VOACAP - Coverage Area Map
What is VOACAP?
VOACAP (Voice of America Coverage Analysis Program) is free professional high-frequency (HF) propagation prediction software from NTIA/ITS, originally developed for Voice of America (VOA). Please note that VOACAP predictions are mostly reliable except on days when solar and geomagnetic storms disrupt the ionosphere.
Useful when planning on reaching many stations over an area for a net using the
Coverage Area Map.
In the context of amateur radio a sked is a pre-arranged or scheduled contact between ham radio operators. It can also be used to schedule a net.
- Go to voacap.com/hf/
- Select your TX QTH (location) from the drop down menu
Select your QSO's RX QTH (contact's location) from the drop down menu
- Click on the boxes on the right side to set your mode and power to SSB and 100W in this case.
- Click on the Settings box on the right and it brings up a window on the left. There select the 20m band, and then the UTC hour (15 UTC for 8:00 am Pacific Time) that are when you want to make the QSO (contact).
- Click on the green button labeled "REL Map" in the bottom of the window. After a few seconds this area coverage map will appear with areas color coded for % Reliability for the contact (for the purpose of this demonstration, I have zoomed in to the area we are working).
You can see a large white area (the skip zone) centered on Salem, OR, that represents 0% chance of successful contact on 20m.
20m is a poor choice for an 8:30 am sked with most of the western US.
- Below is the same map for 40 meters at 8 am. Here Las Vegas, NV, is in the excellent 90-100% red zone, but stations within a few hundred miles of Salem, OR, fall in the 30-50% blue to green zone and may or may not be heard.
- The map below for 80m at 8 am shows excellent coverage of the Pacific Northwest, but Las Vegas, NV, has dropped out of the coverage area.
- The area coverage map below for the in-between band, 60m (5 MHz) at 8 am looks more promising. It predicts 90-100% reliability to Las Vegas, NV, 70-80% reliability within a couple hundred miles of Salem, OR, and 80-90% reliability throughout the rest of the Northwest.
Most modern radios can operate on the five channels on 60m, and we are allowed 100 watts there. A 60m dipole is sufficient.
This spring may be a good time for the net to try 60m.
Thanks to Carol KP4MD for the direction in developing this tutorial.