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Radio Coverage maps.

W4IY Repeater Coverage

2 Meter Repeater Coverage(~500k) - Using Radio mobile to show coverage w/map overlay. Note: Yellow is 50uV = S9. Red is 500uV = S9+20db. The coverage seems to jive with the repeater signal strength on my FT-857 during the morning commute. Of course, this is anecdotal. (Oh no.. another project!)

Here is the URL to the mapquest map. The red star is just about centered on the water tower: Water Tower, Map quest Choose the arial view and zoom in.

Radio Mobile is configured to use the repeater as the transmitter and the mobile unit as the receiver. I used the data from the Woodbridge Wireless web site for the repeater parameters and I used specs from a handheld to configure the mobile parameters.

Network Properties

Systems -
Power Out: 25 W
Sensitivity: 0.1uV
Line Loss: 3db
Antena Gain: 5.25db
Antenna Height: 36m
(I think this works out to about 40W ERP as per the WWI web site.)

Power Out: 15 W
Sensitivity: 0.25uV
Line Loss: 2.0db
Antena Gain: 4dbi
Antenna Height: 1.5m

Parameters -
Net 1:
Frequency: 144MHz
Surface Refractivity: 301
Ground Conductivity: 0.005
Relative Ground Permitivity: 15
Polarization: vertical
Climate: Continental Temperate
Mode of Variablity: Broadcast/50%
Additional Loss: City 5%


The link between the two repeater sites is 19.71KM. It looks like it is a line of site shot. However, there is a ridge between the two sites, which is located just north of RT 3000 and Yates Ford Road. I assumed the antenna at the OVH site (10323 Lomond St, Manassas) is also 100 feet (36M) high. The obstruction is 9.16KM from OVH, with little clearance. From google earth, it looks like this ridge is covered in timber. So my guess is VHF/UHF link will be fine, but it doesn't look promising for a microwave shot.

WWI Repeater - 38D 41' 08" N 77D 18' 59" W - FM18IQ

OVH Repeater - 38d 46' 57.57" N, 77d 30' 21.38" W - FM18FS

Here are the graphs, maps and pictures.

General Map - Shows the OVH-WWI repeater locations on a radio mobile map, with roads

Link Profile - Shows the link profile for the path between the OVH and WWI repeaters. Note, the link on the OVH site is assumed to be similar to the WWI repeater. The link is 19.71KM at 123.5 degrees from OVH to WWI.

Ridge Location - The high spot is located at 38d44m16s N, 77d25m03s W. This appears to be just north of the intersection of the Prince William Co Parkway and Yates Ford Road. (Google earth picture)

Pictures and Info

Lat-Long - Latitude and Longitudes for sites used on this page

Repeater to W7IY - Path profile from WWI to W7IY in Stafford

Relief Map - Map centered near Dumphries, no lines or radio coverage

Manassas Repeater Site - A google earth picture of the NOVEC property in Manassas. I think the OVH antennas are on the tower in the lower right hand corner of the picture. The building and green generator match the picture on the OVH web site. | OVH Repeater Shack

Woodbridge Wireless Repeater Site The water tower (google earth) with the WWI antennas.

Repeater Site Map Shows orientation of the water tower and relative directions to various other sites.


There really isn't a standard, but I found a couple of references that suggest 6db/S-unit and S9=50uV. Some others suggest using the 5db/S-unit scale. Either way, I'll use this as a guide for plotting the colors for RF coverage. That is, S9 = 50uV.

Hospital Notes

  • Hospital = 38 41 08 N 77 18 59 W
  • Link from WA0DYJ to Hospital - no path, high point at 38 38 08 N 77 18 01 W = Giddion and Smoketown
  • Link from Repeater to Hospital - no path, high point at 38 39 37 N 77 18 02 W = Minnieville and Horner

Linking Disparate Systems

There is a need to link communication systems together so different public safety groups can talk to each other. Here are a few links for reference.