Free Online Longley Rice Coverage Calculator

[BobOnTheJob]

For those of us who can't afford ComStudy, I found a nifty free online tool that calculates Longley-Rice FM coverage & allows you to select your transmitter site, enter the height above ground and drag & draw your desired reception area as well as select three color bands to show user selectable contours. It seems to be based on Google maps & gives you a lot of insight by trying various power vs height combinations. It asks for "Power" and "Antenna Gain (dbi)". I've put the ERP in Power & 2.1dbi in the Antenna Gain field as that should equal 0dbd gain.

http://lrcov.crc.ca/cov.php?lang=en

 

[Play Freebird]

I also found this last week (while searching for a ground conductivity map of Canada) and tried making several plots of our translator coverage areas. The results are remarkably close to my own observations, I'm sure I'll use this frequently.

Another handy website is www.heywhatsthat.com; it will generate line-of-sight (aka "visibility cloak") maps and plot terrain profiles along a radial.

 

[rfry]

... It asks for "Power" and "Antenna Gain (dbi)". I've put the ERP in Power & 2.1dbi in the Antenna Gain field as that should equal 0dbd gain.

Thanks for the link, nice find.

The value of ERP for an FM/TV station already incorporates the gain difference between an isotropic radiator and a 1/2-wave dipole in free space. So if ERP is used in this calculator then better to set the antenna gain to 0 dBi. Using 2.1 dBi for the gain will add 2.1 dB to the ERP that is entered.

An alternate would be to set the antenna input power (in watts), then add 2.15 to the rated peak gain (in dBd) of the antenna and enter that as the antenna gain. Of course the transmission line loss for the frequency, and the loss of any filters/combiners/isocouplers in the system would need to be known along with the TPO of the transmitter in order to calculate the antenna input power.

There is no means in this program to enter pattern data as a function of elevation angle and/or the radiation center of the antenna array -- which would lead to inaccurate results sufficiently close to the transmit site.

But the calculator is a good resource if used with due care.

RF
http://rfry.org

 

[rfry]

...An alternate would be to set the antenna input power (in watts), then add 2.15 to the rated peak gain (in dBd) of the antenna...

The peak gain of a center-fed, 1/2-wave dipole in free space is 2.15 dB more than an isotropic radiator. So after I just re-read my last post in this thread, this correction to it is necessary (sorry, all -- I do want to make accurate posts, and to correct them if they're not).

...An alternate would be to set the antenna input power (in watts), then subtract 2.15 from the rated peak gain (in dBd) of the antenna...

As the bottom line it would be easier to use your licensed ERP for either h-pol or v-pol, and set the antenna gain to zero dBi.

RF

 

[BobOnTheJob]

Per Martin-Pierre Lussier
Research Engineer | Ingénieur de recherche
Communications Research Centre Canada | Centre de recherches sur les
communications Canada
3701 Carling Ave. | 3701, avenue Carling
PO Box 11490, Station H | CP 11490, succursale H
Ottawa, Ontario K2H 8S2 | Ottawa (Ontario) K2H 8S2
[email protected] | fax/téléc. (613)993-9950
Web site / Site web : www.crc.ca
Government of Canada | Gouvernement du Canada

"you are correct, you would place the ERP of the station in the "Power (W)" field and 2.15 in the "Antenna Gain (dBi)" field"

 

[Play Freebird]

Bob, did you happen to ask M. Lussier what a single-user license for COVLAB would cost? I'm quite impressed with this and might be interested in purchasing it for client work.

 

[BobOnTheJob]

I didn't, but he's good about answering emails. I too am impressed with this...makes quick work out of deciding just how high on a given tower is high enough.