For esthetic / XYL / neighboor reasons, I'm thinking of running balanced
"ladder" line to the back of my yard, via 1" PVC pipe with appropriate
measures to keep the water out, and burying it maybe a foot underground.
Length of the run might be 20 feet along the bottom of a deck and then 60
feet buried, give or take. Then straight up a tree centered between two
other trees to feed about a 80' center fed dipole.
Nothing else will be in the pipe with the feed line. Anyone have any
thoughts on why this might or might not work? The ground where it could be
buried, is on the moist side most of the year.
Bob
kb8tl

Bob,

I, for one, can't imagine any "easy" way to bury open feed line without
at least some degredation.


Were I in your shoes, I'd be thinking about coax to that tree and
putting some kind of remote tuner out there.


Ed K7AAT

"Bob P" wrote in message
news
For esthetic / XYL / neighboor reasons, I'm thinking of running balanced
"ladder" line to the back of my yard, via 1" PVC pipe with appropriate
measures to keep the water out, and burying it maybe a foot underground.
Length of the run might be 20 feet along the bottom of a deck and then 60
feet buried, give or take. Then straight up a tree centered between two
other trees to feed about a 80' center fed dipole.
Nothing else will be in the pipe with the feed line. Anyone have any
thoughts on why this might or might not work? The ground where it could be
buried, is on the moist side most of the year.

This may be an interesting experiment - and I for one will appreciate a
report of your success.
I would suggest trying it without burying it first - If it works
above-grade, it may work buried.
The biggest challenge will be keeping water out of the pipe.




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Bob:

If I had to do what you are proposing, and could find no alternative, I would go purchase a bunch of the foam pipe
insulation, experimentally determine what spacing 6" chunks of it would still support the line adequately centered in
the pipe, and put that in 1-¼" or 1-½" pipe, whichever it fit the best. Bigger is better as someone else pointed out.
You might want to test some for RF loss, as the black version may well contain carbon. Styrofoam would be the best
choice, but I don't know of a cylindrical form of Polystyrene foam. Maybe 1" strips of it cut from 4' X 8' sheets of 1"
foam would work. Use your imagination, for gosh sakes. The PVC will survive underground satisfactorily, but paint the
exposed ends for longest life (or use short pieces of gray conduit for the exposed portion).

--
Crazy George
Remove N O and S P A M imbedded in return address


"Bob P" wrote in message news
For esthetic / XYL / neighboor reasons, I'm thinking of running balanced
"ladder" line to the back of my yard, via 1" PVC pipe with appropriate
measures to keep the water out, and burying it maybe a foot underground.
Length of the run might be 20 feet along the bottom of a deck and then 60
feet buried, give or take. Then straight up a tree centered between two
other trees to feed about a 80' center fed dipole.
Nothing else will be in the pipe with the feed line. Anyone have any
thoughts on why this might or might not work? The ground where it could be
buried, is on the moist side most of the year.
Bob
kb8tl

Bob, KB8TL wrote:
"Anyone have any thoughts on why this might not work?"

I`ve worked in several medium wave broadcast stations which used buried
coax to feed the towers. No problems..

I worked in a shortwave broadcast plant where we needed a 100 KW dummy
load. So we constructed a parallel wire 600-ohm line only about 2 feet
above the earth using Copperweld wires a few hundred feet long. It could
boil the dew on the groud and bring earth worms to the surface. It also
did a great job of dissipating the 100 KW.

Anytime parallel line such as twinlead or ladderline approaches ordinary
earth, loss soars. Direct burial is impractical even inside fairly large
conduit. Use one or two lengths of waterproof coax as buried line.

Best regards, Richard Harrison, KB5WZI

Could you not create low loss "coax" by using concentric pipes?
Might be easier than all this hacking around..

That, or run heliax in the buried section, and convert to balanced in a
little box on the other end.

"Dave VanHorn" wrote in message
...

Could you not create low loss "coax" by using concentric pipes?
Might be easier than all this hacking around..

They call that hard line, as in Heliax etc.

W4OP

And I thought it were only Black pudding that came from Bury...

Richard Harrison wrote:
Anytime parallel line such as twinlead or ladderline approaches ordinary
earth, loss soars. Direct burial is impractical even inside fairly large
conduit. Use one or two lengths of waterproof coax as buried line.

A ham I know uses parallel runs of buried RG62 as a compromise.
That gives him a characteristic impedance of 186 ohms for his 30
foot underground section. It was interesting to model that setup
using MicroSmith.
--
73, Cecil http://www.qsl.net/w5dxp


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Cecil, W5DXP wrote:
"A ham I knpe uses parallel runs of RG 62 as a compromise. That gives
him a characteristic impedance of 186 ohms for his 30 foot underground
section."

Yes. It`s balanced to ground and has twice the characteristic impedance
of a single run of coax. In the case of twin runs of RG 82, that is
twice a value of 93 ohms, or 186 ohms, center conductor to center
conductor.

I recall analog microwave radios which had their baseband signals wired
with twin runs for each direction of transmission like that to obtain a
shielded and balanced baseband system. It must have been good for the
coax business and it made for a quiet radio too.

Best regards, Richard Harrison, KB5WZI