[TowerTalk] Help on new Tower Installation planning and Feedlines

[ersmar at comcast.net]

Wendell:

      My comments embedded below.

73 de
Gene Smar  AD3F


 -------------- Original message ----------------------
From: Wendell Wyly - W5FL <wendell at wyly.org>

> 
> All wire and conduit is new. Plan to have two HF feedlines and one  
> 144/440 VHF feedline and 8 cond rotor cable for Hy Gain T2X Rotor and  
> a 4 or more small gauge (#24) wires to control the antenna switching  
> for 80,40 dipoles and 10/12/15/17 and 20 meter 2 el quad loops or  
> maybe a better antenna.  Plan to use 360 foot 1 1/2 or 2 inch pvc  
> conduit for the feedlines and 3/4 or 1 inch pvc conduit for the  
> control lines to be buried about 12 to 18 inches.

I'd recommend a single, larger (4 inch) conduit for ALL cables.  Other folks here have suggested corrugated plastic drain conduit; not a bad idea.  No need to separate control cables you're thinking about from the coax as the control voltages are below 50 VDC.  (BIG assumption here.)  

Also, I assume the 144/440 antenna is a dual-band vertical for local repeater work.  See below for applicable comment.


> 
> Budget is kinda skimpy but always wanted to use 1/2 inch hardline due  
> to low loss, but don't know if it pulls through conduit ok.  Trade  
> off is LMR 400 or LMR600 or ???. The conduit run is 140 feet to a  
> pull box and then 220 feet  for a total of 360 feet.  1500 Watts on  
> HF and 50 Watts on 144/440 VHF. Looking at using preamp or two band  
> amp/preamp on tower for 144/440 vhf due to long coax run, but unsure  
> what kind works well and particularly how to power it through the  
> conduit run from the house.

W3LPL has developed a series of tables that I used when I selected my coax runs for my tower:  http://www.k1ttt.net/technote/coaxloss.html#tables .   I selected RG-213 for all the runs (HF tribander, 40 dipole and 6/2/440 vertical) because, at 28 MHz my 110 feet of cable would result in only a little over 1 dB of loss.  I didn't care too much about loss on 440 as I was going to use this antenna for local repeater work, not weak-signal DXing.  For you, half-inch  hardline (LDF4-50A) would give you about 2 dB of loss at 440 MHz and about a half dB at 28 MHz.  

I am not aware of a dual-band pre-amp for 2M and 440.  If I'm correct and you still want to use a single dual-band vertical, you'll have to split the two bands at the antenna with a duplexer, run them through the separate pre-amps, then combine through another duplexer into one run of hardline to the shack.  PITA.  


 Is direct burial coax any better or worse than LMR type or hardline  
> in pvc conduit?  Soil is both sandy and rocky. The site is rural and  
> ups is preferred to truck shipments, so how do they ship hardline so  
> it does not get damaged or it is worth fooling with for this  
> installation?

If you're going to run the coax inside a conduit, I see know particular benefit worth the extra $ for buriable cable.  


> 
> Have never had any coax lightning arrestors, but was considering  
> putting them on the coax lines and control lines at the house single  
> point ground entry panel if I can find a reasonable cost solution and  
> ground the coaxes at the tower base.  The house has both lightning  
> rods and a good perimeter grounding system.

Figure about $65 per coax for an appropriate Polyphaser lightning suppressor and ground connectors.  


> 
> ANY and ALL suggestions and comments will be sincerely appreciated as  
> will suggestions to keep the total costs of materials as low as  
> practical.
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