On 2/10/2013 7:34 AM, Channel Jumper wrote:

snip loads of braggadocio unrelated to what I said.


You still haven't addressed your claim about 70cm.

tom
K0TAR

If you are building a repeater - you use a Station Master - commercial grade antenna, not a cheap vertical like the Diamond X 50.
http://www.wadsworthsales.com/Pages/celwave.aspx

On Mon, 11 Feb 2013 14:15:33 +0000, Channel Jumper
wrote:

If you are building a repeater - you use a Station Master - commercial
grade antenna, not a cheap vertical like the Diamond X 50.
http://www.wadsworthsales.com/Pages/celwave.aspx

Thanks for the sage advice. There were problems with the installation
which prevented the use of heavy antennas with a high wind load. We
were offered a free 20 year old super station monster antenna but
turned it down due to the size (22ft). The Diamond F22a on the VHF
repeater has been quite adequate. While I'm sure the station monster
antenna would work well for those in the distance, we are more
interested in local communications. VHF and UHF coverage:
http://802.11junk.com/jeffl/coverage/k6bj/146mhz/k6bj-146-3d.jpg
http://802.11junk.com/jeffl/coverage/k6bj/440mhz/k6bj-440-3d.jpg

If you look at the photo of the (former) antenna tower[1],
http://www.LearnByDestroying.com/k6bj/K6BJ%20Repeater/slides/Antennas.html
you'll notice that the Diamond X50 was located so that it would not be
inside the antenna pattern of the upper Diamond F22a. The VHF antenna
was also limited in height by the proximity of the county and Verizon
radio vault and tower. This arrangement limited the length of the UHF
antenna to approximately that of an X50. I could have used a longer
UHF antenna, but I wanted altitude to clear some obstructions, rather
than gain. Since the UHF antenna was side mounted, the grounded arm
under the antenna tends to create some uptilt in the antenna pattern.
With a fairly low gain antenna, such as the X50, the effect is
minimal. Were it a higher gain antenna, which would have a narrower
beamwidth, the effect would be sufficient to dramatically reduce
signal strengths below the horizon. I've had to deal with this on
mountain tops quite often, and have sometimes resorted to mounting the
antenna upside-down in order to take advantage of the effect.

For the curious, the black yagi is the 420MHz link to KI6EH. The
coaxial antenna is a spare antenna for plugging in test equipment and
HT's when working on the machines.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Sat, 9 Feb 2013 14:51:37 +0000, Channel Jumper
wrote:

I was under the impression that this person was a HAM and wanted to talk
as well as listen.
Then we got into a discussion about scanners.
Now I am confused.

It may help to understand this is TUUK we are talking about. At least this time
it isn't about saunas.

On 2/10/2013 7:34 AM, Channel Jumper wrote:
tom;801584 Wrote:
snip


Your problem is - you want to use a choke with a off center fed
antenna.
Either to reduce the RF going into the shack or to reduce noise.
If you really want to work DX, you don't want to use a choke.
It would be better to use a BALUN / transformer before the coax enters
the shack then to use a choke.


Please explain the difference between a choke and a balun in this situation.

tom
K0TAR

A balun is an electrical device that converts between a balanced signal (two signals working against each other where ground is irrelevant) and an unbalanced signal (a single signal working against ground or pseudo-ground). A balun can take many forms and may include devices that also transform impedances but need not do so. Transformer baluns can also be used to connect lines of differing impedance. The origin of the word balun is balance + unbalance.

Generally a balun consists of two wires (primary and secondary) and a toroid co it converts the electrical energy of the primary wire into a magnetic field. Depending on how the secondary wire is done the magnetic field is converted back to a electric field.

A Choke - is simply a piece of coax or wire which is wound at the mininum bend radius of the coax. Several turns of coax makes a simple choke.
You have to be very careful not to open up the shield by winding it too tightly.

Baluns can take many forms and their presence is not always obvious. Sometimes, in the case of transformer baluns, they use magnetic coupling but need not do so. COMMON MODE CHOKES ARE ALSO USED AS BALUNS! and work by eliminating, rather than ignoring, common mode signals.

The key word there is - used as baluns.
If it was a Balun - they would call it a Balun

Coax works on the principal of a Faraday Cage.

Maybe you would like to explain for the people on this forum what a Faraday Cage is?

On Tue, 12 Feb 2013 13:36:32 +0000, Channel Jumper
wrote:

A balun is an electrical device that converts between a balanced signal
(two signals working against each other where ground is irrelevant) and
an unbalanced signal (a single signal working against ground or
(...)

http://en.wikipedia.org/wiki/Balun
Please provide a citation when plagerizing.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On 2/12/2013 1:08 PM, Jeff Liebermann wrote:
On Tue, 12 Feb 2013 13:36:32 +0000, Channel Jumper
wrote:

A balun is an electrical device that converts between a balanced signal
(two signals working against each other where ground is irrelevant) and
an unbalanced signal (a single signal working against ground or
(...)

http://en.wikipedia.org/wiki/Balun
Please provide a citation when plagerizing.



He also didn't answer the question I asked, which would have been a much
much shorter answer.

tom
K0TAR

On Sunday, February 10, 2013 9:14:32 AM UTC-6, Ralph Mowery wrote:

When the lower radials were added the Ringo was suspose to work much beter.

By that time, the Ringo had fallen out of favor around here so I do not know

how well they worked. Main thing is that adding the radials defeated the

purpose of the antenna, which was to eliminate the radials.

Well maybe as far as the standard Ringo, which is a half wave.
But the Ringo Ranger was a dual 5/8 collinear. Seems to me that
design was used more to get more gain vs the shorter antennas,
rather than trying to avoid radials.

When it first came out, decoupling from the feed line was not
given too much consideration, at least for lower cost amateur
antennas.. And most that used it, thought it did OK. Likely
because they had nothing better to compare to, or the feed line
lengths, mounting, did not skew that pattern as bad in some
cases, as it did others. The amount of skewing will vary some
in each installation. It was pretty bad in my case.

But then the Isopole came out.. And the roof caved in. lol..
The Isopole was so much better performing than the regular
Ringo Ranger, that Cushcraft had no choice but to add some
method of decoupling to their antenna, if they wanted to
continue to sell many of them.
So they added the lower 50 inches of coax, and a set of
1/4 wave radials at the bottom of that length of coax, which
was grounded at that point, to the mast supporting the antenna.

The decoupling section helped greatly, and saved Cushcraft
from certain VHF vertical sales ruination.
It was still slightly inferior to the method the Isopole
used, but close enough to keep them in the game.
Many preferred the RR2 because it was a bit less ugly than
the Isopole. And maybe a bit cheaper, but I can't remember
how they were priced at the time.

The only band I ever used a 1/2 wave Ringo, was on 10m.
And I ended up adding a Cushcraft type decoupling section
to it. It worked very well. But the 5/8 antennas I used
were better still.. But I didn't use 1/4 wave radials like
most do with 5/8 ground planes. At that time, I used 3/4
wave radials, and the antenna doubled as an appx 1/4 GP
on 30m.

On Sunday, February 10, 2013 11:47:11 AM UTC-6, Jeff Liebermann wrote:

Did you perhaps mount the antenna over a metal roof or on a tower side

arm? Without the decoupling section, the ground under the antenna

will cause pattern uptilt.

Nope.. It was a mounted on a metal mast that was on my
non conducting roof. Probably about 30 feet off the ground or so.
I think most of the skewing in my case was due to feed line
radiation, more than effects from the ground.




Thanks. That explains a few things. Incidentally, my rule "The

uglier the antenna, the better it works" was originally based on the

isopole antenna.

They were kinda ugly, but they sure worked well.
And some other companies have used that type of decoupling,
but most were more like cylinders, instead of funnel like cones.
Those were fairly common on some of the commercial verticals
used for public service, etc..
Also, most of those were 1/2 waves. IE: 1/4 wave upper radiator,
1/4 wave lower cylinder to complete the antenna, and then a lower
1/4 wave cylinder below that one for decoupling.
I think "Dodge" was one company that made those if I remember right.
The upper part of each cylinder was closed, and the bottom open.