Quick Disconnect 450/50 ohm?
N Spokes
the active side to the balun. The "off" position goes to the ground for
lightning-mandated quick disconnects. (I operate the switch with an 18" long
2" dia. PVC pipe that sticks out inside the shack to give me a little
distance, electrically, from the antenna in the event of impending
lightning). The ladder line is bypassed by a couple of spark plugs that are
mounted in a grounded metal (electric junction) box. The whole is contained
in a wooden box that sits in a 2nd story window (and collects wasps which
can be more problem than the lightning). I've taken quite a few lightning
hits in the immediate area and haven't had equipment problems for a while
(fingers crossed) - early and complete equipment disconnection is the rule.
I could probably use gas discharge coax devices too in case I'm too late for
the disconnection.
Why are you using parallel shielded coax? Some kind of transformer? Might
be a good idea to use a current balun with the center grounded to give a
discharge path to ground for static - that is before you ground everything
for the storm or for use in high winds that blow staticky dust or even rain
that interferes with reception (interesting to get a reality check on that
idea from the gurus).
Neil, AB4YK.
--
Terry Crissman wrote in message ...
>Does anyone have a suggestion on how to make a quick disconnect (for
outside
>the shack) where ladder line and shielded parallel coax cable meet?
>
>Thanks
>
>Terry AC5AN
>
>
Gray Frierson Haertig
W6RCecilA wrote:
>
> Terry Crissman wrote:
> > Does anyone have a suggestion on how to make a quick disconnect (for outside
> > the shack) where ladder line and shielded parallel coax cable meet?
>
> I use Banana Plugs/Sockets and just clean them every six months or so.
> --
> 73, Cecil, W6RCA http://www.bigfoot.com/~w6rca
Or buy gold plated bandana plugs/jacks and eliminate the cleaning. They
aren't all that expensive.
Gray
--
Telecommunications Engineering
Gray Frierson Haertig & Assoc.
820 North River Street, Suite 100
Portland, Oregon 97227
503-282-2989
503-282-3181 FAX
g...@haertig.com
Terry Crissman
the shack) where ladder line and shielded parallel coax cable meet?
Thanks
Terry AC5AN
W6RCecilA
> Does anyone have a suggestion on how to make a quick disconnect (for outside
> the shack) where ladder line and shielded parallel coax cable meet?
I use Banana Plugs/Sockets and just clean them every six months or so.
Dan Richardson
wrote:
>Terry Crissman wrote:
>> Does anyone have a suggestion on how to make a quick disconnect (for outside
>> the shack) where ladder line and shielded parallel coax cable meet?
>
>I use Banana Plugs/Sockets and just clean them every six months or so.
Yep, I use them too, however, I have found them to automatically
disconnect when the wind blows... That alright though, as where there
is wind there *may be* lightening.
Danny, K6MHE
W6RCecilA
Yep, around here in East Texas whenever the winds blows hard enough
to disconnect the banana plugs, there's usually lightning and they
should be disconnected anyway.
Terry Crissman
You asked...why am I using shielded parallel coax? I'm feeding my dipole
with ladder line and I only have one place in the attic/wall to run the
line...I already have several other coax coming down the same wall...the
other cables interfere with the ladder line...so running the shielded
parallel coax to just outside the shack seems to be a solution...thanks
Terry
N Spokes wrote in message <7rchoc$2e5$1...@winter.news.rcn.net>...
>>Does anyone have a suggestion on how to make a quick disconnect (for
>outside
>>the shack) where ladder line and shielded parallel coax cable meet?
>>
>>Thanks
>>
>>Terry AC5AN
>>
>>
>
>
Terry Crissman
I'm thinking of using RG8X for the shielded parallel coax....the run will be
about 30 ft and I'll run a max of 1000 watts at times....Do you see any
problem in using this smaller coax?
Terry
W6RCecilA wrote in message <37D9AE9B...@IEEE.org>...
>Terry Crissman wrote:
>> Does anyone have a suggestion on how to make a quick disconnect (for
outside
>> the shack) where ladder line and shielded parallel coax cable meet?
>
>I use Banana Plugs/Sockets and just clean them every six months or so.
R. L. Measures
<tcri...@simplynet.net> wrote:
> Does anyone have a suggestion on how to make a quick disconnect (for outside
> the shack) where ladder line and shielded parallel coax cable meet?
>
The double banana jack works well. When lightning approaches you toss it.
--
- Rich... 805.386.3734. www.vcnet.com/measures, remove plus from adr.
W6RCecilA
> I'm thinking of using RG8X for the shielded parallel coax....the run will be
> about 30 ft and I'll run a max of 1000 watts at times....Do you see any
> problem in using this smaller coax?
You will probably smoke your RG8X. According to the Wirebook III, RG8X
has a maximum voltage limit of 300 volts. With no reflections at 1000
watts, the voltage is 224v. With reflections, it can be *much* higher
than that. Forward power can easily be many multiples of your 1000 watts
of generated power. RG8X is a pretty bad choice for this application.
In comparison, RG8 or RG213 has a voltage limit of 3700 volts.
ARDUJENSKI
wire and a PL-259 connected to the coax. The WIREMAN has a QUICK DISCONNECT for
these at about $2. Alternatively, you can cut about a 1" piece of copper tubing
that just slips over the PL-259 plug end. Use a hacksaw blade to slot the
tubing 3/4 of the way solder it to the base of the plug with the slots towards
the end of the plug.
In either case you would want it in a location that is protected from direct
impingement of rain. You can use an ammo box mounted on end and so the covers
hinge is on the top towards the front. The ammo box is mounted to a short wood
post.
The connector is protected and also just pulls apart for quick disconnect.
Alan KB7MBI
Bob Miller
>Does anyone have a suggestion on how to make a quick disconnect (for outside
>the shack) where ladder line and shielded parallel coax cable meet?
>
>Thanks
>
>Terry AC5AN
>
You might also look at the outdoor Remote Balun that Radio Works sells
at http://www.radioworks.com
The balun receives ladder line at one end, and coaxal cable at the
other end. So it'd just be a matter of unscrewing your coax to
disconnect.
Bob
n5ahy
R. L. Measures
<Cecil....@IEEE.org> wrote:
Good point. I would be tempted to use RG11 coax.
Peter O. Brackett
Antenna Folks:
FWIW I also use the double bannana plugs and sockets for open wire quick
disconnect. Was it General Radio who invented those things? Some of you
old timers might know. They stand off large voltages and offer the quick
wind actuated disconnect feature admired by others on this thread.
Get em from Radio Shack cheap.
For the transitions from coax to open wire I often use either an actual
center feed balun assembly [W2DU or what ever . . ] or one that I have
disassembled and removed the balun torroid/s inside to use for the purpose.
Regards,
Peter AB4BC.
Bob Miller <bmi...@neosoft.com> wrote in message
news:D546C00A1559822A.AE623EF1...@lp.airnews.net...
Robert Lay (W9DMK)
<tcri...@simplynet.net> wrote:
>Does anyone have a suggestion on how to make a quick disconnect (for outside
>the shack) where ladder line and shielded parallel coax cable meet?
Having read all the other advice, there's little to be added other
than the Radio Shack Part No. for the particular type of banana plug
that I use. #274-718 at $3.49 each, which is rather dear.
I say that I use them, but not for the application you are talking
about. I only use them for patching segments of ladder line to one
another in the construction of matching sections and that sort of
thing.
For the application that you are describing, I do not use connectors
at all. The ladder line (450 ohm window line) and the home made open
wire line that I use is terminated or transitioned to RG-8 coax just
before it comes into the shack. At that point the shields of the coax
are earthed to a network of three ground rods all in a small arc of
about 4 ft radius. The coax only has a 6 ft run to the tuner on the
other side of the wall. There are 4 such antenna feedlines all coming
through a PVC pipe at that point.
Have you considered the option to bring the ladder line all the way
down to near earth and keep the coax runs shorter? Or does that make
sense for your shack?
From the standpoint of lightning protection, it seems to make sense to
get the conductors as close to an earth ground as possible BEFORE
coming into the house. I suppose that if you are 100% sure of getting
them DISCONNECTED when lightning is possible, then it shouldn't make
much difference.
73 de Bob, W9DMK, King George, VA
Change "nobody" to "w9dmk" for e-mail
http://www.qsl.net/w9dmk
http://www.fortunecity.com/meltingpot/albania/784
Bob Miller
coax without anything in between other than the plug hardware? Isn't
some sort of a matching device, or isolating device, a balun or
whatever, needed?
Bob
n5ahy
W6RCecilA
> Question... are you simply hooking the ladder line directly to the
> coax without anything in between other than the plug hardware? Isn't
> some sort of a matching device, or isolating device, a balun or
> whatever, needed?
Note one always has that same connection problem with a W2DU balun.
Bob Miller
>Bob Miller wrote:
>> Question... are you simply hooking the ladder line directly to the
>> coax without anything in between other than the plug hardware? Isn't
>> some sort of a matching device, or isolating device, a balun or
>> whatever, needed?
>
>Note one always has that same connection problem with a W2DU balun.
Soooo, okay, it's alright to connect ladder line to coax?
(Please excuse my ignorance -- I'm a relative neophyte in putting
together antennas.)
Bob
Dan Richardson
wrote:
[snip]
>
>Soooo, okay, it's alright to connect ladder line to coax?
>
>(Please excuse my ignorance -- I'm a relative neophyte in putting
>together antennas.)
>
>Bob
Bob,
What can be done is to connect the ladder line to a parallel run of
coax for coming into the shack. The line is connected to center
conductors of the coax, the coax shields are bonded together at both
ends. The bonded shields on the tuner's side is grounded at that
point.
This is an effective way of bringing balanced line into the shack and
close to conductive surfaces.... It works well.
73
Danny, K6MHE
Bob Miller
>On Sun, 12 Sep 1999 14:55:18 -0500, Bob Miller <bmi...@neosoft.com>
>wrote:
>
>[snip]
>>
>>Soooo, okay, it's alright to connect ladder line to coax?
>>
>>(Please excuse my ignorance -- I'm a relative neophyte in putting
>>together antennas.)
>>
>>Bob
>
>Bob,
>
>What can be done is to connect the ladder line to a parallel run of
>coax for coming into the shack. The line is connected to center
>conductors of the coax, the coax shields are bonded together at both
>ends. The bonded shields on the tuner's side is grounded at that
>point.
And then the two coax center conductors attach to the set of balanced
terminals on the tuner?
Thanks,
Bob
Robert Lay (W9DMK)
wrote:
>Question... are you simply hooking the ladder line directly to the
>coax without anything in between other than the plug hardware? Isn't
>some sort of a matching device, or isolating device, a balun or
>whatever, needed?
Dear Bob,
I guess you already have your answer from the posts that I see there
already, but here are some more notes that might help.
First, I don't use a connector at all. the connections from the ladder
line to the inner conductors of the coax lines are soldered, forever
and ever, amen. However, I covered the exposed metal with glue gun
glue, just as a protectant. We'll see if that works - Hi!
The matching device that you are concerned about doesn't apply,
because,
1) I don't care what the impedance is at the point where I make the
transistion. It's academic - and, in general, it is not 450 ohms. It
might be anything from near zero to near infinity.
2) I also don't care what the characteristic impedance of the twin
coax lines are, because at 20 M though 80 M the length of the coax
lines (6 feet) is electrically a very small fraction of a wavelength,
so it produces a transformation from whatever is seen at the ladder
line to something a bit different at the other end of the coax lines.
Again, it's academic - and it will be somewhere from near zero to near
infinity.
All of these uncertainties get resolved at the tuner. The tuner
happens to have a 4:1 balun - not that 4:1 is of any great
significance, it could be 1:4 just as well. The problem is that no
matter what the ratio of the balun and no matter what impedance the
line looks like at this point. it is not likely to be any kind of a
match. If the balun were to be looking into about 200 ohms, that would
be just dumb luck, but it would make the balun work very well. In
general, we just take what we get and live with it. If the T match
tuner can deal successfully with what it is given, then everything is
fine. Otherwise you get some difficulties in tuning. Like you can't
find the null - or you find the null, but it requires a great deal of
sliding around between the inductance and one of the capacitors. And,
worst of all, the controls seem to be very inter-dependant. That
suggests that the impedance is way out of the range that the tuner can
deal with. There are a million solutions to this problem. All of which
require measurements and a great deal of patience and understanding of
matching networks, etc. If you have the time and the instruments and
the curiousity, then you can actually design a proper transfomation
network out of pieces of transmission line of various characteristic
impedances, hung as shorted or open stubs, or as series matching
sections. All of which is great fun and very educational.
The usual way out of the dilemma is to just find a place to hang an
eigth wavelength of extra ladder line in the system and hope that will
make everything tune better. I keep several pieces of line, from 1' to
8' in length with connectors at each end, hanging in the barn for just
this purpose. And I hope they stay there.
Bob Miller
heard of paralleling two lines of coax to bring a ladder line feed
into the shack...
Bob
n5ahy
nob...@crosslink.net (Robert Lay (W9DMK)) wrote:
Richard Clark
wrote:
Hi Bob,
All in all, a very good piece of practical advice. You are right, there are a
number of academic disturbances, and you are equally right that for practical
considerations, they offer little concern.
Your discussion of the difficult tune, I think (uh oh, getting akademic) is more
evidence of the operator becoming part of the measurement. By this, I mean that
as you adjust the tuner, you are also changing the problem. Your point of it
being near the ragged edge of a match is probably justified. Measuring a high
SWR on twin line using voltage probes will encounter a phenomenon whereby the
operator measuring the SWR will observe the nulls shifting away from the probes
as they are moved to find it.
Some think that passing the code test is a right of passage. I think the
standard should be the nulling of a GR1606 down 100 dB. ;-)
73's
Richard Clark, KB7QHC
Dan Richardson
wrote:
[snip]
>
>And then the two coax center conductors attach to the set of balanced
>terminals on the tuner?
>
>Thanks,
>
>Bob
>
>
Yes, that is what I am doing and it works fine for me.... My coax
length is quite short however only about three feet, but it could be
longer.
The reason I choose that method is that one the insolation in my wall
has a metal foil covering and the transmission line is going through
he wall and two, I use a balanced tuner and therefore would not be
using an external balun which could be located out side the shack.
73
Danny
Dan Richardson
>
>First, I don't use a connector at all. the connections from the ladder
>line to the inner conductors of the coax lines are soldered, forever
>and ever, amen. However, I covered the exposed metal with glue gun
>glue, just as a protectant. We'll see if that works - Hi!
>73 de Bob, W9DMK
Bob,
Have you tried liquid electrical tape mfg by Starbrite in Florida? I
have been using for the past several years and it works great.....
Learn about it from some local fishermen who use it for covering
electrical connections on their boats....
Anyway great stuff.... I've had no trouble finding in hardware stores.
73
Danny, K6MHE
Dennis C. O'Connor
single connectors, not the molded shell style...
Denny
Terry Crissman wrote:
> Does anyone have a suggestion on how to make a quick disconnect (for outside
> the shack) where ladder line and shielded parallel coax cable meet?
>
> Thanks
>
> Terry AC5AN
Robert Lay (W9DMK)
wrote:
Dear Danny,
>Have you tried liquid electrical tape mfg by Starbrite in Florida? I
>have been using for the past several years and it works great.....
No - never heard of it, but I will check it out.
I'm one of those people who just looks around the junkbox until I find
something that will do the job quickly - no patience whatsoever when
buiilding something. Hi!
I have used ordinary DuctSeal type of sealant (available in 1 pound
blocks at Loewes') for just about every outdoors application (except
this one) and find it to be excellent - especially for the price.
73 de Bob, W9DMK, King George, VA