[BC] Directional Antenna Proofs <SoM7GjCN0>

[Cowboy]

On Wednesday 20 June 2012 09:11:10 pm James B. Potter wrote:
> I need an authoritative current resource to guide me as to the requirements
> of AM directional antenna proofs -- both partial and full,

 There are at least two on this list who can provide.....

> how often, and 
> other legal and technical details.   I already have a
> current version of the FCC R&R, 

 The latest rules are the bible, regardless of rumor or hearsay.

 The jist is that you need not run a proof unless you have "reason
 to believe" that the pattern is not what's licensed, or you are running
 measurements to support an application.

> but I have been told by other engineers that 
> certain provisions have been relaxed, etc. 

 Over the decades, that's true, but I'm not sure it's relevant.
 For instance, quarterly skeletons are no longer required, and
 even monitor points are only *required* quarterly, and only
 for a non-approved sample system. ( but neglecting them is
 a real, REAL bad idea )

> I just started at a 5-tower 
> directional 560 station with DAD and DAN patterns, and the coverage is
> significantly lower than when this system was originally installed.

 Is it ?

 First thing I'd do, is check ALL on-site parameters, including
 base current ratios, as compared to the licensed or last full proof.
 Second thing I'd do, is check monitor points. ( FCC says first, but usually
 it's a waste of time if on-site parameters are off )

 Next, run what we used to call a skeleton proof.
 3 or 5 points on each radial. Get same points as used in the last full proof.
 If there appears to be a discrepancy in "average" field, then run a partial.
 Minimum 10 points on each radial, one of which must be the monitor point.
 Start about two miles out, and go outward.
 Again, if the average field appears off, now you know something.

 Run a partial Non-D. That will tell you all you need to know about your
 coverage as compared to the original non-D in the last full proof.
 Again, starting about two miles out.
 If *that* appears low, then do as many non-D "walk in" points as you can,
 as accurately as you can. That will tell you all you need to know
 about your ground system.

 The trends uncovered will dictate what you do next, whether it's reporting
 to management that all is well, and/or beyond your control, or whether
 you call someone like me to fix it.

 For instance, if your near-field walk ins show that you are radiating
 what it always did, but your far field is down, ( non-D ) it's due to industrialization.
 There's nothing you can do, save possibly something like contacting
 Mr. Gearing or Mr. Sawyer to see if a power increase is possible.
 If the non-D is OK, but directional is down, then you need me.
 If your pattern shape is out, and you're not comfortable with that level
 of directional tuning and analysis, then you need me. ( not cheap )
 The first thing I'd want to see, would be the partial proof data, both
 directional and non-D, taken at exactly the same power ( within a watt )
 of the original proof. ( though if not possible, we can ratio )

 Hope you're comfortable with a FIM !
 ( I can do that for you, too, but if you're comfortable doing it, you
 will be considerably more cost-effective than I would be )

-- 
Cowboy