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Radio-Locator AM Antenna Pattern maps...

The Dude said:
Very interesting!!

I didnt know that existed on that site,i took a look @ a few local stations in my area :)
Click to expand...

Be careful of radio-locator's AM pattern data. First off, these are not pattern plots; they are not very accurate coverage maps. A good place for AM pattern plots is the AM Query page at fcc.gov. Radio-locator's nighttime coverage maps greatly overstate the nighttime coverage of most AM's. The inner contour is 2.5 mV/m, which is way outside of nearly all AMs' NIF (nighttime interference-free) groundwave coverage. The outer contour is 0.5 mV/m, which applies only to Class A AMs (in New England, only WBZ and WTIC). And not all Class A AMs receive protection to their 0.5 mV/m groundwave contours. In the US, Class A AMs' 0.5 mV/m 50% skywave contour is nominally protected, but that contour covers such a large area that radio-locator does not show it either. If you can keep in mind all of the disclaimers and explanations, you can use the radio-locator maps, but don't take them as gospel or you will be seriously misled.
 
DanStrassberg said:
The Dude said:
Very interesting!!

I didnt know that existed on that site,i took a look @ a few local stations in my area :)
Click to expand...

Be careful of radio-locator's AM pattern data. First off, these are not pattern plots; they are not very accurate coverage maps. A good place for AM pattern plots is the AM Query page at fcc.gov. Radio-locator's nighttime coverage maps greatly overstate the nighttime coverage of most AM's. The inner contour is 2.5 mV/m, which is way outside of nearly all AMs' NIF (nighttime interference-free) groundwave coverage. The outer contour is 0.5 mV/m, which applies only to Class A AMs (in New England, only WBZ and WTIC). And not all Class A AMs receive protection to their 0.5 mV/m groundwave contours. In the US, Class A AMs' 0.5 mV/m 50% skywave contour is nominally protected, but that contour covers such a large area that radio-locator does not show it either. If you can keep in mind all of the disclaimers and explanations, you can use the radio-locator maps, but don't take them as gospel or you will be seriously misled.
Click to expand...

I will echo that caveat. A quick check of a few directional plots on Radio-locator against the FCC data shows variances ranging from virtually insignificant to several volts/meter. I don't know where Radio-locator is getting its data, but for a few of the plots I checked there's a definite variance between R-L and FCC data. Let's also remember that these are plots of electrical field strength at 1 km from the center of the antenna array, the FCC standard for deriving the pattern shape. They are NOT meant to be the equivalent of coverage maps. Their greatest use to hobbyists is to show the azimuths of the maxima (major lobes) and minima (nulls) of the patterns.
 
Be careful of radio-locator's AM pattern data. First off, these are not pattern plots; they are not very accurate coverage maps.
Click to expand...

The link provided IS for pattern plots, Dan...not R-L's "coverage maps", which, I'll readily grant you, may or may not be technically accurate - but even when they are accurate, it only loosely correlates to whether or not you can clearly receive a given station at a given place.

Now hair's mention of the variances between PATTERNS as told by R-L and as told by the FCC...that's more interesting, since it suggests that either R-L is not drawing off the same database as the FCC (which would be odd to say the least...what other database could be used?) or that there's an error in R-L's software in how it parses the database's data and processes it into its own website.

Regardless, it is rather interesting seeing how a given station's pattern can be so drastically impacted by ground conductivity issues and thus result in a much different "coverage map" than the pattern would imply.
 
aaronread said:
Be careful of radio-locator's AM pattern data. First off, these are not pattern plots; they are not very accurate coverage maps.
Click to expand...

The link provided IS for pattern plots, Dan...not R-L's "coverage maps", which, I'll readily grant you, may or may not be technically accurate - but even when they are accurate, it only loosely correlates to whether or not you can clearly receive a given station at a given place.
Click to expand...

Sorry; you are correct! The pattern plots must be a new feature. I had never seen them previously at radio-locator.com and I should have checked the provided link before I shot my mouth off. However, I think that the "coverage maps" are easier to reach on the r-l site and that, therefore, most people will continue to go to them, rather than to the electric-field plots. My caveats about the "coverage maps" are still valid.

I suspect that r-l had gotten enough complaints about the coverage maps that they decided to ameliorate the situation by adding the electric-field plots. It would be even nicer if r-l made the electric-field plots available along with the other station data rather than placing them in their own separate section of the site. Maybe that enhancement will come along in time.
 
aaronread said:
Now hair's mention of the variances between PATTERNS as told by R-L and as told by the FCC...that's more interesting, since it suggests that either R-L is not drawing off the same database as the FCC (which would be odd to say the least...what other database could be used?) or that there's an error in R-L's software in how it parses the database's data and processes it into its own website.
Click to expand...

I'm with you. I can't imagine what other database would provide the tabulated data for each five degrees of azimuth, which is what I checked against the FCC data. The theoretical field strengths seem to be the closest...out of the ones I checked, most were exactly the same in the two tabulations, or at most were a few tenths of a millivolt off. However, there were some significant variations in some of the standard and augmented field strengths...some as high as three or four millivolts.

All of which is relatively insignificant. No one in their right mind is going to use the R-L data for anything official anyhow.
 
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