80m + Rohn 25 in swamp = HELP!

K7LXC at aol.com K7LXC at aol.com
Wed Feb 28 10:25:10 EST 1996

In a message dated 96-02-27 22:01:11 EST, you write:

>How deep would you have to go in the swamp-like condx Charlie's talking
about ?

Hiya, Bob --

   Good question and it got me thinking more about Wizzer's predicament.
 You'd have to go down far enough to reach something solid for the tower
footing.  There's no soil strength available so you'd have to go quite a bit
larger for the base and anchors.  Any engineers out there want to take a stab
at that one?   

    What's the weight of concrete - a ton per yard or two something like
that.  If you poured 2-4 yards, it'd probably settle just fine due to its
weight.  Haven't run into this one before so I don't know other options are
available.  If this was a commercial job, they'd run equipment out there
anyway somehow, etc.  All those things cost money especially when you build
it to the engineering drawings; not your typical ham "budget" project.
 Actually, using a trailer-mounted pumper is pretty reasonable; they can pump
up to 400 feet and they're only $75/hour or so.  The snorkel types run more.
 The hard part will be getting the form installed.

  Thanks for your question and 73,    Steve     K7LXC    

>From Del Seay <seay at alaska.net>  Wed Feb 28 14:40:24 1996
From: Del Seay <seay at alaska.net> (Del Seay)
Date: Wed, 28 Feb 1996 06:40:24 -0800
Subject: Tuner Thread
References: <199602281417.HAA06210 at lynx.csn.net>
Message-ID: <31346958.4D74 at alaska.net>


> Tom, I have to disagree with you on this one.  I had three of the Johnson KW
> Matchboxes and all performed with the same limitations.
> 1)  They can't handle 1500 watts on 10 and 15 meters (and this was to a nominal
> 50 ohm load).  Late in a contest with high duty cycle CQing to a nominal
> Yagi they
> will unsolder their bandswitch connections.  (Why a tuner with a Yagi?  When

Sounds like the wrong Matchbox. The one they now call the KW Matchbox
was really the 250 Watt Matchbox as originally put out. Then, someone
decided that sideband voltages/currents were less than AM so they
started calling it the KW Matchbox. But - as you noted, not so!
The real KW Matchbox will handle 5 KW with ease.

The nicest part of the Matchbox was the link coupling, which eliminated
copper between outside and inside, and you'd be surprised the amount of
receive garbage that can be eliminated that way.

>From John Brosnahan <broz at csn.net>  Wed Feb 28 16:22:04 1996
From: John Brosnahan <broz at csn.net> (John Brosnahan)
Date: Wed, 28 Feb 1996 09:22:04 -0700
Subject: 80m + Rohn 25 in swamp = HELP!
Message-ID: <199602281622.JAA15883 at lynx.csn.net>

At 10:25 AM 2/28/96 -0500, you wrote:
>In a message dated 96-02-27 22:01:11 EST, you write:
>>How deep would you have to go in the swamp-like condx Charlie's talking
>about ?

Somewhat related is the way they set utility poles in the swamps.  They
bring in a utility pole using a helicopter.  The pole has a charge of dynamite
on the bottom, which is detonated and before the goo rushes back into the 
resulting hole the pole is dropped into the hole.

Not sure I would want to be the first guy trying this--experimenting with
just how much dynamite is enough.  Might require splinter removal
and new uses for Preparation H.

Caisson drilling is pretty common but requires special equipment.  It may be
possible to use a caisson technique while pumping out the insides and
settling the caisson as you go.  The real question remains about what are
the details of the soil--how far down before you hit anything solid and just
how liquid is the swamp.

I once had a 4ft long 12 inch diameter concrete pipe that was mounted vertically
to provide access to a water valve.  Over the years the thing had completely
filled up with soil and sand.  Kept thinking that this would be a real pain
to dig out with a little shovel.  Finally "excavated" the inside of the pipe
with a Sears heavy duty Shop Vac.  Didn't take very long at all.  The 
technique won't challenge a back-hoe in normal circumstances but may
be the only answer in some cases.

The ionospheric heater array at Arecibo consists of about 100 towers that are 
100ft tall, supporting a large phased array of log periodics.  It is built on
vegetation floating on a swamp (done deliberately to enhance the ground
conductivity for a vertical beam).  When you jump up and down on the 
"ground" everything shakes. You can drive a car on it but it has just enough 
bounce to be un-nerving.  Once, I was driving 3ft long rebar pieces to act as
temporary guy anchors for a little array of receive antennas.  At the last
tap of 
the hammer the rebar just kept on going--penetrating the "soil" and falling
on down through the water, completely lost.  These towers were built on 
some kind of surface platform of pressure treated logs and were 
guyed to dead-men of more pressure treated logs.  Not sure of the exact 
details of Arecibo but the situation of towers in a swamp is an interesting
problem and I think I will call my friends at Arecibo and find out the exact

73  John  W0UN

John Brosnahan  
La Salle Research Corp      24115 WCR 40     La Salle, CO 80645  USA
voice 970-284-6602            fax 970-284-0979           email broz at csn.net

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