[TenTec] [SMC] OT: Half inch Andrews Heliax LDF4-50A vs LMR-400

[Richards]

On 4/26/2013 4:58 PM, Stuart Rohre wrote:
> As to worrying about buried LMR 400, that would best be done before
> burying.



	Yes... but it has been out there for a few years
	already, so it amounts to a fait accompli !   I
	wonder how long before I will need to replace it.




Any coax candidate for your use should state on its data
> sheet, or catalog page, "non contaminating jacket".



	I used Times-Microwave LMR-400 DB - around 55 ft.
	Seemed like a good idea at the time.






Even if it is that,
> I come from the old school, and to avoid unknown earth character as to
> acid or alkali content; I would bury a conduit of PVC, then insert the
> coax in that.



	Ah.... yes.   Excellent point.  At time time, I was
	trying to remain within budget, minimize the damage
	and visual impact on the lawn, and maximize XYL approval
	of my 65 radials and buried feed line, so some compromise
	was due.  I made no other compromises in the installation, so
	I figured LMR-400 DB would be OK for such a short run -AND
	I was not sure how long it would remain in the yard.

	Did I mention it was the last week of November and it snowed
	as we laid the first batch of 30 radials...?

	And did I mention how much help the XYL was in completing
	the project before it started to snow?   I bet there are
	very few hams with a photos of his young bride helping
	to dig the trench for his buried transmission line...

	http://tinyurl.com/bvjv6lo

	Here is a photo of my most valuable ham shack accessory...

	http://tinyurl.com/bo8tmb6

	



At the mid conduit, you want to put a spacer under it to
> raise the middle, before closing the trench, such that its center is
> slightly higher than either end, so that condensation will flow to the
> ends.  The ends should be weather resistant by putting on an elbow and a
> riser piece, and create by other elbows, a J type exit, with the "J"
> upside down.  The coax then exits facing the ground on each end.  If you
> don't glue the J parts, you can take off the elbows to swab out
> condensation that may collect at the bottom of the conduit.



	All very good considerations.  We decided to eschew such
	precautions in favor of a quick and easy installation
	and figured it would only need to last a few years,
	before I did something else.   If I have to replace it
	in a couple of years, it will be easy enough to do for
	such a short run.   Maybe then I will pay more attention
	to a permanent installation as you describe.  That is
	surely the right way to go.




> The Wireman sells or did, some direct burial coax, and it is identified
> as such; but I still prefer to protect the coax.  Soil is dynamic, and
> rocks rise to the surface or move about, such that one might abrade and
> cut the jacket of direct buried coax.



	Quite right, but there better not be any big
	rocks bubbling to the surface in MY yard...!
	The developer spent good money on clearing, grading
	and dumping clean top soil before doing the lawn.

	Nevertheless, your point is well taken!     ;-)

	



> For safety, be sure and ground the coax shield to a ground rod before
> the coax enters through your wall.  That is a good spot to install a
> coaxial surge arrestor as well, with short conductor without sharp
> turns, direct to the rod clamp  Rods should be driven nearly into the
> ground, leaving just enough for the clamp to be higher than rain water
> accumulates.



	DONE!   I have just such a device on the input patch
	cable that runs between the remote coax switch and the
	house - attached to four 8 foot ground stakes I located
	within ten feet of the shack feed-through point.  I used
	full sized ground rods, and appropriate clamps as reviewed
	by the electrician I hired to run two extra AC lines to the
	shack when I purchased and remodeled the home.


--------------------- K8JHR --------------------------------------







../