[BC] Counterpoise Ground System

[Cowboy]

On Tuesday 19 September 2006 04:02 pm, Bailey, Scott wrote:
> Bill,
>    When they removed the wires, makes me wonder did they retune the
> tower?  Ok, I see another problem here, their tower looks to be series
> feed. I strongly discourage any new installation to be series feed, and
> encourage old series feed towers to be converted to a unipole.
>    If that station was mine, I'd be calling Ron Nott over there and put
> a folded unipole on that tower. They would find that the folded unipole
> will make up for some of the signal loss they are suffering from.
>     If they went from series feed to a unipole, and just 6 wires,
> counterpoise, I bet they get out much better than they ever had since
> the antenna system was built!

 And modeling shows that a conventional series fed radiator is slightly
 more efficient than any folded configuration.
 Basicly, the folded vertical is a feed system, nothing more.
 Folded antennae generally have the skirt wires less than 90 degrees,
 which essentially makes the skirt the last coil in the network, with
 attendant coil loss. Whether it's folded monopole, or multipole makes
 little difference. ( the multipole divides the current in parallel, and
 transforms the radiation resistance upward, so finds use in VLF where
 conductor losses are VERY significant compared to radiation resistance)
 There are very valid reasons to uses skirted towers, but coverage 
 is not one of them.

On Tuesday 19 September 2006 04:08 pm, Bailey, Scott wrote:
> You mean to tell me someone can use uninsulated, stranded, copper wire?

 Sure !
 Copper is copper.

> Wouldn't it stretch, and the weather would get to it too?

 Probably it would stretch, but so will solid wire, and both will be
 similarly affected by weather.

> I knew an old engineer that was working on a old, broken down AM
> facility out in Oklahoma, and he had used aluminum in a pinch for some
> kind of ground system. He said it worked, but I had my doubts.

 I have no doubt.
 The conductivity of aluminum is quite high, though not as high as copper.
 Again, the idea is to take the return currents out of the lossy dirt, and
 put them in something with less loss.
 Aluminum has slightly higher loss than copper, so it wouldn't work as well
 as copper theoreticly, but it would work far, far better than nothing.
 Whether there would be a measurable difference between copper and aluminum
 could be the subject of some debate.
 Rest assured, power companies would not use it if it cost them money in
 terms of conductor losses ! RF behaves slightly differently, true, so the effect
 would be more pronounced at 1 megahertz as opposed to 60 hertz, but in the
 absence of measured data I'd do it in a pinch, in a heartbeat.

 Steel is far worse than either, but is it worth copper plating the whole tower ?

 On Tuesday 19 September 2006 04:49 pm, Bill Harms wrote:
> Scott,
> 
> 	From the technical point of view, I have no reason to doubt what you 
> are saying.  I wonder if the facility was state of art in 1947 when 
> it was originally built.  I also guess that the station sufficiently 
> covers Spokane for the current owners. 
> 
> Bill Harms

 From a technical point of view, I do doubt it !!
 The technology has advanced since 1947 in terms of networks, bandwidth,
 placement and such, but as far as the efficiency of a radiator of given height,
 not at all !

-- 
Cowboy