Effect of hills on propogation

[K7BVT]

We are evaluating sites along the Oregon coast for our 2011 Field Day operation. We plan on using a 3 element beam at 45’ on 10 – 20 meters and a dipole at the same elevation for 40 – 80 meters. Many potential sites face rising slopes to the east. Any rules of thumb on the maximum angle of above the horizon for obstructions such as hills for acceptable propagation? Chuck K7BVT

[KB4QAA]

The signal from the antenna is not like a laser beam. It's more like a kids' party balloon, lobed or pear shaped.

As long as you don't park smack at the base of a hill you'll probably get a usable signal somewhere in most directions.

If you want more detail you need to get the manufacturers manual for the antenna and examine the vertical and horizontal beam patterns.

Good luck on field day!

[K8ERV]

Don't raise the antenna, lower the hill. (Sorry about that Jerry).

TOM K8ERV Montrose Colo

[W0VYE]

We are evaluating sites along the Oregon coast for our 2011 Field Day operation. We plan on using a 3 element beam at 45’ on 10 – 20 meters and a dipole at the same elevation for 40 – 80 meters. Many potential sites face rising slopes to the east. Any rules of thumb on the maximum angle of above the horizon for obstructions such as hills for acceptable propagation? Chuck K7BVT

There's no real "line of sight" effect. A "rising slope" suggests to me that you're not talking about a 3,000-foot mountain a mile away and blocking 120 degrees of the horizon. That might be another story. But I live on the side of a river bluff that blocks all of the western horizon and I've easily work west coast stations on 20, 17 and 15 meters, using a 50-foot random wire and 100 watts peak. So personally, I wouldn't give it a thought. 73

[K4SAV]

Uphill slopes do attenuate low angle signals, but for field day you don't need very low angles, especially on the low bands. On 20 meters from Alabama about 15 to 20 degrees elevation is the best angle for most of the high population centers. That will be a little lower on 15 meters, and higher on 40. It's probably similar for you. If you want a more accurate estimate, you can use HFTA, download the terrain data for the location you are considering from the USGS website, and plot the patterns. Then you can use HamCAP to estimate the angle required to various places on different bands.

Jerry, K4SAV

[WB2WIK]

I wouldn't sweat it for FD unless you're at the bottom of a hill that begins to rise where your shadow can fall on it.

FD is a domestic event, and most contacts will be within 3000 miles. From here on the west coast, pretty much ALL contacts will be within 3000 miles, including KH6 and KL7. A LOT of contacts will be within 1000 miles.

It's hard to run out of stations to work during FD.