[BC] Slant wire feeds vs series fed

[Phil Alexander]

On 24 Jan 2006 at 11:09, Scott Bailey wrote:

> Personally, I like the slant wire 
> antenna.  Makes it easier to co-located other service on the tower. I 
> understand that the commission won't allow this anymore.

They would prefer seeing skirt fed shunt antennas instead.

While slant wires are not exactly prohibited in the rules, that is 
the effect of the rules in practice.

Slant wire fed antennas will not be approved for new nighttime service
although they are permitted for new daytime use. HOWEVER, no new
applications for daytime only service are being granted. Now I suppose
if you had a two site operation, perhaps a DA-N site and an non-DA
daytime site, they would approve a new application for the daytime site
on that basis because the rules specifically say it is not prohibited.

It is far-fetched, but it could happen if the only site that would work
for a frequency at night would not work for daytime in consideration
of perhaps daytime adjacent channel interference. However, in that case,
they probably would prefer a skirt to a slant wire because skirts are
uniform.
 
>     Phil made the statement that if done right, it works well, does 
> it still work in sort of a directional mode.

There is a SLIGHT directional effect where the feed wire field tends
to cancel the tower field however if the feed wire is close in (which
force a higher attachment point) I think that should be very minimal,
almost non-existent. The real problem, as I understand it, is there is
no programming in the FCC computer for a slant wire feed because those
programs predate the NEC. Thus, the FCC is unable to predict the
high angle radiation of a slant wire at night. That, however, did not
stop them from authorizing PSSA's and low power night service to Class
III's back in the days of the show cause orders. So, there are quite 
a few of them in service at night, although none with more than about
240 watts, and most with far less.


Phil Alexander, CSRE, AMD
Broadcast Engineering Services and Technology 
(a Div. of Advanced Parts Corporation) 
Ph. (317) 335-2065   FAX (317) 335-9037





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