
Some things work I cannot model.
I have concluded that direct connection and gamma matches both work
well.

My cumulative experience is that it is difficult to beat the
commercial products at their game.

OTH, the study and construction of antennas has become one of my
favorite recreational pastimes!

John Ferrell W8CCW- Hide quoted text -

- Show quoted text -

A gamma rod is the easiest thing in the world to build...people who
are scared of 'em just don't understand 'em.

On Jun 19, 7:28*pm, tom wrote:
On 6/19/2010 8:33 PM, tom wrote:



I have plans for a very good 6 element beam which is 15.53 feet from
reflector to D4. I could scale it to the element taper you have if needed.

It will not be a direct connect however, as those are almost never
optimal designs for gain, F/B or pattern. They are optimized to be 50
ohms with the rest subservient to that. Most of the designs I have would
be around 22 ohms so this one is probably in that area. A gamma match is
easy to make.

tom
K0TAR

Sorry, I should have looked before leaping, it's 5 elements on 15.5 feet.

tom
K0TAR

Id be interested in the plans.
Hard part is making the strap, Ive no shop tools/materials handy to do
it easy. Ive the tubing and
the RG8 .

Scotty W7PSK.

On 6/21/2010 12:08 PM, R.Scott wrote:

Sorry, I should have looked before leaping, it's 5 elements on 15.5 feet.

tom
K0TAR

Id be interested in the plans.
Hard part is making the strap, Ive no shop tools/materials handy to do
it easy. Ive the tubing and
the RG8 .

Scotty W7PSK.

Send me an email at . It will be valid until
tomorrow morning.

tom
K0TAR

On Jun 21, 5:19*pm, tom wrote:
On 6/21/2010 12:08 PM, R.Scott wrote:



Sorry, I should have looked before leaping, it's 5 elements on 15.5 feet.

tom
K0TAR

Id be interested in the plans.
Hard part is making the strap, Ive no shop tools/materials handy to do
it easy. *Ive the tubing and
the RG8 .

Scotty W7PSK.

Send me an email at . *It will be valid until
tomorrow morning.

tom
K0TAR

Guess I was too slow.

On 6/22/2010 10:03 AM, R.Scott wrote:
On Jun 21, 5:19 pm, wrote:
On 6/21/2010 12:08 PM, R.Scott wrote:



Sorry, I should have looked before leaping, it's 5 elements on 15.5 feet.

tom
K0TAR

Id be interested in the plans.
Hard part is making the strap, Ive no shop tools/materials handy to do
it easy. Ive the tubing and
the RG8 .

Scotty W7PSK.

Send me an email at . It will be valid until
tomorrow morning.

tom
K0TAR

Guess I was too slow.

Actually it's still there. I forgot to disable it. I'll leave it up
for a day or so.

tom
K0TAR

On Jun 22, 5:14*pm, tom wrote:
On 6/22/2010 10:03 AM, R.Scott wrote:



On Jun 21, 5:19 pm, *wrote:
On 6/21/2010 12:08 PM, R.Scott wrote:

Sorry, I should have looked before leaping, it's 5 elements on 15.5 feet.

tom
K0TAR

Id be interested in the plans.
Hard part is making the strap, Ive no shop tools/materials handy to do
it easy. *Ive the tubing and
the RG8 .

Scotty W7PSK.

Send me an email at . *It will be valid until
tomorrow morning.

tom
K0TAR

Guess I was too slow.

Actually it's still there. *I forgot to disable it. *I'll leave it up
for a day or so.

tom
K0TAR


Never did get it to work. maybe you could email me at

W 7 P S K A T W 7 P S K Dot N E T

with what ever addy you need with the information. Im going to be
building it soon.

What did you use for shorting bar ? Thats the hardest for me with no
shop tools to speak of and
limited supply of metals around here.

On Thu, 17 Jun 2010 09:05:11 -0700 (PDT), "R.Scott"
wrote:

The problem with holding a few parameters constant is that you have to
accept whatever gain, patterns and such that come with the deal.

Well I did find plans for a 6 elem on a 17.5ft boom. The boom on the
old A4S is 18Ft. If I use the parts off my old A3
and my A4 I should be able to come up with all the parts for the 6
element. And its direct connect.
I'm a bit late to the party, but...

To me that seems like a lot of elements on a short boom, (I use 7L on
a 29' boom) but properly adjusted they can give more band width rather
than gain as gain is more a function of boom length. Also, how do they
get 50 ohms at the feed point of a dipole driven element in a 6L
Yagi?

Direct connect can work, but how well is another question. It may
give a good match, it may transfer the power efficiently, but again
the question is, how well does it work.

Jim Brown's (K9YC), A Ham's Guide to RFI, Ferrites, Baluns, and Audio
Interfacing ...
www.audiosystemsgroup.com/RFI-Ham.pdf is well worth reading. when it
comes to using toroids and the old "coil of coax" as a rather
inefficient current balun (which I used for years).

I worked a station down in Central America (on six) who had his new
rig on the bench testing it with a short piece of wire stuck in the
coax connector...I'm in Michigan. He could have said, that short piece
of wire on the bench was a good antenna...at that moment.

But given you get a good match, the pattern is still going to be
distorted. You can take 4 2.4" OD toroid cores with 4 or 5 turns of
coax through them to make a very good current balun (bout 5,000 ohms
isolation) and center feed a split driven element, then the antenna
is not really "direct connect" as the "matching device" is between the
feed line and antenna even though it can be the end 5 to 8' of coax
wound on the cores.

BTW, run the coax through the toroids before installing the connector



I wonder how far above the A4 the 6 meter needs to be. I only have a
5ft mast.

Should be and what you can get away with are often quite different. A
friend has a bunch of antennas on one tower that are all way closer
than they *should* be, but he gets acceptable performance, at least to
him and that's all that counts. Having said that, 5' would be
considered very close and 10' would be much better. OTOH you will
probably be satisfied with the performance over a simple antenna.
All antennas are a series of compromises as are installations. IOW we
use what we have and hope for the best. You only have a 5' mast, so I
assume that a taller mast is out of the question which makes "how far
apart do they need to be" a moot question. Then the real question is:
Will they work with only 5' of spacing? The answer is ... Probably and
they probably will work fairly well.

One element to keep in mind (no pun intended) is with the antennas
only 5' apart they may tend to detune one or both a bit and also lower
the feed point impedance. But it's what you have and you won't know
until you try.

Getting things to work is half the fun, at least it is to me...as long
as getting the project to work does not run into frustration. :-))

73 & Good Luck.

Roger (K8RI)

my DX800 rotor should handle it.

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

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

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.


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
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.

73's Kari

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